TWI (IC2) ATMEL (DVK90CAN1 & AT90CAN128)

#include "main.h"

#define FOSC           16000        // 8 MHz External cristal

#define F_CPU          (FOSC*1000L) // Need for AVR GCC

#define SCL_CLOCK  100000L /* I2C clock in Hz */

#define MCP4706A0 0x60 //i2c address for mcp4706A0

void i2c_init(void){

  TWSR = 0;

  TWBR = ((F_CPU/SCL_CLOCK)-16)/2;

}

unsigned char i2c_start(unsigned char address_and_RW_bit){

  uint8_t twst;

  TWCR = (1<< TWINT) | (1<< TWSTA) | (1<<TWEN);

  while(!(TWCR & (1<<TWINT)));

  PORTA = 0x03; //two LEDs on (Bis hier läuft das Programm beim DVK)

  twst = TW_STATUS & 0xF8;

  if ( (twst != TW_START) && (twst != TW_REP_START)) return 0;

  TWDR = address_and_RW_bit;

  TWCR = (1<<TWINT) | (1<<TWEN);

  while(!(TWCR & (1<<TWINT)));

  PORTA = 0x07; // three LEDs on

  twst = TW_STATUS & 0xF8;

  if ( (twst != TW_MT_SLA_ACK) && (twst != TW_MR_SLA_ACK) ) return 0;

  return 1;

}

unsigned char i2c_write(unsigned char data){

  uint8_t   twst;

  TWDR = data;

  TWCR = (1<<TWINT) | (1<<TWEN);

  while(!(TWCR & (1<<TWINT)));

  twst = TW_STATUS & 0xF8;

  if( twst != TW_MT_DATA_ACK) return 1;

  return 0;

}

void i2c_stop(void){

  TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);

  while(TWCR & (1<<TWSTO));

}

int main(void)

{

  //Set direction

  DDRA = 0xFF;

  //Turn off all relays

  PORTA = 0x00;

  i2c_init();

  PORTA = 0x01; // one LED on

  while (1){

    if (i2c_start(MCP4706A0 + 0)){

      PORTA = 0x0F; // four LEDs on 

      i2c_write(MCP4706_0KOhm); //Set up device

      i2c_write(0x0F); // Set digital to analog output (0x00 - 0xFF)

      i2c_stop();

    }

    else{

      i2c_stop();

    }

  }

  return 0;

}