diff --git a/DCCEXParser.cpp b/DCCEXParser.cpp
index b9ac3a9..431093f 100644
--- a/DCCEXParser.cpp
+++ b/DCCEXParser.cpp
@@ -70,8 +70,8 @@ Once a new OPCODE is decided upon, update this list.
   L, Reserved for LCC interface (implemented in EXRAIL)
   m, message to throttles broadcast 
   M, Write DCC packet
-  n,
-  N,
+  n, Reserved for SensorCam
+  N, Reserved for Sensorcam 
   o,
   O, Output broadcast
   p, Broadcast power state
@@ -91,10 +91,10 @@ Once a new OPCODE is decided upon, update this list.
   w, Write CV on main
   W, Write CV
   x,
-  X, Invalid command
-  y,
+  X, Invalid command response
+  y, 
   Y, Output broadcast
-  z,
+  z, Direct output
   Z, Output configuration/control
 */
 
diff --git a/DCCTimer.h b/DCCTimer.h
index 44c85f2..c3fcaf1 100644
--- a/DCCTimer.h
+++ b/DCCTimer.h
@@ -1,5 +1,5 @@
 /*
- *  © 2022-2023 Paul M. Antoine
+ *  © 2022-2024 Paul M. Antoine
  *  © 2021 Mike S
  *  © 2021-2023 Harald Barth
  *  © 2021 Fred Decker
@@ -135,6 +135,8 @@ private:
   #if defined (ARDUINO_ARCH_STM32)
   // bit array of used pins (max 32)
   static uint32_t usedpins;
+  static uint32_t * analogchans;        // Array of channel numbers to be scanned
+  static ADC_TypeDef * * adcchans;      // Array to capture which ADC is each input channel on
 #else
   // bit array of used pins (max 16)
   static uint16_t usedpins;
diff --git a/DCCTimerAVR.cpp b/DCCTimerAVR.cpp
index cb9e685..656ba7e 100644
--- a/DCCTimerAVR.cpp
+++ b/DCCTimerAVR.cpp
@@ -185,8 +185,10 @@ int DCCTimer::freeMemory() {
 }
 
 void DCCTimer::reset() {
-  wdt_enable( WDTO_15MS); // set Arduino watchdog timer for 15ms 
-  delay(50);            // wait for the prescaller time to expire
+  // 250ms chosen to circumwent bootloader bug which
+  // hangs at too short timepout (like 15ms)
+  wdt_enable( WDTO_250MS); // set Arduino watchdog timer for 250ms 
+  delay(500);              // wait for it to happen
 
 }
 
diff --git a/DCCTimerSTM32.cpp b/DCCTimerSTM32.cpp
index 8f98153..fbe19d8 100644
--- a/DCCTimerSTM32.cpp
+++ b/DCCTimerSTM32.cpp
@@ -1,6 +1,6 @@
 /*
  *  © 2023 Neil McKechnie
- *  © 2022-2023 Paul M. Antoine
+ *  © 2022-2024 Paul M. Antoine
  *  © 2021 Mike S
  *  © 2021, 2023 Harald Barth
  *  © 2021 Fred Decker
@@ -34,8 +34,22 @@
 #include "TrackManager.h"
 #endif
 #include "DIAG.h"
+#include <wiring_private.h>
 
-#if defined(ARDUINO_NUCLEO_F401RE) || defined(ARDUINO_NUCLEO_F411RE)
+#if defined(ARDUINO_NUCLEO_F401RE)
+// Nucleo-64 boards don't have additional serial ports defined by default
+// Serial1 is available on the F401RE, but not hugely convenient.
+// Rx pin on PB7 is useful, but all the Tx pins map to Arduino digital pins, specifically:
+//   PA9 == D8
+//   PB6 == D10
+// of which D8 is needed by the standard and EX8874 motor shields. D10 would be used if a second
+// EX8874 is stacked. So only disable this if using a second motor shield.
+HardwareSerial Serial1(PB7, PB6);  // Rx=PB7, Tx=PB6 -- CN7 pin 17 and CN10 pin 17
+// Serial2 is defined to use USART2 by default, but is in fact used as the diag console
+// via the debugger on the Nucleo-64. It is therefore unavailable for other DCC-EX uses like WiFi, DFPlayer, etc.
+// Let's define Serial6 as an additional serial port (the only other option for the F401RE)
+HardwareSerial Serial6(PA12, PA11);  // Rx=PA12, Tx=PA11 -- CN10 pins 12 and 14 - F401RE
+#elif defined(ARDUINO_NUCLEO_F411RE)
 // Nucleo-64 boards don't have additional serial ports defined by default
 HardwareSerial Serial1(PB7, PA15);  // Rx=PB7, Tx=PA15 -- CN7 pins 17 and 21 - F411RE
 // Serial2 is defined to use USART2 by default, but is in fact used as the diag console
@@ -53,7 +67,7 @@ HardwareSerial Serial3(PC11, PC10);  // Rx=PC11, Tx=PC10 -- USART3 - F446RE
 HardwareSerial Serial5(PD2, PC12);  // Rx=PD2, Tx=PC12 -- UART5 - F446RE
 // On the F446RE, Serial4 and Serial6 also use pins we can't readily map while using the Arduino pins
 #elif defined(ARDUINO_NUCLEO_F412ZG) || defined(ARDUINO_NUCLEO_F413ZH) || defined(ARDUINO_NUCLEO_F446ZE) || \
-      defined(ARDUINO_NUCLEO_F429ZI) || defined(ARDUINO_NUCLEO_F439ZI)
+      defined(ARDUINO_NUCLEO_F429ZI) || defined(ARDUINO_NUCLEO_F439ZI) || defined(ARDUINO_NUCLEO_F4X9ZI)
 // Nucleo-144 boards don't have Serial1 defined by default
 HardwareSerial Serial6(PG9, PG14);  // Rx=PG9, Tx=PG14 -- USART6
 HardwareSerial Serial2(PD6, PD5);  // Rx=PD6, Tx=PD5 -- UART2
@@ -363,9 +377,9 @@ void DCCTimer::DCCEXanalogWrite(uint8_t pin, int value, bool invert) {
 uint32_t ADCee::usedpins = 0;         // Max of 32 ADC input channels!
 uint8_t ADCee::highestPin = 0;        // Highest pin to scan
 int * ADCee::analogvals = NULL;       // Array of analog values last captured
-uint32_t * analogchans = NULL;        // Array of channel numbers to be scanned
+uint32_t * ADCee::analogchans = NULL;        // Array of channel numbers to be scanned
 // bool adc1configured = false;
-ADC_TypeDef * * adcchans = NULL;      // Array to capture which ADC is each input channel on
+ADC_TypeDef * * ADCee::adcchans = NULL;      // Array to capture which ADC is each input channel on
 
