/*
Title: I2C_Master_Software_0.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
*/

#define SDA_Pin 2	//PD2
#define SCL_Pin 3	//PD3
 
/* Defining the pin state as macros*/
#define SDA_HIGH 	digitalWrite(SDA_Pin, 1)
#define SDA_LOW 	digitalWrite(SDA_Pin, 0)
#define SCL_HIGH 	digitalWrite(SCL_Pin, 1)
#define SCL_LOW 	digitalWrite(SCL_Pin, 0)

/* Set INITIAL (pause) state condition */
 void I2CInit()
 {
	SDA_HIGH;
	SCL_HIGH;
 }

/* Set START condition */
 void I2CStart()
 {
	SDA_LOW;
	SCL_LOW;
 }

/* Set RESTART condition */
 void I2CRestart()
 {
	SDA_HIGH;
	SCL_HIGH;
	SDA_LOW;
	SCL_LOW;
 }
 
/* Set STOP condition */
 void I2CStop()
 {
	SCL_LOW;
	SDA_LOW;
	SCL_HIGH;
	SDA_HIGH;
 }
 
/* Set ACK condition */
 void I2CAck()
 {
	SDA_LOW;
	SCL_HIGH;
	SCL_LOW;
	SDA_HIGH;
 }
 
/* Set NACK condition */
 void I2CNak()
 {
	SDA_HIGH;
	SCL_HIGH;
	SCL_LOW;
	SDA_HIGH;
 }
 
/* Send a byte (8 bit in length) to I2C Slave */
 unsigned char I2CSend(unsigned char Data)
 {
	 unsigned char i, ack_bit;
	 for (i = 0; i < 8; i++)
	{
		if ((Data & 0x80) == 0) {
			SDA_LOW; }
		else {
			SDA_HIGH; }
	/* Pulse clock signal */
		SCL_HIGH;
	 	SCL_LOW;
	/* Data displacement one bit left */
		Data<<=1;
	 } //end for

	/* Verify (read) Slave ACK */
	 SDA_HIGH;
	 SCL_HIGH;
	 ack_bit = digitalRead(SDA_Pin);
	 SCL_LOW;
	 return ack_bit;
 } //end Send

/* Read a byte (8 bit in length) from I2C Slave */
 unsigned char I2CRead()
 {
	unsigned char i, Data=0;
	for (i = 0; i < 8; i++)
	{
	/* Rise clock signal and read SDA status */
		SCL_HIGH;
		if(digitalRead(SDA_Pin))
			Data |=1;
		if(i<7)
			Data<<=1;
	/* Lower the clock signal level */
		SCL_LOW;
	} //end for

	return Data;
 }


  int main(void)
  {

/* How to use functions above examples */

unsigned char ack, data[3];

/*****************************************
 * Write to slave device with
 * slave address e.g. say 0x20 |write bit = 0
 *****************************************/

	/* Init i2c ports first */
	I2CInit();
	/* Send start condition */
	I2CStart();
	/* Send slave address */
	ack = I2CSend(0x20);
	/*
	* ack == 1 => NAK
 	* ack == 0 => ACK
	*/

	/* Send register address (pointer) to write to*/
	ack = I2CSend(0x07);
	/* Send data and store ack status value */
	ack = I2CSend(0x10);
	/* Send stop condition to end transmission */
	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 = 1
	 * So address is 0x20 | 1 = 0x21
	 */
	I2CSend(0x21);
	/* Read first byte */
	data[0] = I2CRead();
	/* Send ack */
	I2CAck();
	/* Read last byte */
	data[1] = I2CRead();
	/* and so on ....
	 * Send nak for last byte to indicate
	 * End of transmission
	 */
	I2CNak();
	/* Send stop condition to end transmission */
	I2CStop();

  } //end main