basic_din_sync_to_midi.pde

#include <digitalWriteFast.h>

// din sync to midi

// pins
#define DINSYNC_STARTSTOP 3
#define DINSYNC_CLOCK 2
// midi pin 5 > 220ohm resistor > D1
// midi pin 2 > ground
// midi pin 4 > 220ohm resistor > +5V

// leds
#define LED_CLOCK 7

#define DINSYNC_STARTSTOP_OFF 5
#define DINSYNC_CLOCK_OFF 8

// midi commands
#define MIDI_BYTE_CLOCK 248
#define MIDI_BYTE_START 250
#define MIDI_BYTE_STOP 252

#define LED_FLASH_TIME 10 // in milliseconds, hopefully

boolean clockJustHappened = false;
volatile unsigned long clockCount = 0;
boolean startStopJustHappened = false;
boolean startStop = false;
boolean isClockLEDOn = false;

unsigned long clockLEDFlashTimer = 0;

boolean isMidiClockOn = true;
unsigned long midiBeatCount = 0;

void setup()
{
    pinMode(LED_CLOCK, OUTPUT);
    pinMode(DINSYNC_STARTSTOP, INPUT);
    pinMode(DINSYNC_CLOCK, INPUT);

    Serial.begin(31250);

    attachInterrupt(digitalPinToInterrupt(DINSYNC_STARTSTOP), dinsyncStartStopChange, CHANGE);
    attachInterrupt(digitalPinToInterrupt(DINSYNC_CLOCK), dinsyncClockChange, CHANGE);
}


void dinsyncStartStopChange() {
  if (startStop == false) {
    if (digitalReadFast(DINSYNC_STARTSTOP) == HIGH) {
      startStop = true;
      startStopJustHappened = true;  
    }
  } else {
     if (digitalReadFast(DINSYNC_STARTSTOP) == LOW) {
      startStop = false;
      startStopJustHappened = true; 
     }
  }
}

void dinsyncClockChange() {
  if (digitalReadFast(DINSYNC_CLOCK) == HIGH) {
    clockJustHappened = true;
    clockCount = clockCount + 1;
  } else {
    clockJustHappened = false;
  }
}


void loop()
{
  if (startStopJustHappened && startStop) {
    // send midi clock out
    Serial.write(MIDI_BYTE_START);
    startStopJustHappened = false;
    clockCount = 0;
    checkClockLEDOn();
    
  } else if (clockJustHappened && startStop) {
  // } else if (clockJustHappened && startStop && clockCount % 2 == 0) {  // possible divide by 2 for 48ppm Korg DIN sync
    Serial.write(MIDI_BYTE_CLOCK);
    clockJustHappened = false;
    // flash beat light 
    checkClockLEDOn();
    
  } else if (startStopJustHappened && !startStop) {
    Serial.write(MIDI_BYTE_STOP);
    startStopJustHappened = false;
    clockJustHappened = false;
    turnClockLEDOff();
    clockCount = 0;
    // turn off running light
  }  

  checkClockLEDOff();
}


// **************************************************
// switching LED output

void checkClockLEDOn() {
  if (((clockCount - 1) % 12) == 0){ 
    turnClockLEDOn(); 
  }
}

void turnClockLEDOn() {
  digitalWriteFast(LED_CLOCK, HIGH);
  clockLEDFlashTimer = millis();
  isClockLEDOn = true;  
}

void checkClockLEDOff() {
  if (isClockLEDOn && (millis() - clockLEDFlashTimer) >= LED_FLASH_TIME) {
    turnClockLEDOff();   
  }
}

void turnClockLEDOff() {
  digitalWriteFast(LED_CLOCK, LOW);
  isClockLEDOn = false;
}