CommandStation-EX/DCCTimerAVR.cpp

/*
 *  © 2021 Mike S
 *  © 2021-2023 Harald Barth
 *  © 2021 Fred Decker
 *  © 2021 Chris Harlow
 *  © 2021 David Cutting
 *  All rights reserved.
 *  
 *  This file is part of Asbelos DCC 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/>.
 */

// ATTENTION: this file only compiles on a UNO or MEGA
// Please refer to DCCTimer.h for general comments about how this class works
// This is to avoid repetition and duplication.
#ifdef ARDUINO_ARCH_AVR
#include <avr/boot.h> 
#include <avr/wdt.h>
#include "DCCTimer.h"
#include "DIAG.h"
#ifdef DEBUG_ADC
#include "TrackManager.h"
#endif
INTERRUPT_CALLBACK interruptHandler=0;

  // Arduino nano, uno, mega etc
#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
    #define TIMER1_A_PIN   11
    #define TIMER1_B_PIN   12
    #define TIMER1_C_PIN   13
    #define TIMER2_A_PIN   10
    #define TIMER2_B_PIN   9
    
#else
   #define TIMER1_A_PIN   9
   #define TIMER1_B_PIN   10
#endif

void DCCTimer::begin(INTERRUPT_CALLBACK callback) {
    interruptHandler=callback;
    noInterrupts();
    TCCR1A = 0;
    ICR1 = CLOCK_CYCLES;
    TCNT1 = 0;   
    TCCR1B = _BV(WGM13) | _BV(CS10);     // Mode 8, clock select 1
    TIMSK1 = _BV(TOIE1); // Enable Software interrupt
    interrupts();
//diagnostic    pinMode(4,OUTPUT);
  }


void DCCTimer::startRailcomTimer(byte brakePin) {
  (void) brakePin; // Ignored... works on pin 9 only 
  // diagnostic digitalWrite(4,HIGH);   

  /* The Railcom timer is started in such a way that it 
     - First triggers 58+29 uS after the previous TIMER1 tick. 
       This provides an accurate offset (in High Accuracy mode)
       for the start of the Railcom cutout.
     - Sets the Railcom pin high at first tick and subsequent ticks 
       until its reset to setting pin 9 low at next tick.
        
     - Cycles at 436uS so the second tick is the 
        correct distance from the cutout.
        
     - Waveform code is responsible for resetting 
       any time between the first and second tick.
       (there will be 7 DCC timer1 ticks in which to do this.)
    
    */
  const int cutoutDuration = 430; // Desired interval in microseconds
  const int cycle=cutoutDuration/2;
   
  const byte RailcomFudge0=58+58+29;
  
  // Set Timer2 to CTC mode with set on compare match
  TCCR2A = (1 << WGM21) | (1 << COM2B0) | (1 << COM2B1);
  // Prescaler of 32
  TCCR2B =  (1 << CS21) | (1 << CS20); 
  OCR2A = cycle-1; // Compare match value for 430 uS
  // Enable Timer2 output on pin 9 (OC2B)
  DDRB |= (1 << DDB1);

  // RailcomFudge2 is the expected time from idealised 
  // setup call (at previous DCC timer interrupt) to the cutout. 
  // This value should be reduced to reflect the Timer1 value
  // measuring the time since the previous hardware interrupt
  byte tcfudge=TCNT1/16; 
  TCNT2=cycle-RailcomFudge0/2+tcfudge/2;

  
 // Previous TIMER1 Tick was at rising end-of-packet bit
 // Cutout starts half way through first preamble
 // that is 2.5 * 58uS later.
  }

void DCCTimer::ackRailcomTimer() {
  // Change Timer2 to CTC mode with RESET pin 9 on next compare match
  TCCR2A = (1 << WGM21) | (1 << COM2B1);
  // diagnostic digitalWrite(4,LOW);
}


// ISR called by timer interrupt every 58uS
  ISR(TIMER1_OVF_vect){ interruptHandler(); }

