turn off signal pin during cutout as that might switch some H-bridges between high and low side

.gitignore

@@ -9,3 +9,4 @@ Release/*
 config.h
 .vscode/extensions.json
 mySetup.h
+myFilter.cpp

DCCEXParser.cpp

@@ -32,7 +32,7 @@
 #include "DIAG.h"
 #include <avr/wdt.h>
 
-// These keywords are used in the <1> command. The number is what you get if you use the keyword as a parameter.
+// These keywords are used in various commands. 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;
 const int16_t HASH_KEYWORD_MAIN = 11339;
@@ -56,6 +56,7 @@ const int16_t HASH_KEYWORD_LCN = 15137;
 const int16_t HASH_KEYWORD_RESET = 26133;
 const int16_t HASH_KEYWORD_SPEED28 = -17064;
 const int16_t HASH_KEYWORD_SPEED128 = 25816;
+const int16_t HASH_KEYWORD_RAILCOM = -29097;
 
 int16_t DCCEXParser::stashP[MAX_COMMAND_PARAMS];
 bool DCCEXParser::stashBusy;
@@ -776,6 +777,9 @@ bool DCCEXParser::parseD(Print *stream, int16_t params, int16_t p[])
         Diag::LCN = onOff;
         return true;
 
+    case HASH_KEYWORD_RAILCOM: // <D RAILCOM ON/OFF>
+        return DCCWaveform::setUseRailcom(onOff);        
+
     case HASH_KEYWORD_PROGBOOST:
         DCC::setProgTrackBoost(true);
 	      return true;

DCCTimer.cpp

@@ -75,6 +75,11 @@ INTERRUPT_CALLBACK interruptHandler=0;
        (void) pin; 
        return false;  // TODO what are the relevant pins? 
   }
+  
+  bool DCCTimer::isPWMPin(byte pin) {
+       (void) pin; 
+       return false;  // TODO what are the relevant pins? 
+  }
 
  void DCCTimer::setPWM(byte pin, bool high) {
     (void) pin;
@@ -90,24 +95,65 @@ INTERRUPT_CALLBACK interruptHandler=0;
 
 #elif defined(TEENSYDUINO)
   IntervalTimer myDCCTimer;
-
+  bool interruptFlipflop=false; 
+  byte railcomPin[2]={0,0];
+  enum RAILCOM_NEXT:byte {SKIP,CUT_OUT,CUT_IN);
+  RAILCOM_NEXT railcom1Next[]={SKIP,SKIP};
+  
   void DCCTimer::begin(INTERRUPT_CALLBACK callback) {
     interruptHandler=callback;
-
-  myDCCTimer.begin(interruptHandler, DCC_SIGNAL_TIME);
-
+    myDCCTimer.begin(interruptFast, DCC_SIGNAL_TIME/2);
   }
 
+  // This interrupt happens every 29uS, and alternately calls the DCC waveform
+  // or handles any pending Railcom cutout pins. 
+  void interruptFast() {
+       nterruptFlipflop=!interruptFlipflop;
+       if (interruptFiliflop) {
+        interruptHandler();
+        return;
+       }
+      
+       // Railcom interrupt, half way between DCC interruots
+       for (byte channel=0;channel<2;channel++) {
+          byte pin=railcomPin[channel;
+          if (pin) {
+            switch (railcomNext[channel]) {
+              case CUT_OUT: 
+                    digitalWrite(pin,HIGH);
+                    break;
+              case CUT_IN:          
+                    digitalWrite(pin,HIGH);
+                    break;
+              case IGNORE: break;               
+            }
+            railcomNext[channel]=IGNORE;
+          }
+       }
+  }
+  
   bool DCCTimer::isPWMPin(byte pin) {
-       //Teensy: digitalPinHasPWM, todo
       (void) pin;
-       return false;  // TODO what are the relevant pins? 
+       return true;  // We are so fast we can pretend we do support this 
+  }
+
+  bool DCCTimer::isRailcomPin(byte pin) {
+      (void) pin;
+      if (railcomPin[0]==0) railcomPin[0]=pin;
+      else if (railcomPin[1]==0) railcomPin[1]=pin;
+      else return false; 
+      return true;  // We are so fast we can pretend we do support this 
   }
 
