Merge branch 'master-ex-rail'

.gitignore

@@ -9,3 +9,9 @@ Release/*
 config.h
 .vscode/extensions.json
 mySetup.h
+mySetup.cpp
+myAutomation.h
+myFilter.cpp
+myAutomation.h
+myFilter.cpp
+myLayout.h

CommandStation-EX.ino

@@ -44,7 +44,6 @@
  *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-
 #include "DCCEX.h"
 
 // Create a serial command parser for the USB connection, 
@@ -85,11 +84,20 @@ void setup()
   //  detailed pin mappings and may also require modified subclasses of the MotorDriver to implement specialist logic.
   // STANDARD_MOTOR_SHIELD, POLOLU_MOTOR_SHIELD, FIREBOX_MK1, FIREBOX_MK1S are pre defined in MotorShields.h
   DCC::begin(MOTOR_SHIELD_TYPE);
+         
+  // Start RMFT (ignored if no automnation)
+  RMFT::begin();
+  
+  // Link to and call mySetup() function (if defined in the build in mySetup.cpp).
+  //  The contents will depend on the user's system hardware configuration.
+  //  The mySetup.cpp file is a standard C++ module so has access to all of the DCC++EX APIs.
+  extern __attribute__((weak)) void mySetup();
+  if (mySetup) {
+    mySetup();
+  }
 
-  #if defined(RMFT_ACTIVE) 
+  // Invoke any DCC++EX commands in the form "SETUP("xxxx");"" found in optional file mySetup.h.  
-      RMFT::begin();
+  //  This can be used to create turnouts, outputs, sensors etc. throught the normal text commands.
-  #endif
-
   #if __has_include ( "mySetup.h")
         #define SETUP(cmd) serialParser.parse(F(cmd))  
         #include "mySetup.h"
@@ -101,7 +109,7 @@ void setup()
       LCN::init(LCN_SERIAL);
   #endif
 
-  LCD(1,F("Ready")); 
+  LCD(3,F("Ready")); 
 }
 
 void loop()
@@ -123,15 +131,16 @@ void loop()
   EthernetInterface::loop();
 #endif
 
-#if defined(RMFT_ACTIVE) 
+  RMFT::loop();  // ignored if no automation
-  RMFT::loop();
-#endif
 
   #if defined(LCN_SERIAL) 
       LCN::loop();
   #endif
 
   LCDDisplay::loop();  // ignored if LCD not in use 
+
+  // Handle/update IO devices.
+  IODevice::loop();
   
   // Report any decrease in memory (will automatically trigger on first call)
   static int ramLowWatermark = __INT_MAX__; // replaced on first loop 
@@ -140,6 +149,6 @@ void loop()
   if (freeNow < ramLowWatermark)
   {
     ramLowWatermark = freeNow;
-    LCD(2,F("Free RAM=%5db"), ramLowWatermark);
+    LCD(3,F("Free RAM=%5db"), ramLowWatermark);
   }
 }

DCC.cpp

@@ -24,6 +24,7 @@
 #include "GITHUB_SHA.h"
 #include "version.h"
 #include "FSH.h"
+#include "IODevice.h"
 
 // This module is responsible for converting API calls into
 // messages to be sent to the waveform generator.
@@ -52,6 +53,9 @@ void DCC::begin(const FSH * motorShieldName, MotorDriver * mainDriver, MotorDriv
   shieldName=(FSH *)motorShieldName;
   StringFormatter::send(Serial,F("<iDCC-EX V-%S / %S / %S G-%S>\n"), F(VERSION), F(ARDUINO_TYPE), shieldName, F(GITHUB_SHA));
 
+  // Initialise HAL layer before reading EEprom.
+  IODevice::begin();
+
   // Load stuff from EEprom
   (void)EEPROM; // tell compiler not to warn this is unused
   EEStore::init();
@@ -235,6 +239,9 @@ void DCC::updateGroupflags(byte & flags, int16_t functionNumber) {
 }
 
 void DCC::setAccessory(int address, byte number, bool activate) {
+  #ifdef DIAG_IO
+  DIAG(F("DCC::setAccessory(%d,%d,%d)"), address, number, activate);
+  #endif
   // use masks to detect wrong values and do nothing
   if(address != (address & 511))
     return;
@@ -350,8 +357,9 @@ const ackOp FLASH WRITE_BYTE_PROG[] = {
       
 const ackOp FLASH VERIFY_BYTE_PROG[] = {
       BASELINE,
+      BIV,         // ackManagerByte initial value
       VB,WACK,     // validate byte 
-      ITCB,       // if ok callback value
+      ITCB,       // if ok callback value	
       STARTMERGE,    //clear bit and byte values ready for merge pass
       // each bit is validated against 0 and the result inverted in MERGE
       // this is because there tend to be more zeros in cv values than ones.  
@@ -369,7 +377,7 @@ const ackOp FLASH VERIFY_BYTE_PROG[] = {
       V0, WACK, MERGE,
       V0, WACK, MERGE,
       V0, WACK, MERGE,
-      VB, WACK, ITCB,  // verify merged byte and return it if acked ok 
+      VB, WACK, ITCBV,  // verify merged byte and return it if acked ok - with retry report
       FAIL };
       
       
@@ -679,9 +687,15 @@ int DCC::nextLoco = 0;
 
 //ACK MANAGER
 ackOp  const *  DCC::ackManagerProg;
+ackOp  const *  DCC::ackManagerProgStart;
 byte   DCC::ackManagerByte;
+byte   DCC::ackManagerByteVerify;
 byte   DCC::ackManagerStash;
 int    DCC::ackManagerWord;
+byte   DCC::ackManagerRetry;
+byte   DCC::ackRetry = 2;
+int16_t  DCC::ackRetrySum;
+int16_t  DCC::ackRetryPSum;
 int    DCC::ackManagerCv;
 byte   DCC::ackManagerBitNum;
 bool   DCC::ackReceived;
@@ -714,7 +728,10 @@ void  DCC::ackManagerSetup(int cv, byte byteValueOrBitnum, ackOp const program[]
 
   ackManagerCv = cv;
   ackManagerProg = program;
+  ackManagerProgStart = program;
+  ackManagerRetry = ackRetry;
   ackManagerByte = byteValueOrBitnum;
+  ackManagerByteVerify = byteValueOrBitnum;
   ackManagerBitNum=byteValueOrBitnum;
   ackManagerCallback = callback;
 }
@@ -740,6 +757,7 @@ void DCC::ackManagerLoop() {
     // (typically waiting for a reset counter or ACK waiting, or when all finished.)
     switch (opcode) {
       case BASELINE:
+          if (DCCWaveform::progTrack.getPowerMode()==POWERMODE::OVERLOAD) return;
       	  if (checkResets(DCCWaveform::progTrack.autoPowerOff || ackManagerRejoin  ? 20 : 3)) return;
           DCCWaveform::progTrack.setAckBaseline();
           callbackState=READY;
@@ -813,7 +831,18 @@ void DCC::ackManagerLoop() {
             return;
           }
         break;
-
+		    
+      case ITCBV:   // If True callback(byte) - Verify
+          if (ackReceived) {
+            if (ackManagerByte == ackManagerByteVerify) {
+               ackRetrySum ++;
+               LCD(1, F("v %d %d Sum=%d"), ackManagerCv, ackManagerByte, ackRetrySum);
+            }
+            callback(ackManagerByte);
+            return;
+          }
+        break;
+		    
       case ITCB7:   // If True callback(byte & 0x7F)
           if (ackReceived) {
             callback(ackManagerByte & 0x7F);
@@ -831,7 +860,11 @@ void DCC::ackManagerLoop() {
       case FAIL:  // callback(-1)
            callback(-1);
            return;
-           
+
+      case BIV:     // ackManagerByte initial value
+           ackManagerByte = ackManagerByteVerify;
+           break;
+
       case STARTMERGE:
            ackManagerBitNum=7;
            ackManagerByte=0;     
@@ -897,6 +930,15 @@ void DCC::ackManagerLoop() {
 }
 
 void DCC::callback(int value) {
+    // check for automatic retry
+    if (value == -1 && ackManagerRetry > 0) {
+      ackRetrySum ++;
+      LCD(0, F("Retry %d %d Sum=%d"), ackManagerCv, ackManagerRetry, ackRetrySum);
+      ackManagerRetry --;
+      ackManagerProg = ackManagerProgStart;
+      return;
+    }
+
     static unsigned long callbackStart;
     // We are about to leave programming mode
     // Rule 1: If we have written to a decoder we must maintain power for 100mS

DCC.h

@@ -38,9 +38,11 @@ enum ackOp : byte
   ITC1,             // If True Callback(1)  (if prevous WACK got an ACK)
   ITC0,             // If True callback(0);
   ITCB,             // If True callback(byte)
+  ITCBV,            // If True callback(byte) - end of Verify Byte
   ITCB7,            // If True callback(byte &0x7F)
   NAKFAIL,          // if false callback(-1)
   FAIL,             // callback(-1)
+  BIV,              // Set ackManagerByte to initial value for Verify retry
   STARTMERGE,       // Clear bit and byte settings ready for merge pass
   MERGE,            // Merge previous wack response with byte value and decrement bit number (use for readimng CV bytes)
   SETBIT,           // sets bit number to next prog byte
@@ -64,8 +66,10 @@ enum   CALLBACK_STATE : byte {
 
 // Allocations with memory implications..!
 // Base system takes approx 900 bytes + 8 per loco. Turnouts, Sensors etc are dynamically created
-#ifdef ARDUINO_AVR_UNO
+#if defined(ARDUINO_AVR_UNO)
 const byte MAX_LOCOS = 20;
+#elif defined(ARDUINO_AVR_NANO)
+const byte MAX_LOCOS = 30;
 #else
 const byte MAX_LOCOS = 50;
 #endif
@@ -113,6 +117,12 @@ public:
   static inline void setGlobalSpeedsteps(byte s) {
     globalSpeedsteps = s;
   };
+  static inline int16_t setAckRetry(byte retry) {
+    ackRetry = retry;
+    ackRetryPSum = ackRetrySum;
+    ackRetrySum = 0;  // reset running total
+    return ackRetryPSum;
+  };
 
 private:
   struct LOCO
@@ -141,9 +151,15 @@ private:
 
   // ACK MANAGER
   static ackOp const *ackManagerProg;
+  static ackOp const *ackManagerProgStart;
   static byte ackManagerByte;
+  static byte ackManagerByteVerify;
   static byte ackManagerBitNum;
   static int ackManagerCv;
+  static byte ackManagerRetry;
+  static byte ackRetry;
+  static int16_t ackRetrySum;
+  static int16_t ackRetryPSum;
   static int ackManagerWord;
   static byte ackManagerStash;
   static bool ackReceived;

DCCEX.h

@@ -37,10 +37,11 @@
 #include "LCD_Implementation.h"
 #include "LCN.h"
 #include "freeMemory.h"
+#include "IODevice.h"
+#include "Turnouts.h"
+#include "Sensors.h"
+#include "Outputs.h"
+#include "RMFT.h"
 
-#if __has_include ( "myAutomation.h")
-  #include "RMFT.h"
-  #define RMFT_ACTIVE
-#endif
     
 #endif

DCCEXParser.cpp

@@ -27,11 +27,22 @@
 #include "freeMemory.h"
 #include "GITHUB_SHA.h"
 #include "version.h"
+#include "defines.h"
 
 #include "EEStore.h"
 #include "DIAG.h"
 #include <avr/wdt.h>
 
+////////////////////////////////////////////////////////////////////////////////
+//
+// Figure out if we have enough memory for advanced features
+//
+#if defined(ARDUINO_AVR_UNO) || defined(ARDUINO_AVR_NANO)
+// nope
+#else
+#define HAS_ENOUGH_MEMORY
+#endif
+
 // These keywords are used in the <1> command. The number is what you get if you use the keyword as a parameter.
 // To discover new keyword numbers , use the <$ YOURKEYWORD> command
 const int16_t HASH_KEYWORD_PROG = -29718;
@@ -40,8 +51,6 @@ const int16_t HASH_KEYWORD_JOIN = -30750;
 const int16_t HASH_KEYWORD_CABS = -11981;
 const int16_t HASH_KEYWORD_RAM = 25982;
 const int16_t HASH_KEYWORD_CMD = 9962;
-const int16_t HASH_KEYWORD_WIT = 31594;
-const int16_t HASH_KEYWORD_WIFI = -5583;
 const int16_t HASH_KEYWORD_ACK = 3113;
 const int16_t HASH_KEYWORD_ON = 2657;
 const int16_t HASH_KEYWORD_DCC = 6436;
@@ -49,13 +58,26 @@ const int16_t HASH_KEYWORD_SLOW = -17209;
 const int16_t HASH_KEYWORD_PROGBOOST = -6353;
 const int16_t HASH_KEYWORD_EEPROM = -7168;
 const int16_t HASH_KEYWORD_LIMIT = 27413;
-const int16_t HASH_KEYWORD_ETHERNET = -30767;    
 const int16_t HASH_KEYWORD_MAX = 16244;
 const int16_t HASH_KEYWORD_MIN = 15978;
-const int16_t HASH_KEYWORD_LCN = 15137;   
 const int16_t HASH_KEYWORD_RESET = 26133;
+const int16_t HASH_KEYWORD_RETRY = 25704;
 const int16_t HASH_KEYWORD_SPEED28 = -17064;
 const int16_t HASH_KEYWORD_SPEED128 = 25816;
+const int16_t HASH_KEYWORD_SERVO=27709;
+const int16_t HASH_KEYWORD_VPIN=-415;
+const int16_t HASH_KEYWORD_C=67;
+const int16_t HASH_KEYWORD_T=84;
+const int16_t HASH_KEYWORD_LCN = 15137;
+const int16_t HASH_KEYWORD_HAL = 10853;
+const int16_t HASH_KEYWORD_SHOW = -21309;
+const int16_t HASH_KEYWORD_ANIN = -10424;
+const int16_t HASH_KEYWORD_ANOUT = -26399;
+#ifdef HAS_ENOUGH_MEMORY
+const int16_t HASH_KEYWORD_WIFI = -5583;
+const int16_t HASH_KEYWORD_ETHERNET = -30767;
+const int16_t HASH_KEYWORD_WIT = 31594;
+#endif
 
 int16_t DCCEXParser::stashP[MAX_COMMAND_PARAMS];
 bool DCCEXParser::stashBusy;
@@ -253,6 +275,7 @@ void DCCEXParser::parse(const FSH * cmd) {
 }
 
 // See documentation on DCC class for info on this section
+
 void DCCEXParser::parse(Print *stream, byte *com, RingStream * ringStream)
 {
     (void)EEPROM; // tell compiler not to warn this is unused
@@ -344,8 +367,12 @@ void DCCEXParser::parse(Print *stream, byte *com, RingStream * ringStream)
           || ((subaddress & 0x03) != subaddress)  // invalid subaddress (limit 2 bits ) 
           || ((p[activep]  & 0x01) != p[activep]) // invalid activate 0|1
           ) break; 
-            
+          // Honour the configuration option (config.h) which allows the <a> command to be reversed
+#ifdef DCC_ACCESSORY_RCN_213
+          DCC::setAccessory(address, subaddress,p[activep]==0);
+#else
           DCC::setAccessory(address, subaddress,p[activep]==1);
+#endif
         }
         return;
      
@@ -451,6 +478,7 @@ void DCCEXParser::parse(Print *stream, byte *com, RingStream * ringStream)
 		if (mode == POWERMODE::OFF)
 		  DCC::setProgTrackBoost(false);  // Prog track boost mode will not outlive prog track off
                 StringFormatter::send(stream, F("<p%c>\n"), opcode);
+		        LCD(2, F("p%c"), opcode);
                 return;
             }
             switch (p[0])
@@ -458,6 +486,7 @@ void DCCEXParser::parse(Print *stream, byte *com, RingStream * ringStream)
             case HASH_KEYWORD_MAIN:
                 DCCWaveform::mainTrack.setPowerMode(mode);
                 StringFormatter::send(stream, F("<p%c MAIN>\n"), opcode);
+	            LCD(2, F("p%c MAIN"), opcode);
                 return;
 
             case HASH_KEYWORD_PROG:
@@ -465,6 +494,7 @@ void DCCEXParser::parse(Print *stream, byte *com, RingStream * ringStream)
 		if (mode == POWERMODE::OFF)
 		  DCC::setProgTrackBoost(false);  // Prog track boost mode will not outlive prog track off
                 StringFormatter::send(stream, F("<p%c PROG>\n"), opcode);
+		        LCD(2, F("p%c PROG"), opcode);
                 return;
             case HASH_KEYWORD_JOIN:
                 DCCWaveform::mainTrack.setPowerMode(mode);
@@ -473,9 +503,13 @@ void DCCEXParser::parse(Print *stream, byte *com, RingStream * ringStream)
                 {
                     DCC::setProgTrackSyncMain(true);
                     StringFormatter::send(stream, F("<p1 JOIN>\n"), opcode);
+		            LCD(2, F("p1 JOIN"));
                 }
                 else
+		        {
                     StringFormatter::send(stream, F("<p0>\n"));
+		            LCD(2, F("p0"));
+	    	    }
                 return;
             }
             break;
@@ -579,10 +613,8 @@ bool DCCEXParser::parseZ(Print *stream, int16_t params, int16_t p[])
         return true;
 
     case 3: // <Z ID PIN IFLAG>
-        if (p[0] < 0 ||
+        if (p[0] < 0 || p[2] < 0 || p[2] > 7 )
-	    p[1] > 255 || p[1] <= 1 || // Pins 0 and 1 are Serial to USB
+	        return false;
-	    p[2] <   0 || p[2] > 7 )
-	  return false;
         if (!Output::create(p[0], p[1], p[2], 1))
           return false;
         StringFormatter::send(stream, F("<O>\n"));
@@ -600,7 +632,7 @@ bool DCCEXParser::parseZ(Print *stream, int16_t params, int16_t p[])
         for (Output *tt = Output::firstOutput; tt != NULL; tt = tt->nextOutput)
         {
             gotone = true;
-            StringFormatter::send(stream, F("<Y %d %d %d %d>\n"), tt->data.id, tt->data.pin, tt->data.iFlag, tt->data.oStatus);
+            StringFormatter::send(stream, F("<Y %d %d %d %d>\n"), tt->data.id, tt->data.pin, tt->data.flags, tt->data.active);
         }
         return gotone;
     }
@@ -659,11 +691,10 @@ bool DCCEXParser::parseT(Print *stream, int16_t params, int16_t p[])
     case 0: // <T>  list turnout definitions
     {
         bool gotOne = false;
-        for (Turnout *tt = Turnout::firstTurnout; tt != NULL; tt = tt->nextTurnout)
+        for (Turnout *tt = Turnout::first(); tt != NULL; tt = tt->next())
         {
             gotOne = true;
-            StringFormatter::send(stream, F("<H %d %d %d %d>\n"), tt->data.id, tt->data.address, 
+            tt->print(stream);
-                tt->data.subAddress, (tt->data.tStatus & STATUS_ACTIVE)!=0);
         }
         return gotOne; // will <X> if none found
     }
@@ -674,24 +705,62 @@ bool DCCEXParser::parseT(Print *stream, int16_t params, int16_t p[])
         StringFormatter::send(stream, F("<O>\n"));
         return true;
 
-    case 2: // <T id 0|1>  activate turnout
+    case 2: // <T id 0|1|T|C> 
-    {
+        {
-        Turnout *tt = Turnout::get(p[0]);
+          bool state = false;
-        if (!tt)
+          switch (p[1]) {
-            return false;
+            // Turnout messages use 1=throw, 0=close.
-        tt->activate(p[1]);
+            case 0:
-        StringFormatter::send(stream, F("<H %d %d>\n"), tt->data.id, (tt->data.tStatus & STATUS_ACTIVE)!=0);
+            case HASH_KEYWORD_C:
-    }
+              state = true;
-        return true;
+              break;
+            case 1:
+            case HASH_KEYWORD_T:
+              state= false;
+              break;
+            default:
+              return false;  // Invalid parameter
+          }
+          if (!Turnout::setClosed(p[0], state)) return false;
 
-    case 3: // <T id addr subaddr>  define turnout
+          // Send acknowledgement to caller if the command was not received over Serial
-        if (!Turnout::create(p[0], p[1], p[2]))
+          // (acknowledgement messages on Serial are sent by the Turnout class).
-            return false;
+          if (stream != &Serial) Turnout::printState(p[0], stream);
-        StringFormatter::send(stream, F("<O>\n"));
+          return true;
-        return true;
+        }
 
-    default:
+    default: // Anything else is some kind of turnout create function.
-        return false; // will <x>
+      if (params == 6 && p[1] == HASH_KEYWORD_SERVO) { // <T id SERVO n n n n>
+        if (!ServoTurnout::create(p[0], (VPIN)p[2], (uint16_t)p[3], (uint16_t)p[4], (uint8_t)p[5]))
+          return false;
+      } else 
+      if (params == 3 && p[1] == HASH_KEYWORD_VPIN) { // <T id VPIN n>
+        if (!VpinTurnout::create(p[0], p[2])) return false;
+      } else 
+      if (params >= 3 && p[1] == HASH_KEYWORD_DCC) {
+        // <T id DCC addr subadd>   0<=addr<=511, 0<=subadd<=3 (like <a> command).<T>
+        if (params==4 && p[2]>=0 && p[2]<512 && p[3]>=0 && p[3]<4) { // <T id DCC n m>
+          if (!DCCTurnout::create(p[0], p[2], p[3])) return false;
+        } else if (params==3 && p[2]>0 && p[2]<=512*4) { // <T id DCC nn>, 1<=nn<=2048
+          // Linearaddress 1 maps onto decoder address 1/0 (not 0/0!).
+          if (!DCCTurnout::create(p[0], (p[2]-1)/4+1, (p[2]-1)%4)) return false;
+        } else
+          return false;
+      } else 
+      if (params==3) { // legacy <T id addr subadd> for DCC accessory
+        if (p[1]>=0 && p[1]<512 && p[2]>=0 && p[2]<4) {
+          if (!DCCTurnout::create(p[0], p[1], p[2])) return false;
+        } else
+          return false;
+      } 
+      else 
+      if (params==4) { // legacy <T id n n n> for Servo
+        if (!ServoTurnout::create(p[0], (VPIN)p[1], (uint16_t)p[2], (uint16_t)p[3], 1)) return false;
+      } else
+        return false;
+
+      StringFormatter::send(stream, F("<O>\n"));
+      return true;
     }
 }
 
@@ -713,13 +782,13 @@ bool DCCEXParser::parseS(Print *stream, int16_t params, int16_t p[])
         return true;
 
     case 0: // <S> list sensor definitions
-	if (Sensor::firstSensor == NULL)
+      if (Sensor::firstSensor == NULL)
-	    return false;
+        return false;
-        for (Sensor *tt = Sensor::firstSensor; tt != NULL; tt = tt->nextSensor)
+      for (Sensor *tt = Sensor::firstSensor; tt != NULL; tt = tt->nextSensor)
-        {
+      {
-            StringFormatter::send(stream, F("<Q %d %d %d>\n"), tt->data.snum, tt->data.pin, tt->data.pullUp);
+          StringFormatter::send(stream, F("<Q %d %d %d>\n"), tt->data.snum, tt->data.pin, tt->data.pullUp);
-        }
+      }
-        return true;
+      return true;
 
     default: // invalid number of arguments
         break;
@@ -742,17 +811,20 @@ bool DCCEXParser::parseD(Print *stream, int16_t params, int16_t p[])
         StringFormatter::send(stream, F("Free memory=%d\n"), minimumFreeMemory());
         break;
 
-    case HASH_KEYWORD_ACK: // <D ACK ON/OFF> <D ACK [LIMIT|MIN|MAX] Value>
+    case HASH_KEYWORD_ACK: // <D ACK ON/OFF> <D ACK [LIMIT|MIN|MAX|RETRY] Value>
 	if (params >= 3) {
 	    if (p[1] == HASH_KEYWORD_LIMIT) {
 	      DCCWaveform::progTrack.setAckLimit(p[2]);
-	      StringFormatter::send(stream, F("Ack limit=%dmA\n"), p[2]);
+	      LCD(1, F("Ack Limit=%dmA"), p[2]);  // <D ACK LIMIT 42>
 	    } else if (p[1] == HASH_KEYWORD_MIN) {
 	      DCCWaveform::progTrack.setMinAckPulseDuration(p[2]);
-	      StringFormatter::send(stream, F("Ack min=%dus\n"), p[2]);
+	      LCD(0, F("Ack Min=%dus"), p[2]);  //   <D ACK MIN 1500>
 	    } else if (p[1] == HASH_KEYWORD_MAX) {
 	      DCCWaveform::progTrack.setMaxAckPulseDuration(p[2]);
-	      StringFormatter::send(stream, F("Ack max=%dus\n"), p[2]);
+	      LCD(0, F("Ack Max=%dus"), p[2]);  //   <D ACK MAX 9000>
+	    } else if (p[1] == HASH_KEYWORD_RETRY) {
+	      if (p[2] >255) p[2]=3;
+	      LCD(0, F("Ack Retry=%d Sum=%d"), p[2], DCC::setAckRetry(p[2]));  //   <D ACK RETRY 2>
 	    }
 	} else {
 	  StringFormatter::send(stream, F("Ack diag %S\n"), onOff ? F("on") : F("off"));
@@ -764,21 +836,23 @@ bool DCCEXParser::parseD(Print *stream, int16_t params, int16_t p[])
         Diag::CMD = onOff;
         return true;
 
+#ifdef HAS_ENOUGH_MEMORY
     case HASH_KEYWORD_WIFI: // <D WIFI ON/OFF>
         Diag::WIFI = onOff;
         return true;
 
-   case HASH_KEYWORD_ETHERNET: // <D ETHERNET ON/OFF>
+    case HASH_KEYWORD_ETHERNET: // <D ETHERNET ON/OFF>
         Diag::ETHERNET = onOff;
         return true;
 
     case HASH_KEYWORD_WIT: // <D WIT ON/OFF>
         Diag::WITHROTTLE = onOff;
         return true;
-  
+
     case HASH_KEYWORD_LCN: // <D LCN ON/OFF>
         Diag::LCN = onOff;
         return true;
+#endif
 
     case HASH_KEYWORD_PROGBOOST:
         DCC::setProgTrackBoost(true);
@@ -806,6 +880,22 @@ bool DCCEXParser::parseD(Print *stream, int16_t params, int16_t p[])
 	StringFormatter::send(stream, F("128 Speedsteps"));
         return true;
 
+    case HASH_KEYWORD_SERVO:  // <D SERVO vpin position [profile]>
+    case HASH_KEYWORD_ANOUT:  // <D ANOUT vpin position [profile]>
+        IODevice::writeAnalogue(p[1], p[2], params>3 ? p[3] : 0);
+        break;
+
+    case HASH_KEYWORD_ANIN:   // <D ANIN vpin>  Display analogue input value
+        DIAG(F("VPIN=%d value=%d"), p[1], IODevice::readAnalogue(p[1]));
+        break;
+
+#if !defined(IO_MINIMAL_HAL)
+    case HASH_KEYWORD_HAL: 
+        if (p[1] == HASH_KEYWORD_SHOW) 
+          IODevice::DumpAll();
+        break;
+#endif
+
     default: // invalid/unknown
         break;
     }

DCCWaveform.cpp

@@ -17,7 +17,7 @@
  *  You should have received a copy of the GNU General Public License
  *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
  */
- #pragma GCC optimize ("-O3")
+
 #include <Arduino.h>
 
 #include "DCCWaveform.h"
@@ -46,10 +46,8 @@ void DCCWaveform::begin(MotorDriver * mainDriver, MotorDriver * progDriver) {
 				 && (mainDriver->getFaultPin() != UNUSED_PIN));
   // Only use PWM if both pins are PWM capable. Otherwise JOIN does not work
   MotorDriver::usePWM= mainDriver->isPWMCapable() && progDriver->isPWMCapable();
-  if (MotorDriver::usePWM)
+  DIAG(F("Signal pin config: %S accuracy waveform"),
-    DIAG(F("Signal pin config: high accuracy waveform"));
+	 MotorDriver::usePWM ? F("high") : F("normal") );
-  else
-    DIAG(F("Signal pin config: normal accuracy waveform"));
   DCCTimer::begin(DCCWaveform::interruptHandler);     
 }
 
@@ -58,6 +56,8 @@ void DCCWaveform::loop(bool ackManagerActive) {
   progTrack.checkPowerOverload(ackManagerActive);
 }
 
+#pragma GCC push_options
+#pragma GCC optimize ("-O3")
 void DCCWaveform::interruptHandler() {
   // call the timer edge sensitive actions for progtrack and maintrack
   // member functions would be cleaner but have more overhead
@@ -79,7 +79,7 @@ void DCCWaveform::interruptHandler() {
   else if (progTrack.ackPending) progTrack.checkAck();
 
 }
-
+#pragma GCC push_options
 
 // An instance of this class handles the DCC transmissions for one track. (main or prog)
 // Interrupts are marshalled via the statics.
@@ -114,6 +114,7 @@ void DCCWaveform::setPowerMode(POWERMODE mode) {
   powerMode = mode;
   bool ison = (mode == POWERMODE::ON);
   motorDriver->setPower( ison);
+  sentResetsSincePacket=0; 
 }
 
 
@@ -124,6 +125,8 @@ void DCCWaveform::checkPowerOverload(bool ackManagerActive) {
   if (!isMainTrack && !ackManagerActive && !progTrackSyncMain && !progTrackBoosted)
     tripValue=progTripValue;
   
+  // Trackname for diag messages later
+  const FSH*trackname = isMainTrack ? F("MAIN") : F("PROG");
   switch (powerMode) {
     case POWERMODE::OFF:
       sampleDelay = POWER_SAMPLE_OFF_WAIT;
@@ -141,9 +144,9 @@ void DCCWaveform::checkPowerOverload(bool ackManagerActive) {
 	      }
 	      // Write this after the fact as we want to turn on as fast as possible
 	      // because we don't know which output actually triggered the fault pin
-	      DIAG(F("*** COMMON FAULT PIN ACTIVE - TOGGLED POWER on %S ***"), isMainTrack ? F("MAIN") : F("PROG"));
+	      DIAG(F("COMMON FAULT PIN ACTIVE - TOGGLED POWER on %S"), trackname);
 	  } else {
-	      DIAG(F("*** %S FAULT PIN ACTIVE - OVERLOAD ***"), isMainTrack ? F("MAIN") : F("PROG"));
+	    DIAG(F("%S FAULT PIN ACTIVE - OVERLOAD"), trackname);
 	      if (lastCurrent < tripValue) {
 		  lastCurrent = tripValue; // exaggerate
 	      }
@@ -161,7 +164,7 @@ void DCCWaveform::checkPowerOverload(bool ackManagerActive) {
         unsigned int maxmA=motorDriver->raw2mA(tripValue);
 	power_good_counter=0;
         sampleDelay = power_sample_overload_wait;
-        DIAG(F("*** %S TRACK POWER OVERLOAD current=%d max=%d  offtime=%d ***"), isMainTrack ? F("MAIN") : F("PROG"), mA, maxmA, sampleDelay);
+        DIAG(F("%S TRACK POWER OVERLOAD current=%d max=%d offtime=%d"), trackname, mA, maxmA, sampleDelay);
 	if (power_sample_overload_wait >= 10000)
 	    power_sample_overload_wait = 10000;
 	else
@@ -173,7 +176,7 @@ void DCCWaveform::checkPowerOverload(bool ackManagerActive) {
       setPowerMode(POWERMODE::ON);
       sampleDelay = POWER_SAMPLE_ON_WAIT;
       // Debug code....
-      DIAG(F("*** %S TRACK POWER RESET delay=%d ***"), isMainTrack ? F("MAIN") : F("PROG"), sampleDelay);
+      DIAG(F("%S TRACK POWER RESET delay=%d"), trackname, sampleDelay);
       break;
     default:
       sampleDelay = 999; // cant get here..meaningless statement to avoid compiler warning.
@@ -197,6 +200,8 @@ const bool DCCWaveform::signalTransform[]={
    /* WAVE_LOW_0   -> */ LOW,
    /* WAVE_PENDING (should not happen) -> */ LOW};
         
+#pragma GCC push_options
+#pragma GCC optimize ("-O3")
 void DCCWaveform::interrupt2() {
   // calculate the next bit to be sent:
   // set state WAVE_MID_1  for a 1=bit
@@ -252,7 +257,7 @@ void DCCWaveform::interrupt2() {
     }
   }  
 }
-
+#pragma GCC pop_options
 
 
 // Wait until there is no packet pending, then make this pending
@@ -306,6 +311,8 @@ byte DCCWaveform::getAck() {
       return(0);  // pending set off but not detected means no ACK.   
 }
 
+#pragma GCC push_options
+#pragma GCC optimize ("-O3")
 void DCCWaveform::checkAck() {
     // This function operates in interrupt() time so must be fast and can't DIAG 
     if (sentResetsSincePacket > 6) {  //ACK timeout
@@ -355,3 +362,4 @@ void DCCWaveform::checkAck() {
     }      
     ackPulseStart=0;  // We have detected a too-short or too-long pulse so ignore and wait for next leading edge 
 }
+#pragma GCC pop_options

EEStore.cpp

@@ -19,88 +19,87 @@
  *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
  */
 #include "EEStore.h"
-#include "Turnouts.h"
+
-#include "Sensors.h"
-#include "Outputs.h"
 #include "DIAG.h"
+#include "Outputs.h"
+#include "Sensors.h"
+#include "Turnouts.h"
 
 #if defined(ARDUINO_ARCH_SAMD)
 ExternalEEPROM EEPROM;
 #endif
 
-void EEStore::init(){
+void EEStore::init() {
 #if defined(ARDUINO_ARCH_SAMD)
-    EEPROM.begin(0x50);     // Address for Microchip 24-series EEPROM with all three A pins grounded (0b1010000 = 0x50)
+  EEPROM.begin(0x50);  // Address for Microchip 24-series EEPROM with all three
+                       // A pins grounded (0b1010000 = 0x50)
 #endif
 
-    eeStore=(EEStore *)calloc(1,sizeof(EEStore));
+  eeStore = (EEStore *)calloc(1, sizeof(EEStore));
-    
-    EEPROM.get(0,eeStore->data);                                       // get eeStore data
 
-    if(strncmp(eeStore->data.id,EESTORE_ID,sizeof(EESTORE_ID))!=0){    // check to see that eeStore contains valid DCC++ ID
+  EEPROM.get(0, eeStore->data);  // get eeStore data
-        sprintf(eeStore->data.id,EESTORE_ID);                           // if not, create blank eeStore structure (no turnouts, no sensors) and save it back to EEPROM
-        eeStore->data.nTurnouts=0;
-        eeStore->data.nSensors=0;
-        eeStore->data.nOutputs=0;
-        EEPROM.put(0,eeStore->data);
-    }
 
-    reset();            // set memory pointer to first free EEPROM space
+  // check to see that eeStore contains valid DCC++ ID
-    Turnout::load();    // load turnout definitions
+  if (strncmp(eeStore->data.id, EESTORE_ID, sizeof(EESTORE_ID)) != 0) {  
-    Sensor::load();     // load sensor definitions
+    // if not, create blank eeStore structure (no
-    Output::load();     // load output definitions
+    // turnouts, no sensors) and save it back to EEPROM  
+    strncpy(eeStore->data.id, EESTORE_ID, sizeof(EESTORE_ID));  
+    eeStore->data.nTurnouts = 0;
+    eeStore->data.nSensors = 0;
+    eeStore->data.nOutputs = 0;
+    EEPROM.put(0, eeStore->data);
+  }
 
+  reset();          // set memory pointer to first free EEPROM space
+  Turnout::load();  // load turnout definitions
+  Sensor::load();   // load sensor definitions
+  Output::load();   // load output definitions
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
-void EEStore::clear(){
+void EEStore::clear() {
-
+  sprintf(eeStore->data.id,
-    sprintf(eeStore->data.id,EESTORE_ID);                           // create blank eeStore structure (no turnouts, no sensors) and save it back to EEPROM
+          EESTORE_ID);  // create blank eeStore structure (no turnouts, no
-    eeStore->data.nTurnouts=0;
+                        // sensors) and save it back to EEPROM
-    eeStore->data.nSensors=0;
+  eeStore->data.nTurnouts = 0;
-    eeStore->data.nOutputs=0;
+  eeStore->data.nSensors = 0;
-    EEPROM.put(0,eeStore->data);
+  eeStore->data.nOutputs = 0;
-
+  EEPROM.put(0, eeStore->data);
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
-void EEStore::store(){
+void EEStore::store() {
-    reset();
+  reset();
-    Turnout::store();
+  Turnout::store();
-    Sensor::store();
+  Sensor::store();
-    Output::store();
+  Output::store();
-    EEPROM.put(0,eeStore->data);
+  EEPROM.put(0, eeStore->data);
+  DIAG(F("EEPROM used: %d/%d bytes"), EEStore::pointer(), EEPROM.length());
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
-void EEStore::advance(int n){
+void EEStore::advance(int n) { eeAddress += n; }
-    eeAddress+=n;
-}
 
 ///////////////////////////////////////////////////////////////////////////////
 
-void EEStore::reset(){
+void EEStore::reset() { eeAddress = sizeof(EEStore); }
-    eeAddress=sizeof(EEStore);
-}
 ///////////////////////////////////////////////////////////////////////////////
 
-int EEStore::pointer(){
+int EEStore::pointer() { return (eeAddress); }
-    return(eeAddress);
-}
 ///////////////////////////////////////////////////////////////////////////////
 
 void EEStore::dump(int num) {
-    byte b;
+  byte b;
-    DIAG(F("Addr  0x  char"));
+  DIAG(F("Addr  0x  char"));
-    for (int n=0 ; n<num; n++) {
+  for (int n = 0; n < num; n++) {
-	EEPROM.get(n, b);
+    EEPROM.get(n, b);
-	DIAG(F("%d     %x    %c"),n,b,isprint(b) ? b : ' ');
+    DIAG(F("%d     %x    %c"), n, b, isprint(b) ? b : ' ');
-    }
+  }
 }
 ///////////////////////////////////////////////////////////////////////////////
 
-EEStore *EEStore::eeStore=NULL;
+EEStore *EEStore::eeStore = NULL;
-int EEStore::eeAddress=0;
+int EEStore::eeAddress = 0;

EEStore.h

@@ -29,7 +29,7 @@ extern ExternalEEPROM EEPROM;
 #include <EEPROM.h>
 #endif
 
-#define EESTORE_ID "DCC++"
+#define EESTORE_ID "DCC++1"
 
 struct EEStoreData{
   char id[sizeof(EESTORE_ID)];

EthernetInterface.cpp

@@ -17,12 +17,6 @@
  *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
  * 
  */
-#if __has_include ( "config.h")
-  #include "config.h"
-#else
-  #warning config.h not found. Using defaults from config.example.h 
-  #include "config.example.h"
-#endif
 #include "defines.h" 
 #if ETHERNET_ON == true
 #include "EthernetInterface.h"

EthernetInterface.h

@@ -22,12 +22,8 @@
 
 #ifndef EthernetInterface_h
 #define EthernetInterface_h
-#if __has_include ( "config.h")
+
-  #include "config.h"
+#include "defines.h")
-#else
-  #warning config.h not found. Using defaults from config.example.h 
-  #include "config.example.h"
-#endif
 #include "DCCEXParser.h"
 #include <Arduino.h>
 #include <avr/pgmspace.h>

I2CManager.cpp

@@ -18,14 +18,40 @@
  */
 
 #include <stdarg.h>
-#include <Wire.h>
 #include "I2CManager.h"
+#include "DIAG.h"
 
-// If not already initialised, initialise I2C (wire).
+// Include target-specific portions of I2CManager class
+#if defined(I2C_USE_WIRE) 
+#include "I2CManager_Wire.h"
+#elif defined(ARDUINO_ARCH_AVR)
+#include "I2CManager_NonBlocking.h"
+#include "I2CManager_AVR.h"       // Uno/Nano/Mega2560
+#elif defined(ARDUINO_ARCH_MEGAAVR) 
+#include "I2CManager_NonBlocking.h"
+#include "I2CManager_Mega4809.h"  // NanoEvery/UnoWifi
+#else
+#define I2C_USE_WIRE
+#include "I2CManager_Wire.h"      // Other platforms
+#endif
+
+
+// If not already initialised, initialise I2C
 void I2CManagerClass::begin(void) {
+  //setTimeout(25000); // 25 millisecond timeout
   if (!_beginCompleted) {
-    Wire.begin();
     _beginCompleted = true;
+    _initialise();
+
+    // Probe and list devices.
+    bool found = false;
+    for (byte addr=1; addr<127; addr++) {
+      if (exists(addr)) {
+        found = true; 
+        DIAG(F("I2C Device found at x%x"), addr);
+      }
+    }
+    if (!found) DIAG(F("No I2C Devices found"));
   }
 }
 
@@ -34,8 +60,8 @@ void I2CManagerClass::begin(void) {
 void I2CManagerClass::setClock(uint32_t speed) {
   if (speed < _clockSpeed && !_clockSpeedFixed) {
     _clockSpeed = speed;
-    Wire.setClock(_clockSpeed);
   }
+  _setClock(_clockSpeed);
 }
 
 // Force clock speed to that specified.  It can then only 
@@ -44,39 +70,21 @@ void I2CManagerClass::forceClock(uint32_t speed) {
   if (!_clockSpeedFixed) {
     _clockSpeed = speed;
     _clockSpeedFixed = true;
-    Wire.setClock(_clockSpeed);
+    _setClock(_clockSpeed);
   }
 }
 
-// Check if specified I2C address is responding.
+// Check if specified I2C address is responding (blocking operation)
-// Returns 0 if OK, or error code.
+// Returns I2C_STATUS_OK (0) if OK, or error code.
 uint8_t I2CManagerClass::checkAddress(uint8_t address) {
-  begin();
+  return write(address, NULL, 0);
-  Wire.beginTransmission(address);
-  return Wire.endTransmission();
 }
 
-bool I2CManagerClass::exists(uint8_t address) {
-  return checkAddress(address)==0;
-}
 
-// Write a complete transmission to I2C using a supplied buffer of data
+/***************************************************************************
-uint8_t I2CManagerClass::write(uint8_t address, const uint8_t buffer[], uint8_t size) {
+ *  Write a transmission to I2C using a list of data (blocking operation)
-  Wire.beginTransmission(address);
+ ***************************************************************************/
-  Wire.write(buffer, size);
+uint8_t I2CManagerClass::write(uint8_t address, uint8_t nBytes, ...) {
-  return Wire.endTransmission();
-}
-
-// Write a complete transmission to I2C using a supplied buffer of data in Flash
-uint8_t I2CManagerClass::write_P(uint8_t address, const uint8_t buffer[], uint8_t size) {
-  uint8_t ramBuffer[size];
-  memcpy_P(ramBuffer, buffer, size);
-  return write(address, ramBuffer, size);
-}
-  
-
-// Write a complete transmission to I2C using a list of data 
-uint8_t I2CManagerClass::write(uint8_t address, int nBytes, ...) {
   uint8_t buffer[nBytes];
   va_list args;
   va_start(args, nBytes);
@@ -86,30 +94,38 @@ uint8_t I2CManagerClass::write(uint8_t address, int nBytes, ...) {
   return write(address, buffer, nBytes);
 }
 
-// Write a command and read response, returns number of bytes received.
+/***************************************************************************
-//  Different modules use different ways of accessing registers: 
+ *  Initiate a write to an I2C device (blocking operation)
-//    PCF8574 I/O expander justs needs the address (no data);
+ ***************************************************************************/
-//    PCA9685 needs a two byte command to select the register(s) to be read;
+uint8_t I2CManagerClass::write(uint8_t i2cAddress, const uint8_t writeBuffer[], uint8_t writeLen) {
-//    MCP23016 needs a one-byte command to select the register.
+  I2CRB req;
-// Some devices use 8-bit registers exclusively and some have 16-bit registers.
+  uint8_t status = write(i2cAddress, writeBuffer, writeLen, &req);
-// Therefore the following function is general purpose, to apply to any
+  return finishRB(&req, status);
-// type of I2C device.
-//
-uint8_t I2CManagerClass::read(uint8_t address, uint8_t readBuffer[], uint8_t readSize,
-                              uint8_t writeBuffer[], uint8_t writeSize) {
-  if (writeSize > 0) {
-    Wire.beginTransmission(address);
-    Wire.write(writeBuffer, writeSize);
-    Wire.endTransmission(false); // Don't free bus yet
-  }
-  Wire.requestFrom(address, readSize);
-  uint8_t nBytes = 0;
-  while (Wire.available() && nBytes < readSize) 
-    readBuffer[nBytes++] = Wire.read();
-  return nBytes;
 }
 
