/*
* BinaryClock.c
*
* Created: 01.05.2018
* Author : Tobias N.
* Description:
* Current time is displayed by default after each startup and can be set by using the set hour, minute and second buttons respectively.
* Pressing the select button once, displays the current date (day/month/year) which can be set by using the set hour button
* to set the day, minute button to set the month and the second button to set the year.
* Pressing the select button a second time will display the room temperature in °C with a resolution of .25°C.
* By continuing to press the select button, you can cycle between the 3 different modes.
*/

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

#define ACK 0
#define NACK 1

#define DS3231_ADDR (0x68 << 1)				//write address: 7-bit address is shifted to the left by 1 and LSB is 0
#define DS3231_ADDR_READ (0x68 << 1 | 0x1)  //read address: 7-bit address is shifted to the left by 1 and LSB is 1

/* Variables */
uint8_t digit_1, digit_2, digit_3, digit_4, digit_5, digit_6;
uint8_t hour_set, minute_set, second_set, day_set, month_set, year_set;
uint8_t modeCounter;
const uint16_t multiplexTime = 1000;
uint16_t timer1_counter;

/* functions */
void i2c_init(uint32_t scl_f);
void i2c_start(void);
void i2c_stop(void);
void i2c_write(uint8_t byte);
uint8_t i2c_read(uint8_t n_ack);

void DisplayMatrix(void);
void DS3231setTime(void);
void DS3231getTime(void);
void DS3231setDate(void);
void DS3231getDate(void);
void DS3231getTemp(void);

ISR(TIMER1_OVF_vect) {
	TCNT1 = timer1_counter;
	DisplayMatrix();
}

int main(void)
{
	/* setting up ports */
	DDRB |= _BV(PORTB0) | _BV(PORTB1) | _BV(PORTB2) | _BV(PORTB3);
	DDRD |= _BV(PORTD2) | _BV(PORTD3) | _BV(PORTD4) | _BV(PORTD5) | _BV(PORTD6) | _BV(PORTD7);
	DDRC &= ~_BV(PORTC0) & ~_BV(PORTC1) & ~_BV(PORTC2) & ~_BV(PORTC3);
	PORTC |= _BV(PORTC0) | _BV(PORTC1) | _BV(PORTC2) | _BV(PORTC3);
	
	i2c_init(400000);	//init i2c interface with a clock frequency of 400kHz
	
	cli();
	TCCR1A = 0;
	TCCR1B = 0;
	/* 16MHz -> t= 62,5ns * 256 (prescaler) = 16µs
	500Hz -> t = 0,002s
	(0,002 / 2) / 16µs = 62.5
	65536(16bit) - 62 = 65474
	*/
	timer1_counter = 65474;
	TCNT1 = timer1_counter;   // preload timer1
	TCCR1B |= _BV(CS12);    // prescaler 256
	TIMSK1 |= _BV(TOIE1);   // overflow interrupt
	sei();

	while (1)
	{
		switch (modeCounter) {
			case 0 : {
				DS3231setTime();
				DS3231getTime();
			}
			break;
			case 1 : {
				DS3231setDate();
				DS3231getDate();
			}
			break;
			case 2 : {
				DS3231getTemp();
			}
			break;
		}
		if ((PINC & _BV(PINC3)) == 0) {
			modeCounter++;
			_delay_ms(200);
			if (modeCounter > 2) {
				modeCounter = 0;
			}
		}
	}
}

void i2c_init(uint32_t scl_f) {
	
	DDRC &= ~_BV(PORTC4) & ~_BV(PORTC5);   //set SDA & SCL as inputs
	PORTC &= ~_BV(PORTC4) & ~_BV(PORTC5);  //disable internal pullups
	
	TWSR = 0;							   //set prescaler value to 0
	
	TWBR = ((F_CPU / scl_f) - 16) / 2;     // set up bitrate register

	TWCR |= _BV(TWEN);                     //enable TWI
}

void i2c_start(void) {
	
	TWCR = _BV(TWINT) | _BV(TWSTA) | _BV(TWEN);	//clear TWINT flag and send start condition
	
	while((TWCR & _BV(TWINT)) == 0) {
		//wait for TWI to execute task
	}
}

void i2c_stop(void) {
	
	TWCR = _BV(TWINT) | _BV(TWSTO) | _BV(TWEN); //clear TWINT flag and send stop condition
	
