xyFC/src/timer.c

/*
 * Time-Keeping helper
 */

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

#include "timer.h"

volatile time_t systemTime = 0;

void timerInit(void) {
    // Using 8bit Timer1
    TCCR1 |= (1 << CTC1); // CTC Mode
    TCCR1 |= (1 << CS12) | (1 << CS11) | (1 << CS10); // Prescaler: 64
    OCR1A = 250; // Count to 250
    TIMSK |= (1 << OCIE1A); // Enable compare match interrupt
}

ISR(TIMER1_COMPA_vect) {
    systemTime++; // one millisecond has passed
}

time_t timerGet(void) {
    return systemTime;
}