-// Overload of read() to allow command to be specified as a series of bytes.
+/***************************************************************************
+ *  Initiate a write from PROGMEM (flash) to an I2C device (blocking operation)
+ ***************************************************************************/
+uint8_t I2CManagerClass::write_P(uint8_t i2cAddress, const uint8_t * data, uint8_t dataLen) {
+  I2CRB req;
+  uint8_t status = write_P(i2cAddress, data, dataLen, &req);
+  return finishRB(&req, status);
+}
+
+/***************************************************************************
+ *  Initiate a write (optional) followed by a read from the I2C device (blocking operation)
+ ***************************************************************************/
+uint8_t I2CManagerClass::read(uint8_t i2cAddress, uint8_t *readBuffer, uint8_t readLen, 
+    const uint8_t *writeBuffer, uint8_t writeLen)
+{
+  I2CRB req;
+  uint8_t status = read(i2cAddress, readBuffer, readLen, writeBuffer, writeLen, &req);
+  return finishRB(&req, status);
+}
+
+/***************************************************************************
+ *  Overload of read() to allow command to be specified as a series of bytes (blocking operation)
+ ***************************************************************************/
 uint8_t I2CManagerClass::read(uint8_t address, uint8_t readBuffer[], uint8_t readSize, 
                                   uint8_t writeSize, ...) {
   va_list args;
@@ -122,8 +138,104 @@ uint8_t I2CManagerClass::read(uint8_t address, uint8_t readBuffer[], uint8_t rea
   return read(address, readBuffer, readSize, writeBuffer, writeSize);
 }
 
-uint8_t I2CManagerClass::read(uint8_t address, uint8_t readBuffer[], uint8_t readSize) {
+/***************************************************************************
-  return read(address, readBuffer, readSize, NULL, 0);
+ * Finish off request block by posting status, etc. (blocking operation)
+ ***************************************************************************/
+uint8_t I2CManagerClass::finishRB(I2CRB *rb, uint8_t status) {
+  if ((status == I2C_STATUS_OK) && rb)
+    status = rb->wait();
+  return status;
+}
+
+/***************************************************************************
+ * Get a message corresponding to the error status
+ ***************************************************************************/
+const FSH *I2CManagerClass::getErrorMessage(uint8_t status) {
+  switch (status) {
+    case I2C_STATUS_OK: return F("OK");
+    case I2C_STATUS_TRUNCATED: return F("Transmission truncated");
+    case I2C_STATUS_NEGATIVE_ACKNOWLEDGE: return F("No response from device (address NAK)");
+    case I2C_STATUS_TRANSMIT_ERROR: return F("Transmit error (data NAK)");
+    case I2C_STATUS_OTHER_TWI_ERROR: return F("Other Wire/TWI error");
+    case I2C_STATUS_TIMEOUT: return F("Timeout");
+    case I2C_STATUS_ARBITRATION_LOST: return F("Arbitration lost");
+    case I2C_STATUS_BUS_ERROR: return F("I2C bus error");
+    case I2C_STATUS_UNEXPECTED_ERROR: return F("Unexpected error");
+    case I2C_STATUS_PENDING: return F("Request pending");
+    default: return F("Error code not recognised");
+  }
+}
+
+/***************************************************************************
+ *  Declare singleton class instance.
+ ***************************************************************************/
+I2CManagerClass I2CManager = I2CManagerClass();
+
+
+/////////////////////////////////////////////////////////////////////////////
+// Helper functions associated with I2C Request Block
+/////////////////////////////////////////////////////////////////////////////
+
+/***************************************************************************
+ *  Block waiting for request block to complete, and return completion status.
+ *  Since such a loop could potentially last for ever if the RB status doesn't
+ *  change, we set a high limit (1sec, 1000ms) on the wait time and, if it
+ *  hasn't changed by that time we assume it's not going to, and just return
+ *  a timeout status.  This means that CS will not lock up.
+ ***************************************************************************/
+uint8_t I2CRB::wait() {
+  unsigned long waitStart = millis();
+  do {
+    I2CManager.loop();
+    // Rather than looping indefinitely, let's set a very high timeout (1s).
+    if ((millis() - waitStart) > 1000UL) { 
+      DIAG(F("I2C TIMEOUT I2C:x%x I2CRB:x%x"), i2cAddress, this);
+      status = I2C_STATUS_TIMEOUT;
+      // Note that, although the timeout is posted, the request may yet complete.
+      // TODO: Ideally we would like to cancel the request.
+      return status;
+    }
+  } while (status==I2C_STATUS_PENDING);
+  return status;
+}
+
+/***************************************************************************
+ *  Check whether request is still in progress.
+ ***************************************************************************/
+bool I2CRB::isBusy() {
+  I2CManager.loop();
+  return (status==I2C_STATUS_PENDING);
+}
+
+/***************************************************************************
+ *  Helper functions to fill the I2CRequest structure with parameters.
+ ***************************************************************************/
+void I2CRB::setReadParams(uint8_t i2cAddress, uint8_t *readBuffer, uint8_t readLen) {
+  this->i2cAddress = i2cAddress;
+  this->writeLen = 0;
+  this->readBuffer = readBuffer;
+  this->readLen = readLen;
+  this->operation = OPERATION_READ;
+  this->status = I2C_STATUS_OK;
+}
+
+void I2CRB::setRequestParams(uint8_t i2cAddress, uint8_t *readBuffer, uint8_t readLen, 
+    const uint8_t *writeBuffer, uint8_t writeLen) {
+  this->i2cAddress = i2cAddress;
+  this->writeBuffer = writeBuffer;
+  this->writeLen = writeLen;
+  this->readBuffer = readBuffer;
+  this->readLen = readLen;
+  this->operation = OPERATION_REQUEST;
+  this->status = I2C_STATUS_OK;
+}
+
+void I2CRB::setWriteParams(uint8_t i2cAddress, const uint8_t *writeBuffer, uint8_t writeLen) {
+  this->i2cAddress = i2cAddress;
+  this->writeBuffer = writeBuffer;
+  this->writeLen = writeLen;
+  this->readLen = 0;
+  this->operation = OPERATION_SEND;
+  this->status = I2C_STATUS_OK;
 }
 
-I2CManagerClass I2CManager = I2CManagerClass();

I2CManager.h

@@ -17,13 +17,16 @@
  *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-#ifndef I2CManager_h
+#ifndef I2CMANAGER_H
-#define I2CManager_h
+#define I2CMANAGER_H
 
+#include <inttypes.h>
 #include "FSH.h"
 
 /* 
- * Helper class to manage access to the I2C 'Wire' subsystem.
+ * Manager for I2C communications.  For portability, it allows use 
+ * of the Wire class, but also has a native implementation for AVR
+ * which supports non-blocking queued I/O requests.
  * 
  * Helps to avoid calling Wire.begin() multiple times (which is not)
  * entirely benign as it reinitialises).
@@ -33,13 +36,152 @@
  * 
  * Thirdly, it provides a convenient way to check whether there is a 
  * device on a particular I2C address.
+ * 
+ * Non-blocking requests are issued by creating an I2C Request Block
+ * (I2CRB) which is then added to the I2C manager's queue.  The 
+ * application refers to this block to check for completion of the
+ * operation, and for reading completion status.
+ * 
+ * Examples:
+ *  I2CRB rb;
+ *  uint8_t status = I2CManager.write(address, buffer, sizeof(buffer), &rb);
+ *  ...
+ *  if (!rb.isBusy()) {
+ *    status = rb.status;
+ *    // Repeat write
+ *    I2CManager.queueRequest(&rb);
+ *    ...
+ *    status = rb.wait(); // Wait for completion and read status
+ *  }
+ *  ...
+ *  I2CRB rb2;
+ *  outbuffer[0] = 12;  // Register number in I2C device to be read
+ *  rb2.setRequestParams(address, inBuffer, 1, outBuffer, 1);
+ *  status = I2CManager.queueRequest(&rb2);
+ *  if (status == I2C_STATUS_OK) { 
+ *    status = rb2.wait();
+ *    if (status == I2C_STATUS_OK) {
+ *      registerValue = inBuffer[0];
+ *    }
+ *  }
+ *  ...
+ *  
+ * Synchronous (blocking) calls are also possible, e.g. 
+ *  status = I2CManager.write(address, buffer, sizeof(buffer));
+ * 
+ * When using non-blocking requests, neither the I2CRB nor the input or output
+ * buffers should be modified until the I2CRB is complete (not busy).
+ * 
+ * Timeout monitoring is possible, but requires that the following call is made
+ * reasonably frequently in the program's loop() function:
+ *  I2CManager.loop();
+ * 
  */
 
-class I2CManagerClass {
+/* 
+ * Future enhancement possibility:
+ *
+ *  I2C Multiplexer (e.g. TCA9547, TCA9548)
+ * 
+ *  A multiplexer offers a way of extending the address range of I2C devices.  For example, GPIO extenders use address range 0x20-0x27
+ *  to are limited to 8 on a bus.  By adding a multiplexer, the limit becomes 8 for each of the multiplexer's 8 sub-buses, i.e. 64.
+ *  And a single I2C bus can have up to 8 multiplexers, giving up to 64 sub-buses and, in theory, up to 512 I/O extenders; that's 
+ *  as many as 8192 input/output pins!
+ *  Secondly, the capacitance of the bus is an electrical limiting factor of the length of the bus, speed and number of devices.
+ *  The multiplexer isolates each sub-bus from the others, and so reduces the capacitance of the bus.  For example, with one 
+ *  multiplexer and 64 GPIO extenders, only 9 devices are connected to the bus at any time (multiplexer plus 8 extenders). 
+ *  Thirdly, the multiplexer offers the ability to use mixed-speed devices more effectively, by allowing high-speed devices to be
+ *  put on a different bus to low-speed devices, enabling the software to switch the I2C speed on-the-fly between I2C transactions.
+ * 
+ *  Changes required:  Increase the size of the I2CAddress field in the IODevice class from uint8_t to uint16_t.
+ *  The most significant byte would contain a '1' bit flag, the multiplexer number (0-7) and bus number (0-7).  Then, when performing
+ *  an I2C operation, the I2CManager would check this byte and, if zero, do what it currently does.  If the byte is non-zero, then
+ *  that means the device is connected via a multiplexer so the I2C transaction should be preceded by a select command issued to the
+ *  relevant multiplexer.
+ * 
+ *  Non-interrupting I2C:
+ * 
+ *  I2C may be operated without interrupts (undefine I2C_USE_INTERRUPTS).  Instead, the I2C state
+ *  machine handler, currently invoked from the interrupt service routine, is invoked from the loop() function.
+ *  The speed at which I2C operations can be performed then becomes highly dependent on the frequency that 
+ *  the loop() function is called, and may be adequate under some circumstances.  
+ *  The advantage of NOT using interrupts is that the impact of I2C upon the DCC waveform (when accurate timing mode isn't in use)
+ *  becomes almost zero.
+ *  This mechanism is under evaluation and should not be relied upon as yet.
+ * 
+ */
 
+//#define I2C_USE_WIRE
+#ifndef I2C_NO_INTERRUPTS
+#define I2C_USE_INTERRUPTS
+#endif
+
+// Status codes for I2CRB structures.
+enum : uint8_t {
+  // Codes used by Wire and by native drivers
+  I2C_STATUS_OK=0,
+  I2C_STATUS_TRUNCATED=1,
+  I2C_STATUS_NEGATIVE_ACKNOWLEDGE=2,
+  I2C_STATUS_TRANSMIT_ERROR=3,
+  I2C_STATUS_TIMEOUT=5,
+  // Code used by Wire only
+  I2C_STATUS_OTHER_TWI_ERROR=4, // catch-all error
+  // Codes used by native drivers only
+  I2C_STATUS_ARBITRATION_LOST=6,
+  I2C_STATUS_BUS_ERROR=7,
+  I2C_STATUS_UNEXPECTED_ERROR=8,
+  I2C_STATUS_PENDING=253,
+};
+
+// Status codes for the state machine (not returned to caller).
+enum : uint8_t {
+  I2C_STATE_ACTIVE=253,
+  I2C_STATE_FREE=254,
+  I2C_STATE_CLOSING=255,
+};
+
+typedef enum : uint8_t
+{
+  OPERATION_READ = 1,
+  OPERATION_REQUEST = 2,
+  OPERATION_SEND = 3,
+  OPERATION_SEND_P = 4,
+} OperationEnum;
+
+
+// Default I2C frequency
+#ifndef I2C_FREQ
+#define I2C_FREQ    400000L
+#endif
+
+// Class defining a request context for an I2C operation.
+class I2CRB {
 public:
+  volatile uint8_t status; // Completion status, or pending flag (updated from IRC)
+  volatile uint8_t nBytes; // Number of bytes read (updated from IRC)
 
-  I2CManagerClass() {}
+  inline I2CRB() { status = I2C_STATUS_OK; };
+  uint8_t wait();
+  bool isBusy();
+
+  void setReadParams(uint8_t i2cAddress, uint8_t *readBuffer, uint8_t readLen);
+  void setRequestParams(uint8_t i2cAddress, uint8_t *readBuffer, uint8_t readLen, const uint8_t *writeBuffer, uint8_t writeLen);
+  void setWriteParams(uint8_t i2cAddress, const uint8_t *writeBuffer, uint8_t writeLen);
+
+  uint8_t writeLen;
+  uint8_t readLen;
+  uint8_t operation;
+  uint8_t i2cAddress;
+  uint8_t *readBuffer;
+  const uint8_t *writeBuffer;
+#if !defined(I2C_USE_WIRE)
+  I2CRB *nextRequest;
+#endif
+};
+
+// I2C Manager
+class I2CManagerClass {
+public:
 
   // If not already initialised, initialise I2C (wire).
   void begin(void);
@@ -49,28 +191,93 @@ public:
   void forceClock(uint32_t speed);
   // Check if specified I2C address is responding.
   uint8_t checkAddress(uint8_t address);
-  bool exists(uint8_t address);
+  inline bool exists(uint8_t address) {
+    return checkAddress(address)==I2C_STATUS_OK;
+  }
   // Write a complete transmission to I2C from an array in RAM
   uint8_t write(uint8_t address, const uint8_t buffer[], uint8_t size);
+  uint8_t write(uint8_t address, const uint8_t buffer[], uint8_t size, I2CRB *rb);
   // Write a complete transmission to I2C from an array in Flash
   uint8_t write_P(uint8_t address, const uint8_t buffer[], uint8_t size);
+  uint8_t write_P(uint8_t address, const uint8_t buffer[], uint8_t size, I2CRB *rb);
   // Write a transmission to I2C from a list of bytes.
-  uint8_t write(uint8_t address, int nBytes, ...);
+  uint8_t write(uint8_t address, uint8_t nBytes, ...);
   // Write a command from an array in RAM and read response
-  uint8_t read(uint8_t address, uint8_t writeBuffer[], uint8_t writeSize, 
+  uint8_t read(uint8_t address, uint8_t readBuffer[], uint8_t readSize, 
-    uint8_t readBuffer[], uint8_t readSize);
+    const uint8_t writeBuffer[]=NULL, uint8_t writeSize=0);
+  uint8_t read(uint8_t address, uint8_t readBuffer[], uint8_t readSize, 
+    const uint8_t writeBuffer[], uint8_t writeSize, I2CRB *rb);
   // Write a command from an arbitrary list of bytes and read response
   uint8_t read(uint8_t address, uint8_t readBuffer[], uint8_t readSize, 
     uint8_t writeSize, ...);
-  // Write a null command and read the response.
+  void queueRequest(I2CRB *req);
-  uint8_t read(uint8_t address, uint8_t readBuffer[], uint8_t readSize);
+
+  // Function to abort long-running operations.
+  void checkForTimeout();
+
+  // Loop method
+  void loop();
+
+  // Expand error codes into text.  Note that they are in flash so 
+  // need to be printed using FSH.
+  static const FSH *getErrorMessage(uint8_t status);
 
 private:
   bool _beginCompleted = false;
   bool _clockSpeedFixed = false;
   uint32_t _clockSpeed = 400000L;  // 400kHz max on Arduino.
+
+  // Finish off request block by waiting for completion and posting status.
+  uint8_t finishRB(I2CRB *rb, uint8_t status);
+
+  void _initialise();
+  void _setClock(unsigned long);
+
+#if !defined(I2C_USE_WIRE)
+    // I2CRB structs are queued on the following two links.
+    // If there are no requests, both are NULL.
+    // If there is only one request, then queueHead and queueTail both point to it.
+    // Otherwise, queueHead is the pointer to the first request in the queue and
+    // queueTail is the pointer to the last request in the queue.
+    // Within the queue, each request's nextRequest field points to the 
+    // next request, or NULL.
+    // Mark volatile as they are updated by IRC and read/written elsewhere.
+    static I2CRB * volatile queueHead;
+    static I2CRB * volatile queueTail;
+    static volatile uint8_t state;
+
+    static I2CRB * volatile currentRequest;
+    static volatile uint8_t txCount;
+    static volatile uint8_t rxCount;
+    static volatile uint8_t bytesToSend;
+    static volatile uint8_t bytesToReceive;
+    static volatile uint8_t operation;
+    static volatile unsigned long startTime;
+
+    static unsigned long timeout; // Transaction timeout in microseconds.  0=disabled.
+    
+    void startTransaction();
+    
+    // Low-level hardware manipulation functions.
+    static void I2C_init();
+    static void I2C_setClock(unsigned long i2cClockSpeed);
+    static void I2C_handleInterrupt();
+    static void I2C_sendStart();
+    static void I2C_sendStop();
+    static void I2C_close();
+    
+  public:
+    // setTimeout sets the timout value for I2C transactions.
+    // TODO: Get I2C timeout working before uncommenting the code below.
+    void setTimeout(unsigned long value) { (void)value; /* timeout = value; */ };
+
+    // handleInterrupt needs to be public to be called from the ISR function!
+    static void handleInterrupt();
+#endif
+
+
 };
 
 extern I2CManagerClass I2CManager;
 
-#endif
+#endif

I2CManager_AVR.h

@@ -0,0 +1,209 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *
+ *  This file is part of CommandStation-EX
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef I2CMANAGER_AVR_H
+#define I2CMANAGER_AVR_H
+
+#include <Arduino.h>
+#include "I2CManager.h"
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+
+/****************************************************************************
+  TWI State codes
+****************************************************************************/
+// General TWI Master staus codes                      
+#define TWI_START                  0x08  // START has been transmitted  
+#define TWI_REP_START              0x10  // Repeated START has been transmitted
+#define TWI_ARB_LOST               0x38  // Arbitration lost
+
+// TWI Master Transmitter staus codes                      
+#define TWI_MTX_ADR_ACK            0x18  // SLA+W has been tramsmitted and ACK received
+#define TWI_MTX_ADR_NACK           0x20  // SLA+W has been tramsmitted and NACK received 
+#define TWI_MTX_DATA_ACK           0x28  // Data byte has been tramsmitted and ACK received
+#define TWI_MTX_DATA_NACK          0x30  // Data byte has been tramsmitted and NACK received 
+
+// TWI Master Receiver staus codes  
+#define TWI_MRX_ADR_ACK            0x40  // SLA+R has been tramsmitted and ACK received
+#define TWI_MRX_ADR_NACK           0x48  // SLA+R has been tramsmitted and NACK received
+#define TWI_MRX_DATA_ACK           0x50  // Data byte has been received and ACK tramsmitted
+#define TWI_MRX_DATA_NACK          0x58  // Data byte has been received and NACK tramsmitted
+
+// TWI Miscellaneous status codes
+#define TWI_NO_STATE               0xF8  // No relevant state information available
+#define TWI_BUS_ERROR              0x00  // Bus error due to an illegal START or STOP condition
+
+#define TWI_TWBR  ((F_CPU / I2C_FREQ) - 16) / 2 // TWI Bit rate Register setting.
+
+#if defined(I2C_USE_INTERRUPTS)
+#define ENABLE_TWI_INTERRUPT (1<<TWIE)
+#else
+#define ENABLE_TWI_INTERRUPT 0
+#endif
+
+/***************************************************************************
+ *  Set I2C clock speed register.
+ ***************************************************************************/
+void I2CManagerClass::I2C_setClock(unsigned long i2cClockSpeed) {
+  unsigned long temp = ((F_CPU / i2cClockSpeed) - 16) / 2;
+  for (uint8_t preScaler = 0; preScaler<=3; preScaler++) {
+    if (temp <= 255) {
+      TWBR = temp;
+      TWSR = (TWSR & 0xfc) | preScaler;
+      return;
+    } else 
+      temp /= 4;
+  }
+  // Set slowest speed ~= 500 bits/sec
+  TWBR = 255;
+  TWSR |= 0x03;
+}
+
+/***************************************************************************
+ *  Initialise I2C registers.
+ ***************************************************************************/
+void I2CManagerClass::I2C_init()
+{
+  TWSR = 0;
+  TWBR = TWI_TWBR;                                  // Set bit rate register (Baudrate). Defined in header file.
+  TWDR = 0xFF;                                      // Default content = SDA released.
+  TWCR = (1<<TWINT);                                // Clear interrupt flag
+ 
+  pinMode(SDA, INPUT_PULLUP);
+  pinMode(SCL, INPUT_PULLUP);
+}
+
+/***************************************************************************
+ *  Initiate a start bit for transmission.
+ ***************************************************************************/
+void I2CManagerClass::I2C_sendStart() {
+  bytesToSend = currentRequest->writeLen;
+  bytesToReceive = currentRequest->readLen;
+  // We may have initiated a stop bit before this without waiting for it.
+  // Wait for stop bit to be sent before sending start.
+  while (TWCR & (1<<TWSTO)) {}
+  TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT)|(1<<TWEA)|(1<<TWSTA);  // Send Start
+}
+
+/***************************************************************************
+ *  Initiate a stop bit for transmission (does not interrupt)
+ ***************************************************************************/
+void I2CManagerClass::I2C_sendStop() {
+  TWDR = 0xff;  // Default condition = SDA released
+  TWCR = (1<<TWEN)|(1<<TWINT)|(1<<TWEA)|(1<<TWSTO);  // Send Stop
+}
+
+/***************************************************************************
+ *  Close I2C down
+ ***************************************************************************/
+void I2CManagerClass::I2C_close() {
+  // disable TWI
+  I2C_sendStop();
+  while (TWCR & (1<<TWSTO)) {}
+  TWCR = (1<<TWINT);                 // clear any interrupt and stop twi.
+}
+
+/***************************************************************************
+ *  Main state machine for I2C, called from interrupt handler or,
+ *  if I2C_USE_INTERRUPTS isn't defined, from the I2CManagerClass::loop() function
+ *  (and therefore, indirectly, from I2CRB::wait() and I2CRB::isBusy()).
+ ***************************************************************************/
+void I2CManagerClass::I2C_handleInterrupt() {
+  if (!(TWCR & (1<<TWINT))) return;  // Nothing to do.
+
+  uint8_t twsr = TWSR & 0xF8;
+
+  // Cases are ordered so that the most frequently used ones are tested first.
+  switch (twsr) {
+    case TWI_MTX_DATA_ACK:      // Data byte has been transmitted and ACK received
+    case TWI_MTX_ADR_ACK:       // SLA+W has been transmitted and ACK received
+      if (bytesToSend) {  // Send first.
+        if (operation == OPERATION_SEND_P)
+          TWDR = GETFLASH(currentRequest->writeBuffer + (txCount++));
+        else
+          TWDR = currentRequest->writeBuffer[txCount++];
+        bytesToSend--;
+        TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT)|(1<<TWEA);
+      } else if (bytesToReceive) {  // All sent, anything to receive?
+        while (TWCR & (1<<TWSTO)) {}    // Wait for stop to be sent
+        TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT)|(1<<TWEA)|(1<<TWSTA);  // Send Start
+      } else {  // Nothing left to send or receive
+        TWDR = 0xff;  // Default condition = SDA released
+        TWCR = (1<<TWEN)|(1<<TWINT)|(1<<TWEA)|(1<<TWSTO);  // Send Stop
+        state = I2C_STATUS_OK;
+      }
+      break;
+    case TWI_MRX_DATA_ACK:      // Data byte has been received and ACK transmitted
+      if (bytesToReceive > 0) {
+        currentRequest->readBuffer[rxCount++] = TWDR;
+        bytesToReceive--;
+      }
+      /* fallthrough */
+    case TWI_MRX_ADR_ACK:      // SLA+R has been sent and ACK received
+      if (bytesToReceive <= 1) {
+        TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT); // Send NACK after next reception
+      } else {
+        // send ack
+        TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT)|(1<<TWEA);
+      }
+      break;
+    case TWI_MRX_DATA_NACK:     // Data byte has been received and NACK transmitted
+      if (bytesToReceive > 0) {
+        currentRequest->readBuffer[rxCount++] = TWDR;
+        bytesToReceive--;
+      }
+      TWCR = (1<<TWEN)|(1<<TWINT)|(1<<TWEA)|(1<<TWSTO);  // Send Stop
+      state = I2C_STATUS_OK;
+      break;
+    case TWI_START:             // START has been transmitted  
+    case TWI_REP_START:         // Repeated START has been transmitted
+      // Set up address and R/W
+      if (operation == OPERATION_READ || (operation==OPERATION_REQUEST && !bytesToSend))
+        TWDR = (currentRequest->i2cAddress << 1) | 1; // SLA+R
+      else
+        TWDR = (currentRequest->i2cAddress << 1) | 0; // SLA+W
+      TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT)|(1<<TWEA);
+      break;
+    case TWI_MTX_ADR_NACK:      // SLA+W has been transmitted and NACK received
+    case TWI_MRX_ADR_NACK:      // SLA+R has been transmitted and NACK received
+    case TWI_MTX_DATA_NACK:     // Data byte has been transmitted and NACK received
+      TWDR = 0xff;  // Default condition = SDA released
+      TWCR = (1<<TWEN)|(1<<TWINT)|(1<<TWEA)|(1<<TWSTO);  // Send Stop
+      state = I2C_STATUS_NEGATIVE_ACKNOWLEDGE;
+      break;
+    case TWI_ARB_LOST:          // Arbitration lost
+      // Restart transaction from start.
+      I2C_sendStart();
+      break;
+    case TWI_BUS_ERROR:         // Bus error due to an illegal START or STOP condition
+    default:
+      TWDR = 0xff;  // Default condition = SDA released
+      TWCR = (1<<TWEN)|(1<<TWINT)|(1<<TWEA)|(1<<TWSTO);  // Send Stop
+      state = I2C_STATUS_TRANSMIT_ERROR;
+  }
+}
+
+#if defined(I2C_USE_INTERRUPTS)
+ISR(TWI_vect) {
+  I2CManagerClass::handleInterrupt();
+}
+#endif
+
+#endif /* I2CMANAGER_AVR_H */

I2CManager_Mega4809.h

@@ -0,0 +1,160 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *
+ *  This file is part of CommandStation-EX
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef I2CMANAGER_MEGA4809_H
+#define I2CMANAGER_MEGA4809_H
+
+#include <Arduino.h>
+#include "I2CManager.h"
+
+/***************************************************************************
+ *  Set I2C clock speed register.
+ ***************************************************************************/
+void I2CManagerClass::I2C_setClock(unsigned long i2cClockSpeed) {
+  uint16_t t_rise;
+  if (i2cClockSpeed < 200000) {
+    i2cClockSpeed = 100000;
+    t_rise = 1000;
+  } else if (i2cClockSpeed < 800000) {
+    i2cClockSpeed = 400000;
+    t_rise = 300;
+  } else if (i2cClockSpeed < 1200000) {
+    i2cClockSpeed = 1000000;
+    t_rise = 120;
+  } else {
+    i2cClockSpeed = 100000;
+    t_rise = 1000;
+  }
+  uint32_t baud = (F_CPU_CORRECTED / i2cClockSpeed - F_CPU_CORRECTED / 1000 / 1000
+    * t_rise / 1000 - 10) / 2;
+  TWI0.MBAUD = (uint8_t)baud;
+}
+
+/***************************************************************************
+ *  Initialise I2C registers.
+ ***************************************************************************/
+void I2CManagerClass::I2C_init()
+{ 
+  pinMode(PIN_WIRE_SDA, INPUT_PULLUP);
+  pinMode(PIN_WIRE_SCL, INPUT_PULLUP);
+  PORTMUX.TWISPIROUTEA |= TWI_MUX;
+
+#if defined(I2C_USE_INTERRUPTS)
+  TWI0.MCTRLA = TWI_RIEN_bm | TWI_WIEN_bm | TWI_ENABLE_bm;
+#else
+  TWI0.MCTRLA = TWI_ENABLE_bm;
+#endif
+  I2C_setClock(I2C_FREQ);
+  TWI0.MSTATUS = TWI_BUSSTATE_IDLE_gc;
+}
+
+/***************************************************************************
+ *  Initiate a start bit for transmission, followed by address and R/W
+ ***************************************************************************/
+void I2CManagerClass::I2C_sendStart() {
+  bytesToSend = currentRequest->writeLen;
+  bytesToReceive = currentRequest->readLen;
+
+  // If anything to send, initiate write.  Otherwise initiate read.
+  if (operation == OPERATION_READ || (operation == OPERATION_REQUEST & !bytesToSend))
+    TWI0.MADDR = (currentRequest->i2cAddress << 1) | 1;
+  else
+    TWI0.MADDR = (currentRequest->i2cAddress << 1) | 0;
+}
+
+/***************************************************************************
+ *  Initiate a stop bit for transmission.
+ ***************************************************************************/
+void I2CManagerClass::I2C_sendStop() {
+  TWI0.MCTRLB = TWI_MCMD_STOP_gc;
+}
+
+/***************************************************************************
+ *  Close I2C down
+ ***************************************************************************/
+void I2CManagerClass::I2C_close() {
+  I2C_sendStop();
+}
+
+/***************************************************************************
+ *  Main state machine for I2C, called from interrupt handler.
+ ***************************************************************************/
+void I2CManagerClass::I2C_handleInterrupt() {
+  
+  uint8_t currentStatus = TWI0.MSTATUS;
+
+  if (currentStatus & TWI_ARBLOST_bm) {
+    // Arbitration lost, restart
+    TWI0.MSTATUS = currentStatus; // clear all flags
+    I2C_sendStart();   // Reinitiate request
+  } else if (currentStatus & TWI_BUSERR_bm) {
+    // Bus error
+    state = I2C_STATUS_BUS_ERROR;
+    TWI0.MSTATUS = currentStatus; // clear all flags
+  } else if (currentStatus & TWI_WIF_bm) {
+    // Master write completed
+    if (currentStatus & TWI_RXACK_bm) {
+      // Nacked, send stop.
+      TWI0.MCTRLB = TWI_MCMD_STOP_gc;
+      state = I2C_STATUS_NEGATIVE_ACKNOWLEDGE;
+    } else if (bytesToSend) {
+      // Acked, so send next byte
+      if (currentRequest->operation == OPERATION_SEND_P)
+        TWI0.MDATA = GETFLASH(currentRequest->writeBuffer + (txCount++));
+      else
+        TWI0.MDATA = currentRequest->writeBuffer[txCount++];
+      bytesToSend--;
+    } else if (bytesToReceive) {
+        // Last sent byte acked and no more to send.  Send repeated start, address and read bit.
+        TWI0.MADDR = (currentRequest->i2cAddress << 1) | 1;
+    } else {
+      // No more data to send/receive. Initiate a STOP condition.
+      TWI0.MCTRLB = TWI_MCMD_STOP_gc;
+      state = I2C_STATUS_OK;  // Done
+    }
+  } else if (currentStatus & TWI_RIF_bm) {
+    // Master read completed without errors
+    if (bytesToReceive) {
+      currentRequest->readBuffer[rxCount++] = TWI0.MDATA;  // Store received byte
+      bytesToReceive--;
+    } else { 
+      // Buffer full, issue nack/stop
+      TWI0.MCTRLB = TWI_ACKACT_bm | TWI_MCMD_STOP_gc;
+      state = I2C_STATUS_OK;
+    }
+    if (bytesToReceive) {
+      // More bytes to receive, issue ack and start another read
+      TWI0.MCTRLB = TWI_MCMD_RECVTRANS_gc;
+    } else {
+      // Transaction finished, issue NACK and STOP.
+      TWI0.MCTRLB = TWI_ACKACT_bm | TWI_MCMD_STOP_gc;
+      state = I2C_STATUS_OK;
+    }
+  }
+}
+
+
+/***************************************************************************
+ *  Interrupt handler.
+ ***************************************************************************/
+ISR(TWI0_TWIM_vect) {
+  I2CManagerClass::handleInterrupt();
+}
+
+#endif

I2CManager_NonBlocking.h

@@ -0,0 +1,214 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *
+ *  This file is part of CommandStation-EX
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef I2CMANAGER_NONBLOCKING_H
+#define I2CMANAGER_NONBLOCKING_H
+
+#include <Arduino.h>
+#include "I2CManager.h"
+#if defined(I2C_USE_INTERRUPTS)
+#include <util/atomic.h>
+#else
+#define ATOMIC_BLOCK(x) 
+#define ATOMIC_RESTORESTATE
+#endif
+
+// This module is only compiled if I2C_USE_WIRE is not defined, so undefine it here
+// to get intellisense to work correctly.
+#if defined(I2C_USE_WIRE)
+#undef I2C_USE_WIRE
+#endif
+
+/***************************************************************************
+ * Initialise the I2CManagerAsync class.
+ ***************************************************************************/
+void I2CManagerClass::_initialise()
+{
+  queueHead = queueTail = NULL;
+  state = I2C_STATE_FREE;
+  I2C_init();
+}
+
+/***************************************************************************
+ *  Set I2C clock speed.  Normally 100000 (Standard) or 400000 (Fast)
+ *   on Arduino.  Mega4809 supports 1000000 (Fast+) too.
+ ***************************************************************************/
+void I2CManagerClass::_setClock(unsigned long i2cClockSpeed) {
+  I2C_setClock(i2cClockSpeed);
+}
+
+/***************************************************************************
+ * Helper function to start operations, if the I2C interface is free and
+ * there is a queued request to be processed.
+ ***************************************************************************/
+void I2CManagerClass::startTransaction() { 
+  ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
+    if ((state == I2C_STATE_FREE) && (queueHead != NULL)) {
+      state = I2C_STATE_ACTIVE;
+      currentRequest = queueHead;
+      rxCount = txCount = 0;
+      // Copy key fields to static data for speed.
+      operation = currentRequest->operation;
+      // Start the I2C process going.
+      I2C_sendStart();
+      startTime = micros();
+    }
+  }
+}
+
+/***************************************************************************
+ *  Function to queue a request block and initiate operations.
+ ***************************************************************************/
+void I2CManagerClass::queueRequest(I2CRB *req) {
+  req->status = I2C_STATUS_PENDING;
+  req->nextRequest = NULL;
+
+  ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
+    if (!queueTail) 
+      queueHead = queueTail = req;  // Only item on queue
+    else
+      queueTail = queueTail->nextRequest = req; // Add to end
+    startTransaction();
+  }
+
+}
+
+/***************************************************************************
+ *  Initiate a write to an I2C device (non-blocking operation)
+ ***************************************************************************/
+uint8_t I2CManagerClass::write(uint8_t i2cAddress, const uint8_t *writeBuffer, uint8_t writeLen, I2CRB *req) {
+  // Make sure previous request has completed.
+  req->wait();
+  req->setWriteParams(i2cAddress, writeBuffer, writeLen);
+  queueRequest(req);
+  return I2C_STATUS_OK;
+}
+
+/***************************************************************************
+ *  Initiate a write from PROGMEM (flash) to an I2C device (non-blocking operation)
+ ***************************************************************************/
+uint8_t I2CManagerClass::write_P(uint8_t i2cAddress, const uint8_t * writeBuffer, uint8_t writeLen, I2CRB *req) {
+  // Make sure previous request has completed.
+  req->wait();
+  req->setWriteParams(i2cAddress, writeBuffer, writeLen);
+  req->operation = OPERATION_SEND_P;
+  queueRequest(req);
+  return I2C_STATUS_OK;
+}
+
+/***************************************************************************
+ *  Initiate a read from the I2C device, optionally preceded by a write 
+ *   (non-blocking operation)
+ ***************************************************************************/
+uint8_t I2CManagerClass::read(uint8_t i2cAddress, uint8_t *readBuffer, uint8_t readLen, 
+    const uint8_t *writeBuffer, uint8_t writeLen, I2CRB *req)
+{
+  // Make sure previous request has completed.
+  req->wait();
+  req->setRequestParams(i2cAddress, readBuffer, readLen, writeBuffer, writeLen);
+  queueRequest(req);
+  return I2C_STATUS_OK;
+}
+
+/***************************************************************************
+ * checkForTimeout() function, called from isBusy() and wait() to cancel
+ * requests that are taking too long to complete.
+ ***************************************************************************/
+void I2CManagerClass::checkForTimeout() {
+  unsigned long currentMicros = micros();
+  ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
+    I2CRB *t = queueHead;
+    if (state==I2C_STATE_ACTIVE && t!=0 && t==currentRequest && timeout > 0) {
+      // Check for timeout
+      if (currentMicros - startTime > timeout) { 
+        // Excessive time. Dequeue request
+        queueHead = t->nextRequest;
+        if (!queueHead) queueTail = NULL;
+        currentRequest = NULL;
+        // Post request as timed out.
+        t->status = I2C_STATUS_TIMEOUT;
+        // Reset TWI interface so it is able to continue
+        // Try close and init, not entirely satisfactory but sort of works...
+        I2C_close();  // Shutdown and restart twi interface
+        I2C_init();
+        state = I2C_STATE_FREE;
+        
+        // Initiate next queued request if any.
+        startTransaction();
+      }
+    }
+  }
+}
+
+/***************************************************************************
+ *  Loop function, for general background work
+ ***************************************************************************/
+void I2CManagerClass::loop() {
+#if !defined(I2C_USE_INTERRUPTS)
+  handleInterrupt();
+#endif
+  checkForTimeout();
+}
+
+/***************************************************************************
+ * Interupt handler.  Call I2C state machine, and dequeue request
+ * if completed.
+ ***************************************************************************/
+void I2CManagerClass::handleInterrupt() {
+
+  // Update hardware state machine
+  I2C_handleInterrupt();
+
+  // Check if current request has completed.  If there's a current request
+  // and state isn't active then state contains the completion status of the request.
+  if (state != I2C_STATE_ACTIVE && currentRequest != NULL) {
+    // Remove completed request from head of queue
+    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
+      I2CRB * t = queueHead;
+      if (t == queueHead) {
+        queueHead = t->nextRequest;
+        if (!queueHead) queueTail = queueHead;
+        t->nBytes = rxCount;
+        t->status = state;
+        
+        // I2C state machine is now free for next request
+        currentRequest = NULL;
+        state = I2C_STATE_FREE;
+
+        // Start next request (if any)
+        I2CManager.startTransaction();
+      }
+    }
+  }
+}
+
+// Fields in I2CManager class specific to Non-blocking implementation.
+I2CRB * volatile I2CManagerClass::queueHead = NULL;
+I2CRB * volatile I2CManagerClass::queueTail = NULL;
+I2CRB * volatile I2CManagerClass::currentRequest = NULL;
+volatile uint8_t I2CManagerClass::state = I2C_STATE_FREE;
+volatile uint8_t I2CManagerClass::txCount;
+volatile uint8_t I2CManagerClass::rxCount;
+volatile uint8_t I2CManagerClass::operation;
+volatile uint8_t I2CManagerClass::bytesToSend;
+volatile uint8_t I2CManagerClass::bytesToReceive;
+volatile unsigned long I2CManagerClass::startTime;
+unsigned long I2CManagerClass::timeout = 0;
+
+#endif

I2CManager_Wire.h

@@ -0,0 +1,128 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *
+ *  This file is part of CommandStation-EX
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef I2CMANAGER_WIRE_H
+#define I2CMANAGER_WIRE_H
+
+#include <Arduino.h>
+#include <Wire.h>
+#include "I2CManager.h"
+
+// This module is only compiled if I2C_USE_WIRE is defined, so define it here
+// to get intellisense to work correctly.
+#if !defined(I2C_USE_WIRE)
+#define I2C_USE_WIRE
+#endif
+
+/***************************************************************************
+ *  Initialise I2C interface software
+ ***************************************************************************/
+void I2CManagerClass::_initialise() {
+  Wire.begin();
+}
+
+/***************************************************************************
+ *  Set I2C clock speed.  Normally 100000 (Standard) or 400000 (Fast)
+ *   on Arduino.  Mega4809 supports 1000000 (Fast+) too.
+ ***************************************************************************/
+void I2CManagerClass::_setClock(unsigned long i2cClockSpeed) {
+  Wire.setClock(i2cClockSpeed);
+}
+
+/***************************************************************************
+ *  Initiate a write to an I2C device (blocking operation on Wire)
+ ***************************************************************************/
+uint8_t I2CManagerClass::write(uint8_t address, const uint8_t buffer[], uint8_t size, I2CRB *rb) {
+  Wire.beginTransmission(address);
+  if (size > 0) Wire.write(buffer, size);
+  rb->status = Wire.endTransmission();
+  return I2C_STATUS_OK;
+}
+
+/***************************************************************************
+ *  Initiate a write from PROGMEM (flash) to an I2C device (blocking operation on Wire)
+ ***************************************************************************/
+uint8_t I2CManagerClass::write_P(uint8_t address, const uint8_t buffer[], uint8_t size, I2CRB *rb) {
+  uint8_t ramBuffer[size];
+  const uint8_t *p1 = buffer;
+  for (uint8_t i=0; i<size; i++)
+    ramBuffer[i] = GETFLASH(p1++);
+  return write(address, ramBuffer, size, rb);
+}
+
+/***************************************************************************
+ *  Initiate a write (optional) followed by a read from the I2C device (blocking operation on Wire)
+ *  If fewer than the number of requested bytes are received, status is I2C_STATUS_TRUNCATED.
+ ***************************************************************************/
+uint8_t I2CManagerClass::read(uint8_t address, uint8_t readBuffer[], uint8_t readSize,
+                              const uint8_t writeBuffer[], uint8_t writeSize, I2CRB *rb)
+{
+  uint8_t status = I2C_STATUS_OK;
+  uint8_t nBytes = 0;
+  if (writeSize > 0) {
+    Wire.beginTransmission(address);
+    Wire.write(writeBuffer, writeSize);
+    status = Wire.endTransmission(false); // Don't free bus yet
+  }
+  if (status == I2C_STATUS_OK) {
+    Wire.requestFrom(address, (size_t)readSize);
+    while (Wire.available() && nBytes < readSize) 
+      readBuffer[nBytes++] = Wire.read();
+    if (nBytes < readSize) status = I2C_STATUS_TRUNCATED;
+  }
+  rb->nBytes = nBytes;
+  rb->status = status;
+  return I2C_STATUS_OK;
+}
+
+/***************************************************************************
+ *  Function to queue a request block and initiate operations.
+ * 
+ * For the Wire version, this executes synchronously, but the status is
+ * returned in the I2CRB as for the asynchronous version.
+ ***************************************************************************/
+void I2CManagerClass::queueRequest(I2CRB *req) {
+  uint8_t status;
+  switch (req->operation) {
+    case OPERATION_READ:
+      status = read(req->i2cAddress, req->readBuffer, req->readLen, NULL, 0, req);
+      break;
+    case OPERATION_SEND:
+      status = write(req->i2cAddress, req->writeBuffer, req->writeLen, req);
+      break;
+    case OPERATION_SEND_P:
+      status = write_P(req->i2cAddress, req->writeBuffer, req->writeLen, req);
+      break;
+    case OPERATION_REQUEST:
+      status = read(req->i2cAddress, req->readBuffer, req->readLen, req->writeBuffer, req->writeLen, req);
+      break;
+  }
+  req->status = status;
+}
+
+/***************************************************************************
+ *  Loop function, for general background work
+ ***************************************************************************/
+void I2CManagerClass::loop() {}
+
+// Loop function
+void I2CManagerClass::checkForTimeout() {}
+
+
+#endif

