/* p9_3 Generate sine waveform using DAC MCP4725 with Edubase-V2 board
 * 
 * The sine wave lookup table is generated in setup().
 */
#include <Wire.h>

const char SLAVEADDR = 0x60;    /* DAC MCP4725 address */
const int WAVEFORM_LENGTH = 360;
int sinewave[WAVEFORM_LENGTH];

void setup() {
    int i;
    float radian;
#ifndef M_PI    /* M_PI should be defined in GCC, but just in case */
    const float M_PI = 4 * atan(1.0);
#endif

    /* construct data table for a sine wave */
    radian = ((2 * M_PI) / WAVEFORM_LENGTH);
    for (i = 0; i < WAVEFORM_LENGTH; i++) {
        sinewave[i] = 2047 * (sinf(radian * i) + 1);
    }
    
    Wire.begin();               /* initialize I2C */
}

void loop() {
    for (int i = 0; i < WAVEFORM_LENGTH; i++) {
      /* write to MCP4725 DAC through I2C */
      Wire.beginTransmission(SLAVEADDR);   /* start talking to DAC */
      Wire.write(0x40);                    /* send write DAC register command */
      Wire.write(sinewave[i] >> 4) & 0xFF; /* send high byte data (D13-D4) */
      Wire.write(sinewave[i] << 4) & 0xFF; /* send low byte data (D3-D0) */
      Wire.endTransmission();              /* stop */
    }
}