#define F_CPU 16000000UL
#include <avr/io.h>
#include <avr/interrupt.h>

uint8_t seconds = 0;
uint8_t minutes = 0;

// 7-segment display patterns
uint8_t digit[] = {0b00111111, 0b00000110, 0b01011011, 0b01001111, 0b01100110, 0b01101101,
                    0b01111101, 0b00000111, 0b01111111, 0b01101111};

volatile uint8_t blink_DP = 0;  // Flag to blink the decimal point (on/off)

void init_ports() {
    DDRA = 0xFF;  // Set PORTA as output (ones place of seconds)
    DDRC = 0xFF;  // Set PORTC as output (tens place of seconds)
    DDRL = 0xFF;  // Set PORTL as output (ones place of minutes, DP on the 7-segment display)
    DDRK = 0xFF;  // Set PORTK as output (tens place of minutes)
}

void display(uint8_t mins, uint8_t secs) {
    PORTK = digit[mins / 10];  // Tens place of minutes
    PORTL = digit[mins % 10] | (blink_DP << 7);  // Ones place of minutes, blink DP (MSB)
    PORTC = digit[secs / 10];  // Tens place of seconds
    PORTA = digit[secs % 10];  // Ones place of seconds
}

ISR(TIMER1_COMPA_vect) {
    static uint8_t blink_counter = 0;

    // Toggle the decimal point LED every second
    blink_counter++;
    if (blink_counter == 1) {  // Every 1 second toggle
        blink_DP = !blink_DP;  // Toggle the DP (decimal point)
        blink_counter = 0;     // Reset counter
    }

    // Increment the second counter
    seconds++;
    if (seconds == 60) {
        seconds = 0;
        minutes++;
        if (minutes == 60) {
            minutes = 0;
        }
    }

    display(minutes, seconds);  // Update the display every second
}

void init_timer() {
    TCCR1B |= (1 << WGM12);      // CTC mode
    OCR1A = 15624;               // Set compare value for 1 second (assuming 16 MHz clock)
    TIMSK1 |= (1 << OCIE1A);     // Enable interrupt on compare match
    sei();                       // Enable global interrupts
    TCCR1B |= (1 << CS12) | (1 << CS10); // Prescaler 1024
}

int main() {
    init_ports();
    init_timer();
    while (1) {
        // Main loop, do nothing as everything is handled by interrupt
    }
}