i2csoft.c

/**********************************************************

Software I2C Library for AVR Devices.

Copyright 2008-2012
eXtreme Electronics, India
www.eXtremeElectronics.co.in
**********************************************************/

#include <avr/io.h>
#include <avr/cpufunc.h>
#include <util/delay.h>

#include "i2csoft.h"

// We use just "nop" here because we are running MCU @ 250kHz only
#define Q_DEL _NOP();
#define H_DEL _NOP();
// #define Q_DEL _delay_loop_2(3)
// #define H_DEL _delay_loop_2(5)
// #define Q_DEL _delay_us(2)
// #define H_DEL _delay_us(2)

void SoftI2CInit()
{
	SDAPORT &= ~(1 << SDA); // Fixed
	SCLPORT &= ~(1 << SCL);
	
	SOFT_I2C_SDA_HIGH;
	SOFT_I2C_SCL_HIGH;
}

void SoftI2CStart()
{
	SOFT_I2C_SCL_HIGH;
	H_DEL;
	
	SOFT_I2C_SDA_LOW;
	H_DEL;
}

void SoftI2CStop()
{
	SOFT_I2C_SDA_LOW;
	H_DEL;
	SOFT_I2C_SCL_HIGH;
	Q_DEL;
	SOFT_I2C_SDA_HIGH;
	H_DEL;
}

uint8_t SoftI2CWriteByte(uint8_t data)
{	
	uint8_t i;
	
	for(i=0;i<8;i++)
	{
		SOFT_I2C_SCL_LOW;
		Q_DEL;
		
		if(data & 0x80)
		    SOFT_I2C_SDA_HIGH;
		else
		    SOFT_I2C_SDA_LOW;
		
		H_DEL;
		
		SOFT_I2C_SCL_HIGH;
		H_DEL;
		
		while((SCLPIN & (1<<SCL))==0);
		
		data=data<<1;
	}
	
	//The 9th clock (ACK Phase)
	SOFT_I2C_SCL_LOW;
	Q_DEL;
	
	SOFT_I2C_SDA_HIGH;
	H_DEL;
	
	SOFT_I2C_SCL_HIGH;
	H_DEL;
	
	uint8_t ack=!(SDAPIN & (1<<SDA));
	
	SOFT_I2C_SCL_LOW;
	H_DEL;
	
	return ack;
}


uint8_t SoftI2CReadByte(uint8_t ack)
{
	uint8_t data=0x00;
	uint8_t i;
	
	for(i=0;i<8;i++)
	{		
		SOFT_I2C_SCL_LOW;
		H_DEL;
		SOFT_I2C_SCL_HIGH;
		H_DEL;
		
		while((SCLPIN & (1 << SCL)) == 0);
		
		if(SDAPIN &(1<<SDA))
			data |= (0x80 >> i);
	}
	
	SOFT_I2C_SCL_LOW;
	Q_DEL;						//Soft_I2C_Put_Ack
	
	if(ack)
	{
		SOFT_I2C_SDA_LOW;
	}
	else
	{
		SOFT_I2C_SDA_HIGH;
	}
	H_DEL;
	
	SOFT_I2C_SCL_HIGH;
	H_DEL;
	
	SOFT_I2C_SCL_LOW;
	H_DEL;
	
	return data;
}