IODevice.cpp

@@ -0,0 +1,488 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *  
+ *  This file is part of DCC++EX API
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+#include <Arduino.h>
+#include "IODevice.h"
+#include "DIAG.h" 
+#include "FSH.h"
+#include "IO_MCP23017.h"
+
+#if defined(ARDUINO_ARCH_AVR) || defined(ARDUINO_ARCH_MEGAAVR)
+#define USE_FAST_IO
+#endif
+
+//==================================================================================================================
+// Static methods
+//------------------------------------------------------------------------------------------------------------------
+
+// Static functions
+
+// Static method to initialise the IODevice subsystem.  
+
+#if !defined(IO_NO_HAL)
+
+// Create any standard device instances that may be required, such as the Arduino pins 
+// and PCA9685.
+void IODevice::begin() {
+  // Initialise the IO subsystem
+  ArduinoPins::create(2, NUM_DIGITAL_PINS-2);  // Reserve pins for direct access
+  // Predefine two PCA9685 modules 0x40-0x41
+  // Allocates 32 pins 100-131
+  PCA9685::create(100, 16, 0x40);
+  PCA9685::create(116, 16, 0x41);
+  // Predefine two MCP23017 module 0x20/0x21
+  // Allocates 32 pins 164-195
+  MCP23017::create(164, 16, 0x20);
+  MCP23017::create(180, 16, 0x21);
+
+  // Call the begin() methods of each configured device in turn
+  for (IODevice *dev=_firstDevice; dev!=NULL; dev = dev->_nextDevice) {
+    dev->_begin();
+  }
+  _initPhase = false;
+}
+
+// Overarching static loop() method for the IODevice subsystem.  Works through the
+// list of installed devices and calls their individual _loop() method.
+// Devices may or may not implement this, but if they do it is useful for things like animations 
+// or flashing LEDs.
+// The current value of micros() is passed as a parameter, so the called loop function
+// doesn't need to invoke it.
+void IODevice::loop() {
+  unsigned long currentMicros = micros();
+  
+  IODevice *lastLoopDevice = _nextLoopDevice;  // So we know when to stop...
+  // Loop through devices until we find one ready to be serviced.
+  do {
+    if (!_nextLoopDevice) _nextLoopDevice = _firstDevice;
+    if (_nextLoopDevice) {
+      if (_nextLoopDevice->_deviceState != DEVSTATE_FAILED 
+            && ((long)(currentMicros - _nextLoopDevice->_nextEntryTime)) >= 0) {
+        // Found one ready to run, so invoke its _loop method.
+        _nextLoopDevice->_nextEntryTime = currentMicros;
+        _nextLoopDevice->_loop(currentMicros);
+        _nextLoopDevice = _nextLoopDevice->_nextDevice;
+        break;
+      }
+      // Not this one, move to next one
+      _nextLoopDevice = _nextLoopDevice->_nextDevice;
+    }
+  } while (_nextLoopDevice != lastLoopDevice); // Stop looking when we've done all.
+  
+  // Report loop time if diags enabled
+#if defined(DIAG_LOOPTIMES)
+  static unsigned long lastMicros = 0;
+  // Measure time since loop() method started.
+  unsigned long halElapsed = micros() - currentMicros;
+  // Measure time between loop() method entries.
+  unsigned long elapsed = currentMicros - lastMicros;
+  static unsigned long maxElapsed = 0, maxHalElapsed = 0;
+  static unsigned long lastOutputTime = 0;
+  static unsigned long halTotal = 0, total = 0;
+  static unsigned long count = 0;
+  const unsigned long interval = (unsigned long)5 * 1000 * 1000; // 5 seconds in microsec
+
+  // Ignore long loop counts while message is still outputting
+  if (currentMicros - lastOutputTime > 3000UL) {
+    if (elapsed > maxElapsed) maxElapsed = elapsed;
+    if (halElapsed > maxHalElapsed) maxHalElapsed = halElapsed;
+    halTotal += halElapsed;
+    total += elapsed;
+    count++;
+  }
+  if (currentMicros - lastOutputTime > interval) {
+    if (lastOutputTime > 0) 
+      DIAG(F("Loop Total:%lus (%lus max) HAL:%lus (%lus max)"), 
+        total/count, maxElapsed, halTotal/count, maxHalElapsed);
+    maxElapsed = maxHalElapsed = total = halTotal = count = 0;
+    lastOutputTime = currentMicros;
+  }
+  lastMicros = currentMicros;
+#endif
+}
+
+// Display a list of all the devices on the diagnostic stream.
+void IODevice::DumpAll() {
+  for (IODevice *dev = _firstDevice; dev != 0; dev = dev->_nextDevice) {
+    dev->_display();
+  }
+}
+
+// Determine if the specified vpin is allocated to a device.
+bool IODevice::exists(VPIN vpin) {
+  return findDevice(vpin) != NULL;
+}
+
+// check whether the pin supports notification.  If so, then regular _read calls are not required.
+bool IODevice::hasCallback(VPIN vpin) {
+  IODevice *dev = findDevice(vpin);
+  if (!dev) return false;
+  return dev->_hasCallback;
+}
+
+// Display (to diagnostics) details of the device.
+void IODevice::_display() {
+  DIAG(F("Unknown device Vpins:%d-%d %S"), 
+    (int)_firstVpin, (int)_firstVpin+_nPins-1, _deviceState==DEVSTATE_FAILED ? F("OFFLINE") : F(""));
+}
+
+// Find device associated with nominated Vpin and pass configuration values on to it.
+//   Return false if not found.
+bool IODevice::configure(VPIN vpin, ConfigTypeEnum configType, int paramCount, int params[]) {
+  IODevice *dev = findDevice(vpin);
+  if (dev) return dev->_configure(vpin, configType, paramCount, params);
+  return false;
+}
+
+// Write value to virtual pin(s).  If multiple devices are allocated the same pin
+//  then only the first one found will be used.
+void IODevice::write(VPIN vpin, int value) {
+  IODevice *dev = findDevice(vpin);
+  if (dev) {
+    dev->_write(vpin, value);
+    return;
+  }
+#ifdef DIAG_IO
+  DIAG(F("IODevice::write(): Vpin ID %d not found!"), (int)vpin);
+#endif
+}
+
+// Write analogue value to virtual pin(s).  If multiple devices are allocated
+// the same pin then only the first one found will be used.
+//
+// The significance of param1 and param2 may vary from device to device.
+// For servo controllers, param1 is the profile of the transition and param2
+// the duration, i.e. the time that the operation is to be animated over
+// in deciseconds (0-3276 sec)
+//
+void IODevice::writeAnalogue(VPIN vpin, int value, uint8_t param1, uint16_t param2) {
+  IODevice *dev = findDevice(vpin);
+  if (dev) {
+    dev->_writeAnalogue(vpin, value, param1, param2);
+    return;
+  }
+#ifdef DIAG_IO
+  DIAG(F("IODevice::writeAnalogue(): Vpin ID %d not found!"), (int)vpin);
+#endif
+}
+
+// isBusy, when called for a device pin is always a digital output or analogue output,
+//  returns input feedback state of the pin, i.e. whether the pin is busy performing
+//  an animation or fade over a period of time.
+bool IODevice::isBusy(VPIN vpin) {
+  IODevice *dev = findDevice(vpin);
+  if (dev) 
+    return dev->_read(vpin);
+  else
+    return false;
+}
+
+void IODevice::setGPIOInterruptPin(int16_t pinNumber) {
+  if (pinNumber >= 0)
+    pinMode(pinNumber, INPUT_PULLUP);
+  _gpioInterruptPin = pinNumber;
+}
+
+// Private helper function to add a device to the chain of devices.
+void IODevice::addDevice(IODevice *newDevice) {
+  // Link new object to the end of the chain.  Thereby, the first devices to be declared/created
+  // will be located faster by findDevice than those which are created later.
+  // Ideally declare/create the digital IO pins first, then servos, then more esoteric devices.
+  IODevice *lastDevice;
+  if (_firstDevice == 0)
+    _firstDevice = newDevice;
+  else {
+    for (IODevice *dev = _firstDevice; dev != 0; dev = dev->_nextDevice)
+      lastDevice = dev;
+    lastDevice->_nextDevice = newDevice;
+  }
+  newDevice->_nextDevice = 0;
+
+  // If the IODevice::begin() method has already been called, initialise device here.  If not,
+  // the device's _begin() method will be called by IODevice::begin().
+  if (!_initPhase)
+    newDevice->_begin();
+}
+
+// Private helper function to locate a device by VPIN.  Returns NULL if not found.
+//  This is performance-critical, so minimises the calculation and function calls necessary.
+IODevice *IODevice::findDevice(VPIN vpin) { 
+  for (IODevice *dev = _firstDevice; dev != 0; dev = dev->_nextDevice) {
+    VPIN firstVpin = dev->_firstVpin;
+    if (vpin >= firstVpin && vpin < firstVpin+dev->_nPins)
+      return dev;
+  }
+  return NULL;
+}
+  
+//==================================================================================================================
+// Static data
+//------------------------------------------------------------------------------------------------------------------
+
+// Chain of callback blocks (identifying registered callback functions for state changes)
+IONotifyCallback *IONotifyCallback::first = 0;
+
+// Start of chain of devices.
+IODevice *IODevice::_firstDevice = 0;
+
+// Reference to next device to be called on _loop() method.
+IODevice *IODevice::_nextLoopDevice = 0;
+
+// Flag which is reset when IODevice::begin has been called.
+bool IODevice::_initPhase = true;  
+
+
+//==================================================================================================================
+// Instance members
+//------------------------------------------------------------------------------------------------------------------
+
+// Method to check whether the id corresponds to this device
+bool IODevice::owns(VPIN id) {
+  return (id >= _firstVpin && id < _firstVpin + _nPins);
+}
+
+// Read value from virtual pin.
+int IODevice::read(VPIN vpin) {
+  for (IODevice *dev = _firstDevice; dev != 0; dev = dev->_nextDevice) {
+    if (dev->owns(vpin)) 
+      return dev->_read(vpin);
+  }
+#ifdef DIAG_IO
+  DIAG(F("IODevice::read(): Vpin %d not found!"), (int)vpin);
+#endif
+  return false;
+}
+
+// Read analogue value from virtual pin.
+int IODevice::readAnalogue(VPIN vpin) {
+  for (IODevice *dev = _firstDevice; dev != 0; dev = dev->_nextDevice) {
+    if (dev->owns(vpin)) 
+      return dev->_readAnalogue(vpin);
+  }
+#ifdef DIAG_IO
+  DIAG(F("IODevice::readAnalogue(): Vpin %d not found!"), (int)vpin);
+#endif
+  return false;
+}
+
+
+#else // !defined(IO_NO_HAL)
+
+// Minimal implementations of public HAL interface, to support Arduino pin I/O and nothing more.
+
+void IODevice::begin() { DIAG(F("NO HAL CONFIGURED!")); }
+bool IODevice::configure(VPIN pin, ConfigTypeEnum, int, int p[]) {
+  #ifdef DIAG_IO
+  DIAG(F("Arduino _configurePullup Pin:%d Val:%d"), pin, p[0]);
+  #endif
+  if (p[0]) {
+    pinMode(pin, INPUT_PULLUP);
+  } else {
+    pinMode(pin, INPUT);
+  }
+  return true;
+}
+void IODevice::write(VPIN vpin, int value) {
+  digitalWrite(vpin, value);
+  pinMode(vpin, OUTPUT);
+}
+void IODevice::writeAnalogue(VPIN, int, uint8_t, uint16_t) {}
+bool IODevice::isBusy(VPIN) { return false; }
+bool IODevice::hasCallback(VPIN) { return false; }
+int IODevice::read(VPIN vpin) { 
+  return !digitalRead(vpin);  // Return inverted state (5v=0, 0v=1)
+}
+int IODevice::readAnalogue(VPIN vpin) {
+  pinMode(vpin, INPUT);
+  noInterrupts();
+  int value = analogRead(vpin);
+  interrupts();
+  return value;
+}
+void IODevice::loop() {}
+void IODevice::DumpAll() {
+  DIAG(F("NO HAL CONFIGURED!"));
+}
+bool IODevice::exists(VPIN vpin) { return (vpin > 2 && vpin < NUM_DIGITAL_PINS); }
+void IODevice::setGPIOInterruptPin(int16_t) {}
+
+// Chain of callback blocks (identifying registered callback functions for state changes)
+// Not used in IO_NO_HAL but must be declared.
+IONotifyCallback *IONotifyCallback::first = 0;
+
+#endif // IO_NO_HAL
+
+
+/////////////////////////////////////////////////////////////////////////////////////////////////////
+
+// Constructor
+ArduinoPins::ArduinoPins(VPIN firstVpin, int nPins) {
+  _firstVpin = firstVpin;
+  _nPins = nPins;
+  int arrayLen = (_nPins+7)/8;
+  _pinPullups = (uint8_t *)calloc(3, arrayLen);
+  _pinModes = (&_pinPullups[0]) + arrayLen;
+  _pinInUse = (&_pinPullups[0]) + 2*arrayLen;
+  for (int i=0; i<arrayLen; i++) {
+    _pinPullups[i] = 0xff;  // default to pullup on, for inputs
+    _pinModes[i] = 0;
+    _pinInUse[i] = 0;
+  }
+}
+
+// Device-specific pin configuration.  Configure should be called infrequently so simplify 
+// code by using the standard pinMode function.
+bool ArduinoPins::_configure(VPIN vpin, ConfigTypeEnum configType, int paramCount, int params[]) {
+  if (configType != CONFIGURE_INPUT) return false;
+  if (paramCount != 1) return false;
+  bool pullup = params[0];
+
+  int pin = vpin;
+  #ifdef DIAG_IO
+  DIAG(F("Arduino _configurePullup Pin:%d Val:%d"), pin, pullup);
+  #endif
+  uint8_t mask = 1 << ((pin-_firstVpin) % 8);
+  uint8_t index = (pin-_firstVpin) / 8;
+  _pinModes[index] &= ~mask;  // set to input mode
+  if (pullup) {
+    _pinPullups[index] |= mask;
+    pinMode(pin, INPUT_PULLUP);
+  } else {
+    _pinPullups[index] &= ~mask;
+    pinMode(pin, INPUT);
+  }
+  _pinInUse[index] |= mask;
+  return true;
+}
+
+// Device-specific write function.
+void ArduinoPins::_write(VPIN vpin, int value) {
+  int pin = vpin;
+  #ifdef DIAG_IO
+  DIAG(F("Arduino Write Pin:%d Val:%d"), pin, value);
+  #endif
+  uint8_t mask = 1 << ((pin-_firstVpin) % 8);
+  uint8_t index = (pin-_firstVpin) / 8;
+  // First update the output state, then set into write mode if not already.
+  fastWriteDigital(pin, value);
+  if (!(_pinModes[index] & mask)) {
+    // Currently in read mode, change to write mode
+    _pinModes[index] |= mask;
+    // Since mode changes should be infrequent, use standard pinMode function
+    pinMode(pin, OUTPUT);
+    _pinInUse[index] |= mask;
+  }
+}
+
+// Device-specific read function (digital input).
+int ArduinoPins::_read(VPIN vpin) {
+  int pin = vpin;
+  uint8_t mask = 1 << ((pin-_firstVpin) % 8);
+  uint8_t index = (pin-_firstVpin) / 8;
+  if ((_pinModes[index] | ~_pinInUse[index]) & mask) {
+    // Currently in write mode or not initialised, change to read mode
+    _pinModes[index] &= ~mask;
+    // Since mode changes should be infrequent, use standard pinMode function
+    if (_pinPullups[index] & mask) 
+      pinMode(pin, INPUT_PULLUP);
+    else
+      pinMode(pin, INPUT);
+    _pinInUse[index] |= mask;
+  }
+  int value = !fastReadDigital(pin); // Invert (5v=0, 0v=1)
+
+  #ifdef DIAG_IO
+  //DIAG(F("Arduino Read Pin:%d Value:%d"), pin, value);
+  #endif
+  return value;
+}
+
+// Device-specific readAnalogue function (analogue input)
+int ArduinoPins::_readAnalogue(VPIN vpin) {
+  int pin = vpin;
+  uint8_t mask = 1 << ((pin-_firstVpin) % 8);
+  uint8_t index = (pin-_firstVpin) / 8;
+  if (_pinModes[index] & mask) {
+    // Currently in write mode, change to read mode
+    _pinModes[index] &= ~mask;
+    // Since mode changes should be infrequent, use standard pinMode function
+    if (_pinPullups[index] & mask) 
+      pinMode(pin, INPUT_PULLUP);
+    else
+      pinMode(pin, INPUT);
+  }
+
+  // Since AnalogRead is also called from interrupt code, disable interrupts 
+  // while we're using it.  There's only one ADC shared by all analogue inputs 
+  // on the Arduino, so we don't want interruptions.
+  //******************************************************************************
+  // NOTE: If the HAL is running on a computer without the DCC signal generator,
+  // then interrupts needn't be disabled.  Also, the DCC signal generator puts
+  // the ADC into fast mode, so if it isn't present, analogueRead calls will be much
+  // slower!!
+  //******************************************************************************
+  noInterrupts();
+  int value = analogRead(pin);
+  interrupts();
+
+  #ifdef DIAG_IO
+  DIAG(F("Arduino Read Pin:%d Value:%d"), pin, value);
+  #endif
+  return value;
+}
+
+void ArduinoPins::_display() {
+  DIAG(F("Arduino Vpins:%d-%d"), (int)_firstVpin, (int)_firstVpin+_nPins-1);
+}
+
+/////////////////////////////////////////////////////////////////////////////////////////////////////
+
+
+void ArduinoPins::fastWriteDigital(uint8_t pin, uint8_t value) {
+#if defined(USE_FAST_IO)
+  if (pin >= NUM_DIGITAL_PINS) return;
+  uint8_t mask = digitalPinToBitMask(pin);
+  uint8_t port = digitalPinToPort(pin);
+  volatile uint8_t *outPortAdr = portOutputRegister(port);
+  noInterrupts();
+  if (value) 
+    *outPortAdr |= mask;
+  else
+    *outPortAdr &= ~mask;
+  interrupts();
+#else
+  digitalWrite(pin, value);
+#endif
+}
+
+bool ArduinoPins::fastReadDigital(uint8_t pin) {
+#if defined(USE_FAST_IO)
+  if (pin >= NUM_DIGITAL_PINS) return false;
+  uint8_t mask = digitalPinToBitMask(pin);
+  uint8_t port = digitalPinToPort(pin);
+  volatile uint8_t *inPortAdr = portInputRegister(port);
+  // read input
+  bool result = (*inPortAdr & mask) != 0;  
+#else
+  bool result = digitalRead(pin);
+#endif
+  return result;
+}
+

IODevice.h

@@ -0,0 +1,371 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *  
+ *  This file is part of DCC++EX API
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef iodevice_h
+#define iodevice_h
+
+// Define symbol DIAG_IO to enable diagnostic output
+//#define DIAG_IO Y
+
+// Define symbol DIAG_LOOPTIMES to enable CS loop execution time to be reported
+//#define DIAG_LOOPTIMES
+
+// Define symbol IO_NO_HAL to reduce FLASH footprint when HAL features not required
+// The HAL is disabled by default on Nano and Uno platforms, because of limited flash space.
+#if defined(ARDUINO_AVR_NANO) || defined(ARDUINO_AVR_UNO) 
+#define IO_NO_HAL
+#endif
+
+// Define symbol IO_SWITCH_OFF_SERVO to set the PCA9685 output to 0 when an 
+// animation has completed.  This switches off the servo motor, preventing 
+// the continuous buzz sometimes found on servos, and reducing the 
+// power consumption of the servo when inactive.
+// It is recommended to enable this, unless it causes you problems.
+#define IO_SWITCH_OFF_SERVO
+
+#include "DIAG.h"
+#include "FSH.h"
+#include "I2CManager.h"
+#include "inttypes.h"
+
+typedef uint16_t VPIN;
+// Limit VPIN number to max 32767.  Above this number, printing often gives negative values.
+// This should be enough for 99% of users.
+#define VPIN_MAX 32767  
+#define VPIN_NONE 65535
+
+/* 
+ * Callback support for state change notification from an IODevice subclass to a 
+ * handler, e.g. Sensor object handling.
+ */
+
+class IONotifyCallback {
+public: 
+  typedef void IONotifyCallbackFunction(VPIN vpin, int value);
+  static void add(IONotifyCallbackFunction *function) {
+    IONotifyCallback *blk = new IONotifyCallback(function);
+    if (first) blk->next = first;
+    first = blk;
+  }
+  static void invokeAll(VPIN vpin, int value) {
+    for (IONotifyCallback *blk = first; blk != NULL; blk = blk->next)
+      blk->invoke(vpin, value);
+  }
+  static bool hasCallback() {
+    return first != NULL;
+  }
+private:
+  IONotifyCallback(IONotifyCallbackFunction *function) { invoke = function; };
+  IONotifyCallback *next = 0;
+  IONotifyCallbackFunction *invoke = 0;
+  static IONotifyCallback *first;
+};
+
+/*
+ * IODevice class
+ * 
+ * This class is the basis of the Hardware Abstraction Layer (HAL) for
+ * the DCC++EX Command Station.  All device classes derive from this.
+ * 
+ */
+
+class IODevice {
+public:
+
+  // Parameter values to identify type of call to IODevice::configure.
+  typedef enum : uint8_t {
+    CONFIGURE_INPUT = 1,
+    CONFIGURE_SERVO = 2,
+    CONFIGURE_OUTPUT = 3,
+  } ConfigTypeEnum;
+
+  typedef enum : uint8_t {
+    DEVSTATE_DORMANT = 0,
+    DEVSTATE_PROBING = 1,
+    DEVSTATE_INITIALISING = 2,
+    DEVSTATE_NORMAL = 3,
+    DEVSTATE_SCANNING = 4,
+    DEVSTATE_FAILED = 5,
+  } DeviceStateEnum;
+
+  // Static functions to find the device and invoke its member functions
+
+  // begin is invoked to create any standard IODevice subclass instances.
+  // Also, the _begin method of any existing instances is called from here.
+  static void begin();
+
+  // configure is used invoke an IODevice instance's _configure method
+  static bool configure(VPIN vpin, ConfigTypeEnum configType, int paramCount, int params[]);
+
+  // User-friendly function for configuring an input pin.
+  inline static bool configureInput(VPIN vpin, bool pullupEnable) {
+    int params[] = {pullupEnable};
+    return IODevice::configure(vpin, CONFIGURE_INPUT, 1, params);
+  }
+
+  // User-friendly function for configuring a servo pin.
+  inline static bool configureServo(VPIN vpin, uint16_t activePosition, uint16_t inactivePosition, uint8_t profile=0, uint16_t duration=0, uint8_t initialState=0) {
+    int params[] = {(int)activePosition, (int)inactivePosition, profile, (int)duration, initialState};
+    return IODevice::configure(vpin, CONFIGURE_SERVO, 5, params);
+  }
+
+  // write invokes the IODevice instance's _write method.
+  static void write(VPIN vpin, int value);
+
+  // write invokes the IODevice instance's _writeAnalogue method (not applicable for digital outputs)
+  static void writeAnalogue(VPIN vpin, int value, uint8_t profile=0, uint16_t duration=0);
+
+  // isBusy returns true if the device is currently in an animation of some sort, e.g. is changing
+  //  the output over a period of time.
+  static bool isBusy(VPIN vpin);
+
+  // check whether the pin supports notification.  If so, then regular _read calls are not required.
+  static bool hasCallback(VPIN vpin);
+
+  // read invokes the IODevice instance's _read method.
+  static int read(VPIN vpin);
+
+  // read invokes the IODevice instance's _readAnalogue method.
+  static int readAnalogue(VPIN vpin);
+
+  // loop invokes the IODevice instance's _loop method.
+  static void loop();
+
+  static void DumpAll();
+
+  // exists checks whether there is a device owning the specified vpin
+  static bool exists(VPIN vpin);
+
+  // Enable shared interrupt on specified pin for GPIO extender modules.  The extender module
+  // should pull down this pin when requesting a scan.  The pin may be shared by multiple modules.
+  // Without the shared interrupt, input states are scanned periodically to detect changes on 
+  // GPIO extender pins.  If a shared interrupt pin is configured, then input states are scanned
+  // only when the shared interrupt pin is pulled low.  The external GPIO module releases the pin
+  // once the GPIO port concerned has been read.
+  void setGPIOInterruptPin(int16_t pinNumber);
+
+  
+protected:
+  
+  // Constructor
+  IODevice(VPIN firstVpin=0, int nPins=0) {
+    _firstVpin = firstVpin;
+    _nPins = nPins;
+    _nextEntryTime = 0;
+  }
+
+ // Method to perform initialisation of the device (optionally implemented within device class)
+  virtual void _begin() {}
+
+  // Method to configure device (optionally implemented within device class)
+  virtual bool _configure(VPIN vpin, ConfigTypeEnum configType, int paramCount, int params[]) { 
+    (void)vpin; (void)configType; (void)paramCount; (void)params; // Suppress compiler warning.
+    return false;
+  };
+
+  // Method to write new state (optionally implemented within device class)
+  virtual void _write(VPIN vpin, int value) {
+    (void)vpin; (void)value;
+  };
+
+  // Method to write an 'analogue' value (optionally implemented within device class)
+  virtual void _writeAnalogue(VPIN vpin, int value, uint8_t param1, uint16_t param2) {
+    (void)vpin; (void)value; (void) param1; (void)param2;
+  };
+
+  // Method to read digital pin state (optionally implemented within device class)
+  virtual int _read(VPIN vpin) { 
+    (void)vpin; 
+    return 0;
+  };
+
+  // Method to read analogue pin state (optionally implemented within device class)
+  virtual int _readAnalogue(VPIN vpin) { 
+    (void)vpin; 
+    return 0;
+  };
+
+  // Method to perform updates on an ongoing basis (optionally implemented within device class)
+  virtual void _loop(unsigned long currentMicros) {
+    delayUntil(currentMicros + 0x7fffffff); // Largest time in the future!  Effectively disable _loop calls.
+  };
+
+  // Method for displaying info on DIAG output (optionally implemented within device class)
+  virtual void _display();
+
+  // Destructor
+  virtual ~IODevice() {};
+
+  // Non-virtual function
+  void delayUntil(unsigned long futureMicrosCount) {
+    _nextEntryTime = futureMicrosCount;
+  }
+  
+  // Common object fields.
+  VPIN _firstVpin;
+  int _nPins;
+
+  // Flag whether the device supports callbacks.
+  bool _hasCallback = false;
+
+  // Pin number of interrupt pin for GPIO extender devices.  The extender module will pull this
+  //  pin low if an input changes state.
+  int16_t _gpioInterruptPin = -1;
+
+  // Static support function for subclass creation
+  static void addDevice(IODevice *newDevice);
+
+  // Current state of device
+  DeviceStateEnum _deviceState = DEVSTATE_DORMANT;
+
+private:
+  // Method to check whether the vpin corresponds to this device
+  bool owns(VPIN vpin);
+  // Method to find device handling Vpin
+  static IODevice *findDevice(VPIN vpin);
+
+  IODevice *_nextDevice = 0;
+  unsigned long _nextEntryTime;
+  static IODevice *_firstDevice;
+
+  static IODevice *_nextLoopDevice;
+  static bool _initPhase;
+};
+
+
+/////////////////////////////////////////////////////////////////////////////////////////////////////
+/*
+ * IODevice subclass for PCA9685 16-channel PWM module.
+ */
+ 
+class PCA9685 : public IODevice {
+public:
+  static void create(VPIN vpin, int nPins, uint8_t I2CAddress);
+  // Constructor
+  PCA9685(VPIN vpin, int nPins, uint8_t I2CAddress);
+  enum ProfileType : uint8_t {
+    Instant = 0,  // Moves immediately between positions (if duration not specified)
+    UseDuration = 0, // Use specified duration
+    Fast = 1,     // Takes around 500ms end-to-end
+    Medium = 2,   // 1 second end-to-end
+    Slow = 3,     // 2 seconds end-to-end
+    Bounce = 4,   // For semaphores/turnouts with a bit of bounce!!
+    NoPowerOff = 0x80, // Flag to be ORed in to suppress power off after move.
+  };
+
+private:
+  // Device-specific initialisation
+  void _begin() override;
+  bool _configure(VPIN vpin, ConfigTypeEnum configType, int paramCount, int params[]) override;
+  // Device-specific write functions.
+  void _write(VPIN vpin, int value) override;
+  void _writeAnalogue(VPIN vpin, int value, uint8_t profile, uint16_t duration) override;
+  int _read(VPIN vpin) override; // returns the digital state or busy status of the device
+  void _loop(unsigned long currentMicros) override;
+  void updatePosition(uint8_t pin);
+  void writeDevice(uint8_t pin, int value);
+  void _display() override;
+
+  uint8_t _I2CAddress; // 0x40-0x43 possible
+
+  struct ServoData {
+    uint16_t activePosition : 12; // Config parameter
+    uint16_t inactivePosition : 12; // Config parameter
+    uint16_t currentPosition : 12;
+    uint16_t fromPosition : 12;
+    uint16_t toPosition : 12; 
+    uint8_t profile;  // Config parameter
+    uint16_t stepNumber; // Index of current step (starting from 0)
+    uint16_t numSteps;  // Number of steps in animation, or 0 if none in progress.
+    uint8_t currentProfile; // profile being used for current animation.
+    uint16_t duration; // time (tenths of a second) for animation to complete.
+  }; // 14 bytes per element, i.e. per pin in use
+  
+  struct ServoData *_servoData [16];
+
+  static const uint8_t _catchupSteps = 5; // number of steps to wait before switching servo off
+  static const byte FLASH _bounceProfile[30];
+
+  const unsigned int refreshInterval = 50; // refresh every 50ms
+
+  // structures for setting up non-blocking writes to servo controller
+  I2CRB requestBlock;
+  uint8_t outputBuffer[5];
+};
+
+/////////////////////////////////////////////////////////////////////////////////////////////////////
+/*
+ * IODevice subclass for DCC accessory decoder.
+ */
+ 
+class DCCAccessoryDecoder: public IODevice {
+public:
+  static void create(VPIN firstVpin, int nPins, int DCCAddress, int DCCSubaddress);
+  // Constructor
+  DCCAccessoryDecoder(VPIN firstVpin, int nPins, int DCCAddress, int DCCSubaddress);
+
+private:
+  // Device-specific write function.
+  void _begin() override;
+  void _write(VPIN vpin, int value) override;
+  void _display() override;
+  int _packedAddress;
+};
+
+
+/////////////////////////////////////////////////////////////////////////////////////////////////////
+/* 
+ *  IODevice subclass for arduino input/output pins.
+ */
+ 
+class ArduinoPins: public IODevice {
+public:
+  static void create(VPIN firstVpin, int nPins) {
+    addDevice(new ArduinoPins(firstVpin, nPins));
+  }
+  
+  // Constructor
+  ArduinoPins(VPIN firstVpin, int nPins);
+
+  static void fastWriteDigital(uint8_t pin, uint8_t value);
+  static bool fastReadDigital(uint8_t pin);
+
+private:
+  // Device-specific pin configuration
+  bool _configure(VPIN vpin, ConfigTypeEnum configType, int paramCount, int params[]) override;
+  // Device-specific write function.
+  void _write(VPIN vpin, int value) override;
+  // Device-specific read functions.
+  int _read(VPIN vpin) override;
+  int _readAnalogue(VPIN vpin) override;
+  void _display() override;
+
+
+  uint8_t *_pinPullups;
+  uint8_t *_pinModes; // each bit is 1 for output, 0 for input
+  uint8_t *_pinInUse; 
+};
+
+/////////////////////////////////////////////////////////////////////////////////////////////////////
+
+#include "IO_MCP23008.h"
+#include "IO_MCP23017.h"
+#include "IO_PCF8574.h"
+
+#endif // iodevice_h

IO_AnalogueInputs.h

@@ -0,0 +1,165 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *  
+ *  This file is part of DCC++EX API
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef io_analogueinputs_h
+#define io_analogueinputs_h
+
+// Uncomment following line to slow the scan cycle down to 1second ADC samples, with
+// diagnostic output of scanned values.
+//#define IO_ANALOGUE_SLOW
+
+#include "IODevice.h"
+#include "I2CManager.h"
+#include "DIAG.h"
+#include "FSH.h"
+
+/**********************************************************************************************
+ * ADS111x class for I2C-connected analogue input modules ADS1113, ADS1114 and ADS1115.
+ * 
+ * ADS1113 and ADS1114 are restricted to 1 input.  ADS1115 has a multiplexer which allows 
+ * any of four input pins to be read by its ADC.
+ * 
+ * The driver polls the device in accordance with the constant 'scanInterval' below.  On first loop
+ * entry, the multiplexer is set to pin A0 and the ADC is triggered.  On second and subsequent
+ * entries, the analogue value is read from the conversion register and then the multiplexer and
+ * ADC are set up to read the next pin.
+ * 
+ * The ADS111x is set up as follows:
+ *    Single-shot scan
+ *    Data rate 128 samples/sec (7.8ms/sample, but scanned every 10ms)
+ *    Comparator off
+ *    Gain FSR=6.144V
+ * The gain means that the maximum input voltage of 5V (when Vss=5V) gives a reading 
+ * of 32767*(5.0/6.144) = 26666.
+ * 
+ * A device is configured by the following:
+ *   ADS111x::create(firstVpin, nPins, i2cAddress);
+ * for example
+ *   ADS111x::create(300, 1, 0x48);  // single-input ADS1113
+ *   ADS111x::create(300, 4, 0x48);  // four-input ADS1115
+ * 
+ * Note: The device is simple and does not need initial configuration, so it should recover from
+ * temporary loss of communications or power.
+ **********************************************************************************************/
+class ADS111x: public IODevice { 
+public:
+  ADS111x(VPIN firstVpin, int nPins, uint8_t i2cAddress) {
+    _firstVpin = firstVpin;
+    _nPins = min(nPins,4);
+    _i2cAddress = i2cAddress;
+    _currentPin = 0;
+    for (int8_t i=0; i<_nPins; i++)
+      _value[i] = -1;
+    addDevice(this);
+  }
+  static void create(VPIN firstVpin, int nPins, uint8_t i2cAddress) {
+    new ADS111x(firstVpin, nPins, i2cAddress);
+  }
+private:
+  void _begin() {
+    // Initialise ADS device
+    if (I2CManager.exists(_i2cAddress)) {
+      _nextState = STATE_STARTSCAN;
+#ifdef DIAG_IO
+      _display();
+#endif
+    } else {
+      DIAG(F("ADS111x device not found, I2C:%x"), _i2cAddress);
+      _deviceState = DEVSTATE_FAILED;
+    }
+  }
+  void _loop(unsigned long currentMicros) override {
+
+    // Check that previous non-blocking write has completed, if not then wait
+    uint8_t status = _i2crb.status;
+    if (status == I2C_STATUS_PENDING) return;  // Busy, so don't do anything.
+    if (status == I2C_STATUS_OK) {
+      switch (_nextState) {
+        case STATE_STARTSCAN:
+          // Configure ADC and multiplexer for next scan.  See ADS111x datasheet for details
+          // of configuration register settings.
+          _outBuffer[0] = 0x01; // Config register address
+          _outBuffer[1] = 0xC0 + (_currentPin << 4); // Trigger single-shot, channel n
+          _outBuffer[2] = 0xA3;           // 250 samples/sec, comparator off
+          // Write command, without waiting for completion.
+          I2CManager.write(_i2cAddress, _outBuffer, 3, &_i2crb);
+
+          delayUntil(currentMicros + scanInterval);
+          _nextState = STATE_STARTREAD;
+          break;
+
+        case STATE_STARTREAD:
+          // Reading the pin value
+          _outBuffer[0] = 0x00;  // Conversion register address
+          I2CManager.read(_i2cAddress, _inBuffer, 2, _outBuffer, 1, &_i2crb); // Read register
+          _nextState = STATE_GETVALUE;
+          break;
+
+        case STATE_GETVALUE:
+          _value[_currentPin] = ((uint16_t)_inBuffer[0] << 8) + (uint16_t)_inBuffer[1];
+          #ifdef IO_ANALOGUE_SLOW
+          DIAG(F("ADS111x pin:%d value:%d"), _currentPin, _value[_currentPin]);
+          #endif
+
+          // Move to next pin
+          if (++_currentPin >= _nPins) _currentPin = 0;
+          _nextState = STATE_STARTSCAN;
+          break;
+        
+        default:
+          break;
+      }
+    } else { // error status
+      DIAG(F("ADS111x I2C:x%d Error:%d %S"), _i2cAddress, status, I2CManager.getErrorMessage(status));
+      _deviceState = DEVSTATE_FAILED;
+    }
+  }
+
+  int _readAnalogue(VPIN vpin) override {
+    int pin = vpin - _firstVpin;
+    return _value[pin];
+  }
+  
+  void _display() override {
+    DIAG(F("ADS111x I2C:x%x Configured on Vpins:%d-%d %S"), _i2cAddress, _firstVpin, _firstVpin+_nPins-1,
+      _deviceState == DEVSTATE_FAILED ? F("OFFLINE") : F(""));
+  }
+
+  // ADC conversion rate is 250SPS, or 4ms per conversion.  Set the period between updates to 10ms. 
+  // This is enough to allow the conversion to reliably complete in time.
+  #ifndef IO_ANALOGUE_SLOW
+  const unsigned long scanInterval = 10000UL;  // Period between successive ADC scans in microseconds.
+  #else
+  const unsigned long scanInterval = 1000000UL;  // Period between successive ADC scans in microseconds.
+  #endif
+  enum : uint8_t {
+    STATE_STARTSCAN,
+    STATE_STARTREAD, 
+    STATE_GETVALUE,
+  };
+  uint16_t _value[4];
+  uint8_t _i2cAddress;
+  uint8_t _outBuffer[3];
+  uint8_t _inBuffer[2];
+  uint8_t _currentPin;  // ADC pin currently being scanned
+  I2CRB _i2crb;
+  uint8_t _nextState;
+};
+
+#endif // io_analogueinputs_h

IO_DCCAccessory.cpp

@@ -0,0 +1,64 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *  
+ *  This file is part of DCC++EX API
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "DCC.h"
+#include "IODevice.h"
+#include "DIAG.h"
+#include "defines.h"
+
+#define PACKEDADDRESS(addr, subaddr) (((addr) << 2)  + (subaddr))
+#define ADDRESS(packedaddr) ((packedaddr) >> 2)
+#define SUBADDRESS(packedaddr) ((packedaddr) % 4)
+
+void DCCAccessoryDecoder::create(VPIN vpin, int nPins, int DCCAddress, int DCCSubaddress) {
+  new DCCAccessoryDecoder(vpin, nPins, DCCAddress, DCCSubaddress);
+}
+
+// Constructors
+DCCAccessoryDecoder::DCCAccessoryDecoder(VPIN vpin, int nPins, int DCCAddress, int DCCSubaddress) {
+   _firstVpin = vpin;
+  _nPins = nPins;
+  _packedAddress = PACKEDADDRESS(DCCAddress, DCCSubaddress);
+  addDevice(this);
+}
+
+void DCCAccessoryDecoder::_begin() {
+#if defined(DIAG_IO)
+  _display();
+#endif
+}
+
+// Device-specific write function.  State 1=closed, 0=thrown.  Adjust for RCN-213 compliance
+void DCCAccessoryDecoder::_write(VPIN id, int state) {
+  int packedAddress = _packedAddress + id - _firstVpin;
+  #ifdef DIAG_IO
+  DIAG(F("DCC Write Linear Address:%d State:%d"), packedAddress, state);
+  #endif
+#if !defined(DCC_ACCESSORY_RCN_213)
+  state = !state;
+#endif
+  DCC::setAccessory(ADDRESS(packedAddress), SUBADDRESS(packedAddress), state);
+}
+
+void DCCAccessoryDecoder::_display() {
+  int endAddress = _packedAddress + _nPins - 1;
+  DIAG(F("DCCAccessoryDecoder Configured on Vpins:%d-%d Addresses %d/%d-%d/%d)"), _firstVpin, _firstVpin+_nPins-1,
+      ADDRESS(_packedAddress), SUBADDRESS(_packedAddress), ADDRESS(endAddress), SUBADDRESS(endAddress));
+}
+

