Colony

/* I2C.c

*/

#include <avr/interrupt.h>

#include <util/twi.h>

#include "i2c.h"

#include "ring_buffer.h"

static int start_flag;

RING_BUFFER_NEW(i2c_buffer, 64, char, i2c_write_buff, i2c_addr_buff, i2c_read_buff);

void i2c_init(char address) {

        // Enable I2C and turn on the interrupt

  //TWCR = 0;

  /* initialize the buffers */

  RING_BUFFER_CLEAR(i2c_write_buff);

  RING_BUFFER_CLEAR(i2c_addr_buff);

  RING_BUFFER_CLEAR(i2c_read_buff);

        TWCR =  (_BV(TWEA) | _BV(TWEN) | _BV(TWIE));

  //Set bit rate 12 = 100kbit/s

  TWBR = 0x0C;

        TWAR = (address << 1);        //0b0000001 address, 0 for global commands to be off

  //usb_putint(TWAR);

  //i2cTXFlag = 0;

  //i2cRXFlag = 0;

}

char i2c_putc(char dest, char data) {

  if(RING_BUFFER_FULL(i2c_write_buff))

    return -1;

  cli();

  RING_BUFFER_ADD(i2c_write_buff, data);

  RING_BUFFER_ADD(i2c_addr_buff, dest << 1);

  sei();

        //Start bit

  if(!start_flag) {

    start_flag = 1;

    TWCR |= _BV(TWSTA);

    TWCR |= _BV(TWINT);

  }

  return 0;

}

char i2c_getc(char * c) {

  if(RING_BUFFER_EMPTY(i2c_read_buff))

    return -1;

  else

    RING_BUFFER_REMOVE(i2c_read_buff, *c);

  return 0;

}

ISR(TWI_vect) {

  static char data_to_send;

  static char addr_to_send = -1;

  char addr, statusCode;

    //Get status code (only upper 5 bits)

    statusCode = (TWSR & 0xF8);

  switch (statusCode) {

    //Start sent successfully

    case TW_START:

    case TW_REP_START:

      //Send address and write

      //ring_buffer will not be empty

      RING_BUFFER_REMOVE(i2c_addr_buff, addr_to_send);

      RING_BUFFER_REMOVE(i2c_write_buff, data_to_send);

      TWDR = addr_to_send; /* first send the address */

      /* we will send the data next time around */

      //Turn off start bits

      TWCR &= ~_BV(TWSTA);

      break;

    //Address sent successfully

    case TW_MT_SLA_ACK:

      //Send byte

      TWDR = data_to_send;

      break;

    //Packet complete, close line

    case TW_MT_DATA_ACK:

      if(!RING_BUFFER_EMPTY(i2c_write_buff)) {

        RING_BUFFER_PEEK(i2c_addr_buff, addr);

        if(addr == addr_to_send) {

          RING_BUFFER_REMOVE(i2c_addr_buff, addr);

          RING_BUFFER_REMOVE(i2c_write_buff, TWDR);

          break;

        }

        else { /* no more bytes to this addr, bytes to send to new addr */

          /* doing the start signal again */

          TWCR |= _BV(TWSTA);

          break;

        }

      }

      /* there are no bytes to send */

      TWCR |= _BV(TWSTO);

      start_flag = 0;

      break;

    case TW_SR_SLA_ACK:

      break;

    case TW_SR_DATA_ACK:

      if(!RING_BUFFER_FULL(i2c_read_buff))

        RING_BUFFER_ADD(i2c_read_buff, TWDR);

      break;

    case TW_SR_STOP:

      break;

  }

  TWCR |= _BV(TWINT);

}