#ifndef F_CPU
#define F_CPU 1000000UL
#endif // F_CPU

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

#define DELAY_IN_MS 500 /* 0.5 sec */

int numbers[] = {
    0b01000000,
    0b01110011,
    0b00100100,
    0b00100001,
    0b00010011,
    0b00001001,
    0b00001000,
    0b01100011,
    0b00000000,
    0b00000001,
    0b11111111 // off
};

uint8_t digits[3];

void initADC()
{
    ADMUX=(1<<REFS1)|(1<<REFS0);
    ADCSRA=(1<<ADEN)|(1<<ADPS2)|(1<<ADPS1)|(1<<ADPS0);
}

uint16_t ReadADC(uint8_t ch)
{
    //Select ADC Channel ch must be 0-7
    ch=ch&0b00000111;
    ADMUX|=ch;

    //Start Single conversion

    ADCSRA|=(1<<ADSC);

    //Wait for conversion to complete
    while(!(ADCSRA & (1<<ADIF)));

    //Clear ADIF by writing one to it
    ADCSRA|=(1<<ADIF);

    return(ADC);
}

int main()
{
    DDRD = 0xFF;
    PORTD = 0xFF;

    DDRB = 0b00000001;
    PORTB = 1;

    initADC();

    uint16_t adc_value;
    uint16_t res;
    while(1)
    {
        adc_value = 0;
        for (int i = 0; i < 250; i++)
        {
            adc_value += ReadADC(0);
        }

        adc_value=(adc_value/25)/4;
        res = adc_value;

        for(int j = 2; j >= 0; j--) {
            digits[j] = res%10;
            res /= 10;
        }

        uint8_t dig = digits[0];
        PORTD = numbers[dig];
        _delay_ms(DELAY_IN_MS);

        // if following is uncommented there blinks digit two correctly
        // if commented there is unblinking digit 1
        PORTD = numbers[10]; // display off
    }

    return 0;
}