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

// 200000 and 50000 for 10-bit operation,
// F_ADCH can be higher with lower resolutions
#define F_ADCH 200000
#define F_ADCL 50000

#if F_CPU > 64 * F_ADCH
#   define PRESCALERBITS ((1<<ADPS2)|(1<<ADPS1)|(1<<ADPS0))
#elif F_CPU > 32 * F_ADCH
#   define PRESCALERBITS ((1<<ADPS2)|(1<<ADPS1))
#elif F_CPU > 16 * F_ADCH
#   define PRESCALERBITS ((1<<ADPS2)|(1<<ADPS0))
#elif F_CPU > 8 * F_ADCH
#   define PRESCALERBITS ((1<<ADPS2))
#elif F_CPU > 4 * F_ADCH
#   define PRESCALERBITS ((1<<ADPS1)|(1<<ADPS0))
#elif F_CPU > 2 * F_ADCH
#   define PRESCALERBITS ((1<<ADPS1))
#elif F_CPU > 2 * F_ADCL
#   define PRESCALERBITS (0)
#else
#   error "F_CPU is undefined or too low to use the ADC"
#endif

#define LED0 (1<<PB0)
#define LED1 (1<<PB3)

void adcInit(void)
{
    //left-adjust, pb4 input
    ADMUX = (1<<ADLAR)|(1<<MUX1);
    ADCSRA = (1<<ADEN)
            |(1<<ADSC)
            |(1<<ADATE)
            |PRESCALERBITS;
    
}

int main(void)
{ 
    DDRB = 0b11101111; // 0xEF
    adcInit();
    
    while(1)
    {
        if(ADCH<250)
            PORTB &= ~LED0;
        else
            PORTB |= LED0;
    }

    return 0; 
}