#define I2C_OUT DDRB = DDRB | SDA | SCL
#define I2C_IN  DDRB = (DDRB | SCL) & ~SDA

char I2CErrors;
int I2C_MINTIME = 20;


void I2CDelay(int i){									// software delay loop
while (i--);
}

void I2CSendStart(void)
{
I2CErrors = 0;											// reset error counter
I2C_OUT;												// switch ports to output direction
PORTB = PORTB | SDA | SCL;  	I2CDelay(I2C_MINTIME);	// all lines hi and wait
PORTB = PORTB & ~SDA;  			I2CDelay(I2C_MINTIME);	// data line low and wait
PORTB = PORTB & ~SCL;									// also clock line low
}


void I2CSendStop(void)
{
I2C_OUT;
PORTB = PORTB & ~SDA & ~SCL;	I2CDelay(I2C_MINTIME);	// all lines low and wait
PORTB = PORTB | SCL;			I2CDelay(I2C_MINTIME);	// clock hi and wait
PORTB = PORTB | SDA;									// also data line hi
}


void I2CSend0(void)
{
I2C_OUT;
PORTB = PORTB & ~SDA & ~SCL;	I2CDelay(I2C_MINTIME); 	//apply data=0 and wait
PORTB = PORTB | SCL;			I2CDelay(I2C_MINTIME);	//clock hi and wait 
PORTB = PORTB & ~SCL;									//clock low														
}


void I2CSend1(void)
{
I2C_OUT;
PORTB = PORTB | SDA;			I2CDelay(I2C_MINTIME);	//apply data hi and wait
PORTB = PORTB | SCL;			I2CDelay(I2C_MINTIME);	//also clock hi and wait
PORTB = PORTB & ~SCL;									//clock low
}

char I2CGetBit(void)
{
char b;
I2C_IN;
I2CDelay(I2C_MINTIME);									//wait settling time
PORTB = PORTB | SCL;			I2CDelay(I2C_MINTIME);	//clock hi and wait
b = (PINB & SDA) >> BIT_SDA;							//get bit
PORTB = PORTB & ~SCL;									//clock low
return b;
}



void I2CSendByte(char b)
{
char i,p;
	p = 0x80;
    for (i=0; i<8; i++){
    	if ((p & b) == 0) I2CSend0(); else I2CSend1();
    	p = p >> 1;
  		};
    I2CErrors = I2CErrors + I2CGetBit(); 			//Acknowledge
  	return; 
}



char I2CReceiveByte(void)
{
char i;
char b = 0;
    for (i=0; i<8; i++){
		b = b << 1;
    	b = b | I2CGetBit();
  		};
	I2CSend0();										//send Acknowledge
	I2C_IN;											//back to input mode
  	return b;
}



char I2CReceiveLastByte(void)
{
char i;
char b = 0;
    for (i=0; i<8; i++){
		b = b << 1;
    	b = b | I2CGetBit();
  		};
	I2CSend0();										//send Acknowledge
	I2C_IN;											//back to input mode
  	return b;
}