// Alternative pin manipulation via PWM control.
  bool DCCTimer::isPWMPin(byte pin) {
       return pin==TIMER1_A_PIN 
           || pin==TIMER1_B_PIN
       #ifdef TIMER1_C_PIN 
           || pin==TIMER1_C_PIN
       #endif       
       ;
  }

 void DCCTimer::setPWM(byte pin, bool high) {
    if (pin==TIMER1_A_PIN) {
      TCCR1A |= _BV(COM1A1);
      OCR1A= high?1024:0;
    }
    else if (pin==TIMER1_B_PIN) { 
      TCCR1A |= _BV(COM1B1);
      OCR1B= high?1024:0;
    }
 #ifdef TIMER1_C_PIN 
    else if (pin==TIMER1_C_PIN) { 
      TCCR1A |= _BV(COM1C1);
      OCR1C= high?1024:0;
    }
 #endif       
 }

void DCCTimer::clearPWM() {
  TCCR1A= 0;
}

  void DCCTimer::getSimulatedMacAddress(byte mac[6]) {
    for (byte i=0; i<6; i++) {
      // take the fist 3 and last 3 of the serial.
      // the first 5 of 8 are at 0x0E to 0x013
      // the last  3 of 8 are at 0x15 to 0x017
      mac[i]=boot_signature_byte_get(0x0E + i + (i>2? 4 : 0));
    }
    mac[0] &= 0xFE;
    mac[0] |= 0x02;
  }


volatile int DCCTimer::minimum_free_memory=__INT_MAX__;

// Return low memory value... 
int DCCTimer::getMinimumFreeMemory() {
  noInterrupts(); // Disable interrupts to get volatile value 
  int retval = minimum_free_memory;
  interrupts();
  return retval;
}

extern char *__brkval;
extern char *__malloc_heap_start;

int DCCTimer::freeMemory() {
  char top;
  return __brkval ? &top - __brkval : &top - __malloc_heap_start;
}

void DCCTimer::reset() {
  // 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

}

void DCCTimer::DCCEXanalogWriteFrequency(uint8_t pin, uint32_t f) {
  DCCTimer::DCCEXanalogWriteFrequencyInternal(pin, f);
}
void DCCTimer::DCCEXanalogWriteFrequencyInternal(uint8_t pin, uint32_t fbits) {
#if defined(ARDUINO_AVR_UNO)
      (void)fbits;
      (void) pin;
      // Not worth doin something here as:
      // If we are on pin 9 or 10 we are on Timer1 and we can not touch Timer1 as that is our DCC source.
      // If we are on pin 5 or 6 we are on Timer 0 ad we can not touch Timer0 as that is millis() etc.
      // We are most likely not on pin 3 or 11 as no known motor shield has that as brake.
#endif
#if defined(ARDUINO_AVR_MEGA) || defined(ARDUINO_AVR_MEGA2560)
  // Speed mapping is done like this:
  // No functions buttons:   000  0   -> low          131Hz
  // Only F29 pressed        001  1   -> mid          490Hz
  // F30 with or w/o F29     01x  2-3 -> high        3400Hz
  // F31 with or w/o F29/30  1xx  4-7 -> supersonic 62500Hz
  uint8_t abits;
  uint8_t bbits;
  if (pin == 9 || pin == 10) { // timer 2 is different

    if (fbits >= 4)
      abits = B00000011;
    else
      abits = B00000001;

    if (fbits >= 4)
      bbits = B0001;
    else if (fbits >= 2)
      bbits = B0010;
    else if (fbits == 1)
      bbits = B0100;
    else //  fbits == 0
      bbits = B0110;

    TCCR2A = (TCCR2A & B11111100) | abits; // set WGM0 and WGM1
    TCCR2B = (TCCR2B & B11110000) | bbits; // set WGM2 and 3 bits of prescaler
    DIAG(F("Timer 2 A=%x B=%x"), TCCR2A, TCCR2B);

  } else { // not timer 9 or 10
    abits = B01;

    if (fbits >= 4)
      bbits = B1001;
    else if (fbits >= 2)
      bbits = B0010;
    else if (fbits == 1)
      bbits = B0011;
    else
      bbits = B0100;

    switch (pin) {
      // case 9 and 10 taken care of above by if()
    case 6:
    case 7:
    case 8:
      // Timer4
      TCCR4A = (TCCR4A & B11111100) | abits; // set WGM0 and WGM1
      TCCR4B = (TCCR4B & B11100000) | bbits; // set WGM2 and WGM3 and divisor
      //DIAG(F("Timer 4 A=%x B=%x"), TCCR4A, TCCR4B);
      break;
    case 46:
    case 45:
    case 44:
      // Timer5
      TCCR5A = (TCCR5A & B11111100) | abits; // set WGM0 and WGM1
      TCCR5B = (TCCR5B & B11100000) | bbits; // set WGM2 and WGM3 and divisor
      //DIAG(F("Timer 5 A=%x B=%x"), TCCR5A, TCCR5B);
      break;
    default:
      break;
    }
  }
#endif
}

