// Better sequencer which uses interrupts

#include <Adafruit_MCP4728.h>
#include <Wire.h>

Adafruit_MCP4728 mcp;


float tuning[37];
float voltrange = 4.85;  // measured this, probably not accurate
float octave = 4096.0 / voltrange; // number of DAC steps in an octave


// melody

// int pitch[] = { 4, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
// -1, -1, -1, -1, -1, -1, -1, -1,-1, -1, -1, -1,2, -1, -1, -1, };
// int dur[] = { 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
//             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0,  };

// hi hat

int pitch[] = { 1, 3, 4, 10, 6, 3, 11, -1 };
float dur[] = { 1,0.5,0.5,0.5,0.5,0.5,0.5,0.5,0.5, };


int note = 0;
int phrase = 8;

int s;
int bpm = 120;
float beat_s = 60.0 / (float)bpm;
float beat_m = 1000.0 * beat_s; 
bool noteon = false;
int beat = false;
long notestart, notedur, barstart;
int target, slew;
float slewk = 0.005;

void setup() {
  Serial.begin(115200);

  float freq = (float)bpm / 60.0;

  int ocr = round(16000000.0 / (1024.0 * freq )) - 1;
  Serial.println(ocr);
  if( ocr < 65536 ) {

    cli();

    TCCR1A = 0;// set entire TCCR1A register to 0
    TCCR1B = 0;// same for TCCR1B
    TCNT1  = 0;//initialize counter value to 0
    OCR1A = ocr; //ocr; 
    // turn on CTC mode
    TCCR1B |= (1 << WGM12);
    // Set CS10 and CS12 bits for 1024 escaler
    TCCR1B |= (1 << CS12) | (1 << CS10);  
    // enable timer compare interrupt
    TIMSK1 |= (1 << OCIE1A);

    sei();

  } else {
    Serial.println("BPM out of range");
  }

  if (!mcp.begin(0x64)) {
    while (1) {
      delay(100);
    }
  }

  // randomSeed(analogRead(A0));
  mcp.setSpeed(800000L);
  make_tuning(12);
  note=0;
  slew=0;
  barstart=millis();
}

void make_tuning(int edo) {
  float n0 = 0;
  float edof = (float)edo;
  for( int i = 0; i < 37; i++ ) {
      tuning[i] = round(n0 + octave * (float)i / edof);
  }

}


// mod_note argument is milliseconds from the start of last note
float mod_note(int x) {
  float xb = x / (0.2 * beat_m);
  return 0.5 + 0.5 * xb * (xb - 1) * ( xb - 2);
}

// mod_note argument is milliseconds from the start of this bar
float mod_bar(int x) {
  return 0.5 + 0.5 * sin((float)x / (beat_m * 2));
}

void set_mod(MCP4728_channel_t channel, float v) {
  int o;
  o = round(v * 4095.0);
  if( o > 4095 ) {
    o = 4095;
  }
  if( o < 0 ) {
    o = 0;
  } 
  mcp.setChannelValue(channel, o);
}

ISR(TIMER1_COMPA_vect){ // called once every beat
  beat = true;
}


void loop() {
  float mod;
  int o;
  long now = millis();
  if( beat ) {
    beat = false;
    if( pitch[s] > -1 ) {
      notestart = millis();
      notedur = round(beat_m * dur[s]);
      noteOn(pitch[s]);
      noteon = true;
    }
    s += 1;
    if( s == phrase ) {
      s = 0;
      barstart = notestart;
    }
  } else {
    if( noteon ) {
        set_mod(MCP4728_CHANNEL_C, mod_note(now - notestart));
      if( now - notestart > notedur ) {
        noteOff();
        noteon = false;
      }
    }
    set_mod(MCP4728_CHANNEL_D, mod_bar(now - barstart));
    slew += round((float)(target - slew) * slewk);
    if( slew > 4095 ) {
      slew = 4095;
    }
    if( slew < 0 ) {
      slew = 0;
    }
    mcp.setChannelValue(MCP4728_CHANNEL_A, slew);
  }
}


void noteOn(int note) {
  if( note > -1 ) {
    //mcp.setChannelValue(MCP4728_CHANNEL_A, tuning[note]);
    target = tuning[note];
    mcp.setChannelValue(MCP4728_CHANNEL_B, 4095);
  }
}

void noteOff() {
    mcp.setChannelValue(MCP4728_CHANNEL_B, 0);
}