	while(TWCR & _BV(TWSTO)) {
		//wait for TWI to execute task
	}
}

void i2c_write(uint8_t byte) {
	
	TWDR = byte;
	TWCR = _BV(TWINT) | _BV(TWEN);
	
	while((TWCR & _BV(TWINT)) == 0) {
		//wait for TWI to execute task
	}
}

uint8_t i2c_read(uint8_t n_ack ) {
	
	if(n_ack == ACK) {
		TWCR = _BV(TWINT) | _BV(TWEA) | _BV(TWEN);
	}
	if(n_ack == NACK) {
		TWCR = _BV(TWINT) | _BV(TWEN);
	}
	while ((TWCR & _BV(TWINT)) == 0) {
		//wait for TWI to execute task
	}

	return TWDR;
}

void DisplayMatrix(void) {
	PORTB &= ~_BV(PORTB0) & ~_BV(PORTB1) & ~_BV(PORTB2) & ~_BV(PORTB3);
	PORTB |= (0b00001111 & digit_1);
	PORTD |= _BV(PORTD2);
	_delay_us(multiplexTime);
	PORTD &= ~_BV(PORTD2);

	PORTB &= ~_BV(PORTB0) & ~_BV(PORTB1) & ~_BV(PORTB2) & ~_BV(PORTB3);
	PORTB |= (0b00001111 & digit_2);
	PORTD |= _BV(PORTD3);
	_delay_us(multiplexTime);
	PORTD &= ~_BV(PORTD3);

	PORTB &= ~_BV(PORTB0) & ~_BV(PORTB1) & ~_BV(PORTB2) & ~_BV(PORTB3);
	PORTB |= (0b00001111 & digit_3);
	PORTD |= _BV(PORTD4);
	_delay_us(multiplexTime);
	PORTD &= ~_BV(PORTD4);


	PORTB &= ~_BV(PORTB0) & ~_BV(PORTB1) & ~_BV(PORTB2) & ~_BV(PORTB3);
	PORTB |= (0b00001111 & digit_4);
	PORTD |= _BV(PORTD5);
	_delay_us(multiplexTime);
	PORTD &= ~_BV(PORTD5);

	PORTB &= ~_BV(PORTB0) & ~_BV(PORTB1) & ~_BV(PORTB2) & ~_BV(PORTB3);
	PORTB |= (0b00001111 & digit_5);
	PORTD |= _BV(PORTD6);
	_delay_us(multiplexTime);
	PORTD &= ~_BV(PORTD6);

	PORTB &= ~_BV(PORTB0) & ~_BV(PORTB1) & ~_BV(PORTB2) & ~_BV(PORTB3);
	PORTB |= (0b00001111 & digit_6);
	PORTD |= _BV(PORTD7);
	_delay_us(multiplexTime);
	PORTD &= ~_BV(PORTD7);
}

void DS3231setTime(void) {
	if ((PINC & _BV(PINC0)) == 0) {
		uint8_t high, low, bcd;
		high = hour_set / 10;
		low  = hour_set - (high * 10);
		bcd  = (0b00001111 & low) | (0b00110000 & (high << 4));
		i2c_start();
		i2c_write(DS3231_ADDR);
		i2c_write(0x02);
		i2c_write(bcd);
		i2c_stop();
		hour_set++;
		if (hour_set == 24) {
			hour_set = 0;
		}
		_delay_ms(100);
	}
	if ((PINC & _BV(PINC1)) == 0) {
		uint8_t high, low, bcd;
		high = minute_set / 10;
		low  = minute_set - (high * 10);
		bcd  = (0b00001111 & low) | (0b01110000 & (high << 4));
		i2c_start();
		i2c_write(DS3231_ADDR);
		i2c_write(0x01);
		i2c_write(bcd);
		i2c_stop();
		minute_set++;
		if (minute_set == 60) {
			minute_set = 0;
		}
		_delay_ms(100);
	}
	if ((PINC & _BV(PINC2)) == 0) {
		uint8_t high, low, bcd;
		high = second_set / 10;
		low  = second_set - (high * 10);
		bcd  = (0b00001111 & low) | (0b01110000 & (high << 4));
		i2c_start();
		i2c_write(DS3231_ADDR);
		i2c_write(0x00);
		i2c_write(bcd);
		i2c_stop();
		second_set++;
		if (second_set == 60) {
			second_set = 0;
		}
		_delay_ms(100);
	}
}