 int16_t ADCee::ADCmax()
 {
@@ -383,9 +397,10 @@ int ADCee::init(uint8_t pin) {
   uint32_t adcchan =  STM_PIN_CHANNEL(pinmap_function(stmpin, PinMap_ADC)); // find ADC input channel
   ADC_TypeDef *adc = (ADC_TypeDef *)pinmap_find_peripheral(stmpin, PinMap_ADC); // find which ADC this pin is on ADC1/2/3 etc.
   int adcnum = 1;
+  // All variants have ADC1
   if (adc == ADC1)
     DIAG(F("ADCee::init(): found pin %d on ADC1"), pin);
-// Checking for ADC2 and ADC3 being defined helps cater for more variants later
+  // Checking for ADC2 and ADC3 being defined helps cater for more variants
 #if defined(ADC2)
   else if (adc == ADC2)
   {
@@ -432,6 +447,18 @@ int ADCee::init(uint8_t pin) {
         RCC->AHB1ENR |= RCC_AHB1ENR_GPIOFEN; //Power up PORTF
         gpioBase = GPIOF;
         break;
+#endif
+#if defined(GPIOG)
+    case 0x06:
+        RCC->AHB1ENR |= RCC_AHB1ENR_GPIOGEN; //Power up PORTG
+        gpioBase = GPIOG;
+        break;
+#endif
+#if defined(GPIOH)
+    case 0x07:
+        RCC->AHB1ENR |= RCC_AHB1ENR_GPIOHEN; //Power up PORTH
+        gpioBase = GPIOH;
+        break;
 #endif
     default:
       return -1023; // some silly value as error
diff --git a/EXRAIL2.cpp b/EXRAIL2.cpp
index 9293c96..6980f03 100644
--- a/EXRAIL2.cpp
+++ b/EXRAIL2.cpp
@@ -1,4 +1,5 @@
 /*
+ *  © 2024 Paul M. Antoine
  *  © 2021 Neil McKechnie
  *  © 2021-2023 Harald Barth
  *  © 2020-2023 Chris Harlow
@@ -54,6 +55,7 @@
 #include "TrackManager.h"
 #include "Turntables.h"
 #include "IODevice.h"
+#include "EXRAILSensor.h"
 
 
 // One instance of RMFT clas is used for each "thread" in the automation.
@@ -204,15 +206,16 @@ LookList* RMFT2::LookListLoader(OPCODE op1, OPCODE op2, OPCODE op3) {
 
   // Second pass startup, define any turnouts or servos, set signals red
   // add sequences onRoutines to the lookups
-if (compileFeatures & FEATURE_SIGNAL) {
-  onRedLookup=LookListLoader(OPCODE_ONRED);
-  onAmberLookup=LookListLoader(OPCODE_ONAMBER);
-  onGreenLookup=LookListLoader(OPCODE_ONGREEN);
-  for (int sigslot=0;;sigslot++) {
-    VPIN sigid=GETHIGHFLASHW(RMFT2::SignalDefinitions,sigslot*8);
-    if (sigid==0) break;  // end of signal list
-    doSignal(sigid & SIGNAL_ID_MASK, SIGNAL_RED);
-  }
+  if (compileFeatures & FEATURE_SIGNAL) {
+    onRedLookup=LookListLoader(OPCODE_ONRED);
+    onAmberLookup=LookListLoader(OPCODE_ONAMBER);
+    onGreenLookup=LookListLoader(OPCODE_ONGREEN);
+    for (int sigslot=0;;sigslot++) {
+      int16_t sighandle=GETHIGHFLASHW(RMFT2::SignalDefinitions,sigslot*8);
+      if (sighandle==0) break;  // end of signal list
+      VPIN sigid = sighandle & SIGNAL_ID_MASK;
+      doSignal(sigid, SIGNAL_RED);
+    }
   }
 
   int progCounter;
@@ -251,6 +254,14 @@ if (compileFeatures & FEATURE_SIGNAL) {
       break;
     }
 
