// Triggering shaped envelopes

#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

//bool gates[] = { true, false, true, false, true, false, false, true };

bool gates[] = { true, false, false, false, true, false, false, false };


int freqs[8];

int lpattern = 8;
int note = 0;

bool trigger = false;
long t0 = 0;


void setup() {

  cli();

//set timer1 interrupt at 1Hz
  TCCR1A = 0;// set entire TCCR1A register to 0
  TCCR1B = 0;// same for TCCR1B
  TCNT1  = 0;//initialize counter value to 0
  // set compare match register for 1hz increments
  //OCR1A = 15624;// = (16*10^6) / (1*1024) - 1 (must be <65536)
  //OCR1A = 7812;// = (16*10^6) / (1*1024) - 1 (must be <65536)
  OCR1A = 10000;
  // 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();



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

  randomSeed(analogRead(A0));
  mcp.setSpeed(800000L);

  for( int i = 0; i < 8; i++ ) {
    freqs[i] = random(10, 450);
  }

  trigger = true;
}


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



void loop() {
  long now = millis();
  float f1;
  int gate;
  long freq;
  if( trigger ) {
    t0 = now;
    trigger = false;
    freq = freqs[note];
    gate = gates[note];
    note++;
    if( note == lpattern ) {
      note = 0;
    }
  }
  f1 = 0.5 - 0.5 * sin((float)(now - t0) / (float)1000.0);
  mcp.setChannelValue(MCP4728_CHANNEL_A, round(4095.0 * f1));
  mcp.setChannelValue(MCP4728_CHANNEL_B, gate ? 4095 : 0);
}