void DS3231getTime(void) {
	uint8_t hours, minutes, seconds;
	uint8_t hours_h, hours_l, minutes_h, minutes_l, seconds_h, seconds_l;
	i2c_start();
	i2c_write(DS3231_ADDR);
	i2c_write(0);
	i2c_start();
	i2c_write(DS3231_ADDR_READ);
	seconds = i2c_read(ACK);
	minutes = i2c_read(ACK);
	hours   = i2c_read(NACK);
	i2c_stop();

	hours_l   = 0b00001111 & hours;
	hours_h   = 0b00000011 & (hours >> 4);

	minutes_l = 0b00001111 & minutes;
	minutes_h = 0b00000111 & (minutes >> 4);

	seconds_l = 0b00001111 & seconds;
	seconds_h = 0b00000111 & (seconds >> 4);

	digit_1 = hours_h;
	digit_2 = hours_l;
	digit_3 = minutes_h;
	digit_4 = minutes_l;
	digit_5 = seconds_h;
	digit_6 = seconds_l;
}

void DS3231setDate(void) {
	if ((PINC & _BV(PINC0)) == 0) {
		uint8_t high, low, bcd;
		high = day_set / 10;
		low  = day_set - (high * 10);
		bcd  = (0b00001111 & low) | (0b00110000 & (high << 4));
		i2c_start();
		i2c_write(DS3231_ADDR);
		i2c_write(0x04);
		i2c_write(bcd);
		i2c_stop();
		day_set++;
		if (day_set == 32) {
			day_set = 1;
		}
		_delay_ms(100);
	}
	if ((PINC & _BV(PINC1)) == 0) {
		uint8_t high, low, bcd;
		high = month_set / 10;
		low  = month_set - (high * 10);
		bcd  = (0b00001111 & low) | (0b00110000 & (high << 4));
		i2c_start();
		i2c_write(DS3231_ADDR);
		i2c_write(0x05);
		i2c_write(bcd);
		i2c_stop();
		month_set++;
		if (month_set == 13) {
			month_set = 1;
		}
		_delay_ms(100);
	}
	if ((PINC & _BV(PINC2)) == 0) {
		uint8_t high, low, bcd;
		high = year_set / 10;
		low  = year_set - (high * 10);
		bcd  = (0b00001111 & low) | (0b11110000 & (high << 4));
		i2c_start();
		i2c_write(DS3231_ADDR);
		i2c_write(0x06);
		i2c_write(bcd);
		i2c_stop();
		year_set++;
		if (year_set == 80) {
			year_set = 0;
		}
		_delay_ms(100);
	}
}

void DS3231getDate(void) {
	uint8_t days, months, years;
	uint8_t days_h, days_l, months_h, months_l, years_h, years_l;
	i2c_start();
	i2c_write(DS3231_ADDR);
	i2c_write(0x04);
	i2c_start();
	i2c_write(DS3231_ADDR_READ);
	days    = i2c_read(ACK);
	months  = i2c_read(ACK);
	years   = i2c_read(NACK);
	i2c_stop();

	days_l   = 0b00001111 & days;
	days_h   = 0b00000011 & (days >> 4);

	months_l = 0b00001111 & months;
	months_h = 0b00000111 & (months >> 4);

	years_l  = 0b00001111 & years;
	years_h  = 0b00000111 & (years >> 4);

	digit_1 = days_h;
	digit_2 = days_l;
	digit_3 = months_h;
	digit_4 = months_l;
	digit_5 = years_h;
	digit_6 = years_l;
}

void DS3231getTemp(void) {
	uint8_t temp_l, temp_h, temp_bcd_1, temp_bcd_2, temp_bcd_3, temp_bcd_4;
	i2c_start();
	i2c_write(DS3231_ADDR);
	i2c_write(0x11);
	i2c_start();
	i2c_write(DS3231_ADDR_READ);
	temp_h = i2c_read(ACK);
	temp_l = i2c_read(NACK);
	i2c_stop();

	temp_l = (temp_l >> 6) * 25;

	temp_bcd_1 = temp_h / 10;
	temp_bcd_2 = temp_h - (temp_bcd_1 * 10);
	temp_bcd_3 = temp_l / 10;
	temp_bcd_4 = temp_l - (temp_bcd_3 * 10);

	digit_1 = 0;
	digit_2 = 0;
	digit_3 = temp_bcd_1;
	digit_4 = temp_bcd_2;
	digit_5 = temp_bcd_3;
	digit_6 = temp_bcd_4;
}