// code to display both even and odd numbers from 0-9

#include <stdint.h>

#define DDRA  (*(volatile uint8_t*)0x21)
#define PORTA (*(volatile uint8_t*)0x22)

uint8_t seg[10] = {
    0x3F,  // 0
    0x06,  // 1
    0x5B,  // 2
    0x4F,  // 3
    0x66,  // 4
    0x6D,  // 5
    0x7D,  // 6
    0x07,  // 7
    0x7F,  // 8
    0x6F   // 9
};

void delay1sec(void){
    TCNT1 = 0;
    TCCR1A = 0x00;
    TCCR1B = 0x05;
    while (TCNT1 < 15625);
    TCCR1B = 0x00;
}

int main(void){
    DDRA = 0x7F;

    while (1){

        // EVEN numbers
        for (uint8_t i = 0; i <= 8; i += 2){
            PORTA = seg[i];
            delay1sec();
        }

        // ODD numbers
        for (uint8_t i = 1; i <= 9; i += 2){
            PORTA = seg[i];
            delay1sec();
        }
    }
}