  void DCCTimer::setPWM(byte pin, bool high) {
-    // TODO what are the relevant pins?
-    (void) pin;
-    (void) high;
+    // setting pwm on a railcom pin is deferred to the next railcom interruyupt.
+    for (byte channel=0;channel<2;channel++) {
+      if (pin==railcomPin[channel]) {
+        railcomNext[channel]=high?CUT_OUT:CUT_IN;
+        return; 
+      }
+    }
+    digitalWrite(pin,high?HIGH:LOW);
 }
 
   void   DCCTimer::getSimulatedMacAddress(byte mac[6]) {
@@ -152,7 +198,11 @@ void DCCTimer::read(uint8_t word, uint8_t *mac, uint8_t offset) {
     #define TIMER1_A_PIN   11
     #define TIMER1_B_PIN   12
     #define TIMER1_C_PIN   13
-#else
+    //railcom timer facility
+    #define TIMER4_A_PIN   6
+    #define TIMER4_B_PIN   7
+    #define TIMER4_C_PIN   8
+ #else
    #define TIMER1_A_PIN   9
    #define TIMER1_B_PIN   10
 #endif
@@ -163,9 +213,28 @@ void DCCTimer::read(uint8_t word, uint8_t *mac, uint8_t offset) {
     ADCSRA = (ADCSRA & 0b11111000) | 0b00000100;   // speed up analogRead sample time 
     TCCR1A = 0;
     ICR1 = CLOCK_CYCLES;
-    TCNT1 = 0;   
     TCCR1B = _BV(WGM13) | _BV(CS10);     // Mode 8, clock select 1
     TIMSK1 = _BV(TOIE1); // Enable Software interrupt
+    TCNT1 = 0;   
+    
+    #if defined(TIMER4_A_PIN)
+      //railcom timer facility
+      TCCR4A = 0;
+      ICR4 = CLOCK_CYCLES;
+      TCCR4B = _BV(WGM43) | _BV(CS40);     // Mode 8, clock select 1
+      TIMSK4 = 0; // Disable Software interrupt
+      delayMicroseconds(DCC_SIGNAL_TIME/2);  
+      TCNT4 = 0;  // this timer fires half cycle after Timer 1 (no idea why /4 !)     
+      #endif
+    
+      // turn on PWM for the pins here (instead of in setPWM())
+      // only needed if RailCom is inactive as otherwise RailCom
+      // takes care of that. Does not hurt tough
+      onoffPWM(TIMER1_A_PIN, true);
+      onoffPWM(TIMER1_B_PIN, true);
+#ifdef TIMER1_C_PIN
+      onoffPWM(TIMER1_C_PIN, true);
+#endif
     interrupts();
   }
 
@@ -181,20 +250,64 @@ void DCCTimer::read(uint8_t word, uint8_t *mac, uint8_t offset) {
        #endif       
        ;
   }
+// Alternative pin manipulation via PWM control.
+  bool DCCTimer::isRailcomPin(byte pin) {
+       return  
+       #ifdef TIMER4_A_PIN 
+              pin==TIMER4_A_PIN ||
+              pin==TIMER4_B_PIN ||
+              pin==TIMER4_C_PIN ||
+       #endif       
+              false;
+  }
 
- void DCCTimer::setPWM(byte pin, bool high) {
-    if (pin==TIMER1_A_PIN) {
+void DCCTimer::onoffPWM(byte pin, bool on) {
+  if (pin==TIMER1_A_PIN) {
+    if (on)
       TCCR1A |= _BV(COM1A1);
-      OCR1A= high?1024:0;
+    else
+      TCCR1A &= ~(_BV(COM1A1));
+  }
+  else if (pin==TIMER1_B_PIN) {
+    if (on)
+      TCCR1A |= _BV(COM1B1);
+    else
+      TCCR1A &= ~(_BV(COM1B1));
+  }
+#ifdef TIMER1_C_PIN
+  else if (pin==TIMER1_C_PIN) {
+    if (on)
+      TCCR1A |= _BV(COM1C1);
+    else
+      TCCR1A &= ~(_BV(COM1C1));
+  }
+#endif
+}
+ void DCCTimer::setPWM(byte pin, bool high) {
+    uint16_t val=high?1024:0;
+    if (pin==TIMER1_A_PIN) {
+      OCR1A= val;
     }
     else if (pin==TIMER1_B_PIN) { 
-      TCCR1A |= _BV(COM1B1);
-      OCR1B= high?1024:0;
+      OCR1B= val;
     }
  #ifdef TIMER1_C_PIN 
     else if (pin==TIMER1_C_PIN) { 
-      TCCR1A |= _BV(COM1C1);
-      OCR1C= high?1024:0;
+      OCR1C= val;
+    }
+ #endif       
+ #ifdef TIMER4_A_PIN 
+    else if (pin==TIMER4_A_PIN) { 
+      TCCR4A |= _BV(COM4A1); 
+      OCR4A= val;
+    }
+    else if (pin==TIMER4_B_PIN) { 
+      TCCR4A |= _BV(COM4B1); 
+      OCR4B= val;
+    }
+    else if (pin==TIMER4_C_PIN) { 
+      TCCR4A |= _BV(COM4C1); 
+      OCR4C= val;
     }
  #endif       
  }

