arduino-modular/Xmas/Xmas.ino

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

Adafruit_MCP4728 mcp;


float tuning[16];
// 0 = A, 8 = F (tonic)

int m1[] =   { 3, 8, 8, 10, 8, 7, 5, 5, 5, 10, 10, 12, 10, 8, 7, 3, 7, 12, 12, 13, 12, 10, 8, 5, 3, 3, 5, 10, 7, 8, 3, 8, 8, 8, 7, 7, 8, 7, 5, 3, 10, 12, 10, 10, 8, 8, 15, 3, 3, 3, 5, 10, 7, 8  };
int d1[] = { 2, 2, 1, 1, 1, 1, 2, 2, 2, 2, 1, 1, 1, 1, 2, 2, 2, 2, 1,  1, 1, 1, 2, 2, 1, 1, 2, 2, 2, 4, 2, 2, 2, 2, 4, 2, 2, 2, 2, 4, 2, 2, 1, 1, 1, 1,  2, 2, 1, 1, 2, 2, 2, 4 };
int m2[] =   { -1, 8, 1, 2, 3, 4, 5, 0, 1, 3, 8, 8, 3, 5, 7, 8, 7, 0, 1, 3, 8  };
int d2[] = { 2,  6, 6, 6, 6, 6, 4, 2, 4, 2, 6, 6, 6, 6, 6, 6, 4, 2, 4, 2, 4  };
float gate = 0.5;
int bpm = 240;
float beat_s = 60.0 / (float)bpm;
int beat_m = round(1000.0 * beat_s); 
float voltrange = 5.0; 
float octave = 4096.0 / voltrange; // number of DAC steps in an octave
float mod_b = 3.141592653589793 / 4.0;

typedef struct {
  int s = 0;
  bool noteOn = false;
  long play = 0;
  long rel = 0;
  long last = 0;
  long init = 0;
  int *melody;
  int *duration;
  int len = 0;
  MCP4728_channel_t pitch;
  MCP4728_channel_t gate;
} sequencer;

sequencer seq1, seq2;


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");
  }

  mcp.setChannelValue(MCP4728_CHANNEL_B, 0);

  float n0 = 0;
  for( int i = 0; i < 16; i++ ) {
      tuning[i] = round(n0 + octave * (float)i / 12.0);
  }
  long now = millis();
  seq1.last = now;
  seq1.pitch = MCP4728_CHANNEL_A;
  seq1.gate = MCP4728_CHANNEL_B;
  seq1.melody = m1;
  seq1.duration = d1;
  seq1.len = sizeof(m1) / sizeof(m1[0]);

  seq2.last = now;
  seq2.pitch = MCP4728_CHANNEL_C;
  seq2.gate = MCP4728_CHANNEL_D;
  seq2.melody = m2;
  seq2.duration = d2;
  seq2.len = sizeof(m2) / sizeof(m2[0]);

}


void loop() {
  long now = millis();
  runSequencer(seq1, now);
  runSequencer(seq2, now);
}

void runSequencer(sequencer& seq, long now) {
  if( seq.noteOn ) {
    if( now - seq.last > seq.rel ) {
      noteOff(seq);
      seq.last = now;
      seq.play = 0; // no gate for now
      seq.noteOn = false;
      seq.s += 1;
      if( seq.s > seq.len ) {
        seq.s = 0;
      }
    }
  } else {
    if( now - seq.last > seq.play ) {
      noteOn(seq, seq.melody[seq.s]);
      seq.last = now;
      seq.rel = beat_m * seq.duration[seq.s];
      seq.noteOn = true;
    }
  }
  
}


void noteOn(sequencer seq, int note) {
  if( note > -1 ) {
    mcp.setChannelValue(seq.pitch, tuning[note]);
    mcp.setChannelValue(seq.gate, 4095);
  }
}

void noteOff(sequencer seq) {
    mcp.setChannelValue(seq.gate, 0);
}