CommandStation-EX/DCCWaveform.cpp

#include <Arduino.h>
#include <TimerThree.h>
#include "DCCWaveform.h"
#include "DIAG.h"
DCCWaveform  DCCWaveform::mainTrack(MAIN_POWER_PIN,MAIN_SIGNAL_PIN,MAIN_SENSE_PIN,PREAMBLE_BITS_MAIN,true);
DCCWaveform  DCCWaveform::progTrack(PROG_POWER_PIN,PROG_SIGNAL_PIN,PROG_SENSE_PIN,PREAMBLE_BITS_PROG,false);

void DCCWaveform::begin() {
  
   Timer3.initialize(58);
   Timer3.disablePwm(MAIN_SIGNAL_PIN);
   Timer3.disablePwm(PROG_SIGNAL_PIN);
   Timer3.attachInterrupt(interruptHandler);
   mainTrack.beginTrack();
   progTrack.beginTrack();   
}
 
 void DCCWaveform::loop() {
   mainTrack.checkPowerOverload();
   progTrack.checkPowerOverload();
 }
 

// static //
void DCCWaveform::interruptHandler() {
   // call the timer edge sensitive actions for progtrack and maintrack
   bool mainCall2=mainTrack.interrupt1();
   bool progCall2=progTrack.interrupt1();
   
   // call (if necessary) the procs to get the current bits
   // these must complete within 50microsecs of the interrupt
   // but they are only called ONCE PER BIT TRANSMITTED 
   // after the rising edge of the signal
   if (mainCall2) mainTrack.interrupt2();
   if (progCall2) progTrack.interrupt2();
}


// An instance of this class handles the DCC transmissions for one track. (main or prog)
// Interrupts are marshalled via the statics.
// A track has a current transmit buffer, and a pending buffer.
// When the current buffer is exhausted, either the pending buffer (if there is one waiting) or an idle buffer. 


// This bitmask has 9 entries as each byte is trasmitted as a zero + 8 bits.
const byte bitMask[]={0x00,0x80,0x40,0x20,0x10,0x08,0x04,0x02,0x01};


DCCWaveform::DCCWaveform(byte powerPinNo, byte directionPinNo, byte sensePinNo, byte preambleBits, bool isMain) {
   // establish appropriate pins 
   powerPin=Arduino_to_GPIO_pin(powerPinNo);
   directionPin=Arduino_to_GPIO_pin(directionPinNo);
   sensePin=sensePinNo;
   isMainTrack=isMain;
   packetPending=false;
   memcpy(transmitPacket,idlePacket,sizeof(idlePacket));
   state=0;
   requiredPreambles=preambleBits;
   bytes_sent=0;
   bits_sent=0;
   nextSampleDue=0;
}
 void DCCWaveform::beginTrack() {
   pinMode2f(powerPin,OUTPUT);
   pinMode2f(directionPin,OUTPUT);
   pinMode(sensePin,INPUT);
   setPowerMode(POWERMODE::ON); 
   DIAG(F("\nTrack started sensePin=%d\n"),sensePin); 
 }

 POWERMODE DCCWaveform::getPowerMode() {
  return powerMode;
 }

 void DCCWaveform::setPowerMode(POWERMODE mode) {
  powerMode=mode;
  digitalWrite2f(powerPin, mode==POWERMODE::ON ? HIGH:LOW);
  if (mode==POWERMODE::ON) schedulePacket(resetMessage,2,20); 
 }
 
 
void DCCWaveform::checkPowerOverload() {
  if (millis()<nextSampleDue) return;
  int current;
  int delay;
  
  switch (powerMode) {
    case POWERMODE::OFF: 
      delay=POWER_SAMPLE_OFF_WAIT;
      break;
   case POWERMODE::ON: 
      // Check current  
      current=analogRead(sensePin);
      if (current < POWER_SAMPLE_MAX)  delay=POWER_SAMPLE_ON_WAIT;
      else {
        setPowerMode(POWERMODE::OVERLOAD);
        DIAG(F("\n*** %s TRACK POWER OVERLOAD pin=%d current=%d max=%d ***\n"),isMainTrack?"MAIN":"PROG",sensePin,current,POWER_SAMPLE_MAX);
        delay=POWER_SAMPLE_OVERLOAD_WAIT;
      }
      break;
   case POWERMODE::OVERLOAD:
      // Try setting it back on after the OVERLOAD_WAIT
      setPowerMode(POWERMODE::ON);
      delay=POWER_SAMPLE_ON_WAIT;
      break;
    default:
      delay=999;  // cant get here..meaningless statement to avoid compiler warning.  
  }
  nextSampleDue=millis()+delay;
}