IO_DFPlayer.h

@@ -0,0 +1,255 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *  
+ *  This file is part of DCC++EX API
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/*
+ * DFPlayer is an MP3 player module with an SD card holder.  It also has an integrated
+ * amplifier, so it only needs a power supply and a speaker.
+ * 
+ * This driver allows the device to be controlled through IODevice::write() and 
+ * IODevice::writeAnalogue() calls.
+ * 
+ * The driver is configured as follows:
+ * 
+ *       DFPlayer::create(firstVpin, nPins, Serialn);
+ * 
+ * Where firstVpin is the first vpin reserved for reading the device,
+ *       nPins is the number of pins to be allocated (max 5)
+ *   and Serialn is the name of the Serial port connected to the DFPlayer (e.g. Serial1).
+ * 
+ * Example:
+ *   In mySetup function within mySetup.cpp:
+ *       DFPlayer::create(3500, 5, Serial1);
+ * 
+ * Writing an analogue value 0-2999 to the first pin will select a numbered file from the SD card;
+ * Writing an analogue value 0-30 to the second pin will set the volume of the output;
+ * Writing a digital value to the first pin will play or stop the file;
+ * Reading a digital value from any pin will return true(1) if the player is playing, false(0) otherwise.
+ * 
+ * From EX-RAIL, the following commands may be used:
+ *   SET(3500)      -- starts playing the first file on the SD card
+ *   SET(3501)      -- starts playing the second file on the SD card
+ *   etc.
+ *   RESET(3500)    -- stops all playing on the player
+ *   WAITFOR(3500)  -- wait for the file currently being played by the player to complete
+ *   SERVO(3500,23,0)  -- plays file 23 at current volume
+ *   SERVO(3500,23,30)  -- plays file 23 at volume 30 (maximum)
+ *   SERVO(3501,20,0)   -- Sets the volume to 20
+ * 
+ * NB The DFPlayer's serial lines are not 5V safe, so connecting the Arduino TX directly 
+ * to the DFPlayer's RX terminal will cause lots of noise over the speaker, or worse.
+ * A 1k resistor in series with the module's RX terminal will alleviate this.
+ */
+
+#ifndef IO_DFPlayer_h
+#define IO_DFPlayer_h
+
+#include "IODevice.h"
+
+class DFPlayer : public IODevice {
+private: 
+  HardwareSerial *_serial;
+  bool _playing = false;
+  uint8_t _inputIndex = 0;
+  unsigned long _commandSendTime; // Allows timeout processing
+
+public:
+  // Constructor
+  DFPlayer(VPIN firstVpin, int nPins, HardwareSerial &serial) :
+    IODevice(firstVpin, nPins),
+    _serial(&serial) 
+  {
+    addDevice(this);
+  }
+
+  static void create(VPIN firstVpin, int nPins, HardwareSerial &serial) {
+    new DFPlayer(firstVpin, nPins, serial);
+  }
+
+protected:
+  void _begin() override {
+    _serial->begin(9600);
+    _deviceState = DEVSTATE_INITIALISING;
+
+    // Send a query to the device to see if it responds
+    sendPacket(0x42); 
+    _commandSendTime = micros();
+  }
+
+  void _loop(unsigned long currentMicros) override {
+    // Check for incoming data on _serial, and update busy flag accordingly.
+    // Expected message is in the form "7F FF 06 3D xx xx xx xx xx EF"
+    while (_serial->available()) {
+      int c = _serial->read();
+      if (c == 0x7E) 
+        _inputIndex = 1;
+      else if ((c==0xFF && _inputIndex==1)
+            || (c==0x3D && _inputIndex==3) 
+            || (_inputIndex >=4 && _inputIndex <= 8))
+        _inputIndex++;
+      else if (c==0x06 && _inputIndex==2) { 
+        // Valid message prefix, so consider the device online
+        if (_deviceState==DEVSTATE_INITIALISING) {
+          _deviceState = DEVSTATE_NORMAL;
+          #ifdef DIAG_IO
+          _display();
+          #endif
+        }
+        _inputIndex++;
+      } else if (c==0xEF && _inputIndex==9) {
+        // End of play
+        if (_playing) {
+          #ifdef DIAG_IO
+          DIAG(F("DFPlayer: Finished"));
+          #endif
+          _playing = false;
+        }
+        _inputIndex = 0;
+      } else 
+        _inputIndex = 0;  // Unrecognised character sequence, start again!
+    }
+    // Check if the initial prompt to device has timed out.  Allow 1 second
+    if (_deviceState == DEVSTATE_INITIALISING && currentMicros - _commandSendTime > 1000000UL) {
+      DIAG(F("DFPlayer device not responding on serial port"));
+      _deviceState = DEVSTATE_FAILED;
+    }
+    delayUntil(currentMicros + 10000); // Only enter every 10ms
+  }
+
+  // Write with value 1 starts playing a song.  The relative pin number is the file number.
+  // Write with value 0 stops playing.
+  void _write(VPIN vpin, int value) override {
+    int pin = vpin - _firstVpin;
+    if (value) {
+      // Value 1, start playing
+      #ifdef DIAG_IO
+      DIAG(F("DFPlayer: Play %d"), pin+1);
+      #endif
+      sendPacket(0x03, pin+1);
+      _playing = true;
+    } else {
+      // Value 0, stop playing
+      #ifdef DIAG_IO
+      DIAG(F("DFPlayer: Stop"));
+      #endif
+      sendPacket(0x16);
+      _playing = false;
+    }
+  }
+
+  // WriteAnalogue on first pin uses the nominated value as a file number to start playing, if file number > 0.
+  // Volume may be specified as second parameter to writeAnalogue.
+  // If value is zero, the player stops playing.  
+  // WriteAnalogue on second pin sets the output volume.
+  void _writeAnalogue(VPIN vpin, int value, uint8_t volume=0, uint16_t=0) override { 
+    uint8_t pin = vpin - _firstVpin;
+ 
+    // Validate parameter.
+    volume = min(30,volume);
+
+    if (pin == 0) {
+      // Play track 
+      if (value > 0) {
+        #ifdef DIAG_IO
+        DIAG(F("DFPlayer: Play %d"), value);
+        #endif
+        sendPacket(0x03, value); // Play track
+        _playing = true;
+        if (volume > 0) {
+          #ifdef DIAG_IO
+          DIAG(F("DFPlayer: Volume %d"), volume);
+          #endif
+          sendPacket(0x06, volume);  // Set volume
+        }
+      } else {
+        #ifdef DIAG_IO
+        DIAG(F("DFPlayer: Stop"));
+        #endif
+        sendPacket(0x16); // Stop play
+        _playing = false;
+      }
+    } else if (pin == 1) {
+      // Set volume (0-30)
+      if (value > 30) value = 30;
+      else if (value < 0) value = 0;
+      #ifdef DIAG_IO
+      DIAG(F("DFPlayer: Volume %d"), value);
+      #endif
+      sendPacket(0x06, value);      
+    }
+  }
+
+  // A read on any pin indicates whether the player is still playing.
+  int _read(VPIN) override {
+    return _playing;
+  }
+
+  void _display() override {
+    DIAG(F("DFPlayer Configured on Vpins:%d-%d %S"), _firstVpin, _firstVpin+_nPins-1,
+      (_deviceState==DEVSTATE_FAILED) ? F("OFFLINE") : F(""));
+  }
+  
+private:
+  // 7E FF 06 0F 00 01 01 xx xx EF
+  // 0	->	7E is start code
+  // 1	->	FF is version
+  // 2	->	06 is length
+  // 3	->	0F is command
+  // 4	->	00 is no receive
+  // 5~6	->	01 01 is argument
+  // 7~8	->	checksum = 0 - ( FF+06+0F+00+01+01 )
+  // 9	->	EF is end code
+
+  void sendPacket(uint8_t command, uint16_t arg = 0)
+  {
+    uint8_t out[] = { 0x7E,
+        0xFF,
+        06,
+        command,
+        00,
+        static_cast<uint8_t>(arg >> 8),
+        static_cast<uint8_t>(arg & 0x00ff),
+        00,
+        00,
+        0xEF };
+
+    setChecksum(out);
+
+    _serial->write(out, sizeof(out));
+  }
+
+  uint16_t calcChecksum(uint8_t* packet)
+  {
+    uint16_t sum = 0;
+    for (int i = 1; i < 7; i++)
+    {
+      sum += packet[i];
+    }
+    return -sum;
+  }
+
+  void setChecksum(uint8_t* out)
+  {
+    uint16_t sum = calcChecksum(out);
+
+    out[7] = (sum >> 8);
+    out[8] = (sum & 0xff);
+  }
+};
+
+#endif // IO_DFPlayer_h

IO_ExampleSerial.cpp

@@ -0,0 +1,129 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *  
+ *  This file is part of DCC++EX API
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <Arduino.h>
+#include "IO_ExampleSerial.h"
+#include "FSH.h"
+
+// Constructor
+IO_ExampleSerial::IO_ExampleSerial(VPIN firstVpin, int nPins, HardwareSerial *serial, unsigned long baud) {
+  _firstVpin = firstVpin;
+  _nPins = nPins;
+  _pinValues = (uint16_t *)calloc(_nPins, sizeof(uint16_t));
+  _baud = baud;
+  
+  // Save reference to serial port driver
+  _serial = serial;
+
+  addDevice(this);
+}
+
+// Static create method for one module.
+void IO_ExampleSerial::create(VPIN firstVpin, int nPins, HardwareSerial *serial, unsigned long baud) {
+  new IO_ExampleSerial(firstVpin, nPins, serial, baud);
+}
+
+// Device-specific initialisation
+void IO_ExampleSerial::_begin() {
+  _serial->begin(_baud);
+#if defined(DIAG_IO)
+  _display();
+#endif
+
+  // Send a few # characters to the output
+  for (uint8_t i=0; i<3; i++)
+    _serial->write('#');
+}
+
+// Device-specific write function.  Write a string in the form "#Wm,n#"
+//  where m is the vpin number, and n is the value.
+void IO_ExampleSerial::_write(VPIN vpin, int value) {
+  int pin = vpin -_firstVpin;
+  #ifdef DIAG_IO
+  DIAG(F("IO_ExampleSerial::_write Pin:%d Value:%d"), (int)vpin, value);
+  #endif
+  // Send a command string over the serial line
+  _serial->print('#');
+  _serial->print('W');
+  _serial->print(pin);
+  _serial->print(',');
+  _serial->print(value);
+  _serial->println('#');
+  DIAG(F("ExampleSerial Sent command, p1=%d, p2=%d"), vpin, value);
+ }
+
+// Device-specific read function.
+int IO_ExampleSerial::_read(VPIN vpin) {
+
+  // Return a value for the specified vpin.
+  int result = _pinValues[vpin-_firstVpin];
+
+  return result;
+}
+
+// Loop function to do background scanning of the input port.  State 
+//  machine parses the incoming command as it is received.  Command
+//  is in the form "#Nm,n#" where m is the index and n is the value.
+void IO_ExampleSerial::_loop(unsigned long currentMicros) {
+  (void)currentMicros;  // Suppress compiler warnings
+  if (_serial->available()) {
+    // Input data available to read.  Read a character.
+    char c = _serial->read();
+    switch (_inputState) {
+      case 0: // Waiting for start of command
+        if (c == '#')  // Start of command received.
+          _inputState = 1;
+        break;
+      case 1: // Expecting command character
+        if (c == 'N') { // 'Notify' character received
+          _inputState = 2;
+          _inputValue = _inputIndex = 0;
+        } else
+          _inputState = 0; // Unexpected char, reset
+        break;
+      case 2: // reading first parameter (index)
+        if (isdigit(c))
+          _inputIndex = _inputIndex * 10 + (c-'0');
+        else if (c==',') 
+          _inputState = 3;
+        else
+          _inputState = 0; // Unexpected char, reset
+        break;
+      case 3: // reading reading second parameter (value)
+        if (isdigit(c)) 
+          _inputValue = _inputValue * 10 - (c-'0');
+        else if (c=='#') { // End of command
+          // Complete command received, do something with it.
+          DIAG(F("ExampleSerial Received command, p1=%d, p2=%d"), _inputIndex, _inputValue);
+          if (_inputIndex < _nPins) { // Store value
+            _pinValues[_inputIndex] = _inputValue;
+          }
+          _inputState = 0; // Done, start again.
+        } else
+          _inputState = 0; // Unexpected char, reset
+        break;
+    }
+  }
+}
+
+void IO_ExampleSerial::_display() {
+  DIAG(F("IO_ExampleSerial Configured on VPins:%d-%d"), (int)_firstVpin, 
+    (int)_firstVpin+_nPins-1);
+}
+

IO_ExampleSerial.h

@@ -0,0 +1,58 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *  
+ *  This file is part of DCC++EX API
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/*
+ * To declare a device instance, 
+ *    IO_ExampleSerial myDevice(1000, 10, Serial3, 9600);
+ * or to create programmatically,
+ *    IO_ExampleSerial::create(1000, 10, Serial3, 9600);
+ * 
+ * (uses VPINs 1000-1009, talke on Serial 3 at 9600 baud.)
+ * 
+ * See IO_ExampleSerial.cpp for the protocol used over the serial line.
+ * 
+ */
+
+#ifndef IO_EXAMPLESERIAL_H
+#define IO_EXAMPLESERIAL_H
+
+#include "IODevice.h"
+
+class IO_ExampleSerial : public IODevice {
+public:
+  IO_ExampleSerial(VPIN firstVpin, int nPins, HardwareSerial *serial, unsigned long baud);
+  static void create(VPIN firstVpin, int nPins, HardwareSerial *serial, unsigned long baud);  
+
+protected:
+  void _begin() override;
+  void _loop(unsigned long currentMicros) override;
+  void _write(VPIN vpin, int value) override;
+  int _read(VPIN vpin) override;
+  void _display() override;
+
+private:
+  HardwareSerial *_serial;
+  uint8_t _inputState = 0;
+  int _inputIndex = 0;
+  int _inputValue = 0;
+  uint16_t *_pinValues; // Pointer to block of memory containing pin values
+  unsigned long _baud;
+};
+
+#endif // IO_EXAMPLESERIAL_H

IO_GPIOBase.h

@@ -0,0 +1,249 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *  
+ *  This file is part of DCC++EX API
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef IO_GPIOBASE_H
+#define IO_GPIOBASE_H
+
+#include "IODevice.h"
+#include "I2CManager.h"
+#include "DIAG.h"
+
+// GPIOBase is defined as a class template.  This allows it to be instantiated by
+// subclasses with different types, according to the number of pins on the GPIO module.
+// For example, GPIOBase<uint8_t> for 8 pins, GPIOBase<uint16_t> for 16 pins etc.
+// A module with up to 64 pins can be handled in this way (uint64_t).
+
+template <class T>
+class GPIOBase : public IODevice {
+
+protected:
+  // Constructor
+  GPIOBase(FSH *deviceName, VPIN firstVpin, uint8_t nPins, uint8_t I2CAddress, int interruptPin);
+  // Device-specific initialisation
+  void _begin() override;
+  // Device-specific pin configuration function.  
+  bool _configure(VPIN vpin, ConfigTypeEnum configType, int paramCount, int params[]) override;
+  // Pin write function.
+  void _write(VPIN vpin, int value) override;
+  // Pin read function.
+  int _read(VPIN vpin) override;
+  void _display() override;
+  void _loop(unsigned long currentMicros) override;
+
+  // Data fields
+  uint8_t _I2CAddress; 
+  // Allocate enough space for all input pins
+  T _portInputState; 
+  T _portOutputState;
+  T _portMode;
+  T _portPullup;
+  T _portInUse;
+  // Interval between refreshes of each input port
+  static const int _portTickTime = 4000;
+
+  // Virtual functions for interfacing with I2C GPIO Device
+  virtual void _writeGpioPort() = 0;
+  virtual void _readGpioPort(bool immediate=true) = 0;
+  virtual void _writePullups() {};
+  virtual void _writePortModes() {};
+  virtual void _setupDevice() {};
+  virtual void _processCompletion(uint8_t status) {
+    (void)status; // Suppress compiler warning
+  };
+
+  I2CRB requestBlock;
+  FSH *_deviceName;
+};
+
+// Because class GPIOBase is a template, the implementation (below) must be contained within the same
+// file as the class declaration (above).  Otherwise it won't compile!
+
+// Constructor
+template <class T>
+GPIOBase<T>::GPIOBase(FSH *deviceName, VPIN firstVpin, uint8_t nPins, uint8_t I2CAddress, int interruptPin) :
+  IODevice(firstVpin, nPins)
+{
+  _deviceName = deviceName;
+  _I2CAddress = I2CAddress;
+  _gpioInterruptPin = interruptPin;
+  _hasCallback = true;
+  // Add device to list of devices.
+  addDevice(this);
+}
+
+template <class T>
+void GPIOBase<T>::_begin() {
+  // Configure pin used for GPIO extender notification of change (if allocated)
+  if (_gpioInterruptPin >= 0) 
+    pinMode(_gpioInterruptPin, INPUT_PULLUP);
+
+  I2CManager.begin();
+  I2CManager.setClock(400000);
+  if (I2CManager.exists(_I2CAddress)) {
+#if defined(DIAG_IO)
+    _display();
+#endif
+    _portMode = 0;  // default to input mode
+    _portPullup = -1; // default to pullup enabled
+    _portInputState = -1;
+    _portInUse = 0;
+    _setupDevice();
+    _deviceState = DEVSTATE_NORMAL;
+  } else {
+    DIAG(F("%S I2C:x%x Device not detected"), _deviceName, _I2CAddress);
+    _deviceState = DEVSTATE_FAILED;
+  }
+}
+
+// Configuration parameters for inputs: 
+//  params[0]: enable pullup
+//  params[1]: invert input (optional)
+template <class T>
+bool GPIOBase<T>::_configure(VPIN vpin, ConfigTypeEnum configType, int paramCount, int params[]) {
+  if (configType != CONFIGURE_INPUT) return false;
+  if (paramCount == 0 || paramCount > 1) return false;
+  bool pullup = params[0];
+  int pin = vpin - _firstVpin;
+  #ifdef DIAG_IO
+  DIAG(F("%S I2C:x%x Config Pin:%d Val:%d"), _deviceName, _I2CAddress, pin, pullup);
+  #endif
+  uint16_t mask = 1 << pin;
+  if (pullup) 
+    _portPullup |= mask;
+  else
+    _portPullup &= ~mask;
+  // Mark that port has been accessed
+  _portInUse |= mask;
+  // Set input mode
+  _portMode &= ~mask;
+
+  // Call subclass's virtual function to write to device
+  _writePortModes();
+  _writePullups();
+  // Port change will be notified on next loop entry.
+
+  return true;
+}
+
+// Periodically read the input port
+template <class T>
+void GPIOBase<T>::_loop(unsigned long currentMicros) {
+  T lastPortStates = _portInputState;
+  if (_deviceState == DEVSTATE_SCANNING && !requestBlock.isBusy()) {
+    uint8_t status = requestBlock.status;
+    if (status == I2C_STATUS_OK) {
+      _deviceState = DEVSTATE_NORMAL;
+    } else {
+      _deviceState = DEVSTATE_FAILED;
+      DIAG(F("%S I2C:x%x Error:%d %S"), _deviceName, _I2CAddress, status, 
+        I2CManager.getErrorMessage(status));
+    }
+    _processCompletion(status);
+  // Set unused pin and write mode pin value to 1
+    _portInputState |= ~_portInUse | _portMode;
+
+    // Scan for changes in input states and invoke callback (if present)
+    T differences = lastPortStates ^ _portInputState;
+    if (differences && IONotifyCallback::hasCallback()) {
+      // Scan for differences bit by bit
+      T mask = 1;
+      for (int pin=0; pin<_nPins; pin++) {
+        if (differences & mask) {
+          // Change detected.
+          IONotifyCallback::invokeAll(_firstVpin+pin, (_portInputState & mask) == 0);
+        }
+        mask <<= 1;
+      }
+    }
+
+    #ifdef DIAG_IO
+    if (differences)
+      DIAG(F("%S I2C:x%x PortStates:%x"), _deviceName, _I2CAddress, _portInputState);
+    #endif
+  }
+
+  // Check if interrupt configured.  If not, or if it is active (pulled down), then
+  //  initiate a scan.
+  if (_gpioInterruptPin < 0 || !digitalRead(_gpioInterruptPin)) {
+    // TODO: Could suppress reads if there are no pins configured as inputs!
+
+    // Read input
+    if (_deviceState == DEVSTATE_NORMAL) {
+      _readGpioPort(false);  // Initiate non-blocking read
+      _deviceState= DEVSTATE_SCANNING;
+    }
+  }
+  // Delay next entry until tick elapsed.
+  delayUntil(currentMicros + _portTickTime);
+}
+
+template <class T>
+void GPIOBase<T>::_display() {
+  DIAG(F("%S I2C:x%x Configured on Vpins:%d-%d %S"), _deviceName, _I2CAddress, 
+    _firstVpin, _firstVpin+_nPins-1, (_deviceState==DEVSTATE_FAILED) ? F("OFFLINE") : F(""));
+}
+
+template <class T>
+void GPIOBase<T>::_write(VPIN vpin, int value) {
+  int pin = vpin - _firstVpin;
+  T mask = 1 << pin;
+  #ifdef DIAG_IO
+  DIAG(F("%S I2C:x%x Write Pin:%d Val:%d"), _deviceName, _I2CAddress, pin, value);
+  #endif
+
+  // Set port mode output if currently not output mode
+  if (!(_portMode & mask)) {
+    _portInUse |= mask;
+    _portMode |= mask;
+    _writePortModes();
+  }
+
+  // Update port output state
+  if (value) 
+    _portOutputState |= mask;
+  else
+    _portOutputState &= ~mask;
+
+  // Call subclass's virtual function to write to device.
+  return _writeGpioPort();
+}
+
+template <class T>
+int GPIOBase<T>::_read(VPIN vpin) {
+  int pin = vpin - _firstVpin;
+  T mask = 1 << pin;
+
+  // Set port mode to input if currently output or first use
+  if ((_portMode | ~_portInUse) & mask) {
+    _portMode &= ~mask;
+    _portInUse |= mask;
+    _writePullups();
+    _writePortModes();
+    // Port won't have been read yet, so read it now.
+    _readGpioPort();
+  // Set unused pin and write mode pin value to 1
+    _portInputState |= ~_portInUse | _portMode;
+    #ifdef DIAG_IO
+    DIAG(F("%S I2C:x%x PortStates:%x"), _deviceName, _I2CAddress, _portInputState);
+    #endif
+  }
+  return (_portInputState & mask) ? 0 : 1;  // Invert state (5v=0, 0v=1)
+}
+
+#endif

IO_HCSR04.h

@@ -0,0 +1,188 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *  
+ *  This file is part of DCC++EX API
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/*
+ * The HC-SR04 module has an ultrasonic transmitter (40kHz) and a receiver.
+ * It is operated through two signal pins.  When the transmit pin is set to 1
+ * for 10us, on the falling edge the transmitter sends a short transmission of
+ * 8 pulses (like a sonar 'ping').  This is reflected off objects and received
+ * by the receiver.  A pulse is sent on the receive pin whose length is equal
+ * to the delay between the transmission of the pulse and the detection of
+ * its echo.  The distance of the reflecting object is calculated by halving
+ * the time (to allow for the out and back distance), then multiplying by the
+ * speed of sound (assumed to be constant).
+ *
+ * This driver polls the HC-SR04 by sending the trigger pulse and then measuring
+ * the length of the received pulse.  If the calculated distance is less than
+ * the threshold, the output state returned by a read() call changes to 1.  If
+ * the distance is greater than the threshold plus a hysteresis margin, the
+ * output changes to 0. The device also supports readAnalogue(), which returns
+ * the measured distance in cm, or 32767 if the distance exceeds the
+ * offThreshold.
+ *
+ * It might be thought that the measurement would be more reliable if interrupts
+ * were disabled while the pulse is being timed.  However, this would affect
+ * other functions in the CS so the measurement is being performed with
+ * interrupts enabled.  Also, we could use an interrupt pin in the Arduino for
+ * the timing, but the same consideration applies.  In any case, the DCC
+ * interrupt occurs once every 58us, so any IRC code is much faster than that.
+ * And 58us corresponds to 1cm in the calculation, so the effect of
+ * interrupts is negligible.
+ *
+ * Note: The timing accuracy required for measuring the pulse length means that
+ * the pins have to be direct Arduino pins; GPIO pins on an IO Extender cannot
+ * provide the required accuracy.
+ */
+
+#ifndef IO_HCSR04_H
+#define IO_HCSR04_H
+
+#include "IODevice.h"
+
+class HCSR04 : public IODevice {
+
+private:
+  // pins must be arduino GPIO pins, not extender pins or HAL pins.
+  int _trigPin = -1;
+  int _echoPin = -1;
+  // Thresholds for setting active state in cm.
+  uint8_t _onThreshold;  // cm
+  uint8_t _offThreshold; // cm
+  // Last measured distance in cm.
+  uint16_t _distance;
+  // Active=1/inactive=0 state 
+  uint8_t _value = 0;
+  // Factor for calculating the distance (cm) from echo time (ms).
+  //  Based on a speed of sound of 345 metres/second.
+  const uint16_t factor = 58; // ms/cm
+
+public:
+  // Constructor perfroms static initialisation of the device object
+  HCSR04 (VPIN vpin, int trigPin, int echoPin, uint16_t onThreshold, uint16_t offThreshold) {
+    _firstVpin = vpin;
+    _nPins = 1;
+    _trigPin = trigPin;
+    _echoPin = echoPin;
+    _onThreshold = onThreshold;
+    _offThreshold = offThreshold;
+    addDevice(this);
+  }
+
+  // Static create function provides alternative way to create object
+  static void create(VPIN vpin, int trigPin, int echoPin, uint16_t onThreshold, uint16_t offThreshold) {
+    new HCSR04(vpin, trigPin, echoPin, onThreshold, offThreshold);
+  }
+
+protected:
+  // _begin function called to perform dynamic initialisation of the device
+  void _begin() override {
+    pinMode(_trigPin, OUTPUT);
+    pinMode(_echoPin, INPUT);
+    ArduinoPins::fastWriteDigital(_trigPin, 0);
+#if defined(DIAG_IO)
+    _display();
+#endif
+  }
+
+  // _read function - just return _value (calculated in _loop).
+  int _read(VPIN vpin) override {
+    (void)vpin;  // avoid compiler warning
+    return _value;
+  }
+
+  int _readAnalogue(VPIN vpin) override {
+    (void)vpin; // avoid compiler warning
+    return _distance;
+  }
+
+  // _loop function - read HC-SR04 once every 50 milliseconds.
+  void _loop(unsigned long currentMicros) override {
+    read_HCSR04device();
+    // Delay next loop entry until 50ms have elapsed.
+    delayUntil(currentMicros + 50000UL);
+  }
+
+  void _display() override {
+    DIAG(F("HCSR04 Configured on Vpin:%d TrigPin:%d EchoPin:%d On:%dcm Off:%dcm"),
+      _firstVpin, _trigPin, _echoPin, _onThreshold, _offThreshold);
+  }
+
+private:
+  // This polls the HC-SR04 device by sending a pulse and measuring the duration of
+  //  the pulse observed on the receive pin.  In order to be kind to the rest of the CS
+  //  software, no interrupts are used and interrupts are not disabled.  The pulse duration
+  //  is measured in a loop, using the micros() function.  Therefore, interrupts from other
+  //  sources may affect the result.  However, interrupts response code in CS typically takes
+  //  much less than the 58us frequency for the DCC interrupt, and 58us corresponds to only 1cm
+  //  in the HC-SR04.
+  //  To reduce chatter on the output, hysteresis is applied on reset: the output is set to 1 when the 
+  //  measured distance is less than the onThreshold, and is set to 0 if the measured distance is
+  //  greater than the offThreshold.
+  //
+  void read_HCSR04device() {
+    // uint16 enough to time up to 65ms
+    uint16_t startTime, waitTime, currentTime, maxTime;  
+
+    // If receive pin is still set on from previous call, abort the read.
+    if (ArduinoPins::fastReadDigital(_echoPin))
+      return;
+
+    // Send 10us pulse to trigger transmitter
+    ArduinoPins::fastWriteDigital(_trigPin, 1);
+    delayMicroseconds(10);
+    ArduinoPins::fastWriteDigital(_trigPin, 0);
+
+    // Wait for receive pin to be set
+    startTime = currentTime = micros();
+    maxTime = factor * _offThreshold * 2;
+    while (!ArduinoPins::fastReadDigital(_echoPin)) {
+      // lastTime = currentTime;
+      currentTime = micros();
+      waitTime = currentTime - startTime;
+      if (waitTime > maxTime) {
+        // Timeout waiting for pulse start, abort the read
+        return;
+      }
+    }
+
+    // Wait for receive pin to reset, and measure length of pulse
+    startTime = currentTime = micros();
+    maxTime = factor * _offThreshold;
+    while (ArduinoPins::fastReadDigital(_echoPin)) {
+      currentTime = micros();
+      waitTime = currentTime - startTime;
+      // If pulse is too long then set return value to zero,
+      //  and finish without waiting for end of pulse.
+      if (waitTime > maxTime) {
+        // Pulse length longer than maxTime, reset value.
+        _value = 0;
+        _distance = 32767;
+        return;
+      }
+    } 
+    // Check if pulse length is below threshold, if so set value.
+    //DIAG(F("HCSR04: Pulse Len=%l Distance=%d"), waitTime, distance);
+    _distance = waitTime / factor; // in centimetres
+    if (_distance < _onThreshold) 
+      _value = 1;
+  }
+
+};
+
+#endif //IO_HCSR04_H

IO_MCP23008.h

@@ -0,0 +1,100 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *  
+ *  This file is part of DCC++EX API
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef IO_MCP23008_H
+#define IO_MCP23008_H
+
+#include "IO_GPIOBase.h"
+
+class MCP23008 : public GPIOBase<uint8_t> {
+public:
+  static void create(VPIN firstVpin, uint8_t nPins, uint8_t I2CAddress, int interruptPin=-1) {
+    new MCP23008(firstVpin, nPins, I2CAddress, interruptPin);
+  }
+
+  // Constructor
+  MCP23008(VPIN firstVpin, uint8_t nPins, uint8_t I2CAddress, int interruptPin=-1)
+    : GPIOBase<uint8_t>((FSH *)F("MCP23008"), firstVpin, min(nPins, 8), I2CAddress, interruptPin) {
+
+    requestBlock.setRequestParams(_I2CAddress, inputBuffer, sizeof(inputBuffer),
+      outputBuffer, sizeof(outputBuffer));
+    outputBuffer[0] = REG_GPIO;
+  }
+  
+private:
+  void _writeGpioPort() override {
+    I2CManager.write(_I2CAddress, 2, REG_GPIO, _portOutputState);
+  }
+  void _writePullups() override {
+    // Set pullups only for in-use pins.  This prevents pullup being set for a pin that
+    //  is intended for use as an output but hasn't been written to yet.
+    I2CManager.write(_I2CAddress, 2, REG_GPPU, _portPullup & _portInUse);  
+  }
+  void _writePortModes() override {
+    // Write 0 to IODIR for in-use pins that are outputs, 1 for others.
+    uint8_t temp = ~(_portMode & _portInUse);
+    I2CManager.write(_I2CAddress, 2, REG_IODIR, temp);
+    // Enable interrupt-on-change for in-use pins that are inputs (_portMode=0)
+    temp = ~_portMode & _portInUse;
+    I2CManager.write(_I2CAddress, 2, REG_INTCON, 0x00);
+    I2CManager.write(_I2CAddress, 2, REG_GPINTEN, temp);
+  }
+  void _readGpioPort(bool immediate) override {
+    if (immediate) {
+      uint8_t buffer;
+      I2CManager.read(_I2CAddress, &buffer, 1, 1, REG_GPIO);
+      _portInputState = buffer;
+    } else {
+      // Queue new request
+      requestBlock.wait(); // Wait for preceding operation to complete
+      // Issue new request to read GPIO register
+      I2CManager.queueRequest(&requestBlock);
+    }
+  }
+  // This function is invoked when an I/O operation on the requestBlock completes.
+  void _processCompletion(uint8_t status) override {
+    if (status == I2C_STATUS_OK) 
+      _portInputState = inputBuffer[0];
+    else  
+      _portInputState = 0xff;
+  }
+  void _setupDevice() override {
+    // IOCON is set ODR=1 (open drain shared interrupt pin), INTPOL=0 (active-Low)
+    I2CManager.write(_I2CAddress, 2, REG_IOCON, 0x04);
+    _writePortModes();
+    _writePullups();
+    _writeGpioPort();
+  }
+ 
+  uint8_t inputBuffer[1];
+  uint8_t outputBuffer[1];
+
+  enum {
+    // Register definitions for MCP23008
+    REG_IODIR=0x00,
+    REG_GPINTEN=0x02,
+    REG_INTCON=0x04,
+    REG_IOCON=0x05,
+    REG_GPPU=0x06,
+    REG_GPIO=0x09,
+  };
+
+};
+
+#endif

IO_MCP23017.h

@@ -0,0 +1,112 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *  
+ *  This file is part of DCC++EX API
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef io_mcp23017_h
+#define io_mcp23017_h
+
+#include "IO_GPIOBase.h"
+#include "FSH.h"
+
+/////////////////////////////////////////////////////////////////////////////////////////////////////
+/*
+ * IODevice subclass for MCP23017 16-bit I/O expander.
+ */
+ 
+class MCP23017 : public GPIOBase<uint16_t> {
+public:
+  static void create(VPIN vpin, int nPins, uint8_t I2CAddress, int interruptPin=-1) {
+    new MCP23017(vpin, min(nPins,16), I2CAddress, interruptPin);
+  }
+  
+  // Constructor
+  MCP23017(VPIN vpin, int nPins, uint8_t I2CAddress, int interruptPin=-1) 
+    : GPIOBase<uint16_t>((FSH *)F("MCP23017"), vpin, nPins, I2CAddress, interruptPin) 
+  {
+    requestBlock.setRequestParams(_I2CAddress, inputBuffer, sizeof(inputBuffer),
+      outputBuffer, sizeof(outputBuffer));
+    outputBuffer[0] = REG_GPIOA;
+  }
+
+private:
+  void _writeGpioPort() override {
+    I2CManager.write(_I2CAddress, 3, REG_GPIOA, _portOutputState, _portOutputState>>8);
+  }
+  void _writePullups() override {
+    // Set pullups only for in-use pins.  This prevents pullup being set for a pin that
+    //  is intended for use as an output but hasn't been written to yet.
+    uint16_t temp = _portPullup & _portInUse;
+    I2CManager.write(_I2CAddress, 3, REG_GPPUA, temp, temp>>8);  
+  }
+  void _writePortModes() override {
+    // Write 0 to IODIR for in-use pins that are outputs, 1 for others.
+    uint16_t temp = ~(_portMode & _portInUse);
+    I2CManager.write(_I2CAddress, 3, REG_IODIRA, temp, temp>>8);
+    // Enable interrupt for in-use pins which are inputs (_portMode=0)
+    temp = ~_portMode & _portInUse;
+    I2CManager.write(_I2CAddress, 3, REG_INTCONA, 0x00, 0x00);
+    I2CManager.write(_I2CAddress, 3, REG_GPINTENA, temp, temp>>8);
+  }
+  void _readGpioPort(bool immediate) override {
+    if (immediate) {
+      uint8_t buffer[2];
+      I2CManager.read(_I2CAddress, buffer, 2, 1, REG_GPIOA);
+      _portInputState = ((uint16_t)buffer[1]<<8) | buffer[0];
+    } else {
+      // Queue new request
+      requestBlock.wait(); // Wait for preceding operation to complete
+      // Issue new request to read GPIO register
+      I2CManager.queueRequest(&requestBlock);
+    }
+  }
+  // This function is invoked when an I/O operation on the requestBlock completes.
+  void _processCompletion(uint8_t status) override {
+    if (status == I2C_STATUS_OK) 
+      _portInputState = ((uint16_t)inputBuffer[1]<<8) | inputBuffer[0];
+    else  
+      _portInputState = 0xffff;
+  }
+
+  void _setupDevice() override {
+    // IOCON is set MIRROR=1, ODR=1 (open drain shared interrupt pin)
+    I2CManager.write(_I2CAddress, 2, REG_IOCON, 0x44);
+    _writePortModes();
+    _writePullups();
+    _writeGpioPort();
+  }
+ 
+  uint8_t inputBuffer[2];
+  uint8_t outputBuffer[1];
+ 
+  enum {
+    REG_IODIRA = 0x00,
+    REG_IODIRB = 0x01,
+    REG_GPINTENA = 0x04,
+    REG_GPINTENB = 0x05,
+    REG_INTCONA = 0x08,
+    REG_INTCONB = 0x09,
+    REG_IOCON = 0x0A,
+    REG_GPPUA = 0x0C,
+    REG_GPPUB = 0x0D,
+    REG_GPIOA = 0x12,
+    REG_GPIOB = 0x13,
+  };
+
+};
+
+#endif

IO_PCA9685.cpp

@@ -0,0 +1,274 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *  
+ *  This file is part of DCC++EX API
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "IODevice.h"
+#include "I2CManager.h"
+#include "DIAG.h"
+
+// REGISTER ADDRESSES
+static const byte PCA9685_MODE1=0x00;      // Mode Register 
+static const byte PCA9685_FIRST_SERVO=0x06;  /** low byte first servo register ON*/
+static const byte PCA9685_PRESCALE=0xFE;     /** Prescale register for PWM output frequency */
+// MODE1 bits
+static const byte MODE1_SLEEP=0x10;   /**< Low power mode. Oscillator off */
+static const byte MODE1_AI=0x20;      /**< Auto-Increment enabled */
+static const byte MODE1_RESTART=0x80; /**< Restart enabled */
+
+static const float FREQUENCY_OSCILLATOR=25000000.0; /** Accurate enough for our purposes  */
+static const uint8_t PRESCALE_50HZ = (uint8_t)(((FREQUENCY_OSCILLATOR / (50.0 * 4096.0)) + 0.5) - 1);
+static const uint32_t MAX_I2C_SPEED = 1000000L; // PCA9685 rated up to 1MHz I2C clock speed
+
+// Predeclare helper function
+static void writeRegister(byte address, byte reg, byte value);
+
+// Create device driver instance.
+void PCA9685::create(VPIN firstVpin, int nPins, uint8_t I2CAddress) {
+  new PCA9685(firstVpin, nPins, I2CAddress);
+}
+
+// Configure a port on the PCA9685.
+bool PCA9685::_configure(VPIN vpin, ConfigTypeEnum configType, int paramCount, int params[]) {
+  if (configType != CONFIGURE_SERVO) return false;
+  if (paramCount != 5) return false;
+  #ifdef DIAG_IO
+  DIAG(F("PCA9685 Configure VPIN:%d Apos:%d Ipos:%d Profile:%d Duration:%d state:%d"), 
+    vpin, params[0], params[1], params[2], params[3], params[4]);
+  #endif
+
+  int8_t pin = vpin - _firstVpin;
+  struct ServoData *s = _servoData[pin];
+  if (s == NULL) { 
+    _servoData[pin] = (struct ServoData *)calloc(1, sizeof(struct ServoData));
+    s = _servoData[pin];
+    if (!s) return false; // Check for failed memory allocation
+  }
+
+  s->activePosition = params[0];
+  s->inactivePosition = params[1];
+  s->profile = params[2];
+  s->duration = params[3];
+  int state = params[4];
+
+  if (state != -1) {
+    // Position servo to initial state
+    _writeAnalogue(vpin, state ? s->activePosition : s->inactivePosition, 0, 0);
+  } 
+  return true;
+}
+
+// Constructor
+PCA9685::PCA9685(VPIN firstVpin, int nPins, uint8_t I2CAddress) {
+  _firstVpin = firstVpin;
+  _nPins = min(nPins, 16);
+  _I2CAddress = I2CAddress;
+  // To save RAM, space for servo configuration is not allocated unless a pin is used.
+  // Initialise the pointers to NULL.
+  for (int i=0; i<_nPins; i++)
+    _servoData[i] = NULL;
+
+  addDevice(this);
+
+  // Initialise structure used for setting pulse rate
+  requestBlock.setWriteParams(_I2CAddress, outputBuffer, sizeof(outputBuffer));
+}
+
+// Device-specific initialisation
+void PCA9685::_begin() {
+  I2CManager.begin();
+  I2CManager.setClock(1000000); // Nominally able to run up to 1MHz on I2C
+          // In reality, other devices including the Arduino will limit 
+          // the clock speed to a lower rate.
+
+  // Initialise I/O module here.
+  if (I2CManager.exists(_I2CAddress)) {
+    writeRegister(_I2CAddress, PCA9685_MODE1, MODE1_SLEEP | MODE1_AI);    
+    writeRegister(_I2CAddress, PCA9685_PRESCALE, PRESCALE_50HZ);   // 50Hz clock, 20ms pulse period.
+    writeRegister(_I2CAddress, PCA9685_MODE1, MODE1_AI);
+    writeRegister(_I2CAddress, PCA9685_MODE1, MODE1_RESTART | MODE1_AI);
+    // In theory, we should wait 500us before sending any other commands to each device, to allow
+    // the PWM oscillator to get running.  However, we don't do any specific wait, as there's 
+    // plenty of other stuff to do before we will send a command.
+  #if defined(DIAG_IO)
+    _display();
+  #endif
+  } else
+    _deviceState = DEVSTATE_FAILED;
+}
+
+// Device-specific write function, invoked from IODevice::write().  
+// For this function, the configured profile is used.
+void PCA9685::_write(VPIN vpin, int value) {
+  if (_deviceState == DEVSTATE_FAILED) return;
+  #ifdef DIAG_IO
+  DIAG(F("PCA9685 Write Vpin:%d Value:%d"), vpin, value);
+  #endif
+  int pin = vpin - _firstVpin;
+  if (value) value = 1;
+
+  struct ServoData *s = _servoData[pin];
+  if (s != NULL) {
+    // Use configured parameters
+    _writeAnalogue(vpin, value ? s->activePosition : s->inactivePosition, s->profile, s->duration);
+  } // else { /* ignorethe request */ }
+}
+
+// Device-specific writeAnalogue function, invoked from IODevice::writeAnalogue().
+// Profile is as follows:
+//  Bit 7:     0=Set PWM to 0% to power off servo motor when finished
+//             1=Keep PWM pulses on (better when using PWM to drive an LED)
+//  Bits 6-0:  0           Use specified duration (defaults to 0 deciseconds)
+//             1 (Fast)    Move servo in 0.5 seconds
+//             2 (Medium)  Move servo in 1.0 seconds
+//             3 (Slow)    Move servo in 2.0 seconds
+//             4 (Bounce)  Servo 'bounces' at extremes.
+//            
+void PCA9685::_writeAnalogue(VPIN vpin, int value, uint8_t profile, uint16_t duration) {
+  if (_deviceState == DEVSTATE_FAILED) return;
+  #ifdef DIAG_IO
+  DIAG(F("PCA9685 WriteAnalogue Vpin:%d Value:%d Profile:%d Duration:%d"), 
+    vpin, value, profile, duration);
+  #endif
+  int pin = vpin - _firstVpin;
+  if (value > 4095) value = 4095;
+  else if (value < 0) value = 0;
+
+  struct ServoData *s = _servoData[pin];
+  if (s == NULL) {
+    // Servo pin not configured, so configure now using defaults
+    s = _servoData[pin] = (struct ServoData *) calloc(sizeof(struct ServoData), 1);
+    if (s == NULL) return;  // Check for memory allocation failure
+    s->activePosition = 0;
+    s->inactivePosition = 0;
+    s->currentPosition = value;
+    s->profile = Instant;  // Use instant profile (but not this time)
+  }
+
+  // Animated profile.  Initiate the appropriate action.
+  s->currentProfile = profile;
+  uint8_t profileValue = profile & ~NoPowerOff;  // Mask off 'don't-power-off' bit.
+  s->numSteps = profileValue==Fast ? 10 :   // 0.5 seconds
+                profileValue==Medium ? 20 : // 1.0 seconds
+                profileValue==Slow ? 40 :   // 2.0 seconds
+                profileValue==Bounce ? sizeof(_bounceProfile)-1 : // ~ 1.5 seconds
+                duration * 2 + 1; // Convert from deciseconds (100ms) to refresh cycles (50ms)
+  s->stepNumber = 0;
+  s->toPosition = value;
+  s->fromPosition = s->currentPosition;
+}
+
+// _read returns true if the device is currently in executing an animation, 
+//  changing the output over a period of time.
+int PCA9685::_read(VPIN vpin) {
+  if (_deviceState == DEVSTATE_FAILED) return 0;
+  int pin = vpin - _firstVpin;
+  struct ServoData *s = _servoData[pin];
+  if (s == NULL) 
+    return false; // No structure means no animation!
+  else
+    return (s->stepNumber < s->numSteps);
+}
+
+void PCA9685::_loop(unsigned long currentMicros) {
+  for (int pin=0; pin<_nPins; pin++) {
+    updatePosition(pin);
+  }
+  delayUntil(currentMicros + refreshInterval * 1000UL);
+}
+
+// Private function to reposition servo
+// TODO: Could calculate step number from elapsed time, to allow for erratic loop timing.
+void PCA9685::updatePosition(uint8_t pin) {
+  struct ServoData *s = _servoData[pin];
+  
+  if (s == NULL) return; // No pin configuration/state data
+
+  if (s->numSteps == 0) return; // No animation in progress
+
+  if (s->stepNumber == 0 && s->fromPosition == s->toPosition) {
+    // Go straight to end of sequence, output final position.
+    s->stepNumber = s->numSteps-1;
+  }
+
+  if (s->stepNumber < s->numSteps) {
+    // Animation in progress, reposition servo
+    s->stepNumber++;
+    if ((s->currentProfile & ~NoPowerOff) == Bounce) {
+      // Retrieve step positions from array in flash
+      byte profileValue = GETFLASH(&_bounceProfile[s->stepNumber]);
+      s->currentPosition = map(profileValue, 0, 100, s->fromPosition, s->toPosition);
+    } else {
+      // All other profiles - calculate step by linear interpolation between from and to positions.
+      s->currentPosition = map(s->stepNumber, 0, s->numSteps, s->fromPosition, s->toPosition);
+    }
+    // Send servo command
+    writeDevice(pin, s->currentPosition);
+  } else if (s->stepNumber < s->numSteps + _catchupSteps) {
+    // We've finished animation, wait a little to allow servo to catch up
+    s->stepNumber++;
+  } else if (s->stepNumber == s->numSteps + _catchupSteps 
+            && s->currentPosition != 0) {
+#ifdef IO_SWITCH_OFF_SERVO
+    if ((s->currentProfile & NoPowerOff) == 0) {
+      // Wait has finished, so switch off PWM to prevent annoying servo buzz
+      writeDevice(pin, 0);
+    }
+#endif
+    s->numSteps = 0;  // Done now.
+  }
+}
+
+// writeDevice takes a pin in range 0 to _nPins-1 within the device, and a value
+// between 0 and 4095 for the PWM mark-to-period ratio, with 4095 being 100%.
+void PCA9685::writeDevice(uint8_t pin, int value) {
+  #ifdef DIAG_IO
+  DIAG(F("PCA9685 I2C:x%x WriteDevice Pin:%d Value:%d"), _I2CAddress, pin, value);
+  #endif
+  // Wait for previous request to complete
+  uint8_t status = requestBlock.wait();
+  if (status != I2C_STATUS_OK) {
+    _deviceState = DEVSTATE_FAILED;
+    DIAG(F("PCA9685 I2C:x%x failed %S"), _I2CAddress, I2CManager.getErrorMessage(status));
+  } else {
+    // Set up new request.
+    outputBuffer[0] = PCA9685_FIRST_SERVO + 4 * pin;
+    outputBuffer[1] = 0;
+    outputBuffer[2] = (value == 4095 ? 0x10 : 0);  // 4095=full on
+    outputBuffer[3] = value & 0xff;
+    outputBuffer[4] = value >> 8;
+    I2CManager.queueRequest(&requestBlock);
+  }
+}
+
+// Display details of this device.
+void PCA9685::_display() {
+  DIAG(F("PCA9685 I2C:x%x Configured on Vpins:%d-%d %S"), _I2CAddress, (int)_firstVpin, 
+    (int)_firstVpin+_nPins-1, (_deviceState==DEVSTATE_FAILED) ? F("OFFLINE") : F(""));
+}
+
+// Internal helper function for this device
+static void writeRegister(byte address, byte reg, byte value) {
+  I2CManager.write(address, 2, reg, value);
+}
+
+// Profile for a bouncing signal or turnout
+// The profile below is in the range 0-100% and should be combined with the desired limits
+// of the servo set by _activePosition and _inactivePosition.  The profile is symmetrical here,
+// i.e. the bounce is the same on the down action as on the up action.  First entry isn't used.
+const byte FLASH PCA9685::_bounceProfile[30] = 
+    {0,2,3,7,13,33,50,83,100,83,75,70,65,60,60,65,74,84,100,83,75,70,70,72,75,80,87,92,97,100};