#if defined(ARDUINO_AVR_MEGA) || defined(ARDUINO_AVR_MEGA2560)
#define NUM_ADC_INPUTS 16
#else
#define NUM_ADC_INPUTS 8
#endif
uint16_t ADCee::usedpins = 0;
uint8_t ADCee::highestPin = 0;
int * ADCee::analogvals = NULL;
static bool ADCusesHighPort = false;

/*
 * Register a new pin to be scanned
 * Returns current reading of pin and
 * stores that as well
 */
int ADCee::init(uint8_t pin) {
  uint8_t id = pin - A0;
  if (id >= NUM_ADC_INPUTS)
    return -1023;
  if (id > 7)
    ADCusesHighPort = true;
  pinMode(pin, INPUT);
  int value = analogRead(pin);
  if (analogvals == NULL)
    analogvals = (int *)calloc(NUM_ADC_INPUTS, sizeof(int));
  analogvals[id] = value;
  usedpins |= (1<<id);
  if (id > highestPin) highestPin = id;
  return value;
}
int16_t ADCee::ADCmax() {
  return 1023;
}
/*
 * Read function ADCee::read(pin) to get value instead of analogRead(pin)
 */
int ADCee::read(uint8_t pin, bool fromISR) {
  uint8_t id = pin - A0;
  if ((usedpins & (1<<id) ) == 0)
    return -1023;
  // we do not need to check (analogvals == NULL)
  // because usedpins would still be 0 in that case
  if (!fromISR) noInterrupts();
  int a = analogvals[id];
  if (!fromISR) interrupts();
  return a;
}
/*
 * Scan function that is called from interrupt
 */
#pragma GCC push_options
#pragma GCC optimize ("-O3")
void ADCee::scan() {
  static byte id = 0;       // id and mask are the same thing but it is faster to
  static uint16_t mask = 1; // increment and shift instead to calculate mask from id
  static bool waiting = false;

  if (waiting) {
    // look if we have a result
    byte low, high;
    if (bit_is_set(ADCSRA, ADSC))
      return; // no result, continue to wait
    // found value
    low = ADCL; //must read low before high
    high = ADCH;
    bitSet(ADCSRA, ADIF);
    analogvals[id] = (high << 8) | low;
    // advance at least one track
#ifdef DEBUG_ADC
    if (id == 1) TrackManager::track[1]->setBrake(0);
#endif
    waiting = false;
    id++;
    mask = mask << 1;
    if (id > highestPin) {
      id = 0;
      mask = 1;
    }
  }
  if (!waiting) {
    if (usedpins == 0) // otherwise we would loop forever
      return;
    // look for a valid track to sample or until we are around
    while (true) {
      if (mask  & usedpins) {
	// start new ADC aquire on id
#if defined(ADCSRB) && defined(MUX5)
	if (ADCusesHighPort) { // if we ever have started to use high pins)
	  if (id > 7)          // if we use a high ADC pin
	    bitSet(ADCSRB, MUX5); // set MUX5 bit
	  else
	    bitClear(ADCSRB, MUX5);
	}
#endif
	ADMUX=(1<<REFS0)|(id & 0x07); //select AVCC as reference and set MUX
	bitSet(ADCSRA,ADSC); // start conversion
#ifdef DEBUG_ADC
	if (id == 1) TrackManager::track[1]->setBrake(1);
#endif
	waiting = true;
	return;
      }
      id++;
      mask = mask << 1;
      if (id > highestPin) {
      	id = 0;
	      mask = 1;
      }
    }
  }
}
#pragma GCC pop_options

void ADCee::begin() {
  noInterrupts();
  // ADCSRA = (ADCSRA & 0b11111000) | 0b00000100;   // speed up analogRead sample time
  // Set up ADC for free running mode
  ADMUX=(1<<REFS0); //select AVCC as reference. We set MUX later
  ADCSRA = (1<<ADEN)|(1 << ADPS2); // ADPS2 means divisor 32 and 16Mhz/32=500kHz.
  //bitSet(ADCSRA, ADSC); //do not start the ADC yet. Done when we have set the MUX
  interrupts();
}
#endif