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


#define clockPin PD2 // Тактовый вход
#define latchPin PD3 // Защелка
#define dataPin  PD4 // Данные

enum segments { DP, G, F, E, D, C, B, A };

#define zero	(1<<G)|(1<<DP)
#define one		(1<<A)|(1<<D)|(1<<E)|(1<<F)|(1<<G)|(1<<DP)
#define two		(1<<C)|(1<<F)|(1<<DP)
#define three	(1<<E)|(1<<F)|(1<<DP)
#define four	(1<<A)|(1<<D)|(1<<E)|(1<<DP)
#define five	(1<<B)|(1<<E)|(1<<DP)
#define six		(1<<B)|(1<<DP)
#define seven	(1<<D)|(1<<E)|(1<<F)|(1<<G)|(1<<DP)
#define eight	(1<<DP)
#define nine	(1<<E)|(1<<DP)

uint8_t numbers[] = { zero, one, two, three, four, five, six, seven, eight, nine };
uint8_t digits[]  = { 0b10000000, 0b01000000, 0b00100000, 0b00010000 };

uint8_t csec = 0;
uint8_t sec = 0;
uint8_t min = 0;
uint8_t lastdigit = 0;

void begin_shift();
void end_shift();
void shift(uint8_t data);
void drawtime();
void drawdigit(uint8_t digit, uint8_t num);
void drawdigit(uint8_t digit, uint8_t num,bool dot);


int main(void)
{
	// Конфигурируем пины в состояние Output
	DDRD = (1<<clockPin) | (1<<latchPin) | (1<<dataPin);


	TIMSK1 = (1<<OCIE1A);
	TCCR1B = (1<<CS10)|(1<<CS12)|(1<<WGM12);
	OCR1A = F_CPU/1024/200;

	sei();

    while (1)
    {
		if (sec == 59 && min == 59 && csec == 99)
		{
			sec = 0, min = 0;
		}
		if (csec == 99)
		{
			csec = 0;
			if (sec == 59)
			{
				sec = 0;
				++min;
			}
			else
			{
				++sec;
			}
		}
		++csec;
		_delay_ms(10);
    }
}

ISR(TIMER1_COMPA_vect)
{
	drawtime();
}

void drawtime()
{
	if (lastdigit == 0)
	{
		drawdigit(1, sec / 10, false);
	}
	else if (lastdigit == 1)
	{
		drawdigit(2, min % 10,  true);
	}
	else if (lastdigit == 2)
	{
		drawdigit(3, min / 10, false);
	}
	else
	{
		drawdigit(0, sec % 10, false);
	}
}

void drawdigit(uint8_t digit, uint8_t num, bool dot)
{
	if (num>sizeof(numbers)-1 || digit>sizeof(digits)-1) return;

	shift(dot ? numbers[num]&~(1<<DP) : numbers[num]);
	shift(digits[digit]);

	lastdigit = digit;
}

void shift(uint8_t data)
{
	PORTD &= ~(1<<latchPin);
	for (int i = 0; i < 8; i++){
		PORTD &= ~((1<<clockPin)|(1<<dataPin));
		PORTD |= ((data&1)<<dataPin);
		PORTD |= (1<<clockPin);
		data >>= 1;
	}
	PORTD |= (1<<latchPin);
}