i2csw.c

#include "i2csw.h"

#include <util/delay.h>

static uint8_t I2CswGetBit(void)
{
  uint8_t ret;

  _delay_us(5);
  DDR(I2C_SCL) &= ~I2C_SCL_LINE;        // Pullup SCL = 1
  _delay_us(5);
  ret = PIN(I2C_SDA) & I2C_SDA_LINE;
  DDR(I2C_SCL) |= I2C_SCL_LINE;         // Active SCL = 0

  return ret;
}

static void I2CswSendBit(uint8_t bit)
{
  if (bit)
    DDR(I2C_SDA) &= ~I2C_SDA_LINE;      // Pullup SDA = 1
  else
    DDR(I2C_SDA) |= I2C_SDA_LINE;       // Active SDA = 0
  I2CswGetBit();

  return;
}

void I2CswStart(uint8_t addr)
{
  DDR(I2C_SCL) &= ~I2C_SCL_LINE;        // Pullup SCL = 1
  DDR(I2C_SDA) &= ~I2C_SDA_LINE;        // Pullup SDA = 1
  _delay_us(5);
  DDR(I2C_SDA) |= I2C_SDA_LINE;         // Active SDA = 0
  _delay_us(5);
  DDR(I2C_SCL) |= I2C_SCL_LINE;         // Active SCL = 0

  I2CswWriteByte(addr);

  return;
}

void I2CswStop(void)
{
  DDR(I2C_SCL) |= I2C_SCL_LINE;         // Active SCL = 0
  DDR(I2C_SDA) |= I2C_SDA_LINE;         // Active SDA = 0
  _delay_us(5);
  DDR(I2C_SCL) &= ~I2C_SCL_LINE;        // Pullup SCL = 1
  _delay_us(5);
  DDR(I2C_SDA) &= ~I2C_SDA_LINE;        // Pullup SDA = 1

  return;
}

void I2CswWriteByte(uint8_t data)
{
  uint8_t i = 0;

  for (i = 0; i < 8; i++) {
    I2CswSendBit(data & 0x80);
    data <<= 1;
  }
  I2CswSendBit(I2C_ACK);

  return;
}

uint8_t I2CswReadByte(uint8_t ack)
{
  uint8_t i, ret;

  DDR(I2C_SDA) &= ~I2C_SDA_LINE;        // Pullup SDA = 1

  ret = 0;
  for (i = 0; i < 8; i++) {
    ret <<= 1;
    if (I2CswGetBit())
      ret |= 0x01;
  }
  I2CswSendBit(!ack);

  return ret;
}