DCCTimer.h

@@ -9,7 +9,9 @@ class DCCTimer {
   static void begin(INTERRUPT_CALLBACK interrupt);
   static void getSimulatedMacAddress(byte mac[6]);
   static bool isPWMPin(byte pin);
+  static bool isRailcomPin(byte pin);
   static void setPWM(byte pin, bool high);
+  static void onoffPWM(byte pin, bool on);
 #if (defined(TEENSYDUINO) && !defined(__IMXRT1062__))
   static void read_mac(byte mac[6]);
   static void read(uint8_t word, uint8_t *mac, uint8_t offset);

DCCWaveform.cpp

@@ -28,6 +28,8 @@
 DCCWaveform  DCCWaveform::mainTrack(PREAMBLE_BITS_MAIN, true);
 DCCWaveform  DCCWaveform::progTrack(PREAMBLE_BITS_PROG, false);
 
+bool DCCWaveform::useRailcom=false;
+bool DCCWaveform::supportsRailcom=false;
 bool DCCWaveform::progTrackSyncMain=false; 
 bool DCCWaveform::progTrackBoosted=false; 
 int  DCCWaveform::progTripValue=0;
@@ -46,8 +48,16 @@ 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)
+  supportsRailcom= MotorDriver::usePWM && mainDriver->isRailcomCapable() && progDriver->isRailcomCapable();
+  
+  // supportsRailcom depends on hardware caopability
+  // useRailcom is user switchable at run time. 
+  useRailcom=supportsRailcom;
+  
+  if (MotorDriver::usePWM){
     DIAG(F("Signal pin config: high accuracy waveform"));
+    if (supportsRailcom) DIAG(F("Railcom cutout enabled"));
+  }
   else
     DIAG(F("Signal pin config: normal accuracy waveform"));
   DCCTimer::begin(DCCWaveform::interruptHandler);     
@@ -73,8 +83,16 @@ void DCCWaveform::interruptHandler() {
   progTrack.state=stateTransform[progTrack.state];    
 
 
+  // WAVE_START is at start of bit where we need to find
+  // out if this is an railcom start or stop time
+  if (useRailcom) {
+    if (mainTrack.state==WAVE_START) mainTrack.railcom2();
+    if (progTrack.state==WAVE_START) progTrack.railcom2();
+  }
+
   // WAVE_PENDING means we dont yet know what the next bit is
-  if (mainTrack.state==WAVE_PENDING) mainTrack.interrupt2();  
+  // so call interrupt2 to set it
+  if (mainTrack.state==WAVE_PENDING) mainTrack.interrupt2();
   if (progTrack.state==WAVE_PENDING) progTrack.interrupt2();
   else if (progTrack.ackPending) progTrack.checkAck();
 
@@ -116,6 +134,16 @@ void DCCWaveform::setPowerMode(POWERMODE mode) {
   motorDriver->setPower( ison);
 }
 
+bool DCCWaveform::setUseRailcom(bool on) {
+  if (!supportsRailcom) return false; 
+  useRailcom=on;
+  if (!on) {
+    // turn off any existing cutout 
+    mainTrack.motorDriver->setRailcomCutout(false);
+    progTrack.motorDriver->setRailcomCutout(false);
+  }
+  return true;
+}
 