IO_PCF8574.h

@@ -0,0 +1,102 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *  
+ *  This file is part of DCC++EX API
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/* 
+ * The PCF8574 is a simple device; it only has one register.  The device 
+ * input/output mode and pullup are configured through this, and the 
+ * output state is written and the input state read through it too.
+ * 
+ * This is accomplished by having a weak resistor in series with the output,
+ * and a read-back of the other end of the resistor.  As an output, the 
+ * pin state is set to 1 or 0, and the output voltage goes to +5V or 0V
+ * (through the weak resistor).
+ * 
+ * In order to use the pin as an input, the output is written as
+ * a '1' in order to pull up the resistor.  Therefore the input will be
+ * 1 unless the pin is pulled down externally, in which case it will be 0.
+ * 
+ * As a consequence of this approach, it is not possible to use the device for
+ * inputs without pullups.
+ */
+
+#ifndef IO_PCF8574_H
+#define IO_PCF8574_H
+
+#include "IO_GPIOBase.h"
+
+class PCF8574 : public GPIOBase<uint8_t> {
+public:
+  static void create(VPIN firstVpin, uint8_t nPins, uint8_t I2CAddress, int interruptPin=-1) {
+    new PCF8574(firstVpin, nPins, I2CAddress, interruptPin);
+  }
+
+  PCF8574(VPIN firstVpin, uint8_t nPins, uint8_t I2CAddress, int interruptPin=-1)
+    : GPIOBase<uint8_t>((FSH *)F("PCF8574"), firstVpin, min(nPins, 8), I2CAddress, interruptPin) 
+  {
+    requestBlock.setReadParams(_I2CAddress, inputBuffer, 1);
+  }
+  
+private:
+  // The pin state is '1' if the pin is an input or if it is an output set to 1.  Zero otherwise. 
+  void _writeGpioPort() override {
+    I2CManager.write(_I2CAddress, 1, _portOutputState | ~_portMode);
+  }
+
+  // The PCF8574 handles inputs by applying a weak pull-up when output is driven to '1'.
+  // Therefore, writing '1' in _writePortModes is enough to set the module to input mode 
+  // and enable pull-up.
+  void _writePullups() override { }
+
+  // The pin state is '1' if the pin is an input or if it is an output set to 1.  Zero otherwise. 
+  void _writePortModes() override {
+    I2CManager.write(_I2CAddress, 1, _portOutputState | ~_portMode);
+  }
+
+  // In immediate mode, _readGpioPort reads the device GPIO port and updates _portInputState accordingly.
+  //  When not in immediate mode, it initiates a request using the request block and returns.
+  //  When the request completes, _processCompletion finishes the operation.
+  void _readGpioPort(bool immediate) override {
+    if (immediate) {
+      uint8_t buffer[1];
+      I2CManager.read(_I2CAddress, buffer, 1);
+      _portInputState = ((uint16_t)buffer) & 0xff;
+    } else {
+      requestBlock.wait(); // Wait for preceding operation to complete
+      // Issue new request to read GPIO register
+      I2CManager.queueRequest(&requestBlock);
+    }
+  }
+
+  // This function is invoked when an I/O operation on the requestBlock completes.
+  void _processCompletion(uint8_t status) override {
+    if (status == I2C_STATUS_OK) 
+      _portInputState = ((uint16_t)inputBuffer[0]) & 0xff;
+    else  
+      _portInputState = 0xff; 
+  }
+
+  // Set up device ports
+  void _setupDevice() override { 
+    _writePortModes();
+  }
+ 
+  uint8_t inputBuffer[1];
+};
+
+#endif

IO_VL53L0X.h

@@ -0,0 +1,299 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *  
+ *  This file is part of DCC++EX API
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/*
+ * The VL53L0X Time-Of-Flight sensor operates by sending a short laser pulse and detecting
+ * the reflection of the pulse.  The time between the pulse and the receipt of reflections
+ * is measured and used to determine the distance to the reflecting object.
+ * 
+ * For economy of memory and processing time, this driver includes only part of the code 
+ * that ST provide in their API.  Also, the API code isn't very clear and it is not easy
+ * to identify what operations are useful and what are not. 
+ * The operation shown here doesn't include any calibration, so is probably not as accurate
+ * as using the full driver, but it's probably accurate enough for the purpose.
+ * 
+ * The device driver allocates up to 3 vpins to the device.  A digital read on the first pin
+ * will return a value that indicates whether the object is within the threshold range (1)
+ * or not (0).  An analogue read on the first pin returns the last measured distance (in mm), 
+ * the second pin returns the signal strength, and the third pin returns detected 
+ * ambient light level.  By default the device takes around 60ms to complete a ranging 
+ * operation, so we do a 100ms cycle (10 samples per second).
+ * 
+ * The VL53L0X is initially set to respond to I2C address 0x29.  If you only have one module,
+ * you can use this address.  However, the address can be modified by software.  If
+ * you select another address, that address will be written to the device and used until the device is reset.
+ * 
+ * If you have more than one module, then you will need to specify a digital VPIN (Arduino
+ * digital output or I/O extender pin) which you connect to the module's XSHUT pin.  Now,
+ * when the device driver starts, the XSHUT pin is set LOW to turn the module off.  Once 
+ * all VL53L0X modules are turned off, the driver works through each module in turn by
+ * setting XSHUT to HIGH to turn the module on,, then writing the module's desired I2C address.
+ * In this way, many VL53L0X modules can be connected to the one I2C bus, each one 
+ * using a distinct I2C address.
+ * 
+ * WARNING:  If the device's XSHUT pin is not connected, then it is very prone to noise, 
+ * and the device may even reset when handled.  If you're not using XSHUT, then it's 
+ * best to tie it to +5V.
+ * 
+ * The driver is configured as follows:
+ * 
+ * Single VL53L0X module:
+ *      VL53L0X::create(firstVpin, nPins, i2cAddress, lowThreshold, highThreshold);
+ * Where firstVpin is the first vpin reserved for reading the device,
+ *       nPins is 1, 2 or 3,
+ *       i2cAddress is the address of the device (normally 0x29),
+ *       lowThreshold is the distance at which the digital vpin state is set to 1 (in mm),
+ *   and highThreshold is the distance at which the digital vpin state is set to 0 (in mm).
+ * 
+ * Multiple VL53L0X modules:
+ *       VL53L0X::create(firstVpin, nPins, i2cAddress, lowThreshold, highThreshold, xshutPin);
+ *       ...
+ * Where firstVpin is the first vpin reserved for reading the device,
+ *       nPins is 1, 2 or 3,
+ *       i2cAddress is the address of the device (any valid address except 0x29),
+ *       lowThreshold is the distance at which the digital vpin state is set to 1 (in mm),
+ *       highThreshold is the distance at which the digital vpin state is set to 0 (in mm),
+ *   and xshutPin is the VPIN number corresponding to a digital output that is connected to the
+ *       XSHUT terminal on the module.
+ * 
+ * Example:
+ *   In mySetup function within mySetup.cpp:
+ *      VL53L0X::create(4000, 3, 0x29, 200, 250);
+ *      Sensor::create(4000, 4000, 0);  // Create a sensor
+ * 
+ *   When an object comes within 200mm of the sensor, a message 
+ *      <Q 4000>
+ *   will be sent over the serial USB, and when the object moves more than 250mm from the sensor, 
+ *   a message
+ *      <q 4000>
+ *   will be sent. 
+ * 
+ */
+
+#ifndef IO_VL53L0X_h
+#define IO_VL53L0X_h
+
+#include "IODevice.h"
+
+class VL53L0X : public IODevice {
+private: 
+  uint8_t _i2cAddress;
+  uint16_t _ambient;
+  uint16_t _distance;
+  uint16_t _signal;
+  uint16_t _onThreshold;
+  uint16_t _offThreshold;
+  VPIN _xshutPin;
+  bool _value;
+  uint8_t _nextState = 0;
+  I2CRB _rb;
+  uint8_t _inBuffer[12];
+  uint8_t _outBuffer[2];
+  // State machine states.
+  enum : uint8_t {
+    STATE_INIT = 0,
+    STATE_CONFIGUREADDRESS = 1,
+    STATE_SKIP = 2,
+    STATE_CONFIGUREDEVICE = 3,
+    STATE_INITIATESCAN = 4,
+    STATE_CHECKSTATUS = 5,
+    STATE_GETRESULTS = 6,
+    STATE_DECODERESULTS = 7,
+  };
+
+  // Register addresses
+  enum : uint8_t {
+    VL53L0X_REG_SYSRANGE_START=0x00,
+    VL53L0X_REG_RESULT_INTERRUPT_STATUS=0x13,
+    VL53L0X_REG_RESULT_RANGE_STATUS=0x14,
+    VL53L0X_CONFIG_PAD_SCL_SDA__EXTSUP_HV=0x89,
+    VL53L0X_REG_I2C_SLAVE_DEVICE_ADDRESS=0x8A,
+  };
+  const uint8_t VL53L0X_I2C_DEFAULT_ADDRESS=0x29;
+
+public:
+  VL53L0X(VPIN firstVpin, int nPins, uint8_t i2cAddress, uint16_t onThreshold, uint16_t offThreshold, VPIN xshutPin = VPIN_NONE) {
+    _firstVpin = firstVpin;
+    _nPins = min(nPins, 3);
+    _i2cAddress = i2cAddress;
+    _onThreshold = onThreshold;
+    _offThreshold = offThreshold;
+    _xshutPin = xshutPin;
+    _value = 0;
+    addDevice(this);
+  }
+  static void create(VPIN firstVpin, int nPins, uint8_t i2cAddress, uint16_t onThreshold, uint16_t offThreshold, VPIN xshutPin = VPIN_NONE) {
+    new VL53L0X(firstVpin, nPins, i2cAddress, onThreshold, offThreshold, xshutPin);
+  }
+
+protected:
+  void _begin() override {
+    if (_xshutPin == VPIN_NONE) {
+      // Check if device is already responding on the nominated address.
+      if (I2CManager.exists(_i2cAddress)) {
+        // Yes, it's already on this address, so skip the address initialisation.
+        _nextState = STATE_CONFIGUREDEVICE;
+      } else {
+        _nextState = STATE_INIT;
+      }
+    }
+  }
+
+  void _loop(unsigned long currentMicros) override {
+    uint8_t status;
+    switch (_nextState) {
+      case STATE_INIT:
+        // On first entry to loop, reset this module by pulling XSHUT low.  All modules
+        // will be reset in turn.
+        if (_xshutPin != VPIN_NONE) IODevice::write(_xshutPin, 0);
+        _nextState = STATE_CONFIGUREADDRESS;
+        break;
+      case STATE_CONFIGUREADDRESS:
+        // On second entry, set XSHUT pin high to allow the module to restart.
+        // On the module, there is a diode in series with the XSHUT pin to 
+        // protect the low-voltage pin against +5V.
+        if (_xshutPin != VPIN_NONE) IODevice::write(_xshutPin, 1);
+        // Allow the module time to restart
+        delay(10);
+        // Then write the desired I2C address to the device, while this is the only
+        //  module responding to the default address.
+        I2CManager.write(VL53L0X_I2C_DEFAULT_ADDRESS, 2, VL53L0X_REG_I2C_SLAVE_DEVICE_ADDRESS, _i2cAddress);
+        _nextState = STATE_SKIP;
+        break;
+      case STATE_SKIP:
+        // Do nothing on the third entry.
+        _nextState = STATE_CONFIGUREDEVICE;
+        break;
+      case STATE_CONFIGUREDEVICE:
+        // On next entry, check if device address has been set.
+        if (I2CManager.exists(_i2cAddress)) {
+          #ifdef DIAG_IO
+          _display();
+          #endif
+          // Set 2.8V mode
+          write_reg(VL53L0X_CONFIG_PAD_SCL_SDA__EXTSUP_HV, 
+            read_reg(VL53L0X_CONFIG_PAD_SCL_SDA__EXTSUP_HV) | 0x01);
+        } else {
+          DIAG(F("VL53L0X I2C:x%x device not responding"), _i2cAddress);
+          _deviceState = DEVSTATE_FAILED;
+        }
+        _nextState = STATE_INITIATESCAN;
+        break;
+      case STATE_INITIATESCAN:
+        // Not scanning, so initiate a scan
+        _outBuffer[0] = VL53L0X_REG_SYSRANGE_START;
+        _outBuffer[1] = 0x01;
+        I2CManager.write(_i2cAddress, _outBuffer, 2, &_rb);
+        _nextState = STATE_CHECKSTATUS;
+        break;
+      case STATE_CHECKSTATUS:
+        status = _rb.status;
+        if (status == I2C_STATUS_PENDING) return; // try next time
+        if (status != I2C_STATUS_OK) {
+          DIAG(F("VL53L0X I2C:x%x Error:%d %S"), _i2cAddress, status, I2CManager.getErrorMessage(status));
+          _deviceState = DEVSTATE_FAILED;
+          _value = false;
+        } else
+          _nextState = 2;
+        delayUntil(currentMicros + 95000); // wait for 95 ms before checking.
+        _nextState = STATE_GETRESULTS;
+        break;
+      case STATE_GETRESULTS:
+        // Ranging completed.  Request results
+        _outBuffer[0] = VL53L0X_REG_RESULT_RANGE_STATUS;
+        I2CManager.read(_i2cAddress, _inBuffer, 12, _outBuffer, 1, &_rb);
+        _nextState = 3;
+        delayUntil(currentMicros + 5000); // Allow 5ms to get data
+        _nextState = STATE_DECODERESULTS;
+        break;
+      case STATE_DECODERESULTS:
+        // If I2C write still busy, return.
+        status = _rb.status;
+        if (status == I2C_STATUS_PENDING) return; // try again next time
+        if (status == I2C_STATUS_OK) {
+          if (!(_inBuffer[0] & 1)) return; // device still busy
+          uint8_t deviceRangeStatus = ((_inBuffer[0] & 0x78) >> 3);
+          if (deviceRangeStatus == 0x0b) {
+            // Range status OK, so use data
+            _ambient = makeuint16(_inBuffer[7], _inBuffer[6]);
+            _signal = makeuint16(_inBuffer[9], _inBuffer[8]);
+            _distance = makeuint16(_inBuffer[11], _inBuffer[10]);
+            if (_distance <= _onThreshold) 
+              _value = true;
+            else if (_distance > _offThreshold) 
+              _value = false;
+          }
+        }
+        // Completed. Restart scan on next loop entry.
+        _nextState = STATE_INITIATESCAN;
+        break;
+      default:
+        break;
+    }
+  }
+
+  // For analogue read, first pin returns distance, second pin is signal strength, and third is ambient level.
+  int _readAnalogue(VPIN vpin) override {
+    int pin = vpin - _firstVpin;
+    switch (pin) {
+      case 0:
+        return _distance;
+      case 1:
+        return _signal;
+      case 2:
+        return _ambient;
+      default:
+        return -1;
+    }
+  }
+
+  // For digital read, return zero for all but first pin.
+  int _read(VPIN vpin) override {
+    if (vpin == _firstVpin)
+      return _value;
+    else
+      return 0;
+  }
+
+  void _display() override {
+    DIAG(F("VL53L0X I2C:x%x Configured on Vpins:%d-%d On:%dmm Off:%dmm %S"),
+      _i2cAddress, _firstVpin, _firstVpin+_nPins-1, _onThreshold, _offThreshold,
+      (_deviceState==DEVSTATE_FAILED) ? F("OFFLINE") : F(""));
+  }
+  
+
+private:
+  inline uint16_t makeuint16(byte lsb, byte msb) {
+    return (((uint16_t)msb) << 8) | lsb;
+  }
+  uint8_t write_reg(uint8_t reg, uint8_t data) {
+    // write byte to register
+    uint8_t outBuffer[2];
+    outBuffer[0] = reg;
+    outBuffer[1] = data;
+    return I2CManager.write(_i2cAddress, outBuffer, 2);
+  }
+  uint8_t read_reg(uint8_t reg) {
+    // read byte from register and return value
+    I2CManager.read(_i2cAddress, _inBuffer, 1, &reg, 1);
+    return _inBuffer[0];
+  }
+};
+
+#endif // IO_VL53L0X_h

LCDDisplay.cpp

@@ -74,6 +74,10 @@ void LCDDisplay::loop() {
 LCDDisplay *LCDDisplay::loop2(bool force) {
   if (!lcdDisplay) return NULL;
 
+  // If output device is busy, don't do anything on this loop
+  //  This avoids blocking while waiting for the device to complete.
+  if (isBusy()) return NULL;  
+
   unsigned long currentMillis = millis();
 
   if (!force) {

LCDDisplay.h

@@ -19,15 +19,12 @@
 #ifndef LCDDisplay_h
 #define LCDDisplay_h
 #include <Arduino.h>
+#include "defines.h"
 #include "DisplayInterface.h"
 
-#if __has_include ( "config.h")
-  #include "config.h"
-#endif
-
 // Allow maximum message length to be overridden from config.h
 #if !defined(MAX_MSG_SIZE) 
-#define MAX_MSG_SIZE 16
+#define MAX_MSG_SIZE 20
 #endif
 
 // Set default scroll mode (overridable in config.h)
@@ -39,17 +36,18 @@
 
 class LCDDisplay : public DisplayInterface {
  public:
+  LCDDisplay() {};
   static const int MAX_LCD_ROWS = 8;
   static const int MAX_LCD_COLS = MAX_MSG_SIZE;
   static const long LCD_SCROLL_TIME = 3000;  // 3 seconds
 
   // Internally handled functions
   static void loop();
-  LCDDisplay* loop2(bool force);
+  LCDDisplay* loop2(bool force) override;
-  void setRow(byte line);
+  void setRow(byte line) override;
-  void clear();
+  void clear() override;
 
-  size_t write(uint8_t b);
+  size_t write(uint8_t b) override;
 
 protected:
   uint8_t lcdRows;
@@ -63,6 +61,7 @@ protected:
   virtual void clearNative() = 0;
   virtual void setRowNative(byte line) = 0;
   virtual size_t writeNative(uint8_t b) = 0;
+  virtual bool isBusy() = 0;
 
   unsigned long lastScrollTime = 0;
   int8_t hotRow = 0;

LCD_LCD.h

@@ -1,33 +0,0 @@
-/*
- *  © 2021, Chris Harlow, Neil McKechnie. All rights reserved.
- *  
- *  This file is part of CommandStation-EX
- *
- *  This is free software: you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License as published by
- *  the Free Software Foundation, either version 3 of the License, or
- *  (at your option) any later version.
- *
- *  It is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *  GNU General Public License for more details.
- *
- *  You should have received a copy of the GNU General Public License
- *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
- */
-  #include "LiquidCrystal_I2C.h" 
-  LiquidCrystal_I2C LCDDriver(LCD_DRIVER);  // set the LCD address, cols, rows 
-  // DEVICE SPECIFIC LCDDisplay Implementation for LCD_DRIVER
-  LCDDisplay::LCDDisplay() { 
-    lcdDisplay=this;
-    LCDDriver.init();
-    LCDDriver.backlight();
-    interfake(LCD_DRIVER);
-    clear();
-  }
-  void LCDDisplay::interfake(int p1, int p2, int p3) {(void)p1; (void)p2; lcdRows=p3; }   
-  void LCDDisplay::clearNative() {LCDDriver.clear();}
-  void LCDDisplay::setRowNative(byte row) { LCDDriver.setCursor(0, row); }
-  void LCDDisplay::writeNative(char b){ LCDDriver.write(b); }    
-  void LCDDisplay::displayNative() { LCDDriver.display(); }

LCD_NONE.h

@@ -1,27 +0,0 @@
-/*
- *  © 2021, Chris Harlow, Neil McKechnie. All rights reserved.
- *  
- *  This file is part of CommandStation-EX
- *
- *  This is free software: you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License as published by
- *  the Free Software Foundation, either version 3 of the License, or
- *  (at your option) any later version.
- *
- *  It is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *  GNU General Public License for more details.
- *
- *  You should have received a copy of the GNU General Public License
- *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
- */
-
-// dummy LCD shim to keep linker happy
-  LCDDisplay::LCDDisplay() {} 
-  void LCDDisplay::interfake(int p1, int p2, int p3) {(void)p1; (void)p2; (void)p3;}   
-  void LCDDisplay::setRowNative(byte row) { (void)row;} 
-  void LCDDisplay::clearNative() {}
-  void LCDDisplay::writeNative(char b){ (void)b;} //  
-  void LCDDisplay::displayNative(){}
-  

LCD_OLED.h

@@ -1,73 +0,0 @@
-/*
- *  © 2021, Chris Harlow, Neil McKechnie. All rights reserved.
- *
- *  This file is part of CommandStation-EX
- *
- *  This is free software: you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License as published by
- *  the Free Software Foundation, either version 3 of the License, or
- *  (at your option) any later version.
- *
- *  It is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *  GNU General Public License for more details.
- *
- *  You should have received a copy of the GNU General Public License
- *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
- */
-
-// OLED Implementation of LCDDisplay class
-// Note: this file is optionally included by LCD_Implementation.h
-// It is NOT a .cpp file to prevent it being compiled and demanding libraries
-// even when not needed.
-
-#include "I2CManager.h"
-#include "SSD1306Ascii.h"
-SSD1306AsciiWire LCDDriver;
-
-// DEVICE SPECIFIC LCDDisplay Implementation for OLED
-
-LCDDisplay::LCDDisplay() {
-  // Scan for device on 0x3c and 0x3d.
-  I2CManager.begin();
-  I2CManager.setClock(400000L);  // Set max supported I2C speed
-  for (byte address = 0x3c; address <= 0x3d; address++) {
-    if (I2CManager.exists(address)) {
-      // Device found
-      DIAG(F("OLED display found at 0x%x"), address);
-      interfake(OLED_DRIVER, 0);
-      const DevType *devType;
-      if (lcdCols == 132)
-        devType = &SH1106_128x64;  // Actually 132x64 but treated as 128x64
-      else if (lcdCols == 128 && lcdRows == 4)
-        devType = &Adafruit128x32;
-      else
-        devType = &Adafruit128x64;
-      LCDDriver.begin(devType, address);
-      lcdDisplay = this;
-      LCDDriver.setFont(System5x7);  // Normal 1:1 pixel scale, 8 bits high
-      clear();
-      return;
-    }
-  }
-  DIAG(F("OLED display not found"));
-}
-
-void LCDDisplay::interfake(int p1, int p2, int p3) {
-  lcdCols = p1;
-  lcdRows = p2 / 8;
-  (void)p3;
-}
-
-void LCDDisplay::clearNative() { LCDDriver.clear(); }
-
-void LCDDisplay::setRowNative(byte row) {
-  // Positions text write to start of row 1..n
-  int y = row;
-  LCDDriver.setCursor(0, y);
-}
-
-void LCDDisplay::writeNative(char b) { LCDDriver.write(b); }
-
-void LCDDisplay::displayNative() {}

LCN.cpp

@@ -48,18 +48,16 @@ void LCN::loop() {
     }
     else if (ch == 't' || ch == 'T') { // Turnout opcodes
       if (Diag::LCN) DIAG(F("LCN IN %d%c"),id,(char)ch);
-      Turnout * tt = Turnout::get(id);
+      if (!Turnout::exists(id)) LCNTurnout::create(id);
-      if (!tt) Turnout::create(id, LCN_TURNOUT_ADDRESS, 0);
+      Turnout::setClosedStateOnly(id,ch=='t');
-      if (ch == 't') tt->data.tStatus |= STATUS_ACTIVE;
-      else   tt->data.tStatus &= ~STATUS_ACTIVE;
       Turnout::turnoutlistHash++; // signals ED update of turnout data
       id = 0;
     }
     else if (ch == 'S' || ch == 's') {
       if (Diag::LCN) DIAG(F("LCN IN %d%c"),id,(char)ch);
       Sensor * ss = Sensor::get(id);
-      if (!ss) ss = Sensor::create(id, 255,0); // impossible pin
+      if (!ss) ss = Sensor::create(id, VPIN_NONE, 0); // impossible pin
-      ss->active = ch == 'S';
+      ss->setState(ch == 'S');
       id = 0;
     }
     else  id = 0; // ignore any other garbage from LCN

LiquidCrystal_I2C.cpp

@@ -119,7 +119,7 @@ void LiquidCrystal_I2C::clearNative() {
 
 void LiquidCrystal_I2C::setRowNative(byte row) {
   int row_offsets[] = {0x00, 0x40, 0x14, 0x54};
-  if (row > lcdRows) {
+  if (row >= lcdRows) {
     row = lcdRows - 1;  // we count rows starting w/0
   }
   command(LCD_SETDDRAMADDR | (row_offsets[row]));
@@ -196,7 +196,7 @@ void LiquidCrystal_I2C::send(uint8_t value, uint8_t mode) {
   outputBuffer[len++] = highnib;
   outputBuffer[len++] = lownib|En;
   outputBuffer[len++] = lownib;
-  I2CManager.write(_Addr, outputBuffer, len);
+  I2CManager.write(_Addr, outputBuffer, len);  // Write command synchronously
 }
 
 // write 4 data bits to the HD44780 LCD controller.
@@ -208,12 +208,12 @@ void LiquidCrystal_I2C::write4bits(uint8_t value) {
   uint8_t len = 0;
   outputBuffer[len++] = _data|En;
   outputBuffer[len++] = _data;
-  I2CManager.write(_Addr, outputBuffer, len);
+  I2CManager.write(_Addr, outputBuffer, len);  // Write command synchronously
 }
 
 // write a byte to the PCF8574 I2C interface.  We don't need to set
 // the enable pin for this.
 void LiquidCrystal_I2C::expanderWrite(uint8_t value) {
   outputBuffer[0] = value | _backlightval;
-  I2CManager.write(_Addr, outputBuffer, 1);
+  I2CManager.write(_Addr, outputBuffer, 1);  // Write command synchronously
 }

LiquidCrystal_I2C.h

@@ -66,19 +66,17 @@ class LiquidCrystal_I2C : public LCDDisplay {
 public:
   LiquidCrystal_I2C(uint8_t lcd_Addr,uint8_t lcd_cols,uint8_t lcd_rows);
   void begin();
-  void clearNative();
+  void clearNative() override;
-  void setRowNative(byte line);
+  void setRowNative(byte line) override;
-  size_t writeNative(uint8_t c);
+  size_t writeNative(uint8_t c) override;
   
   void display();
   void noBacklight();
   void backlight();
   
   void command(uint8_t);
-  void init();
 
 private:
-  void init_priv();
   void send(uint8_t, uint8_t);
   void write4bits(uint8_t);
   void expanderWrite(uint8_t);
@@ -89,6 +87,8 @@ private:
   uint8_t _backlightval;
 
   uint8_t outputBuffer[4];
+  // I/O is synchronous, so if this is called we're not busy!
+  bool isBusy() override { return false; } 
 };
 
 #endif

Outputs.cpp

@@ -84,28 +84,43 @@ the state of any outputs being monitored or controlled by a separate interface o
 #include "Outputs.h"
 #include "EEStore.h"
 #include "StringFormatter.h"
+#include "IODevice.h"
+
+///////////////////////////////////////////////////////////////////////////////
+// Static function to print all output states to stream in the form "<Y id state>"
 
-// print all output states to stream
 void Output::printAll(Print *stream){
   for (Output *tt = Output::firstOutput; tt != NULL; tt = tt->nextOutput)
-    StringFormatter::send(stream, F("<Y %d %d>\n"), tt->data.id, tt->data.oStatus);
+    StringFormatter::send(stream, F("<Y %d %d>\n"), tt->data.id, tt->data.active);
 } // Output::printAll
 
-void  Output::activate(int s){
+///////////////////////////////////////////////////////////////////////////////
-  data.oStatus=(s>0);                                               // if s>0, set status to active, else inactive
+// Object method to activate / deactivate the Output state.
-  digitalWrite(data.pin,data.oStatus ^ bitRead(data.iFlag,0));      // set state of output pin to HIGH or LOW depending on whether bit zero of iFlag is set to 0 (ACTIVE=HIGH) or 1 (ACTIVE=LOW)
+
-  if(num>0)
+void  Output::activate(uint16_t s){
-    EEPROM.put(num,data.oStatus);
+  s = (s>0);  // Make 0 or 1
+  data.active = s;                     // if s>0, set status to active, else inactive
+  // set state of output pin to HIGH or LOW depending on whether bit zero of iFlag is set to 0 (ACTIVE=HIGH) or 1 (ACTIVE=LOW)
+  IODevice::write(data.pin, s ^ data.invert);  
+
+  // Update EEPROM if output has been stored.    
+  if(EEStore::eeStore->data.nOutputs > 0 && num > 0)
+    EEPROM.put(num, data.oStatus);
 }
 
 ///////////////////////////////////////////////////////////////////////////////
+// Static function to locate Output object specified by ID 'n'.
+//   Return NULL if not found.
 
 Output* Output::get(uint16_t n){
   Output *tt;
   for(tt=firstOutput;tt!=NULL && tt->data.id!=n;tt=tt->nextOutput);
   return(tt);
 }
+
 ///////////////////////////////////////////////////////////////////////////////
+// Static function to delete Output object specified by ID 'n'.
+//   Return false if not found.
 
 bool Output::remove(uint16_t n){
   Output *tt,*pp=NULL;
@@ -125,52 +140,26 @@ bool Output::remove(uint16_t n){
   }
 
 ///////////////////////////////////////////////////////////////////////////////
+// Static function to load configuration and state of all Outputs from EEPROM
 
 void Output::load(){
-  struct BrokenOutputData bdata;
+  struct OutputData data;
   Output *tt;
-  bool isBroken=1;
-
-  // This is a scary kluge. As we have two formats in EEPROM due to an
-  // earlier bug, we don't know which we encounter now. So we guess
-  // that if in all entries this byte has value of 7 or lower this is
-  // an iFlag and thus the broken format. Otherwise it would be a pin
-  // id. If someone uses only pins 0 to 7 of their arduino, they
-  // loose. This is (if you look at an arduino) however unlikely.
 
   for(uint16_t i=0;i<EEStore::eeStore->data.nOutputs;i++){
-    EEPROM.get(EEStore::pointer()+ i*sizeof(struct BrokenOutputData),bdata);
+    EEPROM.get(EEStore::pointer(),data);
-    if (bdata.iFlag > 7) { // it's a pin and not an iFlag!
+    // Create new object, set current state to default or to saved state from eeprom.
-      isBroken=0;
+    tt=create(data.id, data.pin, data.flags);
-      break;
+    uint8_t state = data.setDefault ? data.defaultValue : data.active;
-    }
+    tt->activate(state);
-  }
-  if ( isBroken ) {
-    for(uint16_t i=0;i<EEStore::eeStore->data.nOutputs;i++){
-      EEPROM.get(EEStore::pointer(),bdata);
-      tt=create(bdata.id,bdata.pin,bdata.iFlag);
-      tt->data.oStatus=bitRead(tt->data.iFlag,1)?bitRead(tt->data.iFlag,2):bdata.oStatus;      // restore status to EEPROM value is bit 1 of iFlag=0, otherwise set to value of bit 2 of iFlag
-      digitalWrite(tt->data.pin,tt->data.oStatus ^ bitRead(tt->data.iFlag,0));
-      pinMode(tt->data.pin,OUTPUT);
-      tt->num=EEStore::pointer();
-      EEStore::advance(sizeof(struct BrokenOutputData));
-    }
-  } else {
-    struct OutputData data;
 
-    for(uint16_t i=0;i<EEStore::eeStore->data.nOutputs;i++){
+    if (tt) tt->num=EEStore::pointer() + offsetof(OutputData, oStatus); // Save pointer to flags within EEPROM
-      EEPROM.get(EEStore::pointer(),data);
+    EEStore::advance(sizeof(tt->data));
-      tt=create(data.id,data.pin,data.iFlag);
-      tt->data.oStatus=bitRead(tt->data.iFlag,1)?bitRead(tt->data.iFlag,2):data.oStatus;      // restore status to EEPROM value is bit 1 of iFlag=0, otherwise set to value of bit 2 of iFlag
-      digitalWrite(tt->data.pin,tt->data.oStatus ^ bitRead(tt->data.iFlag,0));
-      pinMode(tt->data.pin,OUTPUT);
-      tt->num=EEStore::pointer();
-      EEStore::advance(sizeof(struct OutputData));
-    }
   }
 }
 
 ///////////////////////////////////////////////////////////////////////////////
+// Static function to store configuration and state of all Outputs to EEPROM
 
 void Output::store(){
   Output *tt;
@@ -179,19 +168,25 @@ void Output::store(){
   EEStore::eeStore->data.nOutputs=0;
 
   while(tt!=NULL){
-    tt->num=EEStore::pointer();
     EEPROM.put(EEStore::pointer(),tt->data);
+    tt->num=EEStore::pointer() + offsetof(OutputData, oStatus); // Save pointer to flags within EEPROM
     EEStore::advance(sizeof(tt->data));
     tt=tt->nextOutput;
     EEStore::eeStore->data.nOutputs++;
   }
 
 }
-///////////////////////////////////////////////////////////////////////////////
 
-Output *Output::create(uint16_t id, uint8_t pin, uint8_t iFlag, uint8_t v){
+///////////////////////////////////////////////////////////////////////////////
+// Static function to create an Output object
+//   The obscurely named parameter 'v' is 0 if called from the load() function
+//   and 1 if called from the <Z> command processing.
+
+Output *Output::create(uint16_t id, VPIN pin, int iFlag, int v){
   Output *tt;
 
+  if (pin > VPIN_MAX) return NULL;
+  
   if(firstOutput==NULL){
     firstOutput=(Output *)calloc(1,sizeof(Output));
     tt=firstOutput;
@@ -204,20 +199,21 @@ Output *Output::create(uint16_t id, uint8_t pin, uint8_t iFlag, uint8_t v){
   }
 
   if(tt==NULL) return tt;
-  
+  tt->num = 0; // make sure new object doesn't get written to EEPROM until store() command
   tt->data.id=id;
   tt->data.pin=pin;
-  tt->data.iFlag=iFlag;
+  tt->data.flags=iFlag;
-  tt->data.oStatus=0;
 
   if(v==1){
-    tt->data.oStatus=bitRead(tt->data.iFlag,1)?bitRead(tt->data.iFlag,2):0;      // sets status to 0 (INACTIVE) is bit 1 of iFlag=0, otherwise set to value of bit 2 of iFlag
+    // sets status to 0 (INACTIVE) is bit 1 of iFlag=0, otherwise set to value of bit 2 of iFlag
-    digitalWrite(tt->data.pin,tt->data.oStatus ^ bitRead(tt->data.iFlag,0));
+    if (tt->data.setDefault) 
-    pinMode(tt->data.pin,OUTPUT);
+      tt->data.active = tt->data.defaultValue;
+    else
+      tt->data.active = 0;
   }
+  IODevice::write(tt->data.pin, tt->data.active ^ tt->data.invert);
 
   return(tt);
-
 }
 
 ///////////////////////////////////////////////////////////////////////////////

Outputs.h

@@ -20,37 +20,43 @@
 #define Outputs_h
 
 #include <Arduino.h>
+#include "IODevice.h"
 
 struct OutputData {
-  uint8_t oStatus;
+  union {
+    uint8_t oStatus;      // (Bit 0=Invert, Bit 1=Set state to default, Bit 2=default state, Bit 7=active)
+    struct {
+      unsigned int flags : 7; // Bit 0=Invert, Bit 1=Set state to default, Bit 2=default state
+      unsigned int : 1;
+    };
+    struct {
+      unsigned int invert : 1;
+      unsigned int setDefault : 1;
+      unsigned int defaultValue : 1;
+      unsigned int: 4;
+      unsigned int active : 1;
+    };
+  };
   uint16_t id;
-  uint8_t pin; 
+  VPIN pin; 
-  uint8_t iFlag; 
 };
 
-struct BrokenOutputData {
-  uint8_t oStatus;
-  uint8_t id;
-  uint8_t pin;
-  uint8_t iFlag;
-};
 
 class Output{
-
 public:
-  void activate(int s);
+  void activate(uint16_t s);
+  bool isActive();
   static Output* get(uint16_t);
   static bool remove(uint16_t);
   static void load();
   static void store();
-  static Output *create(uint16_t, uint8_t, uint8_t, uint8_t=0);
+  static Output *create(uint16_t, VPIN, int, int=0);
   static Output *firstOutput;
   struct OutputData data;
   Output *nextOutput;
   static void printAll(Print *);
-
 private:
-  int num;  // EEPROM pointer (Chris has no idea what this is all about!)
+  uint16_t num;  // EEPROM address of oStatus in OutputData struct, or zero if not stored.
   
