#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
void TimerInit();
unsigned char periode;
ISR (TIMER0_OVF_vect)
    {
    PORTB ^= (1 << PB7);
    TCNT0= - 50;  
    }
/*
 prescaller 8 , Xtal 16MHz
 tick = 8/16Mhz= 0.5 us
 delay=counter*tick
 delay=counter*0.5us
 counter=delayus/0.5us
 untuk sampling rate 8 khz maka Tsampling= 1/40Khz= 25us
 counter = 25/0.5us = 50
 nilai TCNT1= -250 -> karena counter up
 */
int main(void) {
    DDRB |= _BV(PB7);
    TimerInit(); /// schedule 10ms
    sei();
    /// enable global interupsi  
    while (1) {
        sleep_mode(); // sleep
        }
    }
void TimerInit(void) {
    // TCNT0  = -250; // reset counter
    TCCR0B  = (1 << CS01) ; //prescaller 8
    TIMSK0  |= (1 << TOIE0); // enable overflow interrupt
    }