+    case OPCODE_ONSENSOR:
+      if (compileFeatures & FEATURE_SENSOR) 
+        new EXRAILSensor(operand,progCounter+3,true );
+      break;
+    case OPCODE_ONBUTTON:
+      if (compileFeatures & FEATURE_SENSOR) 
+        new EXRAILSensor(operand,progCounter+3,false );
+      break;
     case OPCODE_TURNOUT: {
       VPIN id=operand;
       int addr=getOperand(progCounter,1);
@@ -480,6 +491,8 @@ bool RMFT2::skipIfBlock() {
 }
 
 void RMFT2::loop() {
+  if (compileFeatures & FEATURE_SENSOR) 
+      EXRAILSensor::checkAll();
 
   // Round Robin call to a RMFT task each time
   if (loopTask==NULL) return;
@@ -1084,6 +1097,8 @@ void RMFT2::loop2() {
   case OPCODE_ONGREEN:
   case OPCODE_ONCHANGE:
   case OPCODE_ONTIME:
+  case OPCODE_ONBUTTON:
+  case OPCODE_ONSENSOR:
 #ifndef IO_NO_HAL
   case OPCODE_DCCTURNTABLE: // Turntable definition ignored at runtime
   case OPCODE_EXTTTURNTABLE:  // Turntable definition ignored at runtime
@@ -1129,19 +1144,25 @@ void RMFT2::kill(const FSH * reason, int operand) {
 }
 
 int16_t RMFT2::getSignalSlot(int16_t id) {
-  for (int sigslot=0;;sigslot++) {
-      int16_t sigid=GETHIGHFLASHW(RMFT2::SignalDefinitions,sigslot*8);
-      if (sigid==0) { // end of signal list 
-        DIAG(F("EXRAIL Signal %d not defined"), id);
-        return -1;
-      }
+
+  if (id > 0) {
+    int sigslot = 0;
+    int16_t sighandle = 0;
+    // Trundle down the signal list until we reach the end
+    while ((sighandle = GETHIGHFLASHW(RMFT2::SignalDefinitions, sigslot * 8)) != 0)
+    {
       // sigid is the signal id used in RED/AMBER/GREEN macro
       // for a LED signal it will be same as redpin
-      // but for a servo signal it will also have SERVO_SIGNAL_FLAG set. 
-
-      if ((sigid & SIGNAL_ID_MASK)!= id) continue; // keep looking
-      return sigslot; // relative slot in signals table
-  }  
+      // but for a servo signal it will also have SERVO_SIGNAL_FLAG set.
+      VPIN sigid = sighandle & SIGNAL_ID_MASK;
+      if (sigid == (VPIN)id) // cast to keep compiler happy but id is positive
+        return sigslot;      // found it
+      sigslot++;             // keep looking
+    };
+  }
+  // If we got here, we did not find the signal
+  DIAG(F("EXRAIL Signal %d not defined"), id);
+  return -1;
 }
 
 /* static */ void RMFT2::doSignal(int16_t id,char rag) {
@@ -1162,13 +1183,14 @@ int16_t RMFT2::getSignalSlot(int16_t id) {
  
   // Correct signal definition found, get the rag values
   int16_t sigpos=sigslot*8; 
-  VPIN sigid=GETHIGHFLASHW(RMFT2::SignalDefinitions,sigpos);
+  int16_t sighandle=GETHIGHFLASHW(RMFT2::SignalDefinitions,sigpos);
   VPIN redpin=GETHIGHFLASHW(RMFT2::SignalDefinitions,sigpos+2);
   VPIN amberpin=GETHIGHFLASHW(RMFT2::SignalDefinitions,sigpos+4);
   VPIN greenpin=GETHIGHFLASHW(RMFT2::SignalDefinitions,sigpos+6);
   //if (diag) DIAG(F("signal %d %d %d %d %d"),sigid,id,redpin,amberpin,greenpin);
 
-  VPIN sigtype=sigid & ~SIGNAL_ID_MASK;
+  VPIN sigtype=sighandle & ~SIGNAL_ID_MASK;
+  VPIN sigid = sighandle & SIGNAL_ID_MASK;
 
   if (sigtype == SERVO_SIGNAL_FLAG) {
     // A servo signal, the pin numbers are actually servo positions
@@ -1191,7 +1213,7 @@ int16_t RMFT2::getSignalSlot(int16_t id) {
     byte value=redpin;
     if (rag==SIGNAL_AMBER) value=amberpin;
     if (rag==SIGNAL_GREEN) value=greenpin; 
-    DCC::setExtendedAccessory(sigid & SIGNAL_ID_MASK,value);
+    DCC::setExtendedAccessory(sigid, value);
     return; 
   }
 
@@ -1202,7 +1224,7 @@ int16_t RMFT2::getSignalSlot(int16_t id) {
   if (rag==SIGNAL_AMBER && (amberpin==0)) rag=SIMAMBER; // special case this func only
    
