#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
void TimerInit();
unsigned char periode;
ISR (TIMER0_COMPA_vect)
{
PORTB ^= (1 << PB7);
}
/*
 prescaller 8 , Xtal 16MHz
 tick = 8/16Mhz= 0.5 us
 delay=counter*tick
 delay=counter*0.5us
 untuk sampling rate 40 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 << OCIE0A); // enable compare maatch interrupt
TCCR0A |=_BV(WGM01); //mode Timer CTC
OCR0A =  50;
}