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

Adafruit_MCP4728 mcp;


int bpm = 98;
float beat_s = 60.0 / (float)bpm;
int beat_m = round(1000.0 * beat_s); 
long init_t;

float pi = 3.141592653589793;
float mod_a = pi;
float mod_b = pi / 4.0;
float mod_c = pi / 3.0;
float mod_d = pi / 5.0;



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");
  }

  init_t = millis();
  mcp.setChannelValue(MCP4728_CHANNEL_B, 0);

}


void loop() {
  long now = millis();
  long mod_t = (now - init_t);
  float tf = (float)mod_t / (float)beat_m;
  uint16_t a = round(4095.0 * (0.5 + 0.5 * sin(mod_a * tf)));
  uint16_t b = round(4095.0 * (0.5 + 0.5 * sin(mod_b * tf)));
  uint16_t c = round(4095.0 * (0.5 + 0.5 * sin(mod_c * tf)));
  uint16_t d = round(4095.0 * (0.5 + 0.5 * sin(mod_d * tf)));
  mcp.fastWrite(a, b, c, d);
}