/*
Title: I2C_Master_Software_DS3231_1.ino
Author: Florin Dragan	florind@mas.utcluj.ro
Date Created: 01-10-2017
Last Modified: 02-04-2020

Purpose: This is an example how to communicate with DS32310 RTC
(Real Time Clock) chip, using I2C interface with Software implementation
*/

/*Implementare simpla I2C Master software*/

#define SDA_Pin 2	//PD2
#define SCL_Pin 3	//PD3
 
#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)


/**************************************************
 Functions immplementing Software I2C communication
***************************************************/

 void I2CInit()
 {
	SDA_HIGH;
	SCL_HIGH;
 }

 void I2CStart()
 {
	SDA_LOW;
	SCL_LOW;
 }
 
 void I2CRestart()
 {
	SDA_HIGH;
	SCL_HIGH;
	SDA_LOW;
	SCL_LOW;
 }
 
 void I2CStop()
 {
	SCL_LOW;
	SDA_LOW;
	SCL_HIGH;
	SDA_HIGH;
 }
 
 void I2CAck()
 {
	SDA_LOW;
	SCL_HIGH;
	SCL_LOW;
	SDA_HIGH;
 }
 
 void I2CNak()
 {
	SDA_HIGH;
	SCL_HIGH;
	SCL_LOW;
	SDA_HIGH;
 }
 
 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; }

		SCL_HIGH;
	 	SCL_LOW;
		Data<<=1;
	 } //end for

	 SDA_HIGH;
	 SCL_HIGH;
	 ack_bit = digitalRead(SDA_Pin);
	 SCL_LOW;
	 return ack_bit;
 }
 
 unsigned char I2CRead()
 {
	unsigned char i, Data=0;
	for (i = 0; i < 8; i++)
	{
		SCL_HIGH;
		if(digitalRead(SDA_Pin))
			Data |=1;
		if(i<7)
			Data<<=1;
		SCL_LOW;
	} //end for

	return Data;
 }


 /* Buffer where we will read/write our data */
 /* Loop to read 7 bytes from I2C slave. register 0x00 - 0x06
	Seconds, Minutes, Hours, Day of week, Day, Month, Year */

unsigned char I2CData[] = {0x00, 0x00, 0x00, 0x00, 0x02, 0x04, 0x20};


 /* Simple DS3231 communication example */

 int main(void)
 {

	/*Set Date/Time if necessary*/
 //	SetDateTime();
 
	/* We will now read data from DS3231 */
	/* Reading for a memory based device always starts with a dummy write */

	/* Initialize I2C Port */
	I2CInit();
	/* Send a start condition */
	I2CStart();
	/* Send slave address with write (R/W bit=0) */
	I2CSend(0xD0);
	/* Send (write) address for dummy read operation this register */
	/* address (pointer) 0x00 is actually where we are going to read from */
	I2CSend(0x00);
 
	/* Send a repeated start, after a dummy write to start reading */
	I2CRestart();
	/* send slave address with read bit=1 set, address 0xD0|1 */
	I2CSend(0xD1);
	/* Loop to read 7 bytes from I2C slave. register 0x00 - 0x06
	0x00 -> Seconds, Minutes, Hours, Day of week, Day, Month, Year <- 0x06 */

	for (unsigned char i = 0; i < 7; i++) {

		/* Read one byte by another */
		I2CData[i] = I2CRead();
		/* Send ACK if its not the last byte to read */
		/* if its the last byte then send a NAK */
		if (i < 6)
			I2CAck();
		else
			I2CNak();
	}
	/* Reading 7 bytes finished, Send stop */
	I2CStop();
	/* end of program */

 /* Display Date/Time
   ........
 */
	while(1);
 } //end main


 void SetDateTime() {
	/*Set Date/Time if necessary*/
	/* Initialize I2C Port */
	I2CInit();
	/* Send Start condition */
	I2CStart();
	/* Send DS3231 slave address with write operation bit = 0 */
	I2CSend(0xD0);

 /* Send start register address (pointer) 0x00, we are writing from this location on */

	I2CSend(0x00);
 
	/* Loop to write 7 bytes to I2C slave. register 0x00 - 0x06
	0x00 -> Seconds, Minutes, Hours, Day of week, Day, Month, Year <- 0x06 */

	for (unsigned char i = 0; i < 7; i++) {
		/* send I2C data one by one */
		I2CSend(I2CData[i]);
	}
	/* Send a stop condition - as transfer finishes */
	I2CStop();

 }