// Basic demo for configuring the MCP4728 4-Channel 12-bit I2C DAC
#include <Adafruit_MCP4728.h>
#include <Wire.h>

Adafruit_MCP4728 mcp;


// idea behind this - sequence a cloud of gate events


float hexany[] = { 0.12928301694496647, 0.32192809488736235, 0.3923174227787603, 0.5849625007211562, 0.8073549220576041, 0.9068905956085185 };
float tuning[18];

int chord[10] = { 0, 2, 4, 6, 8, 7, 11, 15, 14, 10 };

int bpm = 60;
float beat_s = 60.0 / (float)bpm;
int beat_m = round(1000.0 * beat_s); 
float mod_b = 3.141592653589793 / 4.0;
float voltrange = 4.85;  // measured this, probably not accurate
float octave = 4096.0 / voltrange; // number of DAC steps in an octave


int gate = 0;
int gatel = 1000;
int tick = 16;
long init_t;
float p_gate = 0.0;

void setup(void) {
  Serial.begin(115200);
  while (!Serial)
    delay(10); // will pause Zero, Leonardo, etc until serial console opens

  if (!mcp.begin(0x64)) {
    Serial.println("Failed to find MCP4728 chip");
    while (1) {
      delay(10);
    }
    Serial.println("MCP4728 initialised");
  }

  float n0 = 0;
  for( int o = 0; o < 3; o++ ) {
    for( int i = 0; i < 18; i++ ) {
      tuning[o * 6 + i] = round(n0 + octave * (o + hexany[i]));
    }
  }


  init_t = millis();

  mcp.setChannelValue(MCP4728_CHANNEL_B, 0);
}



void loop() {
  int note;
  int k = 0;
  if( gate > 0 ) {
    gate--;
    if( gate == 0 ) {
      mcp.setChannelValue(MCP4728_CHANNEL_B, 0);
    } 
  } else {
    long now = millis();
    long mod_t = now - init_t;
    tick--;
    if( tick == 0 ) {
      tick = 32;
      p_gate = sin(mod_b * (float)mod_t / (float)beat_m);
    }
    if( (float)random(10000) / 20.0 < abs(p_gate)) {
      if( p_gate > 0 ) {
        note = random(5);
      } else { 
        note = 5 + random(5);
      }
      mcp.setChannelValue(MCP4728_CHANNEL_B, 4095);
      mcp.setChannelValue(MCP4728_CHANNEL_A, tuning[note]);
      gate = gatel;
    }
  }

}