   // Manage invert (HIGH on) pins
-  bool aHigh=sigid & ACTIVE_HIGH_SIGNAL_FLAG;
+  bool aHigh=sighandle & ACTIVE_HIGH_SIGNAL_FLAG;
       
   // set the three pins 
   if (redpin) {
@@ -1242,8 +1264,9 @@ bool RMFT2::signalAspectEvent(int16_t address, byte aspect ) {
   int16_t sigslot=getSignalSlot(address);
   if (sigslot<0) return false;  // this is not a defined signal 
   int16_t sigpos=sigslot*8; 
-  VPIN sigid=GETHIGHFLASHW(RMFT2::SignalDefinitions,sigpos);
-  VPIN sigtype=sigid & ~SIGNAL_ID_MASK;
+  int16_t sighandle=GETHIGHFLASHW(RMFT2::SignalDefinitions,sigpos);
+  VPIN sigtype=sighandle & ~SIGNAL_ID_MASK;
+  VPIN sigid = sighandle & SIGNAL_ID_MASK;
   if (sigtype!=DCCX_SIGNAL_FLAG) return false; // not a DCCX signal
   // Turn an aspect change into a RED/AMBER/GREEN setting
   if (aspect==GETHIGHFLASHW(RMFT2::SignalDefinitions,sigpos+2)) {
diff --git a/EXRAIL2.h b/EXRAIL2.h
index 7075f26..8750e41 100644
--- a/EXRAIL2.h
+++ b/EXRAIL2.h
@@ -73,7 +73,7 @@ enum OPCODE : byte {OPCODE_THROW,OPCODE_CLOSE,OPCODE_TOGGLE_TURNOUT,
              OPCODE_ROUTE_ACTIVE,OPCODE_ROUTE_INACTIVE,OPCODE_ROUTE_HIDDEN,
              OPCODE_ROUTE_DISABLED,
              OPCODE_STASH,OPCODE_CLEAR_STASH,OPCODE_CLEAR_ALL_STASH,OPCODE_PICKUP_STASH,
-
+             OPCODE_ONBUTTON,OPCODE_ONSENSOR,
              // OPcodes below this point are skip-nesting IF operations
              // placed here so that they may be skipped as a group
              // see skipIfBlock()
@@ -115,6 +115,7 @@ enum BlinkState: byte {
   static const byte FEATURE_ROUTESTATE= 0x10;
   static const byte FEATURE_STASH = 0x08;
   static const byte FEATURE_BLINK = 0x04;
+  static const byte FEATURE_SENSOR = 0x02;
   
  
   // Flag bits for status of hardware and TPL
@@ -185,7 +186,9 @@ class LookList {
   static const FSH *  getTurntableDescription(int16_t id);
   static const FSH *  getTurntablePositionDescription(int16_t turntableId, uint8_t positionId);
   static void startNonRecursiveTask(const FSH* reason, int16_t id,int pc);
-
+  static bool readSensor(uint16_t sensorId);
+  static bool isSignal(int16_t id,char rag); 
+   
 private: 
     static void ComandFilter(Print * stream, byte & opcode, byte & paramCount, int16_t p[]);
     static bool parseSlash(Print * stream, byte & paramCount, int16_t p[]) ;
@@ -194,7 +197,6 @@ private:
     static bool getFlag(VPIN id,byte mask); 
     static int16_t progtrackLocoId;
     static void doSignal(int16_t id,char rag); 
-    static bool isSignal(int16_t id,char rag); 
     static int16_t getSignalSlot(int16_t id);
     static void setTurnoutHiddenState(Turnout * t);
     #ifndef IO_NO_HAL
@@ -208,7 +210,6 @@ private:
     static RMFT2 * pausingTask;
     void delayMe(long millisecs);
     void driveLoco(byte speedo);
-    bool readSensor(uint16_t sensorId);
     bool skipIfBlock();
     bool readLoco();
     void loop2();
diff --git a/EXRAIL2MacroReset.h b/EXRAIL2MacroReset.h
index ce242ea..c799ddf 100644
--- a/EXRAIL2MacroReset.h
+++ b/EXRAIL2MacroReset.h
@@ -114,6 +114,8 @@
 #undef ONGREEN
 #undef ONRED
 #undef ONROTATE
+#undef ONBUTTON
+#undef ONSENSOR
 #undef ONTHROW 
 #undef ONCHANGE
 #undef PARSE
@@ -279,6 +281,8 @@
 #define ONROTATE(turntable_id)
 #define ONTHROW(turnout_id) 
 #define ONCHANGE(sensor_id)
+#define ONSENSOR(sensor_id)
+#define ONBUTTON(sensor_id)
 #define PAUSE
 #define PIN_TURNOUT(id,pin,description...) 
 #define PRINT(msg) 
diff --git a/EXRAIL2Parser.cpp b/EXRAIL2Parser.cpp
index 95375bb..4023633 100644
--- a/EXRAIL2Parser.cpp
+++ b/EXRAIL2Parser.cpp
@@ -214,12 +214,13 @@ bool RMFT2::parseSlash(Print * stream, byte & paramCount, int16_t p[]) {
       // do the signals
       // flags[n] represents the state of the nth signal in the table 
       for (int sigslot=0;;sigslot++) {
-        VPIN sigid=GETHIGHFLASHW(RMFT2::SignalDefinitions,sigslot*8);
-        if (sigid==0) break; // end of signal list 
-        byte flag=flags[sigslot] & SIGNAL_MASK; // obtain signal flags for this id
+        int16_t sighandle=GETHIGHFLASHW(RMFT2::SignalDefinitions,sigslot*8);
+        if (sighandle==0) break; // end of signal list
+	VPIN sigid = sighandle & SIGNAL_ID_MASK;
+	byte flag=flags[sigslot] & SIGNAL_MASK; // obtain signal flags for this id
         StringFormatter::send(stream,F("\n%S[%d]"), 
-          (flag == SIGNAL_RED)? F("RED") : (flag==SIGNAL_GREEN) ? F("GREEN") : F("AMBER"),
-          sigid & SIGNAL_ID_MASK); 
+			      (flag == SIGNAL_RED)? F("RED") : (flag==SIGNAL_GREEN) ? F("GREEN") : F("AMBER"),
+			      sigid);
       } 
     }
 
