xyFC/src/avr/timer.c

/*
 * Time-Keeping helper
 */

//#define MILLISECONDS
//#define MICROSECONDS
//#define TEN_MICROSECONDS
#define HUNDRED_MICROSECONDS

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

#include "timer.h"

volatile time_t systemTime = 0;

void timerInit(void) {
#if defined(__AVR_ATmega328__)

    TCCR2A |= (1 << WGM21); // CTC Mode

#if defined(MILLISECONDS)
    TCCR2B |= (1 << CS22); // Prescaler: 64
    OCR2A = 250; // Count to 250
#elif defined(MICROSECONDS)
    TCCR2B |= (1 << CS20); // Prescaler: 1
    OCR2A = 16; // Count to 16
#elif defined(TEN_MICROSECONDS)
    TCCR2B |= (1 << CS20); // Prescaler: 1
    OCR2A = 160; // Count to 160
#elif defined(HUNDRED_MICROSECONDS)
    TCCR2B |= (1 << CS22); // Prescaler: 64
    OCR2A = 25; // Count to 25
#endif

    TIMSK2 |= (1 << OCIE2A); // Enable compare match interrupt

#elif defined __AVR_ATtiny85__

    // Using 8bit Timer1
    TCCR1 |= (1 << CTC1); // CTC Mode

#if defined(MILLISECONDS)
    TCCR1 |= (1 << CS12) | (1 << CS11) | (1 << CS10); // Prescaler: 64
    OCR1A = 250; // Count to 250
#elif defined(MICROSECONDS)
    TCCR1 |= (1 << CS10); // Prescaler: 1
    OCR1A = 16; // Count to 16
#elif defined(TEN_MICROSECONDS)
    TCCR1 |= (1 << CS10); // Prescaler: 1
    OCR1A = 160; // Count to 160
#elif defined(HUNDRED_MICROSECONDS)
    TCCR1 |= (1 << CS12) | (1 << CS11) | (1 << CS10); // Prescaler: 64
    OCR1A = 25; // Count to 25
#endif

    TIMSK |= (1 << OCIE1A); // Enable compare match interrupt
#endif
}

#if defined(__AVR_ATmega328__)

ISR(TIMER2_COMPA_vect) {

#elif defined __AVR_ATtiny85__

ISR(TIMER1_COMPA_vect) {

#endif

#if defined(MILLISECONDS) || defined(MICROSECONDS)
    systemTime++;
#elif defined(TEN_MICROSECONDS)
    systemTime += 10;
#elif defined(HUNDRED_MICROSECONDS)
    systemTime += 100;
#endif

}

time_t timerGet(void) {
    return systemTime;
}