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

// Segment data for digits 0-9 (common cathode)
const uint8_t segment_map[10] = {
    0b00111111, // 0
    0b00000110, // 1
    0b01011011, // 2
    0b01001111, // 3
    0b01100110, // 4
    0b01101101, // 5
    0b01111101, // 6
    0b00000111, // 7
    0b01111111, // 8
    0b01101111  // 9
};

// Function to initialize ports
void init_ports() {
    DDRF = 0xFF; // Set PORTF as output (A-G, DP)
    DDRK = 0x0F; // Set lower nibble of PORTK as output (Digit 1 to Digit 4)
    PORTF = 0x00; // Turn off all segments initially
    PORTK = 0x0F; // Turn off all digits initially (active low)
}

// Function to display a single digit on the 7-segment display
void display_digit(uint8_t digit, uint8_t position) {
    PORTF = segment_map[digit];  // Set segment data for the corresponding digit
    PORTK = ~(1 << position);    // Enable the selected digit (active low)
    _delay_ms(2);                // Short delay for multiplexing
    PORTK = 0x0F;                // Turn off all digits to prevent ghosting
}

// Function to display a 4-digit number
void display_number(uint16_t number) {
    uint8_t thousands = (number / 1000) % 10;
    uint8_t hundreds = (number / 100) % 10;
    uint8_t tens = (number / 10) % 10;
    uint8_t units = number % 10;

    // Show each digit one by one for multiplexing
    display_digit(thousands, 0); // Display thousands place
    display_digit(hundreds, 1);  // Display hundreds place
    display_digit(tens, 2);      // Display tens place
    display_digit(units, 3);     // Display units place
}

int main(void) {
    init_ports(); // Initialize the ports
    uint16_t counter = 0; // Start counting from 0000

    while (1) {
        for (counter = 0; counter <= 9999; counter++) {
            for (uint16_t i = 0; i < 50; i++) { // Loop to create a fast refresh rate
                display_number(counter); // Display the current number
                _delay_ms(1); // Short delay to maintain a fast count
            }
        }
    }

    return 0;
}