// can fibomod make an interesting noise?


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

Adafruit_MCP4728 mcp;

#define nsamp 256
#define dacmax 256

unsigned int phase = 0;
unsigned int fibo = 20;
unsigned int scale = 0;

byte waveform[nsamp];

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 prescaler
  TCCR1B |= (1 << CS12) | (1 << CS10);  
  // enable timer compare interrupt
  TIMSK1 |= (1 << OCIE1A);

  sei();


  Serial.begin(115200);

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

  mcp.setSpeed(800000L);

  for( int i = 0; i < nsamp; i++ ) {
    waveform[i] = 1;
  }

}

ISR(TIMER1_COMPA_vect){//timer1
  unsigned int flog;
  scale = 10;
  fibo = 3 + analogRead(A0) >> 2;
  flog = fibo;
  while( flog ) {
    flog = flog >> 1;
    scale -= 1;
  }
  Serial.println(fibo);
  Serial.println(scale);
  Serial.println(fibo << scale);
}



void loop() {
  int p0 = phase - 1;
  int p1 = phase + 2;
  if( p0 < 0 ) {
    p0 += nsamp;
  }
  if( p1 < 0 ) {
    p1 += nsamp;
  }
  waveform[phase] = (waveform[p1] + waveform[p0]) % fibo;
  mcp.fastWrite(waveform[phase] << scale, 0, 0, 0);
  phase += 1;
  if( phase >= nsamp ) {
    phase = 0;
  }
}