#define F_CPU 1000000UL

#include <avr/io.h>

#define LED     PB1
const int Light_sensor_threshold=198;                               // compare value to detect dark threshold

void Init_ADC3_8bit_256mV_prescaler16();
void read_ADC3_Light_sensor();

int main()

{
    DDRB  |= (1<<LED);
    while(1)  {
    read_ADC3_Light_sensor();
}
}

// ADC3 - Light sensor
void Init_ADC3_8bit_256mV_prescaler16() {
    ADMUX = (1 << ADLAR);                                                   // left shift result --> 8 bit resolution
    ADMUX |= (1 << REFS2) |  (1 << REFS1) | (0 << REFS0);                   // Sets ref. voltage to 2.56 V without capacitor - Vcc = 000; 2.56 V = 110; 1.1V = 010
    ADMUX |= (0 << MUX3) |  (0 << MUX2) |  (1 << MUX1) | (1 << MUX0);       // ADC3 for input (PB2) = 0010; ADC2 (PB4) = 0010; ADC1 (PB2) = 0001; ADC0 (PB5) = 0000
    ADCSRA = (1 << ADPS2) |  (1 << ADPS1) | (0 << ADPS0);                 // Prescaler = 64 --> 15.625 kHz
    ADCSRA |= (1 << ADEN);                                               // Enable ADC
}

void read_ADC3_Light_sensor(){
    Init_ADC3_8bit_256mV_prescaler16();
    ADCSRA |= (1<<ADSC);                                                                    //start ADC measurement
    while(ADCSRA & (1<<ADSC)){};                                                            //wait until conversion is complete
    if(ADCH > Light_sensor_threshold){                                                      //
         PORTB = (1<<LED);
    }
    else PORTB = 0;
}