diff --git a/EXRAILMacros.h b/EXRAILMacros.h
index 7db52dc..827c1d2 100644
--- a/EXRAILMacros.h
+++ b/EXRAILMacros.h
@@ -75,7 +75,7 @@
 // Pass 1 Implements aliases 
 #include "EXRAIL2MacroReset.h"
 #undef ALIAS
-#define ALIAS(name,value...) const int name= 1##value##0 ==10 ? -__COUNTER__  : value##0/10; 
+#define ALIAS(name,value...) const int name= #value[0] ? value+0: -__COUNTER__ ; 
 #include "myAutomation.h"
 
 // Pass 1d Detect sequence duplicates.
@@ -210,6 +210,10 @@ bool exrailHalSetup() {
 #define STASH(id) | FEATURE_STASH
 #undef BLINK
 #define BLINK(vpin,onDuty,offDuty) | FEATURE_BLINK
+#undef ONBUTTON
+#define ONBUTTON(vpin) | FEATURE_SENSOR
+#undef ONSENSOR
+#define ONSENSOR(vpin) | FEATURE_SENSOR
 
 const byte RMFT2::compileFeatures = 0
    #include "myAutomation.h"
@@ -553,6 +557,8 @@ int RMFT2::onLCCLookup[RMFT2::countLCCLookup];
 #endif
 #define ONTHROW(turnout_id) OPCODE_ONTHROW,V(turnout_id),
 #define ONCHANGE(sensor_id) OPCODE_ONCHANGE,V(sensor_id),
+#define ONSENSOR(sensor_id) OPCODE_ONSENSOR,V(sensor_id),
+#define ONBUTTON(sensor_id) OPCODE_ONBUTTON,V(sensor_id),
 #define PAUSE OPCODE_PAUSE,0,0,
 #define PICKUP_STASH(id) OPCODE_PICKUP_STASH,V(id),
 #define PIN_TURNOUT(id,pin,description...) OPCODE_PINTURNOUT,V(id),OPCODE_PAD,V(pin),
diff --git a/EXRAILSensor.cpp b/EXRAILSensor.cpp
new file mode 100644
index 0000000..218b970
--- /dev/null
+++ b/EXRAILSensor.cpp
@@ -0,0 +1,104 @@
+/*
+ *  © 2024 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/>.
+ */
+
+/**********************************************************************
+EXRAILSensor represents a sensor that should be monitored in order
+to call an exrail ONBUTTON or ONCHANGE handler.
+These are created at EXRAIL startup and thus need no delete or listing
+capability.
+The basic logic is similar to that found in the Sensor class
+except that on the relevant change an EXRAIL thread is started.    
+**********************************************************************/
+
+#include "EXRAILSensor.h"
+#include "EXRAIL2.h"
+
+void EXRAILSensor::checkAll() {
+  if (firstSensor == NULL) return;  // No sensors to be scanned
+  if (readingSensor == NULL) { 
+    // Not currently scanning sensor list
+    unsigned long thisTime = micros();
+    if (thisTime - lastReadCycle < cycleInterval) return;
+    // Required time has elapsed since last read cycle started,
+    // so initiate new scan through the sensor list
+    readingSensor = firstSensor;
+    lastReadCycle = thisTime;
+  }
+  
+  // Loop until either end of list is encountered or we pause for some reason
+  byte sensorCount = 0;
+
+  while (readingSensor != NULL) {
+    bool pause=readingSensor->check();
+    // 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.
+    if (pause || (++sensorCount)>=16) return; 
+  }
+} 
+
+bool EXRAILSensor::check() {
+  // check for debounced change in this sensor 
+  inputState = RMFT2::readSensor(pin);
+
+  // Check if changed since last time, and process changes.
+  if (inputState == active) {// no change
+    latchDelay = minReadCount; // Reset counter
+    return false;  // no change 
+  }
+
+    // Change detected ... has it stayed changed for long enough
+    if (latchDelay > 0) {
+      latchDelay--;
+      return false; 
+    } 
+    
+    // change validated, act on it.
+    active = inputState;
+    latchDelay = minReadCount;  // Reset debounce counter
+    if (onChange || active) {
+      new RMFT2(progCounter);
+      return true;  // Don't check any more sensors on this entry
+    }
+    return false; 
+}
+
+EXRAILSensor::EXRAILSensor(VPIN _pin, int _progCounter, bool _onChange) {
