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  1. #include <avr/interrupt.h>
  2. #include <avr/io.h>
  3. #include <avr/sleep.h>
  4. #include <util/delay.h>
  5.  
  6. #include <stddef.h>
  7. #include <stdint.h>
  8.  
  9. static volatile uint8_t count = 0xffu;
  10. static volatile size_t overflows = 0;
  11.  
  12. enum {
  13.   PRESCALER = 256u,
  14.   TCNT1_START = 65536lu - F_CPU / PRESCALER,
  15.   TCNT1_MAX = 65536lu - TCNT1_START,
  16.   CLOCKS_PER_SECOND = F_CPU / PRESCALER / TCNT1_MAX
  17. };
  18.  
  19. ISR(INT0_vect) {
  20.   PORTB = --count;
  21. }
  22.  
  23. ISR(INT1_vect) {
  24.   TCCR1B ^= _BV(CS12);
  25.   TCNT1H = TCNT1_START >> 8u;
  26.   TCNT1L = TCNT1_START << 8u;
  27. }
  28.  
  29. ISR(TIMER1_OVF_vect) {
  30.   if (++overflows >= CLOCKS_PER_SECOND) {
  31.     PORTB = --count;
  32.     overflows = 0;
  33.   }
  34.   TCNT1H = TCNT1_START >> 8u;
  35.   TCNT1L = TCNT1_START << 8u;
  36. }
  37.  
  38. int main(void) {
  39.   DDRB = 0xffu;
  40.   PORTB = 0xffu;
  41.   GICR |= _BV(INT0) | _BV(INT1);
  42.   MCUCR |= _BV(ISC00) | _BV(ISC01) | _BV(ISC10) | _BV(ISC11);
  43.   TIMSK |= _BV(TOIE1);
  44.   TCCR1B |= _BV(CS12);
  45.   TCNT1H = TCNT1_START >> 8u;
  46.   TCNT1L = TCNT1_START << 8u;
  47.   sei();
  48.   set_sleep_mode(SLEEP_MODE_IDLE);
  49.   for (;;) {
  50.     sleep_mode();
  51.   }
  52. }
  53.  
Not running #stdin #stdout 0s 0KB
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https://ideone.com/wZRiln
language:
C (gcc 8.3)
created:
11 years ago
visibility:
public

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