#ifndef RTC_H_
#define RTC_H_

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>

#define DS1307_ADDRESS 0xD0 // Address of the RTC on the I2C bus
#define SECONDS_REGISTER 0x00
#define MINUTES_REGISTER 0x01
#define HOURS_REGISTER 0x02
#define DAYOFWK_REGISTER 0x03
#define DAYS_REGISTER 0x04
#define MONTHS_REGISTER 0x05
#define YEARS_REGISTER 0x06
void i2c_init(void)
{
	TWSR = 0x00; // Set prescaler to 1
	TWBR = ((F_CPU / 100000UL) - 16) / 2; // Set I2C frequency to 100kHz
}

void i2c_start(void)
{
	TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN); // Send start condition
	while (!(TWCR & (1 << TWINT))); // Wait for TWINT flag to be set
}

void i2c_stop(void)
{
	TWCR = (1 << TWINT) | (1 << TWSTO) | (1 << TWEN); // Send stop condition
	while ((TWCR & (1 << TWSTO))); // Wait for TWSTO flag to be cleared
}

void i2c_write(uint8_t data)
{
	TWDR = data; // Load data into data register
	TWCR = (1 << TWINT) | (1 << TWEN); // Start transmission
	while (!(TWCR & (1 << TWINT))); // Wait for TWINT flag to be set
}

uint8_t i2c_read_ack(void)
{
	TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWEA); // Enable acknowledge bit
	while (!(TWCR & (1 << TWINT))); // Wait for TWINT flag to be set
	return TWDR; // Return data received
}

uint8_t i2c_read_nack(void)
{
	TWCR = (1 << TWINT) | (1 << TWEN); // Disable acknowledge bit
	while (!(TWCR & (1 << TWINT))); // Wait for TWINT flag to be set
	return TWDR; // Return data received
}

void SetTimeDate()
// simple, hard-coded way to set the date 8/13/21013 at 8:51 PM
{
	I2C_WriteRegister(MONTHS_REGISTER, 0x08);
	I2C_WriteRegister(DAYS_REGISTER, 0x31);
	I2C_WriteRegister(YEARS_REGISTER, 0x13);
	I2C_WriteRegister(HOURS_REGISTER, 0x08+0x40); // add 0x40 for PM
	I2C_WriteRegister(MINUTES_REGISTER, 0x00);
	I2C_WriteRegister(SECONDS_REGISTER, 0x00);
}

void rtc_init(void)
{
	i2c_start();
	i2c_write(DS1307_ADDRESS);
	i2c_write(0x00); // Set control register to 0
	i2c_write(0x00); // Enable oscillator and set square-wave output to 1Hz
	i2c_stop();
}

void I2C_WriteRegister(uint8_t deviceRegister, uint8_t data)
{
	i2c_start();
	i2c_write(DS1307_ADDRESS); // send bus address
	i2c_write(deviceRegister); // first byte = device register address
	i2c_write(data); // second byte = data for device register
	i2c_stop();
}

uint8_t rtc_read_register(uint8_t reg)
{
	uint8_t value;

	i2c_start();
	i2c_write(DS1307_ADDRESS);
	i2c_write(reg); // Set register pointer
	i2c_start(); // Send repeated start condition
	i2c_write(DS1307_ADDRESS | 0x01); // Set RTC address with read bit
	value = i2c_read_nack(); // Read value from register
	i2c_stop();

	return value;
}


#endif /* RTC_H_ */