Add Railcom cutout to STM32 platform

Author: mikesmitty

DCCTimer.h

@@ -62,7 +62,7 @@ class DCCTimer {
   static bool isPWMPin(byte pin);
   static void setPWM(byte pin, bool high);
   static void clearPWM();
-  static void startRailcomTimer(byte brakePin);
+  static void startRailcomTimer();
   static void ackRailcomTimer();
   static void DCCEXanalogWriteFrequency(uint8_t pin, uint32_t frequency);
   static void DCCEXanalogWrite(uint8_t pin, int value, bool invert);

DCCTimerAVR.cpp

@@ -61,8 +61,7 @@ void DCCTimer::begin(INTERRUPT_CALLBACK callback) {
   }
 
 
-void DCCTimer::startRailcomTimer(byte brakePin) {
-  (void) brakePin; // Ignored... works on pin 9 only 
+void DCCTimer::startRailcomTimer() {
   // diagnostic digitalWrite(4,HIGH);   
 
   /* The Railcom timer is started in such a way that it 

DCCTimerMEGAAVR.cpp

@@ -80,9 +80,8 @@ extern char *__malloc_heap_start;
     interruptHandler();
   }
 
-void DCCTimer::startRailcomTimer(byte brakePin) {
+void DCCTimer::startRailcomTimer() {
   // TODO: for intended operation see DCCTimerAVR.cpp
-  (void) brakePin; 
 }
 
 void DCCTimer::ackRailcomTimer() {

DCCTimerSAMD.cpp

@@ -76,9 +76,8 @@ void DCCTimer::begin(INTERRUPT_CALLBACK callback) {
   interrupts();
 }
 
-void DCCTimer::startRailcomTimer(byte brakePin) {
+void DCCTimer::startRailcomTimer() {
   // TODO: for intended operation see DCCTimerAVR.cpp
-  (void) brakePin; 
 }
 
 void DCCTimer::ackRailcomTimer() {

DCCTimerSTM32.cpp

@@ -30,9 +30,7 @@
 #ifdef ARDUINO_ARCH_STM32
 
 #include "DCCTimer.h"
-#ifdef DEBUG_ADC
 #include "TrackManager.h"
-#endif
 #include "DIAG.h"
 #include <wiring_private.h>
 
@@ -215,13 +213,49 @@ void DCCTimer::begin(INTERRUPT_CALLBACK callback) {
   interrupts();
 }
 
-void DCCTimer::startRailcomTimer(byte brakePin) {
-  // TODO: for intended operation see DCCTimerAVR.cpp
-  (void) brakePin; 
+static HardwareTimer *railcomTimer = nullptr;
+
+void DCCTimer::startRailcomTimer() {
+  // Initialize main timer if not already done
+  if (!railcomTimer) {
+    railcomTimer = new HardwareTimer(TIM3);
+    railcomTimer->pause();
+  }
+
+  // Start the timer to begin the cutout in ~29us
+  railcomTimer->resume();
+}
+
+void startRailcomCallback() {
+  TrackManager::setMainBrake(true, true);
+  if (railcomTimer) {
+    railcomTimer->pause();
+  }
 }
 
 void DCCTimer::ackRailcomTimer() {
-  // TODO: for intended operation see DCCTimerAVR.cpp
+  uint32_t cutoutOffset;
+
+  // Un-set the track brake
+  TrackManager::setMainBrake(false, true);
+
+  // Immediately end the Railcom cutout and set up the timer for the next
+  // cutout. We're in the no-man's land between the end of the cutout window and
+  // the start of the preamble so we can do time-consuming timer configuration
+  // without disrupting the DCC signal.
+  if (railcomTimer) {
+    railcomTimer->setPrescaleFactor(1);
+
+    // Sync up with the primary DCC timer. It will continue to track while paused.
+    cutoutOffset = dcctimer.getOverflow(MICROSEC_FORMAT) + 26;
+    railcomTimer->setOverflow(cutoutOffset, MICROSEC_FORMAT);
+    railcomTimer->setCount(dcctimer.getCount());
+
+    // Arm the timer for the next cutout
+    railcomTimer->refresh();
+    railcomTimer->attachInterrupt(startRailcomCallback);
+    railcomTimer->pause();
+  }
 }
 
 bool DCCTimer::isPWMPin(byte pin) {

DCCTimerTEENSY.cpp

@@ -39,9 +39,8 @@ void DCCTimer::begin(INTERRUPT_CALLBACK callback) {
   myDCCTimer.begin(interruptHandler, DCC_SIGNAL_TIME);
   }
 
