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  1. #include <avr/interrupt.h>
  2. #include <avr/io.h>
  3. #include <avr/sleep.h>
  4.  
  5. static void forwards(void) {
  6.   /* Set motors 1 and 2 to move forwards */
  7.   PORTB |= _BV(PB0) | _BV(PB2);
  8.   PORTB &= ~(_BV(PB1) | _BV(PB3));
  9.   /* Set both PWMs to 100% duty cycle */
  10.   OCR0A = UINT8_MAX;
  11.   OCR0B = UINT8_MAX;
  12. }
  13.  
  14. static void turning(void) {
  15.   /* Set motor 1 to move forward and motor 2 to move backwards */
  16.   PORTB |= _BV(PB0) | _BV(PB3);
  17.   PORTB &= ~(_BV(PB1) | _BV(PB2));
  18.   /* Set both PWMs to 50% duty cycle */
  19.   OCR0A = UINT8_MAX / 2;
  20.   OCR0B = UINT8_MAX / 2;
  21. }
  22.  
  23. /* Start a timer for 1 second */
  24. static void start_timer(void) {
  25.   TCNT1 = 34285;
  26.   /* Set prescaler as F_CPU / 256 */
  27.   TCCR1B |= _BV(CS12);
  28. }
  29.  
  30. static void stop_timer(void) {
  31.   /* Disable TIMER1 */
  32.   TCCR1B &= ~(_BV(CS12));
  33. }
  34.  
  35. ISR(INT0_vect) {
  36.   turning();
  37.   start_timer();
  38. }
  39.  
  40. ISR(TIMER1_OVF_vect) {
  41.   forwards();
  42.   stop_timer();
  43. }
  44.  
  45. int main(void) {
  46.   /* Enable pins for motor output */
  47.   DDRB |= _BV(PB0) | _BV(PB1) | _BV(PB2) | _BV(PB3);
  48.   /* Enable OC0A and OC0B for PWM */
  49.   DDRD |= _BV(PD5) | _BV(PD6);
  50.  
  51.   /* Enable INT0 */
  52.   EIMSK |= _BV(INT0);
  53.   /* Set INT0 interrupt sense on rising edge */
  54.   EICRA |= _BV(ISC01) | _BV(ISC00);
  55.  
  56.   /* Set non-inverting mode for PWM on OC0A and OC0B */
  57.   TCCR0A |= _BV(COM0A1) | _BV(COM0B1);
  58.   /* Set fast PWM mode on OC0A and OC0B */
  59.   TCCR0A |= _BV(WGM01) | _BV(WGM00);
  60.   /* Set PWM prescaler to F_CPU / 256, start PWM */
  61.   TCCR0B |= _BV(CS02);
  62.  
  63.   /* Enable Timer 1 Overflow Interrupts */
  64.   TIMSK1 |= _BV(TOIE1);
  65.  
  66.   /* Set the CPU sleep mode to Idle */
  67.   set_sleep_mode(SLEEP_MODE_IDLE);
  68.  
  69.   /* Enable interrupts globally */
  70.   sei();
  71.  
  72.   /* Set the starting state (robot moving forwards) */
  73.   forwards();
  74.  
  75.   for (;;) {
  76.     /* Sleep; interrupts will do all the work */
  77.     sleep_mode();
  78.   }
  79.  
  80.   return 0;
  81. }
  82.  
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https://ideone.com/njHUA4
language:
C99 (gcc 8.3)
created:
10 years ago
visibility:
public

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