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)

/*

For each note: pitch, absolute start time (in beats) and duration - either preset these or compute it

For a sequencer: is time-elapsed > start time of next note?

if yes - set the play time to now, increment the note
  - if a note happens to be playing now, doesn't matter, just change the pitch and reset the timer

if no - is there still a note playing?

if still playing, is now - play start > the note's duration? if so, stop playing

the absolute start time should include a count-in

*/

// 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 s1[] =   { 2, 4, 5, 6, 7, 8, 10, 12, 14, 16, 17, 18, 19, 20, 22, 24, 26, 28, 29, 30, 31, 32, 34, 36, 37, 38, 40, 42, 44, 48, 50, 52, 54, 56, 60, 62, 64, 66, 68, 72, 74, 76, 77, 78, 79, 80, 82, 84, 85, 86, 88, 90, 92, 96 };
// 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  };



int m1[] =     { 0,    2,    4,   5,     7,   9,  11, 12 };
int s1[] =     { 0,    3,    5,   7,    9,  11,  13, 15 };
float d1[] =   { 1.0, 0.5, 1.0, 0.5,  1.0, 0.5, 1.0, 0.5  };
int m2[] =     { 0,    4,    7,  12, 0,    4,    7,  12, 0,    4,    7,  12, 0,    4,    7,  12 };
int s2[] =     { 0, 1 ,    2,    3,   4,    5,  6,  7, 8, 9, 10, 11, 12, 13, 14, 15 };
float d2[] =   { 0.5, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5 };


float gate = 0.5;
int bpm = 180;
float beat_s = 60.0 / (float)bpm;
int beat_m = round(1000.0 * beat_s); 

// count_in = number of beats since t0 to wait before we startt playing
// repeat = number of beats to repeat - could be computed from the sequence data

long count_in_m = 4 * beat_m;
int repeat = 16;


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 = -1;
  int playing = 0;
  long play = 0;
  long rel = 0;
  long last = 0;
  long init = 0;
  int *melody;
  int *start;
  float *duration;
  int len = 0;
  MCP4728_channel_t pitch;
  MCP4728_channel_t gate;
} sequencer;

sequencer seq1, seq2;
long start_time;

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 i = 0; i < 16; i++ ) {
      tuning[i] = round(n0 + octave * (float)i / 12.0);
  }
  long now = millis();
  start_time = now;
  seq1.last = now;
  seq1.pitch = MCP4728_CHANNEL_A;
  seq1.gate = MCP4728_CHANNEL_B;
  seq1.melody = m1;
  seq1.start = s1;
  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.start = s2;
  seq2.len = sizeof(m2) / sizeof(m2[0]);

}


void loop() {
  long now = millis();
  long beat_int = (now - start_time - count_in_m) % (beat_m * repeat);
  float beat = (float)(beat_int) / (float)beat_m;
  runSequencer(seq1, now, beat);
  runSequencer(seq2, now, beat);
}

void runSequencer(sequencer& seq, long now, float beat) {
  if( seq.s < seq.len - 1 ) {
    if( beat > (float)seq.start[seq.s + 1] ) {
      seq.s += 1;
      seq.rel = now + round((float)beat_m * seq.duration[seq.s]);
      if( seq.melody[seq.s] > -1 ) {
        mcp.setChannelValue(seq.pitch, tuning[seq.melody[seq.s]]);
        mcp.setChannelValue(seq.gate, 4095);
      }
      seq.playing = 1;
      if( seq.s == seq.len - 1 ) {
        seq.s = -1;
      }
    }
  }
  if( seq.playing ) {
    if( now > seq.rel ) {
      mcp.setChannelValue(seq.gate, 0);
      seq.playing = 0;
    }
  }
}


// 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);
// }