-void DCCTimer::startRailcomTimer(byte brakePin) {
+void DCCTimer::startRailcomTimer() {
   // TODO: for intended operation see DCCTimerAVR.cpp
-  (void) brakePin; 
 }
 
 void DCCTimer::ackRailcomTimer() {

DCCWaveform.cpp

@@ -79,7 +79,7 @@ void DCCWaveform::interruptHandler() {
     cutoutNextTime=false;
     railcomSampleWindow=false; // about to cutout, stop reading railcom data.
     railcomCutoutCounter++;
-    DCCTimer::startRailcomTimer(9);
+    DCCTimer::startRailcomTimer();
   }
   #endif
   byte sigMain=signalTransform[mainTrack.state];
@@ -177,7 +177,7 @@ void DCCWaveform::interrupt2() {
         railcomLastAddressHigh=transmitPacket[0];
         railcomLastAddressLow =transmitPacket[1];
         railcomSampleWindow=true;
-      } else if (remainingPreambles==(requiredPreambles-3)) {
+      } else if (remainingPreambles==(requiredPreambles-6)) {
         // cutout can be ended when read
         // see above for requiredPreambles
         DCCTimer::ackRailcomTimer();

DCCWaveform.h

@@ -30,7 +30,7 @@
 
 
 // Number of preamble bits.
-const byte PREAMBLE_BITS_MAIN = 16;
+const byte PREAMBLE_BITS_MAIN = 18;
 const byte PREAMBLE_BITS_PROG = 22;
 const byte MAX_PACKET_SIZE = 5;     // NMRA standard extended packets, payload size WITHOUT checksum.
 

TrackManager.cpp

@@ -342,7 +342,12 @@ bool TrackManager::setTrackMode(byte trackToSet, TRACK_MODE mode, int16_t dcAddr
       }
       DCCTimer::clearPWM(); // has to be AFTER trackPWM changes because if trackPWM==true this is undone for  that track
     }
+#ifdef ARDUINO_ARCH_STM32
+    // High accuracy mode is not yet implemented or really needed to do Railcom on STM32
+    DCCWaveform::setRailcomPossible(true);
+#else
     DCCWaveform::setRailcomPossible(canDo);
+#endif
 #else
     // For ESP32 we just reinitialize the DCC Waveform
     DCCWaveform::begin();
@@ -655,6 +660,21 @@ void TrackManager::reportGauges(Print* stream) {
     StringFormatter::send(stream,F(">\n"));    
 }
 
+void TrackManager::setMainBrake(bool on, bool interruptContext) {
+  setTrackBrake(TRACK_MODE_MAIN, on, interruptContext);
+  if (progTrackSyncMain) {
+    setTrackBrake(TRACK_MODE_PROG, on, interruptContext);
+  }
+}
+
+void TrackManager::setTrackBrake(TRACK_MODE trackmode, bool on, bool interruptContext) {
+  FOR_EACH_TRACK(t) {
+    if (track[t]->getMode() & trackmode) {
+      track[t]->setBrake(on, interruptContext);
+    }
+  }
+}
+
 void TrackManager::setJoinRelayPin(byte joinRelayPin) {
   joinRelay=joinRelayPin;
   if (joinRelay!=UNUSED_PIN) {

TrackManager.h

@@ -70,6 +70,10 @@ class TrackManager {
     static void setMainPower(POWERMODE mode) {setTrackPower(TRACK_MODE_MAIN, mode);}
     static void setProgPower(POWERMODE mode) {setTrackPower(TRACK_MODE_PROG, mode);}
 
+    static void setTrackBrake(TRACK_MODE trackmode, bool on, bool interruptContext=false);
+    static void setMainBrake(bool on, bool interruptContext=false);
+    static void setProgBrake(bool on, bool interruptContext=false) {setTrackBrake(TRACK_MODE_PROG, on, interruptContext);}
+
     static const int16_t MAX_TRACKS=8;
     static bool setTrackMode(byte track, TRACK_MODE mode, int16_t DCaddr=0);
     static bool parseEqualSign(Print * stream,  int16_t params, int16_t p[]);