 }; // Output
   

PWMServoDriver.cpp

@@ -1,109 +0,0 @@
-/*
- *  (c) 2020 Chris Harlow. All rights reserved.
- *
- *  This file is part of CommandStation-EX
- *
- *  This is free software: you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License as published by
- *  the Free Software Foundation, either version 3 of the License, or
- *  (at your option) any later version.
- *
- *  It is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *  GNU General Public License for more details.
- *
- *  You should have received a copy of the GNU General Public License
- *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
- */
-/*!
- *  @file PWMServoDriver.cpp
- *
- *  @mainpage Adafruit 16-channel PWM & Servo driver, based on Adafruit_PWMServoDriver
- *
- *  @section intro_sec Introduction
- *
- *  This is a library for the 16-channel PWM & Servo driver.
- *
- *  Designed specifically to work with the Adafruit PWM & Servo driver.
- *  This class contains a very small subset of the Adafruit version which
- *  is relevant to driving simple servos at 50Hz through a number of chained 
- *  servo driver boards (ie servos 0-15 on board 0x40, 16-31 on board 0x41 etc.)
- *  
- *  @section author Author
- *  Chris Harlow (TPL) 
- *
- */
-#include <Arduino.h>
-#include "PWMServoDriver.h"
-#include "DIAG.h"
-#include "I2CManager.h"
-
-
-// REGISTER ADDRESSES
-const byte PCA9685_MODE1=0x00;      // Mode Register 
-const byte PCA9685_FIRST_SERVO=0x06;  /** low byte first servo register ON*/
-const byte PCA9685_PRESCALE=0xFE;     /** Prescale register for PWM output frequency */
-// MODE1 bits
-const byte MODE1_SLEEP=0x10;   /**< Low power mode. Oscillator off */
-const byte MODE1_AI=0x20;      /**< Auto-Increment enabled */
-const byte MODE1_RESTART=0x80; /**< Restart enabled */
-
-const byte PCA9685_I2C_ADDRESS=0x40;      /** First PCA9685 I2C Slave Address */
-const float FREQUENCY_OSCILLATOR=25000000.0; /** Accurate enough for our purposes  */
-const uint8_t PRESCALE_50HZ = (uint8_t)(((FREQUENCY_OSCILLATOR / (50.0 * 4096.0)) + 0.5) - 1);
-const uint32_t MAX_I2C_SPEED = 1000000L; // PCA9685 rated up to 1MHz I2C clock speed
-  
-/*!
- *  @brief  Sets the PWM frequency for a chip to 50Hz for servos
- */
-
-byte PWMServoDriver::setupFlags=0;  // boards that have been initialised
-byte PWMServoDriver::failFlags=0;  // boards that have faild initialisation
-
-bool PWMServoDriver::setup(int board) {
-  if (board>3 || (failFlags & (1<<board))) return false; 
-  if (setupFlags & (1<<board)) return true; 
-  
-  I2CManager.begin();
-  I2CManager.setClock(MAX_I2C_SPEED);
-  
-  uint8_t i2caddr=PCA9685_I2C_ADDRESS + board;
-
-  // Test if device is available
-  byte error = I2CManager.checkAddress(i2caddr);
-  if (error) {
-    DIAG(F("I2C Servo device 0x%x Not Found %d"),i2caddr, error);
-    failFlags|=1<<board;  
-    return false;
-  }
-    
-  //DIAG(F("PWMServoDriver::setup %x prescale=%d"),i2caddr,PRESCALE_50HZ); 
-  writeRegister(i2caddr,PCA9685_MODE1, MODE1_SLEEP | MODE1_AI);    
-  writeRegister(i2caddr,PCA9685_PRESCALE, PRESCALE_50HZ);  
-  writeRegister(i2caddr,PCA9685_MODE1,MODE1_AI);
-  writeRegister(i2caddr,PCA9685_MODE1,  MODE1_RESTART | MODE1_AI);
-  setupFlags|=1<<board;
-  return true;
-}
-
-/*!
- *  @brief  Sets the PWM output to a servo
- */
-void PWMServoDriver::setServo(byte servoNum, uint16_t value) {
-  int board=servoNum/16; 
-  int pin=servoNum%16;
-  
-  if (setup(board)) {
-    DIAG(F("SetServo %d %d"),servoNum,value);  
-    uint8_t buffer[] = {(uint8_t)(PCA9685_FIRST_SERVO + 4 * pin), // 4 registers per pin
-      0, 0, (uint8_t)(value & 0xff), (uint8_t)(value >> 8)};
-    if (value == 4095) buffer[2] = 0x10;   // Full on
-    byte error=I2CManager.write(PCA9685_I2C_ADDRESS + board, buffer, sizeof(buffer));
-    if (error!=0) DIAG(F("SetServo error %d"),error); 
-  }
-}
-
-void PWMServoDriver::writeRegister(uint8_t i2caddr,uint8_t hardwareRegister, uint8_t d) {
-  I2CManager.write(i2caddr, 2, hardwareRegister, d);
-}

PWMServoDriver.h

@@ -1,39 +0,0 @@
-/*
- *  (c) 2020 Chris Harlow. All rights reserved.
- *
- *  This file is part of CommandStation-EX
- *
- *  This is free software: you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License as published by
- *  the Free Software Foundation, either version 3 of the License, or
- *  (at your option) any later version.
- *
- *  It is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *  GNU General Public License for more details.
- *
- *  You should have received a copy of the GNU General Public License
- *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
- */
-/*!
- *  @file PWMServoDriver.h
- *
- *  Used to set servo positions on an I2C bus with 1 or more PCA96685 boards.
- */
-#ifndef PWMServoDriver_H
-#define PWMServoDriver_H
-
-
-class PWMServoDriver {
-public:
-    static void setServo(byte servoNum,  uint16_t pos);
-    
-private:
-  static byte setupFlags; 
-  static byte failFlags; 
-  static bool setup(int board);
-  static void writeRegister(uint8_t i2caddr,uint8_t hardwareRegister, uint8_t d);
-};
-
-#endif

RMFT.h

@@ -0,0 +1,23 @@
+#ifndef RMFT_H
+#define RMFT_H
+
+#if defined(RMFT_ACTIVE)
+ #include "RMFT2.h"
+
+  class RMFT {
+    public:
+      static void inline begin() {RMFT2::begin();}
+      static void inline loop() {RMFT2::loop();}
+  };
+
+  #include "RMFTMacros.h"
+  
+#else 
+  // Dummy RMFT 
+  class RMFT {
+    public:
+      static void inline begin() {}
+      static void inline loop() {}
+  };
+#endif
+#endif

RMFT2.cpp

@@ -0,0 +1,767 @@
+/*
+ *  © 2020,2021 Chris Harlow. All rights reserved.
+ *  
+ *  This file is part of CommandStation-EX
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#include <Arduino.h>
+#include "RMFT2.h"
+#include "DCC.h"
+#include "DCCWaveform.h"
+#include "DIAG.h"
+#include "WiThrottle.h"
+#include "DCCEXParser.h"
+#include "Turnouts.h"
+
+
+// Command parsing keywords
+const int16_t HASH_KEYWORD_EXRAIL=15435;    
+const int16_t HASH_KEYWORD_ON = 2657;
+const int16_t HASH_KEYWORD_START=23232;
+const int16_t HASH_KEYWORD_RESERVE=11392;
+const int16_t HASH_KEYWORD_FREE=-23052;
+const int16_t HASH_KEYWORD_LATCH=1618;  
+const int16_t HASH_KEYWORD_UNLATCH=1353;
+const int16_t HASH_KEYWORD_PAUSE=-4142;
+const int16_t HASH_KEYWORD_RESUME=27609;
+const int16_t HASH_KEYWORD_KILL=5218;
+const int16_t HASH_KEYWORD_ROUTES=-3702;
+
+// One instance of RMFT clas is used for each "thread" in the automation.
+// Each thread manages a loco on a journey through the layout, and/or may manage a scenery automation.
+// The thrrads exist in a ring, each time through loop() the next thread in the ring is serviced.
+
+// Statics 
+const int16_t LOCO_ID_WAITING=-99; // waiting for loco id from prog track
+int16_t RMFT2::progtrackLocoId;  // used for callback when detecting a loco on prograck
+bool RMFT2::diag=false;      // <D EXRAIL ON>  
+RMFT2 * RMFT2::loopTask=NULL; // loopTask contains the address of ONE of the tasks in a ring.
+RMFT2 * RMFT2::pausingTask=NULL; // Task causing a PAUSE.
+ // when pausingTask is set, that is the ONLY task that gets any service,
+ // and all others will have their locos stopped, then resumed after the pausing task resumes.
+byte RMFT2::flags[MAX_FLAGS];
+
+#define GET_OPCODE GETFLASH(RMFT2::RouteCode+progCounter)
+#define GET_OPERAND(n) GETFLASHW(RMFT2::RouteCode+progCounter+1+(n*3))
+#define SKIPOP progCounter+=3
+
+/* static */ void RMFT2::begin() { 
+  DCCEXParser::setRMFTFilter(RMFT2::ComandFilter);
+  for (int f=0;f<MAX_FLAGS;f++) flags[f]=0;
+  int progCounter;
+  // first pass startup, define any turnouts or servos, set signals red and count size.
+  for (progCounter=0;; SKIPOP){
+     byte opcode=GET_OPCODE;
+     if (opcode==OPCODE_ENDEXRAIL) break;
+
+     switch (opcode) {
+     case OPCODE_AT:
+     case OPCODE_AFTER:
+     case OPCODE_IF:
+     case OPCODE_IFNOT:
+       IODevice::configureInput((VPIN)GET_OPERAND(0),true);
+     }
+
+     if (opcode==OPCODE_SIGNAL) {
+      VPIN red=GET_OPERAND(0);
+      VPIN amber=GET_OPERAND(1);
+      VPIN green=GET_OPERAND(2);
+      IODevice::write(red,true);
+      if (amber) IODevice::write(amber,false);
+      IODevice::write(green,false);
+      continue;
+     }
+     
+     if (opcode==OPCODE_TURNOUT) {
+      VPIN id=GET_OPERAND(0);
+      int addr=GET_OPERAND(1);
+      byte subAddr=GET_OPERAND(2);
+      DCCTurnout::create(id,addr,subAddr);
+      continue;
+     }
+
+     if (opcode==OPCODE_SERVOTURNOUT) {
+      int16_t id=GET_OPERAND(0);
+      VPIN pin=GET_OPERAND(1);
+      int activeAngle=GET_OPERAND(2);
+      int inactiveAngle=GET_OPERAND(3);
+      int profile=GET_OPERAND(4);
+      ServoTurnout::create(id,pin,activeAngle,inactiveAngle,profile);
+      continue;
+     }
+
+     if (opcode==OPCODE_PINTURNOUT) {
+      int16_t id=GET_OPERAND(0);
+      VPIN pin=GET_OPERAND(1);
+      VpinTurnout::create(id,pin);
+      continue;
+     }
+     // other opcodes are not needed on this pass
+  } 
+  SKIPOP; // include ENDROUTES opcode
+  DIAG(F("EXRAIL %db, MAX_FLAGS=%d"), progCounter,MAX_FLAGS);
+  new RMFT2(0); // add the startup route
+}
+
+// This filter intercepts <> commands to do the following:
+// - Implement RMFT specific commands/diagnostics 
+// - Reject/modify JMRI commands that would interfere with RMFT processing 
+void RMFT2::ComandFilter(Print * stream, byte & opcode, byte & paramCount, int16_t p[]) {
+    (void)stream; // avoid compiler warning if we don't access this parameter 
+    bool reject=false;
+    switch(opcode) {
+        
+     case 'D':
+        if (p[0]==HASH_KEYWORD_EXRAIL) { // <D EXRAIL ON/OFF>
+           diag = paramCount==2 && (p[1]==HASH_KEYWORD_ON || p[1]==1);
+           opcode=0;
+        }
+        break;
+          
+     case '/':  // New EXRAIL command
+          reject=!parseSlash(stream,paramCount,p);
+          opcode=0;
+          break;
+          
+     default:  // other commands pass through 
+     break;       
+   }
+ if (reject) {
+   opcode=0;
+   StringFormatter::send(stream,F("<X>"));
+   }
+}
+     
+bool RMFT2::parseSlash(Print * stream, byte & paramCount, int16_t p[]) {
+
+          if (paramCount==0) { // STATUS
+                 StringFormatter::send(stream, F("<* EXRAIL STATUS"));
+                 RMFT2 * task=loopTask;
+                 while(task) {
+                   StringFormatter::send(stream,F("\nID=%d,PC=%d,LOCO=%d%c,SPEED=%d%c"),
+                         (int)(task->taskId),task->progCounter,task->loco,
+                         task->invert?'I':' ',
+                         task->speedo, 
+                         task->forward?'F':'R'
+                         );
+                   task=task->next;      
+                   if (task==loopTask) break;      
+                 }
+                 // Now stream the flags 
+                 for (int id=0;id<MAX_FLAGS; id++) {
+                   byte flag=flags[id];
+                   if (flag & ~TASK_FLAG) { // not interested in TASK_FLAG only. Already shown above 
+                     StringFormatter::send(stream,F("\nflags[%d} "),id);
+                     if (flag & SECTION_FLAG) StringFormatter::send(stream,F(" RESERVED"));
+                     if (flag & LATCH_FLAG) StringFormatter::send(stream,F(" LATCHED"));
+                     }                 
+                 }
+                 StringFormatter::send(stream,F(" *>\n"));
+                 return true;
+            }
+          switch (p[0]) {
+            case HASH_KEYWORD_PAUSE: // </ PAUSE>
+                 if (paramCount!=1) return false;
+                 DCC::setThrottle(0,1,true);  // pause all locos on the track         
+                 pausingTask=(RMFT2 *)1; // Impossible task address
+                 return true;
+                 
+            case HASH_KEYWORD_RESUME: // </ RESUME>
+                 if (paramCount!=1) return false;
+                 pausingTask=NULL;
+                 {
+                  RMFT2 * task=loopTask;                 
+                  while(task) {
+                      if (task->loco) task->driveLoco(task->speedo);
+                      task=task->next;      
+                      if (task==loopTask) break;      
+                    }
+                 }        
+                 return true;
+                 
+                      
+            case HASH_KEYWORD_START: // </ START [cab] route >
+                 if (paramCount<2 || paramCount>3) return false;
+                 {
+                  int route=(paramCount==2) ? p[1] : p[2];
+                  uint16_t cab=(paramCount==2)? 0 : p[1];
+                  int pc=locateRouteStart(route);                 
+                  if (pc<0) return false;
+                    RMFT2* task=new RMFT2(pc);
+                    task->loco=cab;                    
+                 }
+              return true;
+
+            case HASH_KEYWORD_ROUTES: // </ ROUTES > JMRI withrottle support 
+                 if (paramCount>1) return false;
+                 StringFormatter::send(stream,F("</ROUTES "));
+                 emitWithrottleRouteList(stream);                                  
+                 StringFormatter::send(stream,F(">"));
+              return true;
+              
+            default:
+              break;
+          }
+          
+          // all other / commands take 1 parameter 0 to MAX_FLAGS-1     
+
+          if (paramCount!=2 || p[1]<0  || p[1]>=MAX_FLAGS) return false;
+
+          switch (p[0]) {  
+               case HASH_KEYWORD_KILL: // Kill taskid
+                    {
+                    RMFT2 * task=loopTask;
+                    while(task) {
+                      if (task->taskId==p[1]) {
+                         delete task;
+                         return  true;
+                      }
+                      task=task->next;      
+                      if (task==loopTask) break;      
+                    }
+                 }
+                 return false;
+                    
+            case HASH_KEYWORD_RESERVE:  // force reserve a section
+                 setFlag(p[1],SECTION_FLAG);
+                 return true;
+    
+            case HASH_KEYWORD_FREE:  // force free a section
+                 setFlag(p[1],0,SECTION_FLAG);
+                 return true;
+                
+            case HASH_KEYWORD_LATCH:
+                 setFlag(p[1], LATCH_FLAG);
+                 return true;
+   
+            case HASH_KEYWORD_UNLATCH:
+                 setFlag(p[1], 0, LATCH_FLAG);
+                 return true;
+                  
+            default:
+                 return false;                 
+          }
+    }
+
+
+// This emits Routes and Automations to Withrottle
+// Automations are given a state to set the button to "handoff" which implies 
+// handing over the loco to the automation.
+// Routes are given "Set" buttons and do not cause the loco to be handed over. 
+void RMFT2::emitWithrottleRouteList(Print* stream) {
+   StringFormatter::send(stream,F("PRT]\\[Routes}|{Route]\\[Set}|{2]\\[Handoff}|{4\nPRL"));
+   emitWithrottleDescriptions(stream);
+   StringFormatter::send(stream,F("\n"));
+}
+
+
+RMFT2::RMFT2(int progCtr) {
+  progCounter=progCtr;
+
+  // get an unused  task id from the flags table 
+  taskId=255; // in case of overflow
+  for (int f=0;f<MAX_FLAGS;f++) {
+    if (!getFlag(f,TASK_FLAG)) {
+      taskId=f;
+      setFlag(f, TASK_FLAG);
+      break;
+    }
+  }
+  delayTime=0;
+  loco=0;
+  speedo=0;
+  forward=true;
+  invert=false;
+  stackDepth=0;
+  onTurnoutId=0; // Not handling an ONTHROW/ONCLOSE
+   
+  // chain into ring of RMFTs
+  if (loopTask==NULL) {
+    loopTask=this;
+    next=this;
+  }
+  else {
+        next=loopTask->next;
+        loopTask->next=this;
+  }
+}
+
+
+RMFT2::~RMFT2() {
+  driveLoco(1); // ESTOP my loco if any 
+  setFlag(taskId,0,TASK_FLAG); // we are no longer using this id
+  if (next==this) loopTask=NULL;
+  else for (RMFT2* ring=next;;ring=ring->next) if (ring->next == this) {
+           ring->next=next;
+           loopTask=next;
+           break;
+       }
+}
+
+void RMFT2::createNewTask(int route, uint16_t cab) {
+      int pc=locateRouteStart(route);
+      if (pc<0) return;
+      RMFT2* task=new RMFT2(pc);
+      task->loco=cab;
+}
+
+   
+int RMFT2::locateRouteStart(int16_t _route) {
+  if (_route==0) return 0; // Route 0 is always start of ROUTES for default startup 
+  for (int progCounter=0;;SKIPOP) {
+    byte opcode=GET_OPCODE;
+    if (opcode==OPCODE_ENDEXRAIL) {
+      DIAG(F("RMFT2 sequence %d not found"), _route);
+      return -1;
+    }
+    if ((opcode==OPCODE_ROUTE || opcode==OPCODE_AUTOMATION || opcode==OPCODE_SEQUENCE) 
+       &&  _route==(int)GET_OPERAND(0)) return progCounter;
+  }
+  return -1;
+}
+
+
+void RMFT2::driveLoco(byte speed) {
+     if (loco<=0) return;  // Prevent broadcast! 
+     if (diag) DIAG(F("EXRAIL drive %d %d %d"),loco,speed,forward^invert);
+     if (DCCWaveform::mainTrack.getPowerMode()==POWERMODE::OFF) {
+        DCCWaveform::mainTrack.setPowerMode(POWERMODE::ON); 
+        Serial.println(F("<p1>")); // tell JMRI
+     }
+     DCC::setThrottle(loco,speed, forward^invert);
+     speedo=speed;
+}
+
+bool RMFT2::readSensor(uint16_t sensorId) {
+  // Exrail operands are unsigned but we need the signed version as inserted by the macros.  
+  int16_t sId=(int16_t) sensorId;
+
+  VPIN vpin=abs(sId);
+  if (getFlag(vpin,LATCH_FLAG)) return true; // latched on
+
+  // negative sensorIds invert the logic (e.g. for a break-beam sensor which goes OFF when detecting)
+  bool s= IODevice::read(vpin) ^ (sId<0);
+  if (s && diag) DIAG(F("EXRAIL Sensor %d hit"),sId);
+  return s;
+}
+
+bool RMFT2::skipIfBlock() {
+  // returns false if killed
+  short nest = 1;
+  while (nest > 0) {
+    SKIPOP;
+    byte opcode =  GET_OPCODE;
+    switch(opcode) {
+      case OPCODE_ENDEXRAIL: 
+           kill(F("missing ENDIF"), nest);
+           return false;  
+      case OPCODE_IF:
+      case OPCODE_IFNOT:
+      case OPCODE_IFRANDOM:
+      case OPCODE_IFRESERVE:
+           nest++;
+           break;
+      case OPCODE_ENDIF:
+           nest--;
+           break;
+      default:
+      break;
+    }
+  }
+  return true; 
+}
+
+
+
+/* static */ void RMFT2::readLocoCallback(int16_t cv) {
+     progtrackLocoId=cv;
+}
+
+void RMFT2::loop() {
+  
+  // Round Robin call to a RMFT task each time 
+     if (loopTask==NULL) return; 
+     
+     loopTask=loopTask->next;
+ 
+     if (pausingTask==NULL || pausingTask==loopTask) loopTask->loop2();
+}    
+
+  
+void RMFT2::loop2() {
+   if (delayTime!=0 && millis()-delayStart < delayTime) return;
+     
+  byte opcode = GET_OPCODE;
+  int16_t operand =  GET_OPERAND(0);
+  // if (diag) DIAG(F("RMFT2 %d %d"),opcode,operand); 
+  // Attention: Returning from this switch leaves the program counter unchanged.
+  //            This is used for unfinished waits for timers or sensors.
+  //            Breaking from this switch will step to the next step in the route. 
+  switch ((OPCODE)opcode) {
+    
+    case OPCODE_THROW:
+         Turnout::setClosed(operand, false);
+         break;
+          
+    case OPCODE_CLOSE:
+         Turnout::setClosed(operand, true);
+         break; 
+    
+    case OPCODE_REV:
+      forward = false;
+      driveLoco(operand);
+      break;
+    
+    case OPCODE_FWD:
+      forward = true;
+      driveLoco(operand);
+      break;
+      
+    case OPCODE_SPEED:
+      driveLoco(operand);
+      break;
+    
+    case OPCODE_INVERT_DIRECTION:
+      invert= !invert;
+      driveLoco(speedo);
+      break;
+      
+    case OPCODE_RESERVE:
+      if (getFlag(operand,SECTION_FLAG)) {
+        driveLoco(0);
+        delayMe(500);
+        return;
+      }
+      setFlag(operand,SECTION_FLAG);
+      break;
+    
+    case OPCODE_FREE:
+      setFlag(operand,0,SECTION_FLAG);
+      break;
+    
+    case OPCODE_AT:
+      if (readSensor(operand)) break;
+      delayMe(50);
+      return;
+    
+    case OPCODE_AFTER: // waits for sensor to hit and then remain off for 0.5 seconds. (must come after an AT operation)
+      if (readSensor(operand)) {
+        // reset timer to half a second and keep waiting
+        waitAfter=millis();
+        delayMe(50);
+        return; 
+      }
+      if (millis()-waitAfter < 500 ) return;   
+      break;
+    
+    case OPCODE_LATCH:
+      setFlag(operand,LATCH_FLAG);
+      break;
+    
+    case OPCODE_UNLATCH:
+      setFlag(operand,0,LATCH_FLAG);
+      break;
+
+    case OPCODE_SET:
+      IODevice::write(operand,true);
+      break;
+  
+    case OPCODE_RESET:
+      IODevice::write(operand,false);
+      break;
+    
+    case OPCODE_PAUSE:
+         DCC::setThrottle(0,1,true);  // pause all locos on the track
+         pausingTask=this;
+         break;
+
+    case OPCODE_POM:
+        if (loco) DCC::writeCVByteMain(loco, operand, GET_OPERAND(1));
+        break;
+
+    case OPCODE_POWEROFF:
+        DCCWaveform::mainTrack.setPowerMode(POWERMODE::OFF);
+        DCCWaveform::progTrack.setPowerMode(POWERMODE::OFF);
+        DCC::setProgTrackSyncMain(false);       
+        Serial.println(F("<p0>")); // Tell JMRI
+        break;
+
+    case OPCODE_RESUME:
+         pausingTask=NULL;
+         driveLoco(speedo);
+         for (RMFT2 * t=next; t!=this;t=t->next) if (t->loco >0) t->driveLoco(t->speedo);
+          break;        
+    
+    case OPCODE_IF: // do next operand if sensor set
+      if (!readSensor(operand)) if (!skipIfBlock()) return;
+      break;
+    
+    case OPCODE_IFNOT: // do next operand if sensor not set
+      if (readSensor(operand)) if (!skipIfBlock()) return;
+      break;
+   
+    case OPCODE_IFRANDOM: // do block on random percentage
+      if (random(100)>=operand) if (!skipIfBlock()) return;
+      break;
+   
+    case OPCODE_IFRESERVE: // do block if we successfully RERSERVE
+      if (!getFlag(operand,SECTION_FLAG)) setFlag(operand,SECTION_FLAG);
+      else if (!skipIfBlock()) return;
+      break;
+      
+    case OPCODE_ENDIF:
+      break;
+    
+    case OPCODE_DELAY:
+      delayMe(operand*100L);
+      break;
+   
+    case OPCODE_DELAYMINS:
+      delayMe(operand*60L*1000L);
+      break;
+    
+    case OPCODE_RANDWAIT:
+      delayMe(random(operand)*100L);
+      break;
+    
+    case OPCODE_RED:
+      doSignal(operand,true,false,false);
+      break;
+    
+    case OPCODE_AMBER:
+      doSignal(operand,false,true,false);
+      break;
+    
+    case OPCODE_GREEN:
+      doSignal(operand,false,false,true);
+      break;
+       
+    case OPCODE_FON:      
+      if (loco) DCC::setFn(loco,operand,true);
+      break;
+     
+    case OPCODE_FOFF:
+      if (loco) DCC::setFn(loco,operand,false);
+      break;
+    
+    case OPCODE_XFON:      
+      DCC::setFn(operand,GET_OPERAND(1),true);
+      break;
+   
+    case OPCODE_XFOFF:      
+      DCC::setFn(operand,GET_OPERAND(1),false);
+      break;
+   
+    case OPCODE_FOLLOW:
+      progCounter=locateRouteStart(operand);
+      if (progCounter<0) kill(F("FOLLOW unknown"), operand); 
+      return;
+  
+    case OPCODE_CALL:
+      if (stackDepth==MAX_STACK_DEPTH) {
+        kill(F("CALL stack"), stackDepth);
+        return;
+      }
+      callStack[stackDepth++]=progCounter+3;
+      progCounter=locateRouteStart(operand);
+      if (progCounter<0) kill(F("CALL unknown"),operand); 
+      return;
+
+    case OPCODE_RETURN:
+      if (stackDepth==0) {
+        kill(F("RETURN stack"));
+        return;
+      }
+      progCounter=callStack[--stackDepth];
+      return;
+      
+    case OPCODE_ENDTASK:
+    case OPCODE_ENDEXRAIL:
+      kill();
+      return;
+      
+    case OPCODE_JOIN:
+       DCCWaveform::mainTrack.setPowerMode(POWERMODE::ON); 
+       DCCWaveform::progTrack.setPowerMode(POWERMODE::ON); 
+       DCC::setProgTrackSyncMain(true);
+       Serial.println(F("<p1 JOIN>")); // Tell JMRI
+       break;
+
+    case OPCODE_UNJOIN:
+       DCC::setProgTrackSyncMain(false);
+       break;
+       
+    case OPCODE_READ_LOCO1: // READ_LOCO is implemented as 2 separate opcodes
+       progtrackLocoId=LOCO_ID_WAITING;  // Nothing found yet
+       DCC::getLocoId(readLocoCallback);
+       break;
+      
+      case OPCODE_READ_LOCO2:
+       if (progtrackLocoId==LOCO_ID_WAITING) {
+        delayMe(100);
+        return; // still waiting for callback
+       }
+       if (progtrackLocoId<0) {
+        kill(F("No Loco Found"),progtrackLocoId);
+        return; // still waiting for callback
+       }
+       
+       loco=progtrackLocoId;
+       speedo=0;
+       forward=true;
+       invert=false;
+       break;
+       
+       case OPCODE_START:
+           {
+            int newPc=locateRouteStart(operand);
+            if (newPc<0) break; 
+            new RMFT2(newPc); 
+           }
+           break;
+           
+      case OPCODE_SENDLOCO:  // cab, route
+           {
+            int newPc=locateRouteStart(GET_OPERAND(1));
+            if (newPc<0) break; 
+            RMFT2* newtask=new RMFT2(newPc); // create new task 
+            newtask->loco=operand; 
+           }
+           break;
+           
+       case OPCODE_SETLOCO:
+           {
+             loco=operand; 
+             speedo=0;
+             forward=true;
+             invert=false;
+            }
+       break;
+
+          
+       case OPCODE_SERVO: // OPCODE_SERVO,V(vpin),OPCODE_PAD,V(position),OPCODE_PAD,V(profile),OPCODE_PAD,V(duration)
+        IODevice::writeAnalogue(operand,GET_OPERAND(1),GET_OPERAND(2),GET_OPERAND(3));          
+        break;
+       
+       case OPCODE_WAITFOR: // OPCODE_SERVO,V(pin)
+            if (IODevice::isBusy(operand)) {
+              delayMe(100);
+              return;
+            }
+            break;
+
+       case OPCODE_PRINT:
+            printMessage(operand);
+            break;
+               
+       case OPCODE_ROUTE:
+       case OPCODE_AUTOMATION:
+       case OPCODE_SEQUENCE:
+          if (diag) DIAG(F("EXRAIL begin(%d)"),operand);
+          break;
+
+       case OPCODE_PAD: // Just a padding for previous opcode needing >1 operad byte.
+       case OPCODE_SIGNAL: // Signal definition ignore at run time
+       case OPCODE_TURNOUT: // Turnout definition ignored at runtime
+       case OPCODE_SERVOTURNOUT: // Turnout definition ignored at runtime
+       case OPCODE_PINTURNOUT: // Turnout definition ignored at runtime
+       case OPCODE_ONCLOSE: // Turnout event catcers ignored here
+       case OPCODE_ONTHROW: // Turnout definition ignored at runtime
+       break;
+    
+    default:
+      kill(F("INVOP"),operand);
+    }
+    // Falling out of the switch means move on to the next opcode
+    SKIPOP;
+}
+
+void RMFT2::delayMe(long delay) {
+     delayTime=delay;
+     delayStart=millis();
+}
+
+void RMFT2::setFlag(VPIN id,byte onMask, byte offMask) {  
+   if (FLAGOVERFLOW(id)) return; // Outside range limit
+   byte f=flags[id];
+   f &= ~offMask;
+   f |= onMask;
+   flags[id]=f;
+}
+
+bool RMFT2::getFlag(VPIN id,byte mask) {
+   if (FLAGOVERFLOW(id)) return 0; // Outside range limit
+   return flags[id]&mask;   
+}
+
+void RMFT2::kill(const FSH * reason, int operand) {
+     if (reason) DIAG(F("EXRAIL ERROR pc=%d, cab=%d, %S %d"), progCounter,loco, reason, operand);
+     else if (diag) DIAG(F("ENDTASK at pc=%d"), progCounter); 
+     delete this;
+}
+
+/* static */ void RMFT2::doSignal(VPIN id,bool red, bool amber, bool green) { 
+  // CAUTION: hides class member progCounter
+  for (int progCounter=0;; SKIPOP){
+     byte opcode=GET_OPCODE;
+     if (opcode==OPCODE_ENDEXRAIL) return;
+     if (opcode!=OPCODE_SIGNAL) continue;
+     byte redpin=GET_OPERAND(0);
+     if (redpin!=id)continue;
+     byte amberpin=GET_OPERAND(1);
+     byte greenpin=GET_OPERAND(2);
+     // If amberpin is zero, synthesise amber from red+green
+     IODevice::write(redpin,red || (amber && (amberpin==0)));
+     if (amberpin) IODevice::write(amberpin,amber);
+     if (greenpin) IODevice::write(greenpin,green || (amber && (amberpin==0)));
+     return;
+   }
+  } 
+ void RMFT2::turnoutEvent(int16_t turnoutId, bool closed) {
+    
+    // Check we dont already have a task running this turnout
+    RMFT2 * task=loopTask;                 
+    while(task) {
+      if (task->onTurnoutId==turnoutId) {
+        DIAG(F("Recursive ONTHROW/ONCLOSE for Turnout %d"),turnoutId);
+        return;
+        }
+      task=task->next;      
+      if (task==loopTask) break;      
+      }
+    // Hunt for an ONTHROW/ONCLOSE for this turnout   
+    byte huntFor=closed ?  OPCODE_ONCLOSE : OPCODE_ONTHROW ;
+    // caution hides class progCounter;
+    for (int progCounter=0;; SKIPOP){
+     byte opcode=GET_OPCODE;
+     if (opcode==OPCODE_ENDEXRAIL) return;
+     if (opcode!=huntFor) continue;
+     if (turnoutId!=(int16_t)GET_OPERAND(0)) continue;
+     task=new RMFT2(progCounter);  // new task starts at this instruction
+     task->onTurnoutId=turnoutId; // flag for recursion detector
+     return;
+   }
+ }
+ 
+ void RMFT2::printMessage2(const FSH * msg) {
+        DIAG(F("EXRAIL(%d) %S"),loco,msg);
+   }
+
+// This is called by emitRouteDescriptions to emit a withrottle description for a route or autoomation. 
+void RMFT2::emitRouteDescription(Print * stream, char type, int id, const FSH * description) {
+ StringFormatter::send(stream,F("]\\[%c%d}|{%S}|{%c"),
+              type,id,description, type=='R'?'2':'4');
+}
+ 

RMFT2.h

@@ -0,0 +1,117 @@
+/*
+ *  © 2020, Chris Harlow. All rights reserved.
+ *  
+ *  This file is part of CommandStation-EX
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#ifndef RMFT2_H
+#define RMFT2_H
+#include "FSH.h"
+#include "IODevice.h"
+   
+// The following are the operation codes (or instructions) for a kind of virtual machine.
+// Each instruction is normally 2 bytes long with an operation code followed by a parameter.
+// In cases where more than one parameter is required, the first parameter is followed by one  
+// or more OPCODE_PAD instructions with the subsequent parameters. This wastes a byte but makes 
+// searching easier as a parameter can never be confused with an opcode. 
+// 
+enum OPCODE : byte {OPCODE_THROW,OPCODE_CLOSE,
+             OPCODE_FWD,OPCODE_REV,OPCODE_SPEED,OPCODE_INVERT_DIRECTION,
+             OPCODE_RESERVE,OPCODE_FREE,
+             OPCODE_AT,OPCODE_AFTER,
+             OPCODE_LATCH,OPCODE_UNLATCH,OPCODE_SET,OPCODE_RESET,
+             OPCODE_IF,OPCODE_IFNOT,OPCODE_ENDIF,OPCODE_IFRANDOM,OPCODE_IFRESERVE,
+             OPCODE_DELAY,OPCODE_DELAYMINS,OPCODE_RANDWAIT,
+             OPCODE_FON,OPCODE_FOFF,OPCODE_XFON,OPCODE_XFOFF,
+             OPCODE_RED,OPCODE_GREEN,OPCODE_AMBER,
+             OPCODE_SERVO,OPCODE_SIGNAL,OPCODE_TURNOUT,OPCODE_WAITFOR,
+             OPCODE_PAD,OPCODE_FOLLOW,OPCODE_CALL,OPCODE_RETURN,
+             OPCODE_JOIN,OPCODE_UNJOIN,OPCODE_READ_LOCO1,OPCODE_READ_LOCO2,OPCODE_POM,
+             OPCODE_START,OPCODE_SETLOCO,OPCODE_SENDLOCO,
+             OPCODE_PAUSE, OPCODE_RESUME,OPCODE_POWEROFF,
+             OPCODE_ONCLOSE, OPCODE_ONTHROW, OPCODE_SERVOTURNOUT, OPCODE_PINTURNOUT,
+             OPCODE_PRINT,
+             OPCODE_ROUTE,OPCODE_AUTOMATION,OPCODE_SEQUENCE,OPCODE_ENDTASK,OPCODE_ENDEXRAIL
+             };
+
+
+ 
+  // Flag bits for status of hardware and TPL
+  static const byte SECTION_FLAG = 0x01;
+  static const byte LATCH_FLAG = 0x02;
+  static const byte TASK_FLAG = 0x04;
+
+  static const byte  MAX_STACK_DEPTH=4;
+ 
+   static const short MAX_FLAGS=256;
+  #define FLAGOVERFLOW(x) x>=MAX_FLAGS
+
+ class RMFT2 {
+   public:
+    static void begin();
+    static void loop();
+    RMFT2(int progCounter);
+    RMFT2(int route, uint16_t cab);
+    ~RMFT2();
+    static void readLocoCallback(int16_t cv);
+    static void emitWithrottleRouteList(Print* stream); 
+    static void createNewTask(int route, uint16_t cab);
+    static void turnoutEvent(int16_t id, bool closed);  
+private: 
+    static void ComandFilter(Print * stream, byte & opcode, byte & paramCount, int16_t p[]);
+    static bool parseSlash(Print * stream, byte & paramCount, int16_t p[]) ;
+    static void streamFlags(Print* stream);
+    static void setFlag(VPIN id,byte onMask, byte OffMask=0);
+    static bool getFlag(VPIN id,byte mask);   
+    static int locateRouteStart(int16_t _route);
+    static int16_t progtrackLocoId;
+    static void doSignal(VPIN id,bool red, bool amber, bool green); 
+    static void emitRouteDescription(Print * stream, char type, int id, const FSH * description);
+    static void emitWithrottleDescriptions(Print * stream);
+    
+    static RMFT2 * loopTask;
+    static RMFT2 * pausingTask;
+    void delayMe(long millisecs);
+    void driveLoco(byte speedo);
+    bool readSensor(uint16_t sensorId);
+    bool skipIfBlock();
+    bool readLoco();
+    void loop2();
+    void kill(const FSH * reason=NULL,int operand=0);          
+    void printMessage(uint16_t id);  // Built by RMFTMacros.h
+    void printMessage2(const FSH * msg);
+
+    
+   static bool diag;
+   static const  FLASH  byte RouteCode[];
+   static byte flags[MAX_FLAGS];
+ 
+  // Local variables - exist for each instance/task 
+    RMFT2 *next;   // loop chain 
+    int progCounter;    // Byte offset of next route opcode in ROUTES table
+    unsigned long delayStart; // Used by opcodes that must be recalled before completing
+    unsigned long waitAfter; // Used by OPCODE_AFTER
+    unsigned long  delayTime;
+    byte  taskId;
+    
+    uint16_t loco;
+    bool forward;
+    bool invert;
+    byte speedo;
+    int16_t onTurnoutId;
+    byte stackDepth;
+    int callStack[MAX_STACK_DEPTH];
+};
+#endif

RMFTMacros.h

@@ -0,0 +1,311 @@
+/*
+ *  © 2020,2021 Chris Harlow. All rights reserved.
+ *  
+ *  This file is part of CommandStation-EX
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#ifndef RMFTMacros_H
+#define RMFTMacros_H
+
+// remove normal code LCD & SERIAL macros (will be restored later)
+#undef LCD
+#undef SERIAL
+
+
+// This file will include and build the EXRAIL script and associated helper tricks.
+// It does this by incliding myAutomation.h several times, each with a set of macros to 
+// extract the relevant parts.
+
+// The entire automation script is contained within a byte array RMFT2::RouteCode[]
+// made up of opcode and parameter pairs.
+// ech opcode is a 1 byte operation plus 2 byte operand. 
+// The array is normally built using the macros below as this makes it easier 
+// to manage the cases where:
+// - padding must be applied to ensure the correct alignment of the next instruction
+// - large parameters must be split up
+// - multiple parameters aligned correctly
+// - a single macro requires multiple operations
+
+// Descriptive texts for routes and animations are created in a sepaerate function which
+// can be called to emit a list of routes/automatuions in a form suitable for Withrottle. 
+ 
+// PRINT(msg) and LCD(row,msg) is implemented in a separate pass to create 
+// a getMessageText(id) function.  
+
+// CAUTION: The macros below are multiple passed over myAutomation.h
+
+// Pass 1 Implements aliases and 
+// converts descriptions to  withrottle format emitter function
+// Most macros are simply ignored in this pass.
+
+
+#define ALIAS(name,value) const int name=value; 
+#define EXRAIL  void  RMFT2::emitWithrottleDescriptions(Print * stream) {(void)stream;
+#define ROUTE(id, description) emitRouteDescription(stream,'R',id,F(description));
+#define AUTOMATION(id, description) emitRouteDescription(stream,'A',id,F(description));
+#define ENDEXRAIL  }
+ 
+#define AFTER(sensor_id)
+#define AMBER(signal_id)
+#define AT(sensor_id)
+#define CALL(route) 
+#define CLOSE(id) 
+#define DELAY(mindelay)
+#define DELAYMINS(mindelay)
+#define DELAYRANDOM(mindelay,maxdelay) 
+#define DONE
+#define ENDIF  
+#define ENDTASK
+#define ESTOP 
+#define FADE(pin,value,ms)
+#define FOFF(func)
+#define FOLLOW(route) 
+#define FON(func) 
+#define FREE(blockid) 
+#define FWD(speed) 
+#define GREEN(signal_id)
+#define IF(sensor_id) 
+#define IFNOT(sensor_id)
+#define IFRANDOM(percent) 
+#define IFRESERVE(block)
+#define INVERT_DIRECTION 
+#define JOIN 
+#define LATCH(sensor_id) 
+#define LCD(row,msg) 
+#define LCN(msg) 
+#define ONCLOSE(turnout_id)
+#define ONTHROW(turnout_id) 
+#define PAUSE
+#define PRINT(msg) 
+#define POM(cv,value)
+#define POWEROFF
+#define READ_LOCO 
+#define RED(signal_id) 
+#define RESERVE(blockid) 
+#define RESET(pin) 
+#define RESUME 
+#define RETURN 
+#define REV(speed) 
+#define START(route) 
+#define SENDLOCO(cab,route) 
+#define SERIAL(msg) 
+#define SERIAL1(msg) 
+#define SERIAL2(msg) 
+#define SERIAL3(msg) 
+#define SERVO(id,position,profile) 
+#define SERVO2(id,position,duration) 
+#define SETLOCO(loco) 
+#define SET(pin) 
+#define SEQUENCE(id) 
+#define SPEED(speed) 
+#define STOP 
+#undef SIGNAL
+#define SIGNAL(redpin,amberpin,greenpin) 
+#define SERVO_TURNOUT(id,pin,activeAngle,inactiveAngle,profile) 
+#define PIN_TURNOUT(id,pin) 
+#define THROW(id)  
+#define TURNOUT(id,addr,subaddr) 
+#define UNJOIN 
+#define UNLATCH(sensor_id) 
+#define WAITFOR(pin)
+#define XFOFF(cab,func)
+#define XFON(cab,func)
+
+#include "myAutomation.h"
+
+// setup for pass 2... Create getMessageText function
+#undef ALIAS
+#undef ROUTE
+#undef AUTOMATION  
+#define ROUTE(id, description)
+#define AUTOMATION(id, description)  
+
+#undef EXRAIL 
+#undef PRINT
+#undef LCN
+#undef SERIAL
+#undef SERIAL1
+#undef SERIAL2
+#undef SERIAL3
+#undef ENDEXRAIL  
+#undef LCD
+const int StringMacroTracker1=__COUNTER__;
+#define ALIAS(name,value) 
+#define EXRAIL void  RMFT2::printMessage(uint16_t id) { switch(id) {
+#define ENDEXRAIL  default: DIAG(F("printMessage error %d %d"),id,StringMacroTracker1); return ; }}
+#define PRINT(msg)    case (__COUNTER__ - StringMacroTracker1) : printMessage2(F(msg));break;
+#define LCN(msg)      case (__COUNTER__ - StringMacroTracker1) : StringFormatter::send(&LCN_SERIAL,F(msg));break;
+#define SERIAL(msg)   case (__COUNTER__ - StringMacroTracker1) : StringFormatter::send(&Serial,F(msg));break;
+#define SERIAL1(msg)  case (__COUNTER__ - StringMacroTracker1) : StringFormatter::send(&Serial1,F(msg));break;
+#define SERIAL2(msg)  case (__COUNTER__ - StringMacroTracker1) : StringFormatter::send(&Serial2,F(msg));break;
+#define SERIAL3(msg)  case (__COUNTER__ - StringMacroTracker1) : StringFormatter::send(&Serial3,F(msg));break;
+#define LCD(id,msg)   case (__COUNTER__ - StringMacroTracker1) : StringFormatter::lcd(id,F(msg));break;
+#include "myAutomation.h"
+
+// Setup for Pass 3: create main routes table 
+#undef AFTER
+#undef AMBER
+#undef AT
+#undef AUTOMATION 
+#undef CALL
+#undef CLOSE
+#undef DELAY
+#undef DELAYMINS
+#undef DELAYRANDOM
+#undef DONE
+#undef ENDIF
+#undef ENDEXRAIL
+#undef ENDTASK
+#undef ESTOP
+#undef EXRAIL
+#undef FOFF
+#undef FOLLOW
+#undef FON
+#undef FREE
+#undef FWD
+#undef GREEN
+#undef IF
+#undef IFNOT
+#undef IFRANDOM
+#undef IFRESERVE
+#undef INVERT_DIRECTION
+#undef JOIN
+#undef LATCH
+#undef LCD
+#undef LCN
+#undef ONCLOSE
+#undef ONTHROW
+#undef PAUSE
+#undef POM
+#undef POWEROFF
+#undef PRINT
+#undef READ_LOCO
+#undef RED
+#undef RESERVE
+#undef RESET
+#undef RESUME
+#undef RETURN
+#undef REV
+#undef ROUTE 
+#undef START
+#undef SEQUENCE 
+#undef SERVO
+#undef SERVO2
+#undef FADE
+#undef SENDLOCO
+#undef SERIAL
+#undef SERIAL1
+#undef SERIAL2
+#undef SERIAL3
+#undef SETLOCO
+#undef SET
+#undef SPEED
+#undef STOP
+#undef SIGNAL
+#undef SERVO_TURNOUT
+#undef PIN_TURNOUT
+#undef THROW
+#undef TURNOUT
+#undef UNJOIN
+#undef UNLATCH
+#undef WAITFOR
+#undef XFOFF
+#undef XFON
+
+// Define macros for route code creation 
+#define V(val) ((int16_t)(val))&0x00FF,((int16_t)(val)>>8)&0x00FF
+#define NOP 0,0
+
+#define ALIAS(name,value) 
+#define EXRAIL const  FLASH  byte RMFT2::RouteCode[] = {
+#define AUTOMATION(id, description)  OPCODE_AUTOMATION, V(id), 
+#define ROUTE(id, description)  OPCODE_ROUTE, V(id), 
+#define SEQUENCE(id)  OPCODE_SEQUENCE, V(id), 
+#define ENDTASK OPCODE_ENDTASK,NOP,
+#define DONE OPCODE_ENDTASK,NOP,
+#define ENDEXRAIL OPCODE_ENDTASK,NOP,OPCODE_ENDEXRAIL,NOP };
+ 
+#define AFTER(sensor_id) OPCODE_AT,V(sensor_id),OPCODE_AFTER,V(sensor_id),
+#define AMBER(signal_id) OPCODE_AMBER,V(signal_id),
+#define AT(sensor_id) OPCODE_AT,V(sensor_id),
+#define CALL(route) OPCODE_CALL,V(route),
+#define CLOSE(id)  OPCODE_CLOSE,V(id),
+#define DELAY(ms) OPCODE_DELAY,V(ms/100L),
+#define DELAYMINS(mindelay) OPCODE_DELAYMINS,V(mindelay),
+#define DELAYRANDOM(mindelay,maxdelay) OPCODE_DELAY,V(mindelay/100L),OPCODE_RANDWAIT,V((maxdelay-mindelay)/100L),
+#define ENDIF  OPCODE_ENDIF,NOP,
+#define ESTOP OPCODE_SPEED,V(1), 
+#define FADE(pin,value,ms) OPCODE_SERVO,V(pin),OPCODE_PAD,V(value),OPCODE_PAD,V(PCA9685::ProfileType::UseDuration|PCA9685::NoPowerOff),OPCODE_PAD,V(ms/100L),
+#define FOFF(func) OPCODE_FOFF,V(func),
+#define FOLLOW(route) OPCODE_FOLLOW,V(route),
+#define FON(func) OPCODE_FON,V(func),
+#define FREE(blockid) OPCODE_FREE,V(blockid),
+#define FWD(speed) OPCODE_FWD,V(speed),
+#define GREEN(signal_id) OPCODE_GREEN,V(signal_id),
+#define IF(sensor_id) OPCODE_IF,V(sensor_id),
+#define IFNOT(sensor_id) OPCODE_IFNOT,V(sensor_id),
+#define IFRANDOM(percent) OPCODE_IFRANDOM,V(percent),
+#define IFRESERVE(block) OPCODE_IFRESERVE,V(block),
+#define INVERT_DIRECTION OPCODE_INVERT_DIRECTION,NOP,
+#define JOIN OPCODE_JOIN,NOP,
+#define LATCH(sensor_id) OPCODE_LATCH,V(sensor_id),
+#define LCD(id,msg) PRINT(msg)
+#define LCN(msg) PRINT(msg)
+#define ONCLOSE(turnout_id) OPCODE_ONCLOSE,V(turnout_id),
+#define ONTHROW(turnout_id) OPCODE_ONTHROW,V(turnout_id),
+#define PAUSE OPCODE_PAUSE,NOP,
+#define POM(cv,value) OPCODE_POM,V(cv),OPCODE_PAD,V(value),
+#define POWEROFF OPCODE_POWEROFF,NOP,
+#define PRINT(msg) OPCODE_PRINT,V(__COUNTER__ - StringMacroTracker2),
+#define READ_LOCO OPCODE_READ_LOCO1,NOP,OPCODE_READ_LOCO2,NOP,
+#define RED(signal_id) OPCODE_RED,V(signal_id),
+#define RESERVE(blockid) OPCODE_RESERVE,V(blockid),
+#define RESET(pin) OPCODE_RESET,V(pin),
+#define RESUME OPCODE_RESUME,NOP,
+#define RETURN OPCODE_RETURN,NOP,
+#define REV(speed) OPCODE_REV,V(speed),
+#define SENDLOCO(cab,route) OPCODE_SENDLOCO,V(cab),OPCODE_PAD,V(route),
+#define SERIAL(msg) PRINT(msg)
+#define SERIAL1(msg) PRINT(msg)
+#define SERIAL2(msg) PRINT(msg)
+#define SERIAL3(msg) PRINT(msg)
+#define START(route) OPCODE_START,V(route),
+#define SERVO(id,position,profile) OPCODE_SERVO,V(id),OPCODE_PAD,V(position),OPCODE_PAD,V(PCA9685::profile),OPCODE_PAD,V(0),
+#define SERVO2(id,position,ms) OPCODE_SERVO,V(id),OPCODE_PAD,V(position),OPCODE_PAD,V(PCA9685::Instant),OPCODE_PAD,V(ms/100L),
+#define SETLOCO(loco) OPCODE_SETLOCO,V(loco),
+#define SET(pin) OPCODE_SET,V(pin),
+#define SPEED(speed) OPCODE_SPEED,V(speed),
+#define STOP OPCODE_SPEED,V(0), 
+#define SIGNAL(redpin,amberpin,greenpin) OPCODE_SIGNAL,V(redpin),OPCODE_PAD,V(amberpin),OPCODE_PAD,V(greenpin), 
+#define SERVO_TURNOUT(id,pin,activeAngle,inactiveAngle,profile) OPCODE_SERVOTURNOUT,V(id),OPCODE_PAD,V(pin),OPCODE_PAD,V(activeAngle),OPCODE_PAD,V(inactiveAngle),OPCODE_PAD,V(PCA9685::ProfileType::profile),
+#define PIN_TURNOUT(id,pin) OPCODE_PINTURNOUT,V(id),OPCODE_PAD,V(pin), 
+#define THROW(id)  OPCODE_THROW,V(id),
+#define TURNOUT(id,addr,subaddr) OPCODE_TURNOUT,V(id),OPCODE_PAD,V(addr),OPCODE_PAD,V(subaddr),
+#define UNJOIN OPCODE_UNJOIN,NOP,
+#define UNLATCH(sensor_id) OPCODE_UNLATCH,V(sensor_id),
+#define WAITFOR(pin) OPCODE_WAITFOR,V(pin),
+#define XFOFF(cab,func) OPCODE_XFOFF,V(cab),OPCODE_PAD,V(func),
+#define XFON(cab,func) OPCODE_XFON,V(cab),OPCODE_PAD,V(func),
+
+// PASS2 Build RouteCode
+const int StringMacroTracker2=__COUNTER__;
+#include "myAutomation.h"
+
+// Restore normal code LCD & SERIAL  macro
+#undef LCD
+#define LCD   StringFormatter::lcd
+#undef SERIAL
+#define SERIAL  0x0
+#endif

SSD1306Ascii.cpp

@@ -158,13 +158,15 @@ void SSD1306AsciiWire::setRowNative(uint8_t line) {
   if (row < m_displayHeight) {
     m_row = row;
     m_col = m_colOffset;
+    // Before using buffer, wait for last request to complete
+    requestBlock.wait();
     // Build output buffer for I2C
     uint8_t len = 0;
     outputBuffer[len++] = 0x00;  // Set to command mode
     outputBuffer[len++] = SSD1306_SETLOWCOLUMN | (m_col & 0XF);
     outputBuffer[len++] = SSD1306_SETHIGHCOLUMN | (m_col >> 4);
     outputBuffer[len++] = SSD1306_SETSTARTPAGE | (m_row/8);
-    I2CManager.write(m_i2cAddr, outputBuffer, len);
+    I2CManager.write(m_i2cAddr, outputBuffer, len, &requestBlock);
   }
 }
 //------------------------------------------------------------------------------
@@ -189,6 +191,8 @@ size_t SSD1306AsciiWire::writeNative(uint8_t ch) {
 #endif
   ch -= m_fontFirstChar;
   base += fontWidth * ch;
+  // Before using buffer, wait for last request to complete
+  requestBlock.wait();
   // Build output buffer for I2C
   outputBuffer[0] = 0x40;     // set SSD1306 controller to data mode
   uint8_t bufferPos = 1;
@@ -200,7 +204,7 @@ size_t SSD1306AsciiWire::writeNative(uint8_t ch) {
     outputBuffer[bufferPos++] = 0;
 
   // Write the data to I2C display
-  I2CManager.write(m_i2cAddr, outputBuffer, bufferPos);
+  I2CManager.write(m_i2cAddr, outputBuffer, bufferPos, &requestBlock);
   m_col += fontWidth + letterSpacing;
   return 1;
 }

SSD1306Ascii.h

@@ -58,22 +58,24 @@ class SSD1306AsciiWire : public LCDDisplay {
   void begin(const DevType* dev, uint8_t i2cAddr);
 
   // Clear the display and set the cursor to (0, 0).
-  void clearNative();
+  void clearNative() override;
 
   // Set cursor to start of specified text line
-  void setRowNative(byte line);
+  void setRowNative(byte line) override;
 
   // Initialize the display controller.
   void init(const DevType* dev);
   
   // Write one character to OLED
-  size_t writeNative(uint8_t c);
+  size_t writeNative(uint8_t c) override;
 
   // Display characteristics / initialisation
   static const DevType FLASH Adafruit128x32;
   static const DevType FLASH Adafruit128x64;
   static const DevType FLASH SH1106_132x64;
 
+  bool isBusy() override { return requestBlock.isBusy(); }
+
  private:
   // Cursor column.
   uint8_t m_col;
@@ -97,6 +99,7 @@ class SSD1306AsciiWire : public LCDDisplay {
 
   uint8_t m_i2cAddr;
 
+  I2CRB requestBlock;
   uint8_t outputBuffer[fontWidth+letterSpacing+1];
 
   static const uint8_t blankPixels[];

Sensors.cpp

@@ -1,5 +1,6 @@
 /*
  *  © 2020, Chris Harlow. All rights reserved.
+ *  © 2021, modified by Neil McKechnie. All rights reserved.
  *  
  *  This file is part of Asbelos DCC API
  *
@@ -27,9 +28,9 @@ or be allowed to float HIGH if use of the Arduino Pin's internal pull-up resisto
 To ensure proper voltage levels, some part of the Sensor circuitry
 MUST be tied back to the same ground as used by the Arduino.
 
