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#include "led.h"
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#include <avr/io.h>
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#define PRESCALE 64
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#define CLOCK_SEL 3
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/* F_CPU / PRESCALE = OCR * 1000 + ERROR */
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#define OCR (F_CPU / PRESCALE / 1000UL)
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#define ERROR (F_CPU / PRESCALE - OCR * 1000UL)
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char count;
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uint16_t period;
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uint16_t ms;
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uint16_t error;
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static void blink() {
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  count--;
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  if (count % 2) {
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    led_yellow();
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  } else {
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    led_off();
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  }
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}
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ISR(TIMER0_COMPA_vect) {
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  error += ERROR;
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  if (error >= 1000) {
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    error -= 1000;
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  } else {
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    ms++;
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    if (ms == period) {
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      blink();
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      if (count = 0) {
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        TCCR0B = 0;
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      }
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      ms = 0;
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    }
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  }
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}
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void led_blink_start(unsigned int period_ms, char n_times) {
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  led_yellow();
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  ms = 0;
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  error = 0;
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  count = n_times*2-1;
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  period = period_ms;
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  OCR0A = OCR;
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  TCCR0A = _BV(WGM01);
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  TCCR0B = CLOCK_SEL;
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}
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char led_blink_done() {
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  return count == 0;
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}