#define I2C_SDA_LO DDRB = (DDRB | SDA) & ~SCL
#define I2C_SCL_LO DDRB = (DDRB | SCL) & ~SDA
#define I2C_ALL_LO DDRB = DDRB | SDA | SCL
#define I2C_ALL_HI DDRB = DDRB & (~SDA & ~SCL)



char I2CErrors;
int I2C_MINTIME = 40;


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

void I2CStretch(){							// wait until clock hi
while(!(PINB & SCL));
}

void I2CSendStart(void)
{
I2CErrors = 0;											// reset error counter												// switch ports to output direction
I2C_ALL_HI;  					I2CDelay(I2C_MINTIME); I2CStretch();	// all lines hi and wait
I2C_SDA_LO;  					I2CDelay(I2C_MINTIME); 	// data line low and wait
I2C_ALL_LO;												// also clock line low
}


void I2CSendStop(void)
{
I2C_ALL_LO;						I2CDelay(I2C_MINTIME); 	// all lines low and wait
I2C_SDA_LO;						I2CDelay(I2C_MINTIME); 	I2CStretch();// clock hi and wait
I2C_ALL_HI;							                 	// also data line hi
}


void I2CSend0(void)
{
I2C_ALL_LO;						I2CDelay(I2C_MINTIME); 	//apply data=0 and wait
I2C_SDA_LO;						I2CDelay(I2C_MINTIME); I2CStretch();	//clock hi and wait 
I2C_ALL_LO;												//clock low														
}


void I2CSend1(void)
{
I2C_SCL_LO;						I2CDelay(I2C_MINTIME);	//apply data hi and wait
I2C_ALL_HI;						I2CDelay(I2C_MINTIME); I2CStretch();	//also clock hi and wait
I2C_SCL_LO;												//clock low
}


char I2CGetBit(void)									//open collector
{
char b;
I2C_SCL_LO;						I2CDelay(I2C_MINTIME);	//SDA Hi Z and wait
I2C_ALL_HI;						I2CDelay(I2C_MINTIME);	I2CStretch();	//clock hi and wait
b = (PINB & SDA) >> BIT_SDA;							//get bit
I2C_SCL_LO;												//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)							//open collector
{
char i;
char b = 0;
    for (i=0; i<8; i++){
		b = b << 1;
    	b = b | I2CGetBit();
  		};
	I2CSend0();										//send Acknowledge
  	return b;
}


char I2CReceiveLastByte(void)						//open collector
{
char i;
char b = 0;
    for (i=0; i<8; i++){
		b = b << 1;
    	b = b | I2CGetBit();
  		};
	I2CSend1();										//send Acknowledge
  	return b;
}