-The Sensor code below utilizes exponential smoothing to "de-bounce" spikes generated by
+The Sensor code below utilises "de-bounce" logic to remove spikes generated by
 mechanical switches and transistors.  This avoids the need to create smoothing circuitry
-for each sensor.  You may need to change these parameters through trial and error for your specific sensors.
+for each sensor.  You may need to change the parameters through trial and error for your specific sensors.
 
 To have this sketch monitor one or more Arduino pins for sensor triggers, first define/edit/delete
 sensor definitions using the following variation of the "S" command:
@@ -68,45 +69,108 @@ decide to ignore the <q ID> return and only react to <Q ID> triggers.
 #include "StringFormatter.h"
 #include "Sensors.h"
 #include "EEStore.h"
+#include "IODevice.h"
 
 
 ///////////////////////////////////////////////////////////////////////////////
-//
+// checks a number of defined sensors per entry and prints _changed_ sensor state
-// checks one defined sensors and prints _changed_ sensor state
 // to stream unless stream is NULL in which case only internal
 // state is updated. Then advances to next sensor which will
-// be checked att next invocation.
+// be checked at next invocation.  Each cycle of reading all sensors will
+// be initiated no more frequently than the time set by 'cycleInterval' microseconds.
 //
+// The list of sensors is divided such that the first part of the list
+// contains sensors that support change notification via callback, and the second
+// part of the list contains sensors that require cyclic polling.  The start of the
+// second part of the list is determined from by the 'firstPollSensor' pointer.
 ///////////////////////////////////////////////////////////////////////////////
 
 void Sensor::checkAll(Print *stream){
+  uint16_t sensorCount = 0;
 
-  if (firstSensor == NULL) return;
+#ifdef USE_NOTIFY
-  if (readingSensor == NULL) readingSensor=firstSensor;
+  // Register the event handler ONCE!
+  if (!inputChangeCallbackRegistered)
+    IONotifyCallback::add(inputChangeCallback);
+  inputChangeCallbackRegistered = true;
+#endif
 
-  bool sensorstate = digitalRead(readingSensor->data.pin);
+  if (firstSensor == NULL) return;  // No sensors to be scanned
-
+  if (readingSensor == NULL) { 
-  if (!sensorstate == readingSensor->active) { // active==true means sensorstate=0/false so sensor unchanged
+    // Not currently scanning sensor list
-    // no change
+    unsigned long thisTime = micros();
-    if (readingSensor->latchdelay != 0) {
+    if (thisTime - lastReadCycle >= cycleInterval) {
-      // enable if you want to debug contact jitter
+      // Required time elapsed since last read cycle started,
-      //if (stream != NULL) StringFormatter::send(stream, F("JITTER %d %d\n"), 
+      // so initiate new scan through the sensor list
-      //                                          readingSensor->latchdelay, readingSensor->data.snum);
+      readingSensor = firstSensor;
-       readingSensor->latchdelay=0; // reset
+      lastReadCycle = thisTime;
     }
-  } else if (readingSensor->latchdelay < 127) { // byte, max 255, good value unknown yet
-    // change but first increase anti-jitter counter
-    readingSensor->latchdelay++;
-  } else {
-    // make the change
-    readingSensor->active = !sensorstate;
-    readingSensor->latchdelay=0; // reset 
-    if (stream != NULL) StringFormatter::send(stream, F("<%c %d>\n"), readingSensor->active ? 'Q' : 'q', readingSensor->data.snum);
   }
 
-  readingSensor=readingSensor->nextSensor;
+  // Loop until either end of list is encountered or we pause for some reason
+  bool pause = false;
+  while (readingSensor != NULL && !pause) {
+
+    // Where the sensor is attached to a pin, read pin status.  For sources such as LCN,
+    // which don't have an input pin to read, the LCN class calls setState() to update inputState when
+    // a message is received.  The IODevice::read() call returns 1 for active pins (0v) and 0 for inactive (5v).
+    // Also, on HAL drivers that support change notifications, the driver calls the notification callback
+    // routine when an input signal change is detected, and this updates the inputState directly,
+    // so these inputs don't need to be polled here.
+    VPIN pin = readingSensor->data.pin;
+    if (readingSensor->pollingRequired && pin != VPIN_NONE)
+      readingSensor->inputState = IODevice::read(pin);
+
+    // Check if changed since last time, and process changes.
+    if (readingSensor->inputState == readingSensor->active) {
+      // no change
+      readingSensor->latchDelay = minReadCount; // Reset counter
+    } else if (readingSensor->latchDelay > 0) {
+      // change detected, but first decrement delay
+      readingSensor->latchDelay--;
+    } else { 
+      // change validated, act on it.
+      readingSensor->active = readingSensor->inputState;
+      readingSensor->latchDelay = minReadCount;  // Reset counter
+      
+      if (stream != NULL) {
+        StringFormatter::send(stream, F("<%c %d>\n"), readingSensor->active ? 'Q' : 'q', readingSensor->data.snum);
+        pause = true;  // Don't check any more sensors on this entry
+      }
+    }
+
+    // Move to next sensor in list.
+    readingSensor = readingSensor->nextSensor;
+
+    // Currently process max of 16 sensors per entry.
+    // Performance measurements taken during development indicate that, with 128 sensors configured
+    // on 8x 16-pin MCP23017 GPIO expanders with polling (no change notification), all inputs can be read from the devices
+    // within 1.4ms (400Mhz I2C bus speed), and a full cycle of checking 128 sensors for changes takes under a millisecond.
+    sensorCount++;
+    if (sensorCount >= 16) pause = true;
+  }
+
 } // Sensor::checkAll
 
+
+#ifdef USE_NOTIFY
+// Callback from HAL (IODevice class) when a digital input change is recognised.
+// Updates the inputState field, which is subsequently scanned for changes in the checkAll 
+// method.  Ideally the <Q>/<q> message should be sent from here, instead of waiting for
+// the checkAll method, but the output stream is not available at this point.
+void Sensor::inputChangeCallback(VPIN vpin, int state) {
+  Sensor *tt;
+  // This bit is not ideal since it has, potentially, to look through the entire list of
+  // sensors to find the one that has changed.  Ideally this should be improved somehow.
+  for (tt=firstSensor; tt!=NULL ; tt=tt->nextSensor) {
+    if (tt->data.pin == vpin) break;
+  }
+  if (tt != NULL) { // Sensor found
+    tt->inputState = (state != 0); 
+  }
+}
+#endif
+
 ///////////////////////////////////////////////////////////////////////////////
 //
 // prints all sensor states to stream
@@ -115,40 +179,62 @@ void Sensor::checkAll(Print *stream){
 
 void Sensor::printAll(Print *stream){
 
-  for(Sensor * tt=firstSensor;tt!=NULL;tt=tt->nextSensor){
+  if (stream != NULL) {
-    if (stream != NULL)
+    for(Sensor * tt=firstSensor;tt!=NULL;tt=tt->nextSensor){
       StringFormatter::send(stream, F("<%c %d>\n"), tt->active ? 'Q' : 'q', tt->data.snum);
+    }
   } // loop over all sensors
 } // Sensor::printAll
 
 ///////////////////////////////////////////////////////////////////////////////
+// Static Function to create/find Sensor object.
 
-Sensor *Sensor::create(int snum, int pin, int pullUp){
+Sensor *Sensor::create(int snum, VPIN pin, int pullUp){
   Sensor *tt;
 
-  if(firstSensor==NULL){
+  if (pin > VPIN_MAX && pin != VPIN_NONE) return NULL;
-    firstSensor=(Sensor *)calloc(1,sizeof(Sensor));
-    tt=firstSensor;
-  } else if((tt=get(snum))==NULL){
-    tt=firstSensor;
-    while(tt->nextSensor!=NULL)
-      tt=tt->nextSensor;
-    tt->nextSensor=(Sensor *)calloc(1,sizeof(Sensor));
-    tt=tt->nextSensor;
-  }
 
-  if(tt==NULL) return tt;       // problem allocating memory
+  remove(snum);  // Unlink and free any existing sensor with the same id, before creating the new one.
 
-  tt->data.snum=snum;
+  tt = (Sensor *)calloc(1,sizeof(Sensor));
-  tt->data.pin=pin;
+  if (!tt) return tt;     // memory allocation failure
-  tt->data.pullUp=(pullUp==0?LOW:HIGH);
+
-  tt->active=false;
+  if (pin == VPIN_NONE) 
-  tt->latchdelay=0;
+    tt->pollingRequired = false;
-  pinMode(pin,INPUT);         // set mode to input
+  #ifdef USE_NOTIFY
-  digitalWrite(pin,pullUp);   // don't use Arduino's internal pull-up resistors for external infrared sensors --- each sensor must have its own 1K external pull-up resistor
+  else if (IODevice::hasCallback(pin)) 
+    tt->pollingRequired = false;
+  #endif
+  else 
+    tt->pollingRequired = true;
+
+  // Add to the start of the list
+  tt->nextSensor = firstSensor;
+  firstSensor = tt;
+
+  tt->data.snum = snum;
+  tt->data.pin = pin;
+  tt->data.pullUp = pullUp;
+  tt->active = 0;
+  tt->inputState = 0;
+  tt->latchDelay = minReadCount;
+
+  if (pin != VPIN_NONE) 
+    IODevice::configureInput(pin, pullUp);   
+    // Generally, internal pull-up resistors are not, on their own, sufficient 
+    // for external infrared sensors --- each sensor must have its own 1K external pull-up resistor
 
   return tt;
+}
 
+///////////////////////////////////////////////////////////////////////////////
+// Object method to directly change the input state, for sensors such as LCN which are updated
+//  by means other than by polling an input.
+
+void Sensor::setState(int value) {
+  // Trigger sensor change to be reported on next checkAll loop.
+  inputState = (value != 0);
+  latchDelay = 0; // Don't wait for anti-jitter logic
 }
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -166,13 +252,23 @@ bool Sensor::remove(int n){
   for(tt=firstSensor;tt!=NULL && tt->data.snum!=n;pp=tt,tt=tt->nextSensor);
 
   if (tt==NULL)  return false;
-  
-  if(tt==firstSensor)
-    firstSensor=tt->nextSensor;
-  else
-    pp->nextSensor=tt->nextSensor;
 
+  // Unlink the sensor from the list
+  if(tt==firstSensor) 
+    firstSensor=tt->nextSensor;
+  else 
+    pp->nextSensor=tt->nextSensor;
+#ifdef USE_NOTIFY
+  if (tt==lastSensor)
+    lastSensor = pp;
+  if (tt==firstPollSensor)
+    firstPollSensor = tt->nextSensor;
+#endif
+
+  // Check if the sensor being deleted is the next one to be read.  If so, 
+  // make the following one the next one to be read.
   if (readingSensor==tt) readingSensor=tt->nextSensor;
+
   free(tt);
 
   return true;
@@ -184,9 +280,10 @@ void Sensor::load(){
   struct SensorData data;
   Sensor *tt;
 
-  for(uint16_t i=0;i<EEStore::eeStore->data.nSensors;i++){
+  uint16_t i=EEStore::eeStore->data.nSensors;
+  while(i--){
     EEPROM.get(EEStore::pointer(),data);
-    tt=create(data.snum,data.pin,data.pullUp);
+    tt=create(data.snum, data.pin, data.pullUp);
     EEStore::advance(sizeof(tt->data));
   }
 }
@@ -211,3 +308,10 @@ void Sensor::store(){
 
 Sensor *Sensor::firstSensor=NULL;
 Sensor *Sensor::readingSensor=NULL;
+unsigned long Sensor::lastReadCycle=0;
+
+#ifdef USE_NOTIFY
+Sensor *Sensor::firstPollSensor = NULL;
+Sensor *Sensor::lastSensor = NULL;
+bool Sensor::inputChangeCallbackRegistered = false;
+#endif

Sensors.h

@@ -20,29 +20,74 @@
 #define Sensor_h
 
 #include "Arduino.h"
+#include "IODevice.h"
 
-#define  SENSOR_DECAY  0.03
+// Uncomment the following #define statement to use callback notification
+//  where the driver supports it.
+//  The principle of callback notification is to avoid the Sensor class
+//  having to poll the device driver cyclically for input values, and then scan 
+//  for changes.  Instead, when the driver scans the inputs, if it detects
+//  a change it invokes a callback function in the Sensor class.  In the current
+//  implementation, the advantages are limited because (a) the Sensor class 
+//  performs debounce checks, and (b) the Sensor class does not have a 
+//  static reference to the output stream for sending <Q>/<q> messages
+//  when a change is detected.  These restrictions mean that the checkAll() 
+//  method still has to iterate through all of the Sensor objects looking 
+//  for changes.
+#define USE_NOTIFY
 
 struct SensorData {
   int snum;
-  uint8_t pin;
+  VPIN pin;
   uint8_t pullUp;
 };
 
-struct Sensor{
+class Sensor{
-  static Sensor *firstSensor;
+  // The sensor list is a linked list where each sensor's 'nextSensor' field points to the next.
-  static Sensor *readingSensor;
+  //   The pointer is null in the last on the list.
+
+public:
   SensorData data;
-  boolean active;
+  struct {
-  byte latchdelay;
+    uint8_t active:1;
+    uint8_t inputState:1;
+    uint8_t latchDelay:6;
+  };   // bit 7=active; bit 6=input state; bits 5-0=latchDelay
+
+  static Sensor *firstSensor;
+#ifdef USE_NOTIFY
+  static Sensor *firstPollSensor;
+  static Sensor *lastSensor;
+#endif
+  // readingSensor points to the next sensor to be polled, or null if the poll cycle is completed for
+  // the period.
+  static Sensor *readingSensor;
+
+  // Constructor
+  Sensor(); 
   Sensor *nextSensor;
+
+  void setState(int state);
   static void load();
   static void store();
-  static Sensor *create(int, int, int);
+  static Sensor *create(int id, VPIN vpin, int pullUp);
-  static Sensor* get(int);  
+  static Sensor* get(int id);  
-  static bool remove(int);  
+  static bool remove(int id);  
-  static void checkAll(Print *);
+  static void checkAll(Print *stream);
-  static void printAll(Print *);
+  static void printAll(Print *stream);
+  static unsigned long lastReadCycle; // value of micros at start of last read cycle
+  static const unsigned int cycleInterval = 10000; // min time between consecutive reads of each sensor in microsecs.
+                                                   // should not be less than device scan cycle time.
+  static const unsigned int minReadCount = 1; // number of additional scans before acting on change
+                                        // E.g. 1 means that a change is ignored for one scan and actioned on the next.
+                                        // Max value is 63
+  bool pollingRequired = true;
+
+#ifdef USE_NOTIFY
+  static void inputChangeCallback(VPIN vpin, int state);
+  static bool inputChangeCallbackRegistered;
+#endif
+  
 }; // Sensor
 
 #endif

Turnouts.cpp

@@ -1,4 +1,5 @@
 /*
+ *  © 2021 Restructured Neil McKechnie
  *  © 2013-2016 Gregg E. Berman
  *  © 2020, Chris Harlow. All rights reserved.
  *  © 2020, Harald Barth.
@@ -18,166 +19,507 @@
  *  You should have received a copy of the GNU General Public License
  *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
  */
-#include "Turnouts.h"
+
+
+#include "defines.h"  // includes config.h
 #include "EEStore.h"
-#include "PWMServoDriver.h"
 #include "StringFormatter.h"
+#include "RMFT2.h"
+#include "Turnouts.h"
+#include "DCC.h"
+#include "LCN.h"
 #ifdef EESTOREDEBUG
 #include "DIAG.h"
 #endif
 
-// print all turnout states to stream
+  /* 
-void Turnout::printAll(Print *stream){
+   * Protected static data
-  for (Turnout *tt = Turnout::firstTurnout; tt != NULL; tt = tt->nextTurnout)
+   */ 
-    StringFormatter::send(stream, F("<H %d %d>\n"), tt->data.id, (tt->data.tStatus & STATUS_ACTIVE)!=0);
-} // Turnout::printAll
 
-bool Turnout::activate(int n,bool state){
+  /* static */ Turnout *Turnout::_firstTurnout = 0;
-#ifdef EESTOREDEBUG
-  DIAG(F("Turnout::activate(%d,%d)"),n,state);
-#endif
-  Turnout * tt=get(n);
-  if (tt==NULL) return false;
-  tt->activate(state);
-  turnoutlistHash++;
-  return true;
-}
 
-bool Turnout::isActive(int n){
+  /* 
-  Turnout * tt=get(n);
+   * Public static data
-  if (tt==NULL) return false;
+   */
-  return tt->data.tStatus & STATUS_ACTIVE;
+  /* static */ int Turnout::turnoutlistHash = 0;
-}
+ 
+  /*
+   * Protected static functions
+   */
 
-// activate is virtual here so that it can be overridden by a non-DCC turnout mechanism
+  /* static */ Turnout *Turnout::get(uint16_t id) {
-void Turnout::activate(bool state) {
+    // Find turnout object from list.
-#ifdef EESTOREDEBUG
+    for (Turnout *tt = _firstTurnout; tt != NULL; tt = tt->_nextTurnout)
-  DIAG(F("Turnout::activate(%d)"),state);
+      if (tt->_turnoutData.id == id) return tt;
-#endif
+    return NULL;
-  if (data.address==LCN_TURNOUT_ADDRESS) {
-     // A LCN turnout is transmitted to the LCN master.
-     LCN::send('T',data.id,state);
-     return;   // The tStatus will be updated by a message from the LCN master, later.    
-  }
-  if (state)
-    data.tStatus|=STATUS_ACTIVE;
-  else
-    data.tStatus &= ~STATUS_ACTIVE;
-  if (data.tStatus & STATUS_PWM)
-    PWMServoDriver::setServo(data.tStatus & STATUS_PWMPIN, (data.inactiveAngle+(state?data.moveAngle:0)));
-  else
-    DCC::setAccessory(data.address,data.subAddress, state);
-  // Save state if stored in EEPROM
-  if (EEStore::eeStore->data.nTurnouts > 0 && num > 0) 
-    EEPROM.put(num, data.tStatus);
-}
-///////////////////////////////////////////////////////////////////////////////
-
-Turnout* Turnout::get(int n){
-  Turnout *tt;
-  for(tt=firstTurnout;tt!=NULL && tt->data.id!=n;tt=tt->nextTurnout);
-  return(tt);
-}
-///////////////////////////////////////////////////////////////////////////////
-
-bool Turnout::remove(int n){
-  Turnout *tt,*pp=NULL;
-
-  for(tt=firstTurnout;tt!=NULL && tt->data.id!=n;pp=tt,tt=tt->nextTurnout);
-
-  if(tt==NULL) return false;
-  
-  if(tt==firstTurnout)
-    firstTurnout=tt->nextTurnout;
-  else
-    pp->nextTurnout=tt->nextTurnout;
-
-  free(tt);
-  turnoutlistHash++;
-  return true; 
-}
-
-///////////////////////////////////////////////////////////////////////////////
-
-void Turnout::load(){
-  struct TurnoutData data;
-  Turnout *tt;
-
-  for(uint16_t i=0;i<EEStore::eeStore->data.nTurnouts;i++){
-    EEPROM.get(EEStore::pointer(),data);
-    if (data.tStatus & STATUS_PWM) tt=create(data.id,data.tStatus & STATUS_PWMPIN, data.inactiveAngle,data.moveAngle);
-    else tt=create(data.id,data.address,data.subAddress);
-    tt->data.tStatus=data.tStatus;
-    tt->num=EEStore::pointer()+offsetof(TurnoutData,tStatus); // Save pointer to status byte within EEPROM
-    EEStore::advance(sizeof(tt->data));
-#ifdef EESTOREDEBUG
-    tt->print(tt);
-#endif
-  }
-}
-
-///////////////////////////////////////////////////////////////////////////////
-
-void Turnout::store(){
-  Turnout *tt;
-
-  tt=firstTurnout;
-  EEStore::eeStore->data.nTurnouts=0;
-
-  while(tt!=NULL){
-#ifdef EESTOREDEBUG
-    tt->print(tt);
-#endif
-    tt->num=EEStore::pointer()+offsetof(TurnoutData,tStatus); // Save pointer to tstatus byte within EEPROM
-    EEPROM.put(EEStore::pointer(),tt->data);
-    EEStore::advance(sizeof(tt->data));
-    tt=tt->nextTurnout;
-    EEStore::eeStore->data.nTurnouts++;
   }
 
-}
+  // Add new turnout to end of chain
-///////////////////////////////////////////////////////////////////////////////
+  /* static */ void Turnout::add(Turnout *tt) {
-
+    if (!_firstTurnout) 
-Turnout *Turnout::create(int id, int add, int subAdd){
+      _firstTurnout = tt;
-  Turnout *tt=create(id);
+    else {
-  tt->data.address=add;
+      // Find last object on chain
-  tt->data.subAddress=subAdd;
+      Turnout *ptr = _firstTurnout;
-  tt->data.tStatus=0;
+      for ( ; ptr->_nextTurnout!=0; ptr=ptr->_nextTurnout) {}
-  return(tt);
+      // Line new object to last object.
-}
+      ptr->_nextTurnout = tt;
-
-Turnout *Turnout::create(int id, byte pin, int activeAngle, int inactiveAngle){
-  Turnout *tt=create(id);
-  tt->data.tStatus= STATUS_PWM | (pin &  STATUS_PWMPIN);
-  tt->data.inactiveAngle=inactiveAngle;
-  tt->data.moveAngle=activeAngle-inactiveAngle;
-  return(tt);
-}
-
-Turnout *Turnout::create(int id){
-  Turnout *tt=get(id);
-  if (tt==NULL) { 
-     tt=(Turnout *)calloc(1,sizeof(Turnout));
-     tt->nextTurnout=firstTurnout;
-     firstTurnout=tt;
-     tt->data.id=id;
     }
-  turnoutlistHash++;
+    turnoutlistHash++;
-  return tt;
+  }
+  
+  // For DCC++ classic compatibility, state reported to JMRI is 1 for thrown and 0 for closed; 
+  void Turnout::printState(Print *stream) { 
+    StringFormatter::send(stream, F("<H %d %d>\n"), 
+      _turnoutData.id, !_turnoutData.closed);
   }
 
-///////////////////////////////////////////////////////////////////////////////
+  // Remove nominated turnout from turnout linked list and delete the object.
-//
+  /* static */ bool Turnout::remove(uint16_t id) {
-// print debug info about the state of a turnout
+    Turnout *tt,*pp=NULL;
-//
+
-#ifdef EESTOREDEBUG
+    for(tt=_firstTurnout; tt!=NULL && tt->_turnoutData.id!=id; pp=tt, tt=tt->_nextTurnout) {}
-void Turnout::print(Turnout *tt) {
+    if (tt == NULL) return false;
-    if (tt->data.tStatus & STATUS_PWM )
+    
-      DIAG(F("Turnout %d ZeroAngle %d MoveAngle %d Status %d"),tt->data.id, tt->data.inactiveAngle, tt->data.moveAngle,tt->data.tStatus & STATUS_ACTIVE);
+    if (tt == _firstTurnout)
+      _firstTurnout = tt->_nextTurnout;
     else
-	DIAG(F("Turnout %d Addr %d Subaddr %d Status %d"),tt->data.id, tt->data.address, tt->data.subAddress,tt->data.tStatus & STATUS_ACTIVE);
+      pp->_nextTurnout = tt->_nextTurnout;
-}
+
+    delete (ServoTurnout *)tt;
+
+    turnoutlistHash++;
+    return true; 
+  } 
+
+
+  /*
+   * Public static functions
+   */
+
+  /* static */ bool Turnout::isClosed(uint16_t id) {
+    Turnout *tt = get(id);
+    if (tt) 
+      return tt->isClosed();
+    else
+      return false;
+  }
+
+  /* static */ bool Turnout::setClosedStateOnly(uint16_t id, bool closeFlag) {
+    Turnout *tt = get(id);
+    if (!tt) return false;
+    tt->_turnoutData.closed = closeFlag;
+
+    // I know it says setClosedStateOnly, but we need to tell others
+    //  that the state has changed too.
+    #if defined(RMFT_ACTIVE)
+      RMFT2::turnoutEvent(id, closeFlag);
+    #endif
+
+      // Send message to JMRI etc. over Serial USB.  This is done here
+      // to ensure that the message is sent when the turnout operation
+      // is not initiated by a Serial command.
+      tt->printState(&Serial);
+    return true;
+  }
+
+
+  // Static setClosed function is invoked from close(), throw() etc. to perform the 
+  //  common parts of the turnout operation.  Code which is specific to a turnout
+  //  type should be placed in the virtual function setClosedInternal(bool) which is
+  //  called from here.
+  /* static */ bool Turnout::setClosed(uint16_t id, bool closeFlag) { 
+  #if defined(DIAG_IO)
+    if (closeFlag) 
+      DIAG(F("Turnout::close(%d)"), id);
+    else
+      DIAG(F("Turnout::throw(%d)"), id);
+  #endif
+    Turnout *tt = Turnout::get(id);
+    if (!tt) return false;
+    bool ok = tt->setClosedInternal(closeFlag);
+
+    if (ok) {
+      turnoutlistHash++;  // let withrottle know something changed
+    
+      // Write byte containing new closed/thrown state to EEPROM if required.  Note that eepromAddress
+      // is always zero for LCN turnouts.
+      if (EEStore::eeStore->data.nTurnouts > 0 && tt->_eepromAddress > 0) 
+        EEPROM.put(tt->_eepromAddress, tt->_turnoutData.flags);  
+
+    #if defined(RMFT_ACTIVE)
+      RMFT2::turnoutEvent(id, closeFlag);
+    #endif
+
+      // Send message to JMRI etc. over Serial USB.  This is done here
+      // to ensure that the message is sent when the turnout operation
+      // is not initiated by a Serial command.
+      tt->printState(&Serial);
+    }
+    return ok;
+  }
+
+  // Load all turnout objects
+  /* static */ void Turnout::load() {
+    for (uint16_t i=0; i<EEStore::eeStore->data.nTurnouts; i++) {
+      Turnout::loadTurnout();
+    }
+  }
+
+  // Save all turnout objects
+  /* static */ void Turnout::store() {
+    EEStore::eeStore->data.nTurnouts=0;
+    for (Turnout *tt = _firstTurnout; tt != 0; tt = tt->_nextTurnout) {
+      tt->save();
+      EEStore::eeStore->data.nTurnouts++;
+    }
+  }
+
+  // Load one turnout from EEPROM
+  /* static */ Turnout *Turnout::loadTurnout () {
+    Turnout *tt = 0;
+    // Read turnout type from EEPROM
+    struct TurnoutData turnoutData;
+    int eepromAddress = EEStore::pointer() + offsetof(struct TurnoutData, flags); // Address of byte containing the closed flag.
+    EEPROM.get(EEStore::pointer(), turnoutData);
+    EEStore::advance(sizeof(turnoutData));
+
+    switch (turnoutData.turnoutType) {
+      case TURNOUT_SERVO:
+        // Servo turnout
+        tt = ServoTurnout::load(&turnoutData);
+        break;
+      case TURNOUT_DCC:
+        // DCC Accessory turnout
+        tt = DCCTurnout::load(&turnoutData);
+        break;
+      case TURNOUT_VPIN:
+        // VPIN turnout
+        tt = VpinTurnout::load(&turnoutData);
+        break;
+      default:
+        // If we find anything else, then we don't know what it is or how long it is, 
+        // so we can't go any further through the EEPROM!
+        return NULL;
+    }
+    if (tt) {
+      // Save EEPROM address in object.  Note that LCN turnouts always have eepromAddress of zero.
+      tt->_eepromAddress = eepromAddress + offsetof(struct TurnoutData, flags);
+    }
+
+#ifdef EESTOREDEBUG
+    printAll(&Serial);
+#endif
+    return tt;
+  }
+
+  // Display, on the specified stream, the current state of the turnout (1=thrown or 0=closed).
+  /* static */ void Turnout::printState(uint16_t id, Print *stream) {
+    Turnout *tt = get(id);
+    if (tt) tt->printState(stream);
+  }
+
+
+/*************************************************************************************
+ * ServoTurnout - Turnout controlled by servo device.
+ * 
+ *************************************************************************************/
+
+  // Private Constructor
+  ServoTurnout::ServoTurnout(uint16_t id, VPIN vpin, uint16_t thrownPosition, uint16_t closedPosition, uint8_t profile, bool closed) :
+    Turnout(id, TURNOUT_SERVO, closed) 
+  {
+    _servoTurnoutData.vpin = vpin;
+    _servoTurnoutData.thrownPosition = thrownPosition; 
+    _servoTurnoutData.closedPosition = closedPosition;
+    _servoTurnoutData.profile = profile;
+  }
+
+  // Create function
+  /* static */ Turnout *ServoTurnout::create(uint16_t id, VPIN vpin, uint16_t thrownPosition, uint16_t closedPosition, uint8_t profile, bool closed) {
+#ifndef IO_NO_HAL
+    Turnout *tt = get(id);
+    if (tt) { 
+      // Object already exists, check if it is usable
+      if (tt->isType(TURNOUT_SERVO)) {
+        // Yes, so set parameters
+        ServoTurnout *st = (ServoTurnout *)tt;
+        st->_servoTurnoutData.vpin = vpin;
+        st->_servoTurnoutData.thrownPosition = thrownPosition;
+        st->_servoTurnoutData.closedPosition = closedPosition;
+        st->_servoTurnoutData.profile = profile;
+        // Don't touch the _closed parameter, retain the original value.
+
+        // We don't really need to do the following, since a call to IODevice::_writeAnalogue 
+        //  will provide all the data that is required!  However, if someone has configured 
+        //  a Turnout, we should ensure that the SET() RESET() and other commands that use write() 
+        //  behave consistently with the turnout commands.
+        IODevice::configureServo(vpin, thrownPosition, closedPosition, profile, 0, closed);
+
+        // Set position directly to specified position - we don't know where it is moving from.
+        IODevice::writeAnalogue(vpin, closed ? closedPosition : thrownPosition, PCA9685::Instant);
+
+        return tt;
+      } else {
+        // Incompatible object, delete and recreate
+        remove(id);
+      }
+    }
+    tt = (Turnout *)new ServoTurnout(id, vpin, thrownPosition, closedPosition, profile, closed);
+    IODevice::writeAnalogue(vpin, closed ? closedPosition : thrownPosition, PCA9685::Instant);
+    return tt;
+#else
+    (void)id; (void)vpin; (void)thrownPosition; (void)closedPosition;
+    (void)profile; (void)closed;          // avoid compiler warnings.
+    return NULL;
+#endif
+  }
+
+  // Load a Servo turnout definition from EEPROM.  The common Turnout data has already been read at this point.
+  Turnout *ServoTurnout::load(struct TurnoutData *turnoutData) {
+    ServoTurnoutData servoTurnoutData;
+    // Read class-specific data from EEPROM
+    EEPROM.get(EEStore::pointer(), servoTurnoutData);
+    EEStore::advance(sizeof(servoTurnoutData));
+    
+    // Create new object
+    Turnout *tt = ServoTurnout::create(turnoutData->id, servoTurnoutData.vpin, servoTurnoutData.thrownPosition,
+      servoTurnoutData.closedPosition, servoTurnoutData.profile, turnoutData->closed);
+    return tt;
+  }
+
+  // For DCC++ classic compatibility, state reported to JMRI is 1 for thrown and 0 for closed
+  void ServoTurnout::print(Print *stream) {
+    StringFormatter::send(stream, F("<H %d SERVO %d %d %d %d %d>\n"), _turnoutData.id, _servoTurnoutData.vpin, 
+      _servoTurnoutData.thrownPosition, _servoTurnoutData.closedPosition, _servoTurnoutData.profile, 
+      !_turnoutData.closed);
+  }
+
+  // ServoTurnout-specific code for throwing or closing a servo turnout.
+  bool ServoTurnout::setClosedInternal(bool close) {
+#ifndef IO_NO_HAL
+    IODevice::writeAnalogue(_servoTurnoutData.vpin, 
+      close ? _servoTurnoutData.closedPosition : _servoTurnoutData.thrownPosition, _servoTurnoutData.profile);
+    _turnoutData.closed = close;
+#else
+    (void)close;  // avoid compiler warnings
+#endif
+    return true;
+  }
+
+  void ServoTurnout::save() {
+    // Write turnout definition and current position to EEPROM
+    // First write common servo data, then
+    // write the servo-specific data
+    EEPROM.put(EEStore::pointer(), _turnoutData);
+    EEStore::advance(sizeof(_turnoutData));
+    EEPROM.put(EEStore::pointer(), _servoTurnoutData);
+    EEStore::advance(sizeof(_servoTurnoutData));
+  }
+
+/*************************************************************************************
+ * DCCTurnout - Turnout controlled by DCC Accessory Controller.
+ * 
+ *************************************************************************************/
+
+#if defined(DCC_TURNOUTS_RCN_213)
+  const bool DCCTurnout::rcn213Compliant = true;
+#else
+  const bool DCCTurnout::rcn213Compliant = false;
 #endif
 
-Turnout *Turnout::firstTurnout=NULL;
+  // DCCTurnoutData contains data specific to this subclass that is 
-int Turnout::turnoutlistHash=0; //bump on every change so clients know when to refresh their lists
+  // written to EEPROM when the turnout is saved.
+  struct DCCTurnoutData {
+    // DCC address (Address in bits 15-2, subaddress in bits 1-0
+    uint16_t address; // CS currently supports linear address 1-2048
+      // That's DCC accessory address 1-512 and subaddress 0-3.
+  } _dccTurnoutData; // 2 bytes
+
+  // Constructor
+  DCCTurnout::DCCTurnout(uint16_t id, uint16_t address, uint8_t subAdd) :
+    Turnout(id, TURNOUT_DCC, false)
+  {
+    _dccTurnoutData.address = address;
+    _dccTurnoutData.subAddress = subAdd;
+  }
+
+  // Create function
+  /* static */ Turnout *DCCTurnout::create(uint16_t id, uint16_t add, uint8_t subAdd) {
+    Turnout *tt = get(id);
+    if (tt) { 
+      // Object already exists, check if it is usable
+      if (tt->isType(TURNOUT_DCC)) {
+        // Yes, so set parameters<T>
+        DCCTurnout *dt = (DCCTurnout *)tt;
+        dt->_dccTurnoutData.address = add;
+        dt->_dccTurnoutData.subAddress = subAdd;
+        // Don't touch the _closed parameter, retain the original value.
+        return tt;
+      } else {
+        // Incompatible object, delete and recreate
+        remove(id);
+      }
+    }
+    tt = (Turnout *)new DCCTurnout(id, add, subAdd);
+    return tt;
+  }
+
+  // Load a DCC turnout definition from EEPROM.  The common Turnout data has already been read at this point.
+  /* static */ Turnout *DCCTurnout::load(struct TurnoutData *turnoutData) {
+    DCCTurnoutData dccTurnoutData;
+    // Read class-specific data from EEPROM
+    EEPROM.get(EEStore::pointer(), dccTurnoutData);
+    EEStore::advance(sizeof(dccTurnoutData));
+    
+    // Create new object
+    DCCTurnout *tt = new DCCTurnout(turnoutData->id, dccTurnoutData.address, dccTurnoutData.subAddress);
+
+    return tt;
+  }
+
+  void DCCTurnout::print(Print *stream) {
+    StringFormatter::send(stream, F("<H %d DCC %d %d %d>\n"), _turnoutData.id, 
+      _dccTurnoutData.address, _dccTurnoutData.subAddress, !_turnoutData.closed); 
+    // Also report using classic DCC++ syntax for DCC accessory turnouts, since JMRI expects this.
+    StringFormatter::send(stream, F("<H %d %d %d %d>\n"), _turnoutData.id, 
+      _dccTurnoutData.address, _dccTurnoutData.subAddress, !_turnoutData.closed); 
+  }
+
+  bool DCCTurnout::setClosedInternal(bool close) {
+    // DCC++ Classic behaviour is that Throw writes a 1 in the packet,
+    // and Close writes a 0.  
+    // RCN-213 specifies that Throw is 0 and Close is 1.
+    DCC::setAccessory(_dccTurnoutData.address, _dccTurnoutData.subAddress, close ^ !rcn213Compliant);
+    _turnoutData.closed = close;
+    return true;
+  }
+
+  void DCCTurnout::save() {
+    // Write turnout definition and current position to EEPROM
+    // First write common servo data, then
+    // write the servo-specific data
+    EEPROM.put(EEStore::pointer(), _turnoutData);
+    EEStore::advance(sizeof(_turnoutData));
+    EEPROM.put(EEStore::pointer(), _dccTurnoutData);
+    EEStore::advance(sizeof(_dccTurnoutData));
+  }
+
+
+
+/*************************************************************************************
+ * VpinTurnout - Turnout controlled through a HAL vpin.
+ * 
+ *************************************************************************************/
+
+  // Constructor
+  VpinTurnout::VpinTurnout(uint16_t id, VPIN vpin, bool closed) :
+    Turnout(id, TURNOUT_VPIN, closed)
+  {
+    _vpinTurnoutData.vpin = vpin;
+  }
+
+  // Create function
+  /* static */ Turnout *VpinTurnout::create(uint16_t id, VPIN vpin, bool closed) {
+    Turnout *tt = get(id);
+    if (tt) { 
+      // Object already exists, check if it is usable
+      if (tt->isType(TURNOUT_VPIN)) {
+        // Yes, so set parameters
+        VpinTurnout *vt = (VpinTurnout *)tt;
+        vt->_vpinTurnoutData.vpin = vpin;
+        // Don't touch the _closed parameter, retain the original value.
+        return tt;
+      } else {
+        // Incompatible object, delete and recreate
+        remove(id);
+      }
+    }
+    tt = (Turnout *)new VpinTurnout(id, vpin, closed);
+    return tt;
+  }
+
+  // Load a VPIN turnout definition from EEPROM.  The common Turnout data has already been read at this point.
+  /* static */ Turnout *VpinTurnout::load(struct TurnoutData *turnoutData) {
+    VpinTurnoutData vpinTurnoutData;
+    // Read class-specific data from EEPROM
+    EEPROM.get(EEStore::pointer(), vpinTurnoutData);
+    EEStore::advance(sizeof(vpinTurnoutData));
+    
+    // Create new object
+    VpinTurnout *tt = new VpinTurnout(turnoutData->id, vpinTurnoutData.vpin, turnoutData->closed);
+
+    return tt;
+  }
+
+  // Report 1 for thrown, 0 for closed.
+  void VpinTurnout::print(Print *stream) {
+    StringFormatter::send(stream, F("<H %d VPIN %d %d>\n"), _turnoutData.id, _vpinTurnoutData.vpin, 
+      !_turnoutData.closed); 
+  }
+
+  bool VpinTurnout::setClosedInternal(bool close) {
+    IODevice::write(_vpinTurnoutData.vpin, close);
+    _turnoutData.closed = close;
+    return true;
+  }
+
+  void VpinTurnout::save() {
+    // Write turnout definition and current position to EEPROM
+    // First write common servo data, then
+    // write the servo-specific data
+    EEPROM.put(EEStore::pointer(), _turnoutData);
+    EEStore::advance(sizeof(_turnoutData));
+    EEPROM.put(EEStore::pointer(), _vpinTurnoutData);
+    EEStore::advance(sizeof(_vpinTurnoutData));
+  }
+
+
+/*************************************************************************************
+ * LCNTurnout - Turnout controlled by Loconet
+ * 
+ *************************************************************************************/
+
+  // LCNTurnout has no specific data, and in any case is not written to EEPROM!
+  // struct LCNTurnoutData {
+  // } _lcnTurnoutData; // 0 bytes
+
+  // Constructor
+  LCNTurnout::LCNTurnout(uint16_t id, bool closed) :
+    Turnout(id, TURNOUT_LCN, closed)
+  { }
+
+  // Create function
+  /* static */ Turnout *LCNTurnout::create(uint16_t id, bool closed) {
+    Turnout *tt = get(id);
+    if (tt) { 
+      // Object already exists, check if it is usable
+      if (tt->isType(TURNOUT_LCN)) {
+        // Yes, so return this object
+        return tt;
+      } else {
+        // Incompatible object, delete and recreate
+        remove(id);
+      }
+    }
+    tt = (Turnout *)new LCNTurnout(id, closed);
+    return tt;
+  }
+
+  bool LCNTurnout::setClosedInternal(bool close) {
+    // Assume that the LCN command still uses 1 for throw and 0 for close...
+    LCN::send('T', _turnoutData.id, !close);
+    // The _turnoutData.closed flag should be updated by a message from the LCN master, later.
+    return true;
+  }
+
+  // LCN turnouts not saved to EEPROM.
+  //void save() override {  }
+  //static Turnout *load(struct TurnoutData *turnoutData) {
+
+  // Report 1 for thrown, 0 for closed.
+  void LCNTurnout::print(Print *stream) {
+    StringFormatter::send(stream, F("<H %d LCN %d>\n"), _turnoutData.id, 
+    !_turnoutData.closed); 
+  }
+