+  // Add to the start of the list
+  //DIAG(F("ONthing vpin=%d at %d"), _pin, _progCounter);
+  nextSensor = firstSensor;
+  firstSensor = this;
+
+  pin=_pin;
+  progCounter=_progCounter;
+  onChange=_onChange;
+
+  IODevice::configureInput(pin, true);   
+  active = IODevice::read(pin);
+  inputState = active;
+  latchDelay = minReadCount;
+}
+
+EXRAILSensor *EXRAILSensor::firstSensor=NULL;
+EXRAILSensor *EXRAILSensor::readingSensor=NULL;
+unsigned long EXRAILSensor::lastReadCycle=0;
diff --git a/EXRAILSensor.h b/EXRAILSensor.h
new file mode 100644
index 0000000..b5b00c6
--- /dev/null
+++ b/EXRAILSensor.h
@@ -0,0 +1,50 @@
+/*
+ *  © 2024 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 EXRAILSensor_h
+#define EXRAILSensor_h 
+#include "IODevice.h"
+class EXRAILSensor {
+  static EXRAILSensor * firstSensor;
+ static EXRAILSensor * readingSensor;
+ static unsigned long lastReadCycle;
+ 
+  public:
+  static void checkAll();
+  
+  EXRAILSensor(VPIN _pin, int _progCounter, bool _onChange);
+  bool check();
+  
+  private:
+  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 byte minReadCount = 4; // 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
+  
+  EXRAILSensor* nextSensor;
+  VPIN pin; 
+  int progCounter; 
+  bool active; 
+  bool inputState;
+  bool onChange;
+  byte latchDelay;
+};
+#endif
\ No newline at end of file
diff --git a/GITHUB_SHA.h b/GITHUB_SHA.h
index 82af0ef..c007d27 100644
--- a/GITHUB_SHA.h
+++ b/GITHUB_SHA.h
@@ -1 +1 @@
-#define GITHUB_SHA "devel-stm32ECa-202404070538Z"
\ No newline at end of file
+#define GITHUB_SHA "devel-stm32ECa-202405230400Z"
diff --git a/IO_EXFastclock.h b/IO_EXFastclock.h
index 5ed237e..11aaea7 100644
--- a/IO_EXFastclock.h
+++ b/IO_EXFastclock.h
@@ -51,6 +51,7 @@ static void create(I2CAddress i2cAddress) {
   // Start by assuming we will find the clock
   // Check if specified I2C address is responding (blocking operation)
   // Returns I2C_STATUS_OK (0) if OK, or error code.
+  I2CManager.begin();
   uint8_t _checkforclock = I2CManager.checkAddress(i2cAddress);
   DIAG(F("Clock check result - %d"), _checkforclock);
   // XXXX change thistosave2 bytes
diff --git a/IO_HALDisplay.h b/IO_HALDisplay.h
index f2ca3af..24ffde7 100644
--- a/IO_HALDisplay.h
+++ b/IO_HALDisplay.h
@@ -1,7 +1,9 @@
 /*
- *  © 2023, Neil McKechnie. All rights reserved.
+ *  © 2024, Paul Antoine
+ *  © 2023, Neil McKechnie
+ *  All rights reserved.
  *  
- *  This file is part of DCC++EX API
+ *  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
@@ -112,13 +114,14 @@ protected:
     // Fill buffer with spaces
     memset(_buffer, ' ', _numCols*_numRows);
 
-    _displayDriver->clearNative();
-
     // Add device to list of HAL devices (not necessary but allows
     // status to be displayed using <D HAL SHOW> and device to be
     // reinitialised using <D HAL RESET>).
     IODevice::addDevice(this);
 
+    // Moved after addDevice() to ensure I2CManager.begin() has been called fisrt
+    _displayDriver->clearNative();
+
     // Also add this display to list of display handlers
     DisplayInterface::addDisplay(displayNo);
 
diff --git a/MotorDriver.cpp b/MotorDriver.cpp
index 66d1b71..da9d3ee 100644
--- a/MotorDriver.cpp
+++ b/MotorDriver.cpp
@@ -1,5 +1,5 @@
 /*
- *  © 2022-2023 Paul M Antoine
+ *  © 2022-2024 Paul M Antoine
  *  © 2021 Mike S
  *  © 2021 Fred Decker
  *  © 2020-2023 Harald Barth
@@ -38,6 +38,8 @@ volatile portreg_t shadowPORTC;
 volatile portreg_t shadowPORTD;
 volatile portreg_t shadowPORTE;
 volatile portreg_t shadowPORTF;
+volatile portreg_t shadowPORTG;
+volatile portreg_t shadowPORTH;
 #endif
 