 void DCCWaveform::checkPowerOverload(bool ackManagerActive) {
   if (millis() - lastSampleTaken  < sampleDelay) return;
@@ -196,7 +224,27 @@ const bool DCCWaveform::signalTransform[]={
    /* WAVE_MID_0   -> */ LOW,
    /* WAVE_LOW_0   -> */ LOW,
    /* WAVE_PENDING (should not happen) -> */ LOW};
-        
+
+void DCCWaveform::railcom2() {
+  bool cutout;
+  if (remainingPreambles==(requiredPreambles-2)) {
+    cutout=true;
+  } else if (remainingPreambles==(requiredPreambles-6)) {
+    cutout=false;
+  } else {
+    return; // neiter start or end of cutout, do nothing
+  }
+
+  if (isMainTrack) {
+    if (progTrackSyncMain) // we are main track and synced so we take care of prog track as well
+      progTrack.motorDriver->setRailcomCutout(cutout);
+    mainTrack.motorDriver->setRailcomCutout(cutout);
+  } else {
+    if (!progTrackSyncMain) // we are prog track and not synced so we take care of ourselves
+      progTrack.motorDriver->setRailcomCutout(cutout);
+  }
+}
+
 void DCCWaveform::interrupt2() {
   // calculate the next bit to be sent:
   // set state WAVE_MID_1  for a 1=bit
@@ -205,9 +253,12 @@ void DCCWaveform::interrupt2() {
   if (remainingPreambles > 0 ) {
     state=WAVE_MID_1;  // switch state to trigger LOW on next interrupt
     remainingPreambles--;
+
     // Update free memory diagnostic as we don't have anything else to do this time.
     // Allow for checkAck and its called functions using 22 bytes more.
-    updateMinimumFreeMemory(22); 
+    // Don't need to do that more than once per packet
+    if (remainingPreambles == 3)
+      updateMinimumFreeMemory(22);
     return;
   }
 

DCCWaveform.h

@@ -53,10 +53,14 @@ class DCCWaveform {
     static void loop(bool ackManagerActive);
     static DCCWaveform  mainTrack;
     static DCCWaveform  progTrack;
+    static bool supportsRailcom;
+    static bool useRailcom;
 
     void beginTrack();
     void setPowerMode(POWERMODE);
     POWERMODE getPowerMode();
+    static bool setUseRailcom(bool on); 
+    
     void checkPowerOverload(bool ackManagerActive);
     inline int get1024Current() {
 	  if (powerMode == POWERMODE::ON)
@@ -118,6 +122,7 @@ class DCCWaveform {
   
     static void interruptHandler();
     void interrupt2();
+    void railcom2();
     void checkAck();
     
     bool isMainTrack;

MotorDriver.cpp

@@ -84,6 +84,10 @@ bool MotorDriver::isPWMCapable() {
     return (!dualSignal) && DCCTimer::isPWMPin(signalPin); 
 }
 
+bool MotorDriver::isRailcomCapable() {
+    return (!dualSignal) && DCCTimer::isRailcomPin(brakePin); 
+}
+
 
 void MotorDriver::setPower(bool on) {
   if (on) {
@@ -110,6 +114,11 @@ void MotorDriver::setBrake(bool on) {
   else setLOW(fastBrakePin);
 }
 
+void MotorDriver::setRailcomCutout(bool on) {
+  DCCTimer::onoffPWM(signalPin,!on);
+  DCCTimer::setPWM(brakePin,on ^ invertBrake);
+}
+
 void MotorDriver::setSignal( bool high) {
    if (usePWM) {
     DCCTimer::setPWM(signalPin,high);

MotorDriver.h

@@ -54,7 +54,9 @@ class MotorDriver {
 	    return rawCurrentTripValue;
     }
     bool isPWMCapable();
+    bool isRailcomCapable();
     bool canMeasureCurrent();
+    void setRailcomCutout(bool on);
     static bool usePWM;
     static bool commonFaultPin; // This is a stupid motor shield which has only a common fault pin for both outputs
     inline byte getFaultPin() {

MotorDrivers.h

@@ -27,6 +27,11 @@
                               new MotorDriver(3, 12, UNUSED_PIN, UNUSED_PIN, A0, 2.99, 2000, UNUSED_PIN), \
                               new MotorDriver(11, 13, UNUSED_PIN, UNUSED_PIN, A1, 2.99, 2000, UNUSED_PIN)
 
+// Arduino standard Motor Shield with railcom (mega brakes on 6,7 require jumpers )
+#define STANDARD_WITH_RAILCOM F("STANDARD_WITH_RAILCOM"),                                                 \
+                              new MotorDriver(3, 12, UNUSED_PIN, 6, A0, 2.99, 2000, UNUSED_PIN), \
+                              new MotorDriver(11, 13, UNUSED_PIN, 7, A1, 2.99, 2000, UNUSED_PIN)
+
 // Pololu Motor Shield
 #define POLOLU_MOTOR_SHIELD F("POLOLU_MOTOR_SHIELD"),                                                 \
                             new MotorDriver( 9, 7, UNUSED_PIN,         -4, A0, 18, 3000, 12), \