Arduino MCP4922 SPI DAC demo code

gistfile1.c

/*
  MCP4922 test
  Steve Woodward, 2010
  most code borrowed from
  http://mrbook.org/blog/2008/11/22/controlling-a-gakken-sx-150-synth-with-arduino/

    connections
====================================================

+5v           > 4922 pin 1
Ard pin 10    > 4922 pin 3   (SS - slave select)
Ard pin 13    > 4922 pin 4   (SCK - clock)
Ard pin 11    > 4922 pin 5   (MOSI - data out)
Ground        > 4922 pin 8   (LDAC)
+5v           > 4922 pin 11  (voltage ref DAC B)
Ground        > 4922 pin 12
+5v           > 4922 pin 13  (voltage ref DAC A)

  4922 pin 14 DAC A > 1k resistor > synth CV in

   */


// MCP4922 DAC out
#define DATAOUT 11//MOSI
#define DATAIN 12//MISO - not used, but part of builtin SPI
#define SPICLOCK  13//sck
#define SLAVESELECT0 10//ss

int i = 0;

void setup() {
    SPI_setup();
    Serial.begin(9600);
}

void loop() {
    i++;
    Serial.println(i);
    write_note(i);
    if(i>=4096) {
        i=0;
    }
}

void write_note(int i) {
    write_valueY(i);
    write_valueX(i);
}

// **************************************************
// SPI for DAC

void SPI_setup(){

  byte clr;
  pinMode(DATAOUT, OUTPUT);
pinMode(SPICLOCK,OUTPUT);
pinMode(SLAVESELECT0,OUTPUT);
digitalWrite(SLAVESELECT0,HIGH); //disable device

  SPCR = (1<<SPE)|(1<<MSTR) | (0<<SPR1) | (0<<SPR0);
clr=SPSR;
clr=SPDR;
delay(10);
}

// write out through DAC A
void write_valueX(int sample)
{
// splits int sample in to two bytes
byte dacSPI0 = 0;
byte dacSPI1 = 0;
dacSPI0 = (sample >> 8) & 0x00FF; //byte0 = takes bit 15 - 12
dacSPI0 |= (1 << 7);
  // A/B: DACa or DACb - Forces 7th bit  of    x to be 1. all other bits left alone.
dacSPI0 |= 0x10;
dacSPI1 = sample & 0x00FF; //byte1 = takes bit 11 - 0
dacSPI0 |= (1<<5);  // set gain of 1
digitalWrite(SLAVESELECT0,LOW);
SPDR = dacSPI0;  // Start the transmission
while (!(SPSR & (1<<SPIF)))     // Wait the end of the transmission
{
};

  SPDR = dacSPI1;
while (!(SPSR & (1<<SPIF)))     // Wait the end of the transmission
{
};
digitalWrite(SLAVESELECT0,HIGH);
//delay(2);
}

// write out through DAC B
void write_valueY(int sample)
{
// splits int sample in to two bytes
byte dacSPI0 = 0;
byte dacSPI1 = 0;
dacSPI0 = (sample >> 8) & 0x00FF; //byte0 = takes bit 15 - 12
dacSPI0 |= 0x10;

    dacSPI1 = sample & 0x00FF; //byte1 = takes bit 11 - 0
dacSPI0 |= (1<<5);  // set gain of 1

    digitalWrite(SLAVESELECT0,LOW);
SPDR = dacSPI0;  // Start the transmission
while (!(SPSR & (1<<SPIF)))     // Wait the end of the transmission
{
};

  SPDR = dacSPI1;
while (!(SPSR & (1<<SPIF)))     // Wait the end of the transmission
{
};
digitalWrite(SLAVESELECT0,HIGH);
}