#include <avr/io.h>
#include <avr/interrupt.h>

void pwm_init(void)
{
    TCCR0 |= (1<<COM01) | (1<<CS01) | (1<<WGM01) | (1<<WGM00); //4KHZ, NON-INVERTING MODE, FAST PWM MODE,
}

void adcinit (void){
    ADCSRA |= (1 << ADPS2) | (1 << ADPS1); // | (1 << ADPS0); // Set ADC prescalar to 64(128) - 125KHz sample rate @ 16MHz
    ADMUX |= (1 << REFS0); // Set ADC reference to AVCC
    ADMUX |= (1 << ADLAR); // Left adjust ADC result to allow easy 8 bit reading
    ADCSRA |= (1 << ADATE);  // Set ADC to Free-Running Mode
    ADCSRA |= (1 << ADEN);  // Enable ADC
    ADCSRA |= (1 << ADIE);  // Enable ADC Interrupt
    ADCSRA |= (1 << ADSC);  // Start A2D Conversions

}

int main(void)
{
    DDRB |= (1<<PB3);
    pwm_init();
    adcinit();
    OCR0 = 128;
    //sei();

    for(;;){}

    return 0;
}

ISR(ADC_vect)
{

    int adc_val = ADCH;

    OCR0 = adc_val;

}