 MotorDriver::MotorDriver(int16_t power_pin, byte signal_pin, byte signal_pin2, int16_t brake_pin,
@@ -88,6 +90,16 @@ MotorDriver::MotorDriver(int16_t power_pin, byte signal_pin, byte signal_pin2, i
     fastSignalPin.shadowinout = fastSignalPin.inout;
     fastSignalPin.inout = &shadowPORTF;
   }
+  if (HAVE_PORTG(fastSignalPin.inout == &PORTG)) {
+    DIAG(F("Found PORTG pin %d"),signalPin);
+    fastSignalPin.shadowinout = fastSignalPin.inout;
+    fastSignalPin.inout = &shadowPORTG;
+  }
+  if (HAVE_PORTH(fastSignalPin.inout == &PORTH)) {
+    DIAG(F("Found PORTH pin %d"),signalPin);
+    fastSignalPin.shadowinout = fastSignalPin.inout;
+    fastSignalPin.inout = &shadowPORTF;
+  }
 
   signalPin2=signal_pin2;
   if (signalPin2!=UNUSED_PIN) {
@@ -126,6 +138,16 @@ MotorDriver::MotorDriver(int16_t power_pin, byte signal_pin, byte signal_pin2, i
       fastSignalPin2.shadowinout = fastSignalPin2.inout;
       fastSignalPin2.inout = &shadowPORTF;
     }
+    if (HAVE_PORTG(fastSignalPin2.inout == &PORTG)) {
+      DIAG(F("Found PORTG pin %d"),signalPin2);
+      fastSignalPin2.shadowinout = fastSignalPin2.inout;
+      fastSignalPin2.inout = &shadowPORTG;
+    }
+    if (HAVE_PORTH(fastSignalPin2.inout == &PORTH)) {
+      DIAG(F("Found PORTH pin %d"),signalPin2);
+      fastSignalPin2.shadowinout = fastSignalPin2.inout;
+      fastSignalPin2.inout = &shadowPORTH;
+    }
   }
   else dualSignal=false; 
   
@@ -393,6 +415,18 @@ void MotorDriver::setDCSignal(byte speedcode, uint8_t frequency /*default =0*/)
     setSignal(tDir);
     HAVE_PORTF(PORTF=shadowPORTF);
     interrupts();
+  } else if (HAVE_PORTG(fastSignalPin.shadowinout == &PORTG)) {
+    noInterrupts();
+    HAVE_PORTG(shadowPORTG=PORTG);
+    setSignal(tDir);
+    HAVE_PORTG(PORTG=shadowPORTG);
+    interrupts();
+  } else if (HAVE_PORTH(fastSignalPin.shadowinout == &PORTH)) {
+    noInterrupts();
+    HAVE_PORTH(shadowPORTH=PORTH);
+    setSignal(tDir);
+    HAVE_PORTH(PORTH=shadowPORTH);
+    interrupts();
   } else {
     noInterrupts();
     setSignal(tDir);
diff --git a/MotorDriver.h b/MotorDriver.h
index a6ed1f6..3438c05 100644
--- a/MotorDriver.h
+++ b/MotorDriver.h
@@ -1,5 +1,5 @@
 /*
- *  © 2022-2023 Paul M. Antoine
+ *  © 2022-2024 Paul M. Antoine
  *  © 2021 Mike S
  *  © 2021 Fred Decker
  *  © 2020 Chris Harlow
@@ -26,6 +26,7 @@
 #include "FSH.h"
 #include "IODevice.h"
 #include "DCCTimer.h"
+#include <wiring_private.h>
 
 // use powers of two so we can do logical and/or on the track modes in if clauses.
 // RACK_MODE_DCX is (TRACK_MODE_DC|TRACK_MODE_INV)
@@ -83,6 +84,14 @@ enum TRACK_MODE : byte {TRACK_MODE_NONE = 1, TRACK_MODE_MAIN = 2, TRACK_MODE_PRO
 #define PORTF GPIOF->ODR
 #define HAVE_PORTF(X) X
 #endif
+#if defined(GPIOG)
+#define PORTG GPIOG->ODR
+#define HAVE_PORTG(X) X
+#endif
+#if defined(GPIOH)
+#define PORTH GPIOH->ODR
+#define HAVE_PORTH(X) X
+#endif
 #endif
 
 // if macros not defined as pass-through we define
@@ -106,6 +115,12 @@ enum TRACK_MODE : byte {TRACK_MODE_NONE = 1, TRACK_MODE_MAIN = 2, TRACK_MODE_PRO
 #ifndef HAVE_PORTF
 #define HAVE_PORTF(X) byte TOKENPASTE2(Unique_, __LINE__) __attribute__((unused)) =0
 #endif
+#ifndef HAVE_PORTG
+#define HAVE_PORTG(X) byte TOKENPASTE2(Unique_, __LINE__) __attribute__((unused)) =0
+#endif
+#ifndef HAVE_PORTH
+#define HAVE_PORTH(X) byte TOKENPASTE2(Unique_, __LINE__) __attribute__((unused)) =0
+#endif
 
 // Virtualised Motor shield 1-track hardware Interface
 
@@ -145,6 +160,8 @@ extern volatile portreg_t shadowPORTC;
 extern volatile portreg_t shadowPORTD;
 extern volatile portreg_t shadowPORTE;
 extern volatile portreg_t shadowPORTF;
+extern volatile portreg_t shadowPORTG;
+extern volatile portreg_t shadowPORTH;
 
 enum class POWERMODE : byte { OFF, ON, OVERLOAD, ALERT };
 
diff --git a/Release_Notes/Exrail mods.txt b/Release_Notes/Exrail mods.txt
index 68f57b7..6f8287f 100644
--- a/Release_Notes/Exrail mods.txt	
+++ b/Release_Notes/Exrail mods.txt	
@@ -1,3 +1,24 @@
+// 5.2.49 
+
+Which is a more efficient than the AT/AFTER/IF methods 
+of handling buttons and switches, especially on MIMIC panels. 
+
+ONBUTTON(vpin) 
+  handles debounce and starts a task if a button is used to 
+  short a pin to ground. 
+
+  for example:
+     ONBUTTON(30) TOGGLE_TURNOUT(30) DONE
+
+ONSENSOR(vpin) 
+   handles debounce and starts a task if the pin changes.
+   You may want to check the pin state with an IF ...
+
+Note the ONBUTTON and ONSENSOR are not generally useful 
+for track sensors and running trains, because you dont know which
+train triggered the sensor.  
+
+// 5.2.47
 
