EEPROM 24c16

#define SDA_LOW DDRB |= (1<<PB0);    // low, open drain

#define SDA_HIGH DDRB &= ~(1<<PB0);    // high, Z

#define SCL_LOW DDRB |= (1<<PB1);    // low, open drain

#define SCL_HIGH DDRB &= ~(1<<PB1);    // high, Z

#define SDA (PINB & (1<<PB0))      // get SDA

void i2c_write_byte(uint16_t address, uint8_t data);

uint8_t i2c_read_byte(uint16_t address);

void i2c_read_block(uint16_t address, uint8_t *buffer, uint16_t count);

void i2c_write_cblock(uint16_t address, uint8_t cnt, uint8_t data);

/*

Quick and Dirty I2C Access

*/

#include <avr/io.h>

#include "i2c.h"

void i2c_start(void)

{

  SDA_LOW

  asm("nop");

  SCL_LOW

}

void i2c_stop(void)

{

  SDA_HIGH

  asm("nop");

  SCL_HIGH

}

uint8_t i2c_write(uint8_t data)

{

  uint8_t cnt=8;

  for (; cnt>0; cnt--) {

    if (data & 0x80)

      SDA_HIGH

    else

      SDA_LOW

    SCL_HIGH

    data <<= 1;

    SCL_LOW

  }

  SDA_HIGH

  SCL_HIGH

  asm("nop");              // WICHTG, wegen des Eingangsverzögerung!

  if (SDA) cnt=0; else cnt=1;      // check ACK

  SCL_LOW

  return cnt;

}

uint8_t i2c_read(uint8_t ack)

{

  uint8_t tmp=0, cnt=8;

  for (; cnt>0; cnt--) {

    SCL_HIGH

    tmp <<= 1;

    if (SDA) tmp |= 0x01;

    SCL_LOW

  }

  if (ack) SDA_LOW else SDA_HIGH

  SCL_HIGH

  SCL_LOW

  SDA_HIGH

  return tmp;

}

// ein Byte in den EEPROM per I2C schreiben

void i2c_write_byte(uint16_t address, uint8_t data) {

  i2c_start();

  i2c_write(0xA0);

  i2c_write(address>>8);

  i2c_write(address & 0xFF);

  i2c_write(data);

  i2c_stop();

}

// ein Byte aus dem EEPROM per I2C lesen

uint8_t i2c_read_byte(uint16_t address) {

  uint8_t tmp;

  // Adresse schreiben

  i2c_start();

  i2c_write(0xA0);

  i2c_write(address>>8);

  i2c_write(address & 0xFF);

  i2c_stop();

  // Byte lesen

  i2c_start();

  i2c_write(0xA1);

  tmp=i2c_read(0);

  i2c_stop();

  return tmp;

}

// einen Block aus dem EEPROM per I2C lesen

void i2c_read_block(uint16_t address, uint8_t *buffer, uint16_t count) {

  // Adresse schreiben

  i2c_start();

  i2c_write(0xA0);

  i2c_write(address>>8);

  i2c_write(address & 0xFF);

  i2c_stop();

  i2c_start();

  i2c_write(0xA1);

  while(count>1) {

    *buffer=i2c_read(1);

    buffer++;

  }

  *buffer=i2c_read(0);    // NACK für letztes Byte

  i2c_stop();

}

// einen Block konstanter Daten in den EEPROM scheiben

// Page Ausrichtung muss vom aufrufenden Programm geprüft werden

void i2c_write_cblock(uint16_t address, uint8_t cnt, uint8_t data) {

  // Adresse schreiben

  i2c_start();

  i2c_write(0xA0);

  i2c_write(address>>8);

  i2c_write(address & 0xFF);

  for(; cnt>0; cnt--) {

    i2c_write(data);

  }

  i2c_stop();        // Start des Schreibzugriffs

}