Tooltron

#include "led.h"

#include <avr/io.h>

#define PRESCALE 64

#define CLOCK_SEL 3

/* F_CPU / PRESCALE = OCR * 1000 + ERROR */

#define OCR (F_CPU / PRESCALE / 1000UL)

#define ERROR (F_CPU / PRESCALE - OCR * 1000UL)

char count;

uint16_t period;

uint16_t ms;

uint16_t error;

static void blink() {

  count--;

  if (count % 2) {

    led_yellow();

  } else {

    led_off();

  }

}

ISR(TIMER0_COMPA_vect) {

  error += ERROR;

  if (error >= 1000) {

    error -= 1000;

  } else {

    ms++;

    if (ms == period) {

      blink();

      if (count = 0) {

        TCCR0B = 0;

      }

      ms = 0;

    }

  }

}

void led_blink_start(unsigned int period_ms, char n_times) {

  led_yellow();

  ms = 0;

  error = 0;

  count = n_times*2-1;

  period = period_ms;

  OCR0A = OCR;

  TCCR0A = _BV(WGM01);

  TCCR0B = CLOCK_SEL;

}

char led_blink_done() {

  return count == 0;

}