 BLINK(vpin, onMs,offMs)
 
diff --git a/TrackManager.cpp b/TrackManager.cpp
index d66b999..512452d 100644
--- a/TrackManager.cpp
+++ b/TrackManager.cpp
@@ -35,7 +35,7 @@
     
 #define APPLY_BY_MODE(findmode,function) \
         FOR_EACH_TRACK(t) \
-	    if (track[t]->getMode()==findmode)	\
+	    if (track[t]->getMode() & findmode)	\
                 track[t]->function;
 
 MotorDriver * TrackManager::track[MAX_TRACKS] = { NULL };
@@ -398,7 +398,7 @@ bool TrackManager::parseEqualSign(Print *stream, int16_t params, int16_t p[])
     if (params==2  && p[1]=="AUTO"_hk) // <= id AUTO>
       return setTrackMode(p[0], track[p[0]]->getMode() | TRACK_MODE_AUTOINV);
 
-    if (params==2  && p[1]=="INV"_hk) // <= id AUTO>
+    if (params==2  && p[1]=="INV"_hk) // <= id INV>
       return setTrackMode(p[0], track[p[0]]->getMode() | TRACK_MODE_INV);
 
     if (params==3  && p[1]=="DC"_hk && p[2]>0) // <= id DC cab>
diff --git a/Turnouts.cpp b/Turnouts.cpp
index 83603fc..ca5f890 100644
--- a/Turnouts.cpp
+++ b/Turnouts.cpp
@@ -123,7 +123,6 @@
     return true;
   }
 
-#define DIAG_IO
   // 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
diff --git a/WifiInterface.cpp b/WifiInterface.cpp
index 1f96998..769741c 100644
--- a/WifiInterface.cpp
+++ b/WifiInterface.cpp
@@ -1,4 +1,5 @@
 /*
+ *  © 2022-2024 Paul M. Antoine
  *  © 2021 Fred Decker
  *  © 2020-2022 Harald Barth
  *  © 2020-2022 Chris Harlow
@@ -70,7 +71,7 @@ Stream * WifiInterface::wifiStream;
 #define SERIAL3 Serial5
 #elif defined(ARDUINO_NUCLEO_F413ZH) || defined(ARDUINO_NUCLEO_F429ZI) \
     || defined(ARDUINO_NUCLEO_F446ZE) || defined(ARDUINO_NUCLEO_F412ZG) \
-    || defined(ARDUINO_NUCLEO_F439ZI)
+    || defined(ARDUINO_NUCLEO_F439ZI) || defined(ARDUINO_NUCLEO_F4X9ZI)
 #define NUM_SERIAL 3
 #define SERIAL1 Serial6
 #define SERIAL3 Serial2
diff --git a/version.h b/version.h
index 0372f71..5800b3b 100644
--- a/version.h
+++ b/version.h
@@ -3,9 +3,25 @@
 
 #include "StringFormatter.h"
 
-#define VERSION "5.3.10"
+#define VERSION "5.3.11"
+// 5.2.59 - STM32 bugfix correct Serial1 definition for Nucleo-F401RE
+//        - STM32 add support for ARDUINO_NUCLEO_F4X9ZI type to span F429/F439 in upcoming STM32duino release v2.8 as a result of our PR
+// 5.2.58 - EXRAIL ALIAS allows named pins
+// 5.2.57 - Bugfix autoreverse: Apply mode by binart bit match and not by equality
+// 5.2.56 - Bugfix and refactor for EXRAIL getSignalSlot
+// 5.2.55 - Move EXRAIL isSignal() to public to allow use in STEALTH call
+// 5.2.54 - Bugfix for EXRAIL signal handling for active high 
+// 5.2.53 - Bugfix for EX-Fastclock, call I2CManager.begin() before checking I2C address 
+// 5.2.52 - Bugfix for ADCee() to handle ADC2 and ADC3 channel inputs on F446ZE and others
+//        - Add support for ports G and H on STM32 for ADCee() and MotorDriver pins/shadow regs 
+// 5.2.51 - Bugfix for SIGNAL: Distinguish between sighandle and sigid
+// 5.2.50 - EXRAIL ONBUTTON/ONSENSOR observe LATCH
+// 5.2.49 - EXRAIL additions:
+//          ONBUTTON, ONSENSOR
+// 5.2.48 - Bugfix: HALDisplay was generating I2C traffic prior to I2C being initialised
+//
 // 5.3.10 - myCMRI.h example  
-
+//
 // 5.2.47 - EXRAIL additions:
 //          STEALTH_GLOBAL
 //          BLINK