Turnouts.h

@@ -1,4 +1,6 @@
 /*
+ *  © 2021 Restructured Neil McKechnie
+ *  © 2013-2016 Gregg E. Berman
  *  © 2020, Chris Harlow. All rights reserved.
  *  
  *  This file is part of Asbelos DCC API
@@ -16,46 +18,283 @@
  *  You should have received a copy of the GNU General Public License
  *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
  */
-#ifndef Turnouts_h
-#define Turnouts_h
 
-#include <Arduino.h>
+#ifndef TURNOUTS_H
-#include "DCC.h"
+#define TURNOUTS_H
-#include "LCN.h"
 
-const byte STATUS_ACTIVE=0x80; // Flag as activated
+//#define EESTOREDEBUG 
-const byte STATUS_PWM=0x40; // Flag as a PWM turnout
+#include "Arduino.h"
-const byte STATUS_PWMPIN=0x3F; // PWM  pin 0-63
+#include "IODevice.h"
-const int  LCN_TURNOUT_ADDRESS=-1;  // spoof dcc address -1 indicates a LCN turnout
+
-struct TurnoutData {
+
-   int id;
+// Turnout type definitions
-   uint8_t tStatus; // has STATUS_ACTIVE, STATUS_PWM, STATUS_PWMPIN  
+enum {
-   union {uint8_t subAddress; char moveAngle;}; //DCC  sub addrerss or PWM difference from inactiveAngle  
+  TURNOUT_DCC = 1,
-   union {int address; int inactiveAngle;}; // DCC address or PWM servo angle 
+  TURNOUT_SERVO = 2,
+  TURNOUT_VPIN = 3,
+  TURNOUT_LCN = 4,
 };
 
+/*************************************************************************************
+ * Turnout - Base class for turnouts.
+ * 
+ *************************************************************************************/
+
 class Turnout {
-  public:
+protected:
-  static Turnout *firstTurnout;
+  /* 
-  static int turnoutlistHash;
+   * Object data
-  TurnoutData data;
+   */
-  Turnout *nextTurnout;
+
-  static  bool activate(int n, bool state);
+  // The TurnoutData struct contains data common to all turnout types, that 
-  static Turnout* get(int);
+  // is written to EEPROM when the turnout is saved.
-  static bool remove(int);
+  // The first byte of this struct contains the 'closed' flag which is
-  static bool isActive(int);
+  // updated whenever the turnout changes from thrown to closed and
-  static void load();
+  // vice versa.  If the turnout has been saved, then this byte is rewritten
-  static void store();
+  // when changed in RAM.  The 'closed' flag must be located in the first byte.
-  static Turnout *create(int id , int address , int subAddress);
+  struct TurnoutData {
-  static Turnout *create(int id , byte pin , int activeAngle, int inactiveAngle);
+    union {
-  static Turnout *create(int id);
+      struct {
-  void activate(bool state);
+        bool closed : 1;
-  static void printAll(Print *);
+        bool _rfu: 2;
-#ifdef EESTOREDEBUG
+        uint8_t turnoutType : 5;
-  void print(Turnout *tt);
+      };
-#endif
+      uint8_t flags;
-private:
+    };
-  int num;  // EEPROM address of tStatus in TurnoutData struct, or zero if not stored.
+    uint16_t id;
-}; // Turnout
+  } _turnoutData;  // 3 bytes
+
+  // Address in eeprom of first byte of the _turnoutData struct (containing the closed flag).
+  // Set to zero if the object has not been saved in EEPROM, e.g. for newly created Turnouts, and 
+  // for all LCN turnouts.
+  uint16_t _eepromAddress = 0;
+
+  // Pointer to next turnout on linked list.
+  Turnout *_nextTurnout = 0;
+
+  /*
+   * Constructor
+   */
+  Turnout(uint16_t id, uint8_t turnoutType, bool closed) {
+    _turnoutData.id = id;
+    _turnoutData.turnoutType = turnoutType;
+    _turnoutData.closed = closed;
+    add(this);
+  }
+
+  /* 
+   * Static data
+   */ 
+
+  static Turnout *_firstTurnout;
+  static int _turnoutlistHash;
+
+  /* 
+   * Virtual functions
+   */
+
+  virtual bool setClosedInternal(bool close) = 0;  // Mandatory in subclass
+  virtual void save() {}
   
+  /*
+   * Static functions
+   */
+
+  static Turnout *get(uint16_t id);
+
+  static void add(Turnout *tt);
+  
+public:
+  /* 
+   * Static data
+   */
+  static int turnoutlistHash;
+  static const bool useClassicTurnoutCommands;
+  
+  /*
+   * Public base class functions
+   */
+  inline bool isClosed() { return _turnoutData.closed; };
+  inline bool isThrown() { return !_turnoutData.closed; }
+  inline bool isType(uint8_t type) { return _turnoutData.turnoutType == type; }
+  inline uint16_t getId() { return _turnoutData.id; }
+  inline Turnout *next() { return _nextTurnout; }
+  void printState(Print *stream);
+  /* 
+   * Virtual functions
+   */
+  virtual void print(Print *stream) {
+    (void)stream;  // avoid compiler warnings.
+  }
+  virtual ~Turnout() {}   // Destructor
+
+  /*
+   * Public static functions
+   */
+  inline static bool exists(uint16_t id) { return get(id) != 0; }
+
+  static bool remove(uint16_t id);
+
+  static bool isClosed(uint16_t id);
+
+  inline static bool isThrown(uint16_t id) {
+    return !isClosed(id);
+  }
+
+  static bool setClosed(uint16_t id, bool closeFlag);
+
+  inline static bool setClosed(uint16_t id) {
+    return setClosed(id, true);
+  }
+
+  inline static bool setThrown(uint16_t id) {
+    return setClosed(id, false);
+  }
+
+  static bool setClosedStateOnly(uint16_t id, bool close);
+
+  inline static Turnout *first() { return _firstTurnout; }
+
+  // Load all turnout definitions.
+  static void load();
+  // Load one turnout definition
+  static Turnout *loadTurnout();
+  // Save all turnout definitions
+  static void store();
+
+  static void printAll(Print *stream) {
+    for (Turnout *tt = _firstTurnout; tt != 0; tt = tt->_nextTurnout)
+      tt->printState(stream);
+  }
+
+  static void printState(uint16_t id, Print *stream);
+};
+
+
+/*************************************************************************************
+ * ServoTurnout - Turnout controlled by servo device.
+ * 
+ *************************************************************************************/
+class ServoTurnout : public Turnout {
+private:
+  // ServoTurnoutData contains data specific to this subclass that is 
+  // written to EEPROM when the turnout is saved.
+  struct ServoTurnoutData {
+    VPIN vpin;
+    uint16_t closedPosition : 12;
+    uint16_t thrownPosition : 12;
+    uint8_t profile;
+  } _servoTurnoutData; // 6 bytes
+
+  // Constructor
+  ServoTurnout(uint16_t id, VPIN vpin, uint16_t thrownPosition, uint16_t closedPosition, uint8_t profile, bool closed);
+
+public:
+  // Create function
+  static Turnout *create(uint16_t id, VPIN vpin, uint16_t thrownPosition, uint16_t closedPosition, uint8_t profile, bool closed=true);
+
+  // Load a Servo turnout definition from EEPROM.  The common Turnout data has already been read at this point.
+  static Turnout *load(struct TurnoutData *turnoutData);
+  void print(Print *stream) override;
+
+protected:
+  // ServoTurnout-specific code for throwing or closing a servo turnout.
+  bool setClosedInternal(bool close) override;
+  void save() override;
+
+};
+
+/*************************************************************************************
+ * DCCTurnout - Turnout controlled by DCC Accessory Controller.
+ * 
+ *************************************************************************************/
+class DCCTurnout : public Turnout {
+private:
+  // DCCTurnoutData contains data specific to this subclass that is 
+  // written to EEPROM when the turnout is saved.
+  struct DCCTurnoutData {
+    // DCC address (Address in bits 15-2, subaddress in bits 1-0)
+    struct {
+      uint16_t address : 14;
+      uint8_t subAddress : 2;
+    };
+  } _dccTurnoutData; // 2 bytes
+
+  // Constructor
+  DCCTurnout(uint16_t id, uint16_t address, uint8_t subAdd);
+
+public:
+  // Create function
+  static Turnout *create(uint16_t id, uint16_t add, uint8_t subAdd);
+  // Load a VPIN turnout definition from EEPROM.  The common Turnout data has already been read at this point.
+  static Turnout *load(struct TurnoutData *turnoutData);
+  void print(Print *stream) override;
+  // Flag whether DCC Accessory packets are to contain 1=close/0=throw(RCN-213) or 1=throw/0-close (DCC++ Classic)
+  static const bool rcn213Compliant;
+
+protected:
+  bool setClosedInternal(bool close) override;
+  void save() override;
+
+};
+
+
+/*************************************************************************************
+ * VpinTurnout - Turnout controlled through a HAL vpin.
+ * 
+ *************************************************************************************/
+class VpinTurnout : public Turnout {
+private:
+  // VpinTurnoutData contains data specific to this subclass that is 
+  // written to EEPROM when the turnout is saved.
+  struct VpinTurnoutData {
+    VPIN vpin;
+  } _vpinTurnoutData; // 2 bytes
+
+  // Constructor
+ VpinTurnout(uint16_t id, VPIN vpin, bool closed);
+
+public:
+  // Create function
+  static Turnout *create(uint16_t id, VPIN vpin, bool closed=true);
+
+  // Load a VPIN turnout definition from EEPROM.  The common Turnout data has already been read at this point.
+  static Turnout *load(struct TurnoutData *turnoutData);
+  void print(Print *stream) override;
+
+protected:
+  bool setClosedInternal(bool close) override;
+  void save() override;
+
+};
+
+
+/*************************************************************************************
+ * LCNTurnout - Turnout controlled by Loconet
+ * 
+ *************************************************************************************/
+class LCNTurnout : public Turnout {
+private:
+  // LCNTurnout has no specific data, and in any case is not written to EEPROM!
+  // struct LCNTurnoutData {
+  // } _lcnTurnoutData; // 0 bytes
+
+  // Constructor 
+  LCNTurnout(uint16_t id, bool closed);
+
+public:
+  // Create function
+  static Turnout *create(uint16_t id, bool closed=true);
+
+
+  bool setClosedInternal(bool close) override;
+
+  // LCN turnouts not saved to EEPROM.
+  //void save() override {  }
+  //static Turnout *load(struct TurnoutData *turnoutData) {
+
+  void print(Print *stream) override;
+
+};
+
 #endif

WiThrottle.cpp

@@ -40,6 +40,7 @@
  *  WiThrottle.h sets the max locos per client at 10, this is ok to increase but requires just an extra 3 bytes per loco per client.      
 */
 #include <Arduino.h>
+#include "defines.h"
 #include "WiThrottle.h"
 #include "DCC.h"
 #include "DCCWaveform.h"
@@ -48,12 +49,13 @@
 #include "DIAG.h"
 #include "GITHUB_SHA.h"
 #include "version.h"
+#include "RMFT2.h"
+
 
 #define LOOPLOCOS(THROTTLECHAR, CAB)  for (int loco=0;loco<MAX_MY_LOCO;loco++) \
       if ((myLocos[loco].throttle==THROTTLECHAR || '*'==THROTTLECHAR) && (CAB<0 || myLocos[loco].cab==CAB))
 
 WiThrottle * WiThrottle::firstThrottle=NULL;
-bool WiThrottle::annotateLeftRight=false;
 
 WiThrottle* WiThrottle::getThrottle( int wifiClient) {
   for (WiThrottle* wt=firstThrottle; wt!=NULL ; wt=wt->nextThrottle)  
@@ -83,6 +85,8 @@ WiThrottle::WiThrottle( int wificlientid) {
    initSent=false; // prevent sending heartbeats before connection completed
    heartBeatEnable=false; // until client turns it on
    turnoutListHash = -1;  // make sure turnout list is sent once
+   exRailSent=false;
+   mostRecentCab=0;                
    for (int loco=0;loco<MAX_MY_LOCO; loco++) myLocos[loco].throttle='\0';
 }
 
@@ -116,12 +120,21 @@ void WiThrottle::parse(RingStream * stream, byte * cmdx) {
     // Send turnout list if changed since last sent (will replace list on client)
     if (turnoutListHash != Turnout::turnoutlistHash) {
       StringFormatter::send(stream,F("PTL"));
-      for(Turnout *tt=Turnout::firstTurnout;tt!=NULL;tt=tt->nextTurnout){
+      for(Turnout *tt=Turnout::first();tt!=NULL;tt=tt->next()){
-          StringFormatter::send(stream,F("]\\[%d}|{%d}|{%c"), tt->data.id, tt->data.id, Turnout::isActive(tt->data.id)?'4':'2');
+          int id=tt->getId();
+          StringFormatter::send(stream,F("]\\[%d}|{%d}|{%c"), id, id, Turnout::isClosed(id)?'2':'4');
       }
       StringFormatter::send(stream,F("\n"));
       turnoutListHash = Turnout::turnoutlistHash; // keep a copy of hash for later comparison
     }
+
+    else if (!exRailSent) {
+      // Send ExRail routes list if not already sent (but not at same time as turnouts above)
+      exRailSent=true;
+#ifdef RMFT_ACTIVE
+      RMFT2::emitWithrottleRouteList(stream);
+#endif    
+    }
   }
 
    while (cmd[0]) {
@@ -138,25 +151,40 @@ void WiThrottle::parse(RingStream * stream, byte * cmdx) {
               StringFormatter::send(stream,F("PPA%x\n"),DCCWaveform::mainTrack.getPowerMode()==POWERMODE::ON);
               lastPowerState = (DCCWaveform::mainTrack.getPowerMode()==POWERMODE::ON); //remember power state sent for comparison later
             }
+#if defined(RMFT_ACTIVE)
+            else if (cmd[1]=='R' && cmd[2]=='A' && cmd[3]=='2' ) { // Route activate
+              // exrail routes are RA2Rn , Animations are RA2An 
+              int route=getInt(cmd+5);
+              uint16_t cab=cmd[4]=='A' ? mostRecentCab : 0; 
+              RMFT2::createNewTask(route, cab);
+            }
+#endif    
             else if (cmd[1]=='T' && cmd[2]=='A') { // PTA accessory toggle 
                 int id=getInt(cmd+4); 
-                bool newstate=false;
+                if (!Turnout::exists(id)) {
-                Turnout * tt=Turnout::get(id);
-                if (!tt) {
                   // If turnout does not exist, create it
                   int addr = ((id - 1) / 4) + 1;
                   int subaddr = (id - 1) % 4;
-                  Turnout::create(id,addr,subaddr);
+                  DCCTurnout::create(id,addr,subaddr);
                   StringFormatter::send(stream, F("HmTurnout %d created\n"),id);
                 }
                 switch (cmd[3]) {
-                    case 'T': newstate=true; break;
+            		  // T and C according to RCN-213 where 0 is Stop, Red, Thrown, Diverging.
-                    case 'C': newstate=false; break;
+            		  case 'T': 
-                    case '2': newstate=!Turnout::isActive(id);                 
+            		     Turnout::setClosed(id,false);
+                     break;
+            		  case 'C': 
+                     Turnout::setClosed(id,true);
+                     break;
+            		  case '2': 
+            		     Turnout::setClosed(id,!Turnout::isClosed(id));
+                     break;
+            		  default :
+            		     Turnout::setClosed(id,true);
+                     break;
                 }
-		            Turnout::activate(id,newstate);
+		            StringFormatter::send(stream, F("PTA%c%d\n"),Turnout::isClosed(id)?'2':'4',id );
-                StringFormatter::send(stream, F("PTA%c%d\n"),newstate?'4':'2',id );   
+		        }
-            }
             break;
        case 'N':  // Heartbeat (2), only send if connection completed by 'HU' message
             if (initSent) { 
@@ -170,8 +198,7 @@ void WiThrottle::parse(RingStream * stream, byte * cmdx) {
             if (cmd[1] == 'U') {
               StringFormatter::send(stream,F("VN2.0\nHTDCC-EX\nRL0\n"));
               StringFormatter::send(stream,F("HtDCC-EX v%S, %S, %S, %S\n"), F(VERSION), F(ARDUINO_TYPE), DCC::getMotorShieldName(), F(GITHUB_SHA));
-              if (annotateLeftRight) StringFormatter::send(stream,F("PTT]\\[Turnouts}|{Turnout]\\[Left}|{2]\\[Right}|{4\n"));
+              StringFormatter::send(stream,F("PTT]\\[Turnouts}|{Turnout]\\[THROW}|{2]\\[CLOSE}|{4\n"));
-              else                   StringFormatter::send(stream,F("PTT]\\[Turnouts}|{Turnout]\\[Closed}|{2]\\[Thrown}|{4\n"));
               StringFormatter::send(stream,F("PPA%x\n"),DCCWaveform::mainTrack.getPowerMode()==POWERMODE::ON);
               lastPowerState = (DCCWaveform::mainTrack.getPowerMode()==POWERMODE::ON); //remember power state sent for comparison later
               StringFormatter::send(stream,F("*%d\n"),HEARTBEAT_SECONDS);
@@ -244,6 +271,7 @@ void WiThrottle::multithrottle(RingStream * stream, byte * cmd){
                   if (myLocos[loco].throttle=='\0') { 
                     myLocos[loco].throttle=throttleChar;
                     myLocos[loco].cab=locoid;
+                    mostRecentCab=locoid;
                     StringFormatter::send(stream, F("M%c+%c%d<;>\n"), throttleChar, cmd[3] ,locoid); //tell client to add loco
                     //Get known Fn states from DCC 
                     for(int fKey=0; fKey<=28; fKey++) { 
@@ -278,6 +306,7 @@ void WiThrottle::locoAction(RingStream * stream, byte* aval, char throttleChar,
              { 
               int witSpeed=getInt(aval+1);
               LOOPLOCOS(throttleChar, cab) {
+                mostRecentCab=myLocos[loco].cab;
                 DCC::setThrottle(myLocos[loco].cab, WiTToDCCSpeed(witSpeed), DCC::getThrottleDirection(myLocos[loco].cab));
                 StringFormatter::send(stream,F("M%cA%c%d<;>V%d\n"), throttleChar, LorS(myLocos[loco].cab), myLocos[loco].cab, witSpeed);
                 }
@@ -311,7 +340,8 @@ void WiThrottle::locoAction(RingStream * stream, byte* aval, char throttleChar,
             case 'R':
             { 
               bool forward=aval[1]!='0';
-              LOOPLOCOS(throttleChar, cab) {              
+              LOOPLOCOS(throttleChar, cab) {
+                mostRecentCab=myLocos[loco].cab;
                 DCC::setThrottle(myLocos[loco].cab, DCC::getThrottleSpeed(myLocos[loco].cab), forward);
                 StringFormatter::send(stream,F("M%cA%c%d<;>R%d\n"), throttleChar, LorS(myLocos[loco].cab), myLocos[loco].cab, forward);
               }
@@ -327,6 +357,7 @@ void WiThrottle::locoAction(RingStream * stream, byte* aval, char throttleChar,
             case 'I': // Idle, set speed to 0
             case 'Q': // Quit, set speed to 0
               LOOPLOCOS(throttleChar, cab) {
+                mostRecentCab=myLocos[loco].cab;
                 DCC::setThrottle(myLocos[loco].cab, 0, DCC::getThrottleDirection(myLocos[loco].cab));
                 StringFormatter::send(stream,F("M%cA%c%d<;>V%d\n"), throttleChar, LorS(myLocos[loco].cab), myLocos[loco].cab, 0);
               }

WiThrottle.h

@@ -31,7 +31,7 @@ class WiThrottle {
     static void loop(RingStream * stream);
     void parse(RingStream * stream, byte * cmd);
     static WiThrottle* getThrottle( int wifiClient); 
-    static bool annotateLeftRight;
+    
   private: 
     WiThrottle( int wifiClientId);
     ~WiThrottle();
@@ -53,6 +53,8 @@ class WiThrottle {
       bool heartBeatEnable;
       unsigned long heartBeat;
       bool initSent; // valid connection established
+      bool exRailSent; // valid connection established
+      uint16_t mostRecentCab;
       int turnoutListHash;  // used to check for changes to turnout list
       bool lastPowerState;  // last power state sent to this client
       int DCCToWiTSpeed(int DCCSpeed);

WifiInboundHandler.cpp

@@ -85,7 +85,9 @@ void WifiInboundHandler::loop1() {
          CommandDistributor::parse(clientId,cmd,outboundRing);
          // The commit call will either write the lenbgth bytes 
          // OR rollback to the mark because the reply is empty or commend generated more than fits the buffer 
-         outboundRing->commit();
+         if (!outboundRing->commit()) {
+            DIAG(F("OUTBOUND FULL processing cmd:%s"),cmd);
+         }
          return;
       }
    }
@@ -243,7 +245,7 @@ WifiInboundHandler::INBOUND_STATE WifiInboundHandler::loop2() {
 
 void WifiInboundHandler::purgeCurrentCIPSEND() {
          // A CIPSEND was sent but errored... or the client closed just toss it away
-         if (Diag::WIFI) DIAG(F("Wifi: DROPPING CIPSEND=%d,%d"),clientPendingCIPSEND,currentReplySize);
+         DIAG(F("Wifi: DROPPING CIPSEND=%d,%d"),clientPendingCIPSEND,currentReplySize);
          for (int i=0;i<=currentReplySize;i++) outboundRing->read();
          pendingCipsend=false;  
          clientPendingCIPSEND=-1;

config.example.h

@@ -113,18 +113,38 @@ The configuration file for DCC-EX Command Station
 //
 // DEFINE LCD SCREEN USAGE BY THE BASE STATION
 //
-// Note: This feature requires an I2C enabled LCD screen using a PCF8574 based chipset.
+// Note: This feature requires an I2C enabled LCD screen using a Hitachi HD44780
-//       or one using a Hitachi  HD44780.
+//       controller and a commonly available PCF8574 based I2C 'backpack'.
-//       OR an I2C Oled screen.
+// To enable, uncomment one of the #define lines below
-// To enable, uncomment one of the lines below
 
-// define LCD_DRIVER for I2C LCD address 0x3f,16 cols, 2 rows
+// define LCD_DRIVER for I2C address 0x27, 16 cols, 2 rows
-// #define LCD_DRIVER  0x3F,16,2
+// #define LCD_DRIVER  0x27,16,2
 
 //OR define OLED_DRIVER width,height in pixels (address auto detected)
 // 128x32 or 128x64 I2C SSD1306-based devices are supported.
-// Also 132x64 I2C SH1106 devices.
+// Also 132x64 I2C SH1106 devices
 // #define OLED_DRIVER 128,32
 
-/////////////////////////////////////////////////////////////////////////////////////
+// Define scroll mode as 0, 1 or 2
+#define SCROLLMODE 1
 
+/////////////////////////////////////////////////////////////////////////////////////
+//
+// DEFINE TURNOUTS/ACCESSORIES FOLLOW NORM RCN-213
+//
+// According to norm RCN-213 a DCC packet with a 1 is closed/straight
+// and one with a 0 is thrown/diverging.  In DCC++ Classic, and in previous
+// versions of DCC++EX, a turnout throw command was implemented in the packet as 
+// '1' and a close command as '0'. The #define below makes the states
+// match with the norm.  But we don't want to cause havoc on existent layouts,
+// so we define this only for new installations. If you don't want this,
+// don't add it to your config.h.
+//#define DCC_TURNOUTS_RCN_213
+
+// The following #define likewise inverts the behaviour of the <a> command 
+// for triggering DCC Accessory Decoders, so that <a addr subaddr 0> generates a 
+// DCC packet with D=1 (close turnout) and <a addr subaddr 1> generates D=0 
+// (throw turnout).
+//#define DCC_ACCESSORY_RCN_213
+
+/////////////////////////////////////////////////////////////////////////////////////

defines.h

@@ -18,12 +18,28 @@
 
 */
 
+#ifndef DEFINES_H
+#define DEFINES_H
+
+// defines.h relies on macros defined in config.h
+// but it may have already been included (for cosmetic convenence) by the .ino
+#ifndef MOTOR_SHIELD_TYPE
+  #if __has_include ( "config.h")
+    #include "config.h"
+  #else
+    #include "config.example.h"
+  #endif
+#endif
+
 ////////////////////////////////////////////////////////////////////////////////
 //
 // WIFI_ON: All prereqs for running with WIFI are met
 // Note: WIFI_CHANNEL may not exist in early config.h files so is added here if needed.
 
-#if ENABLE_WIFI && (defined(ARDUINO_AVR_MEGA) || defined(ARDUINO_AVR_MEGA2560) || defined(ARDUINO_SAMD_ZERO)  || defined(TEENSYDUINO))
+#if (defined(ARDUINO_AVR_MEGA) || defined(ARDUINO_AVR_MEGA2560) || defined(ARDUINO_SAMD_ZERO)  || defined(TEENSYDUINO))
+ #define BIG_RAM
+#endif 
+#if ENABLE_WIFI && defined(BIG_RAM)
 #define WIFI_ON true
 #ifndef WIFI_CHANNEL
 #define WIFI_CHANNEL 1
@@ -32,7 +48,7 @@
 #define WIFI_ON false
 #endif
 
-#if ENABLE_ETHERNET && (defined(ARDUINO_AVR_MEGA) || defined(ARDUINO_AVR_MEGA2560) || defined(ARDUINO_SAMD_ZERO) || defined(TEENSYDUINO)) 
+#if ENABLE_ETHERNET && defined(BIG_RAM)
 #define ETHERNET_ON true
 #else
 #define ETHERNET_ON false
@@ -48,3 +64,9 @@
 // Currently only devices which can communicate at 115200 are supported.
 //
 #define WIFI_SERIAL_LINK_SPEED 115200
+
+#if __has_include ( "myAutomation.h") && defined(BIG_RAM)
+  #define RMFT_ACTIVE
+#endif
+
+#endif

myAutomation.example.h

@@ -0,0 +1,84 @@
+/* This is an automation example file.
+ *  The presence of a file calle "myAutomation.h" brings EX-RAIL code into
+ *  the command station.
+ *  The auotomation may have multiple concurrent tasks. 
+ *  A task may 
+ *  - Act as a ROUTE setup macro for a user to drive over 
+ *  - drive a loco through an AUTOMATION 
+ *  - automate some cosmetic part of the layout without any loco.
+ *  
+ *  At startup, a single task is created to execute the first 
+ *  instruction after E$XRAIL. 
+ *  This task may simply follow a route, or may START  
+ *  further tasks (thats is.. send a loco out along a route).
+ *  
+ *  Where the loco id is not known at compile time, a new task 
+ *  can be creatd with the command:
+ *  </ START [cab] route> 
+ *  
+ *  A ROUTE, AUTOMATION or SEQUENCE are internally identical in ExRail terms  
+ *  but are just represented differently to a Withrottle user:
+ *  ROUTE(n,"name") - as Route_n .. to setup a route through a layout
+ *  AUTOMATION(n,"name") as Auto_n .. to send the current loco off along an automated journey
+ *  SEQUENCE(n) is not visible to Withrottle.
+ *  
+ */
+
+EXRAIL   // myAutomation must start with the EXRAIL instruction
+  // This is the default starting route, AKA SEQUENCE(0)  
+  SENDLOCO(3,1) // send loco 3 off along route 1
+  SENDLOCO(10,2) // send loco 10 off along route 2
+  DONE     // This just ends the startup thread, leaving 2 others running.
+
+/* SEQUENCE(1) is a simple shuttle between 2 sensors      
+ *  S20 and S21 are sensors on arduino pins 20 and 21 
+ *  S20                    S21                   
+ *  === START->================
+ */
+   SEQUENCE(1) 
+     DELAY(10000)   // wait 10 seconds
+     FON(3)       // Set Loco Function 3, Horn on
+     DELAY(1000)    // wait 1 second
+     FOFF(3)      // Horn off
+     FWD(80)      // Move forward at speed 80
+     AT(21)       // until we hit sensor id 21
+     STOP         // then stop
+     DELAY(5000)    // Wait 5 seconds
+     FON(2)       // ring bell
+     REV(60)      // reverse at speed 60
+     AT(20)       // until we get to S20
+     STOP         // then stop
+     FOFF(2)      // Bell off 
+     FOLLOW(1)    // and follow sequence 1 again
+   
+/* SEQUENCE(2) is an automation example for a single loco Y shaped journey
+ *  S31,S32,S33 are sensors, T4 is a turnout
+ *  
+ *  S33                      T4                            S31
+ *  ===-START->=============================================
+ *                          //
+ *  S32                    //
+ *  ======================//
+ *  
+ *  Train runs from START to S31, back to S32, again to S31, Back to start.
+ */
+  SEQUENCE(2)
+   FWD(60)     // go forward at DCC speed 60 
+   AT(31) STOP  // when we get to sensor 31 
+   DELAY(10000)  // wait 10 seconds 
+   THROW(4)    // throw turnout for route to S32
+   REV(45)     // go backwards at speed 45
+   AT(32) STOP  // until we arrive at sensor 32
+   DELAY(5000)   // wait 5 seconds
+   FWD(50)     // go forwards at speed 50
+   AT(31) STOP  // and stop at sensor 31
+   DELAY(5000)   // wait 5 seconds 
+   CLOSE(4)    // set turnout closed
+   REV(50)     // reverse back to S3
+   AT(33) STOP
+   DELAY(20000)  // wait 20 seconds 
+   FOLLOW(2)   // follow sequence 2... ie repeat the process
+   
+   ENDEXRAIL    // marks the end of the EXRAIL program. 
+    
+   

mySetup.cpp_example.txt

@@ -0,0 +1,214 @@
+//  Sample mySetup.cpp file.
+//
+// To use this file, copy it to mySetup.cpp and uncomment the directives and/or
+// edit them to satisfy your requirements.  
+
+// Note that if the file has a .cpp extension it WILL be compiled into the build
+// and the mySetup() function WILL be invoked.
+//
+// To prevent this, temporarily rename it to mySetup.txt or similar.
+//
+
+#include "IODevice.h"
+#include "Turnouts.h"
+#include "Sensors.h"
+#include "IO_HCSR04.h"
+#include "IO_VL53L0X.h"
+
+
+// The #if directive prevent compile errors for Uno and Nano by excluding the 
+//  HAL directives from the build.
+#if !defined(IO_NO_HAL)
+
+
+// Examples of statically defined HAL directives (alternative to the create() call).
+// These have to be outside of the mySetup() function.
+
+//=======================================================================
+// The following directive defines a PCA9685 PWM Servo driver module.
+//=======================================================================
+// The parameters are: 
+//   First Vpin=100
+//   Number of VPINs=16 (numbered 100-115)
+//   I2C address of module=0x40
+
+//PCA9685 pwmModule1(100, 16, 0x40);
+
+
+//=======================================================================
+// The following directive defines an MCP23017 16-port I2C GPIO Extender module.
+//=======================================================================
+// The parameters are: 
+//   First Vpin=196
+//   Number of VPINs=16 (numbered 196-211)
+//   I2C address of module=0x22
+
+//MCP23017 gpioModule2(196, 16, 0x22);
+
+
+// Alternative form, which allows the INT pin of the module to request a scan
+// by pulling Arduino pin 40 to ground.  Means that the I2C isn't being polled
+// all the time, only when a change takes place. Multiple modules' INT pins
+// may be connected to the same Arduino pin.
+
+//MCP23017 gpioModule2(196, 16, 0x22, 40);
+
+
+//=======================================================================
+// The following directive defines an MCP23008 8-port I2C GPIO Extender module.
+//=======================================================================
+// The parameters are: 
+//   First Vpin=300
+//   Number of VPINs=8 (numbered 300-307)
+//   I2C address of module=0x22
+
+//MCP23008 gpioModule3(300, 8, 0x22);
+
+
+//=======================================================================
+// The following directive defines a PCF8574 8-port I2C GPIO Extender module.
+//=======================================================================
+// The parameters are: 
+//   First Vpin=200
+//   Number of VPINs=8 (numbered 200-207)
+//   I2C address of module=0x23
+
+//PCF8574 gpioModule4(200, 8, 0x23);
+
+
+// Alternative form using INT pin (see above)
+
+//PCF8574 gpioModule4(200, 8, 0x23, 40);
+
+
+//=======================================================================
+// The following directive defines an HCSR04 ultrasonic ranging module.
+//=======================================================================
+// The parameters are: 
+//   Vpin=2000 (only one VPIN per directive)
+//   Number of VPINs=1
+//   Arduino pin connected to TRIG=30
+//   Arduino pin connected to ECHO=31
+//   Minimum trigger range=20cm (VPIN goes to 1 when <20cm)
+//   Maximum trigger range=25cm (VPIN goes to 0 when >25cm)
+// Note: Multiple devices can be configured by using a different ECHO pin
+// for each one.  The TRIG pin can be shared between multiple devices.
+// Be aware that the 'ping' of one device may be received by another
+// device and position them accordingly!
+
+//HCSR04 sonarModule1(2000, 30, 31, 20, 25);
+//HCSR04 sonarModule2(2001, 30, 32, 20, 25);
+
+
+//=======================================================================
+// The following directive defines a single VL53L0X Time-of-Flight range sensor.
+//=======================================================================
+// The parameters are:
+//   VPIN=5000
+//   Number of VPINs=1
+//   I2C address=0x29 (default for this chip)
+//   Minimum trigger range=200mm (VPIN goes to 1 when <20cm)
+//   Maximum trigger range=250mm (VPIN goes to 0 when >25cm)
+
+//VL53L0X tofModule1(5000, 1, 0x29, 200, 250); 
+
+// For multiple VL53L0X modules, add another parameter which is a VPIN connected to the
+// module's XSHUT pin.  This allows the modules to be configured, at start,
+// with distinct I2C addresses.  In this case, the address 0x29 is only used during
+// initialisation to configure each device in turn with the desired unique I2C address.
+// The examples below have the modules' XSHUT pins connected to the first two pins of 
+// the first MCP23017 module (164 and 165), but Arduino pins may be used instead.
+// The first module here is given I2C address 0x30 and the second is 0x31.
+
+//VL53L0X tofModule1(5000, 1, 0x30, 200, 250, 164); 
+//VL53L0X tofModule2(5001, 1, 0x31, 200, 250, 165); 
+
+
+//=======================================================================
+// The function mySetup() is invoked from CS if it exists within the build.
+// It is called just before mysetup.h is executed, so things set up within here can be
+// referenced by commands in mySetup.h.
+//=======================================================================
+
+void mySetup() {
+
+  // Alternative way of creating a module driver, which has to be within the mySetup() function
+  // The other devices can also be created in this way.  The parameter lists for the
+  // create() function are identical to the parameter lists for the declarations.
+
+  //MCP23017::create(196, 16, 0x22);
+
+
+  //=======================================================================
+  // Creating a Turnout
+  //=======================================================================
+  // Parameters: same as <T> command for Servo turnouts
+  // ID and VPIN are 100, sonar moves between positions 102 and 490 with slow profile.
+  // Profile may be Instant, Fast, Medium, Slow or Bounce.
+
+  //ServoTurnout::create(100, 100, 490, 102, PCA9685::Slow);
+
+
+  //=======================================================================
+  // DCC Accessory turnout
+  //=======================================================================
+  // Parameters: same as <T> command for DCC Accessory turnouts
+  //  ID=3000
+  //  Decoder address=23
+  //  Decoder subaddress = 1
+
+  //DCCTurnout::create(3000, 23, 1);
+
+
+  //=======================================================================
+  // Creating a Sensor
+  //=======================================================================
+  // Parameters: As for the <S> command,
+  //  id = 164,
+  //  Vpin = 164 (configured above as pin 0 of an MCP23017)
+  //  Pullup enable = 1 (enabled)
+
+  //Sensor::create(164, 164, 1);
+
+
+  //=======================================================================
+  // Way of creating lots of identical sensors in a range
+  //=======================================================================
+
+  //for (int i=165; i<180; i++) 
+  //  Sensor::create(i, i, 1);
+
+
+  //=======================================================================
+  // Play mp3 files from a Micro-SD card, using a DFPlayer MP3 Module.
+  //=======================================================================
+  // Parameters: 
+  //   10000 = first VPIN allocated.
+  //   10 = number of VPINs allocated.
+  //   Serial1 = name of serial port (usually Serial1 or Serial2).
+  // With these parameters, up to 10 files may be played on pins 10000-10009.
+  // Play is started from EX-RAIL with SET(10000) for first mp3 file, SET(10001)
+  // for second file, etc.  Play may also be initiated by writing an analogue
+  // value to the first pin, e.g. SERVO(10000,23,0) will play the 23rd mp3 file.
+  // SERVO(10000,23,30) will do the same thing, as well as setting the volume to 
+  // 30 (maximum value).
+  // Play is stopped by RESET(10000) (or any other allocated VPIN).
+  // Volume may also be set by writing an analogue value to the second pin for the player, 
+  // e.g. SERVO(10001,30,0) sets volume to maximum (30).
+  // The EX-RAIL script may check for completion of play by calling WAITFOR(pin), which will only proceed to the
+  // following line when the player is no longer busy.
+  // E.g.
+  //    SEQUENCE(1)
+  //      AT(164)           // Wait for sensor attached to pin 164 to activate
+  //      SET(10003)        // Play fourth MP3 file
+  //      LCD(4, "Playing") // Display message on LCD/OLED
+  //      WAITFOR(10003)    // Wait for playing to finish
+  //      LCD(4, " ")       // Clear LCD/OLED line 
+  //      FOLLOW(1)         // Go back to start
+
+  // DFPlayer::create(10000, 10, Serial1);
+
+
+}
+
+#endif

platformio.ini

@@ -12,9 +12,14 @@
 default_envs = 
 	mega2560
 	uno
+	mega328
+	unowifiR2
+	nano
 src_dir = .
+include_dir = .
 
 [env]
+build_flags = -Wall -Wextra
 
 [env:samd21]
 platform = atmelsam
@@ -27,6 +32,42 @@ lib_deps =
 monitor_speed = 115200
 monitor_flags = --echo
 
+[env:mega2560-debug]
+platform = atmelavr
+board = megaatmega2560
+framework = arduino
+lib_deps = 
+	${env.lib_deps}
+	arduino-libraries/Ethernet
+	SPI
+monitor_speed = 115200
+monitor_flags = --echo
+build_flags = -DDIAG_IO -DDIAG_LOOPTIMES
+
+[env:mega2560-no-HAL]
+platform = atmelavr
+board = megaatmega2560
+framework = arduino
+lib_deps = 
+	${env.lib_deps}
+	arduino-libraries/Ethernet
+	SPI
+monitor_speed = 115200
+monitor_flags = --echo
+build_flags = -DIO_NO_HAL
+
+[env:mega2560-I2C-wire]
+platform = atmelavr
+board = megaatmega2560
+framework = arduino
+lib_deps = 
+	${env.lib_deps}
+	arduino-libraries/Ethernet
+	SPI
+monitor_speed = 115200
+monitor_flags = --echo
+build_flags = -DI2C_USE_WIRE
+
 [env:mega2560]
 platform = atmelavr
 board = megaatmega2560
@@ -59,7 +100,20 @@ lib_deps =
 	SPI
 monitor_speed = 115200
 monitor_flags = --echo
-build_flags = "-DF_CPU=16000000L -DARDUINO=10813 -DARDUINO_AVR_UNO_WIFI_DEV_ED -DARDUINO_ARCH_AVR -DESP_CH_UART -DESP_CH_UART_BR=19200"g
+build_flags = "-DF_CPU=16000000L -DARDUINO=10813 -DARDUINO_AVR_UNO_WIFI_DEV_ED -DARDUINO_ARCH_AVR -DESP_CH_UART -DESP_CH_UART_BR=19200"
+
+[env:nanoevery]
+platform = atmelmegaavr
+board = nano_every
+framework = arduino
+lib_deps = 
+	${env.lib_deps}
+	arduino-libraries/Ethernet
+	SPI
+monitor_speed = 115200
+monitor_flags = --echo
+upload_speed = 19200
+build_flags = -DDIAG_IO
 
 [env:uno]
 platform = atmelavr
@@ -71,3 +125,13 @@ lib_deps =
 	SPI
 monitor_speed = 115200
 monitor_flags = --echo
+
+[env:nano]
+platform = atmelavr
+board = nanoatmega328new
+board_upload.maximum_size = 32256
+framework = arduino
+lib_deps = 
+	${env.lib_deps}
+monitor_speed = 115200
+monitor_flags = --echo

version.h

@@ -3,8 +3,25 @@
 
 #include "StringFormatter.h"
 
-
+#define VERSION "3.2.0"
-#define VERSION "3.1.7"
+// 3.2.0 Major functional and non-functional changes.
+//       New HAL added for I/O (digital and analogue inputs and outputs, servos etc).
+//         Support for MCP23008, MCP23017 and PCF9584 I2C GPIO Extender modules.
+//         Support for PCA9685 PWM (servo) control modules.
+//         Support for analogue inputs on Arduino pins and on ADS111x I2C modules.
+//         Support for MP3 sound playback via DFPlayer module.
+//         Support for HC-SR04 Ultrasonic range sensor module.
+//         Support for VL53L0X Laser range sensor module (Time-Of-Flight).
+//       Native non-blocking I2C drivers for AVR and Nano architectures (fallback
+//       to blocking Wire library for other platforms).
+//       EEPROM layout change - deletes EEPROM contents on first start following upgrade.
+//       New EX-RAIL automation capability.
+//       Turnout class revised to expand turnout capabilities, new commands added.
+//       Output class now allows ID > 255.
+//       Configuration options to globally flip polarity of DCC Accessory states when driven
+//       from <a> command and <T> command.
+//       Increased use of display for showing loco decoder programming information.
+//       ...
 // 3.1.7 Bugfix: Unknown locos should have speed forward 
 // 3.1.6 Make output ID two bytes and guess format/size of registered outputs found in EEPROM
 // 3.1.5 Fix LCD corruption on power-up