/*
Title: I2C_Master_Software_1.ino
Author: Florin Dragan	florind@mas.utcluj.ro
Date Created: 01-10-2017
Last Modified: 02-03-2020

Purpose: This is an example how to use I2C interface with
Software implementation and Arduino functions
*/

#define SDA_Pin 2	//PD2
#define SCL_Pin 3	//PD3
 
void I2CInit()
{
	digitalWrite(SDA_Pin, 1);
	digitalWrite(SCL_Pin, 1);
}
 
void I2CStart()
{
	digitalWrite(SDA_Pin, 0);
	digitalWrite(SCL_Pin, 0);
}
 
void I2CRestart()
{
	digitalWrite(SDA_Pin, 1);
	digitalWrite(SCL_Pin, 1);
	digitalWrite(SDA_Pin, 0);
	digitalWrite(SCL_Pin, 0);
}
 
void I2CStop()
{
	digitalWrite(SCL_Pin, 0);
	digitalWrite(SDA_Pin, 0);
	digitalWrite(SCL_Pin, 1);
	digitalWrite(SDA_Pin, 1);
}
 
void I2CAck()
{
	digitalWrite(SDA_Pin, 0);
	digitalWrite(SCL_Pin, 1);
	digitalWrite(SCL_Pin, 0);
	digitalWrite(SDA_Pin, 1);
}
 
void I2CNak()
{
	digitalWrite(SDA_Pin, 1);
	digitalWrite(SCL_Pin, 1);
	digitalWrite(SCL_Pin, 0);
	digitalWrite(SDA_Pin, 1);
}
 
unsigned char I2CSend(unsigned char Data)
{
	 unsigned char i, ack_bit;
	 for (i = 0; i < 8; i++) {
		if ((Data & 0x80) == 0)
			digitalWrite(SDA_Pin, 0);
		else
			digitalWrite(SDA_Pin, 1);
		digitalWrite(SCL_Pin, 1);
	 	digitalWrite(SCL_Pin, 0);
		Data<<=1;
	 }
	 digitalWrite(SDA_Pin, 1);
	 digitalWrite(SCL_Pin, 1);
	 ack_bit = digitalRead(SDA_Pin);
	 digitalWrite(SCL_Pin, 0);
	 return ack_bit;
}
 
unsigned char I2CRead()
{
	unsigned char i, Data=0;
	for (i = 0; i < 8; i++) {
		digitalWrite(SCL_Pin, 1);
		if(digitalRead(SDA_Pin))
			Data |=1;
		if(i<7)
			Data<<=1;
		digitalWrite(SCL_Pin, 0);
	}
	return Data;
}


   int main(void)
 {

unsigned char ack, data;

/*****************************************
 * Write to slave device with
 * slave address e.g. say 0x20
 *****************************************/
	/* Init i2c ports first */
	I2CInit();
	/* Send start condition */
	I2CStart();
	/* Send slave address */
	ack = I2CSend(0x20);
	/*
	 * ack == 1 => NAK
	 * ack == 0 => ACK
	 */
	ack = I2CSend(0x07);
	/* Send another data */
	ack = I2CSend(0x10);
	/* Send stop condition */
	I2CStop();
 
/*****************************************
 * Read from slave device with
 * slave address e.g. say 0x20
 *****************************************/
	/* Init i2c ports first - Should be done once in main */
	I2CInit();
	/* Send start condition */
	I2CStart();
	/*
	 * Send slave address with Read bit set
	 * So address is 0x20 | 1 = 0x21
	 */
	I2CSend(0x21);
	data = I2CRead();
	/* Send ack */
	I2CAck();
	/* Read last byte */
	data = I2CRead();
	/*
	 * Send nak for last byte to indicate
	 * End of transmission
	 */
	I2CNak();
	/* Send stop condition */
	I2CStop();

}