// process time-edge sensitive part of interrupt
// return true if second level required  
bool DCCWaveform::interrupt1() {
  // NOTE: this must consume transmission buffers even if the power is off 
  // otherwise can cause hangs in main loop waiting for the pendingBuffer. 
  switch (state) {
    case 0:  // start of bit transmission
      digitalWrite2f(directionPin, HIGH);
      state = 1;
      return true; // must call interrupt2

    case 1:  // 58Ms after case 0
      if (currentBit) {
        digitalWrite2f(directionPin, LOW);
        state = 0;
      }
      else state = 2;
      break;
    case 2:  digitalWrite2f(directionPin, LOW);
      state = 3;
      break;
    case 3:  state = 0;
    break;
  }
  return false;
 
}


void DCCWaveform::interrupt2() {
  // set currentBit to be the next bit to be sent.
  
  if (remainingPreambles > 0 ) {
    currentBit=true;
    remainingPreambles--;
    return;
  }
  
  // beware OF 9-BIT MASK  generating a zero to start each byte   
  currentBit=transmitPacket[bytes_sent] & bitMask[bits_sent];
  bits_sent++;

  // If this is the last bit of a byte, prepare for the next byte 
  
  if (bits_sent==9) { // zero followed by 8 bits of a byte
      //end of Byte
      bits_sent=0;
      bytes_sent++;
      // if this is the last byte, prepere for next packet
      if (bytes_sent >= transmitLength) { 
         // end of transmission buffer... repeat or switch to next message
        bytes_sent = 0;
        remainingPreambles=requiredPreambles;

        if (transmitRepeats > 0) {
          transmitRepeats--;
        }
        else if (packetPending) {
          // Copy pending packet to transmit packet
          for (int b=0;b<pendingLength;b++) transmitPacket[b]= pendingPacket[b];
          transmitLength=pendingLength;
          transmitRepeats=pendingRepeats;
          packetPending=false;
        }
        else {
          // Fortunately reset and idle packets are the same length
         memcpy( transmitPacket,isMainTrack?idlePacket:resetPacket, sizeof(idlePacket));
          transmitLength=sizeof(idlePacket);
          transmitRepeats=0;
        }
      }
    }
  }


  // Wait until there is no packet pending, then make this pending  
void DCCWaveform::schedulePacket(const byte buffer[], byte byteCount, byte repeats) {
    if (byteCount>=MAX_PACKET_SIZE) return; // allow for chksum
    while(packetPending) delay(1);
    
    byte checksum=0;
    for (int b=0;b<byteCount; b++) {
      checksum^=buffer[b];
      pendingPacket[b]=buffer[b];
    }
    pendingPacket[byteCount]=checksum;
    pendingLength=byteCount+1;
    pendingRepeats=repeats;
    packetPending=true;
  }
 


bool DCCWaveform::getAck()
{
  
   if (isMainTrack) return false; // cant do this on main track
 
  while(packetPending) delay(1); // wait until transmitter has started transmitting the message
  unsigned long timeout=millis()+ACK_TIMEOUT;
  int maxCurrent=0;
  bool result=false;
  int upsamples=0;
  int downsamples=0;

  // Monitor looking for a reading high enough to be an ack 
  while(result==false && timeout>millis()) {
    upsamples++;
    int current=analogRead(sensePin);
    maxCurrent=max(maxCurrent,current);
    result=current > ACK_MIN_PULSE;
  }

  // Monitor current until ack signal dies back
  if (result) while( true) {
     downsamples++;
     int current=analogRead(sensePin);
     maxCurrent=max(maxCurrent,current);
     if (current<= ACK_MAX_NOT_PULSE) break;
  }
  // The following DIAG is really useful as it can show how long and how far the 
  // current changes during an ACK from the decoder.
 // DIAG(F("\nack=%d  max=%d, up=%d, down=%d "),result,maxCurrent, upsamples,downsamples);
  return result;
}