roboforum.ru

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

static const uint8_t IR_LED = PB1; // Will use PWM.
static const uint8_t TSOP = PB3;

static const uint8_t STATUS_LED = PA2;


static const uint8_t  PULSE_BUNGLE_SIZE = 15; // Counts from Zero.
static const uint8_t  PULSE_INTERBUNGLE_PAUSE = 30;  // In pulses. Counts from Zero.

// 64000000/16/(TOP_VALUE + 1) ~= XXx kHz.
//static const uint8_t  TOP_VALUE = 132; // 30 kHz
//static const uint8_t  TOP_VALUE = 120; // 33 kHz
//static const uint8_t  TOP_VALUE = 110; // 36 kHz
static const uint8_t  TOP_VALUE = 104; // 38 kHz
//static const uint8_t  TOP_VALUE =  99; // 40 kHz
//static const uint8_t  TOP_VALUE =  70; // 56 kHz

// 104/50 ~= 50 % duty. Good.
static const uint8_t  PULSE_DUTY_VAL = 50; // OCR1A value.


void initIO(){
   DDRA = (1 << STATUS_LED);
   
   DDRB = (1 << IR_LED);
   PORTB |= (1 << TSOP); // Eliminate Z state...
}

void initPWM(){
   
   // Do Async operation.
   PLLCSR = (1 << PLLE); 
   loop_until_bit_is_set(PLLCSR, PLOCK);
   PLLCSR |= (1 << PCKE);

   TCCR1A = (1 << PWM1A)|(1 << COM1A1)|(0 << COM1A0); // See table 35 on page 77

   // PCK/16
   // See table 34 on page 74
   TCCR1B = (0 << CS13)|(1 << CS12)|(0 << CS11)|(1 << CS10); 
   OCR1C= TOP_VALUE; 
   
   TIMSK |= (1<<TOIE1); //Enable Timer1 OVF interrupt
}


static uint8_t curPulse = 0;
static uint8_t isPause = 0;
volatile static uint8_t mayMeasure = 0;
ISR(TIMER1_OVF1_vect){

   curPulse++;
   
   if(isPause){
      mayMeasure = 1;
      if(curPulse > PULSE_INTERBUNGLE_PAUSE){
         curPulse = 0;
         isPause = 0;
         OCR1A = PULSE_DUTY_VAL;
      }
   }else{
      mayMeasure = 0;
      if(curPulse > PULSE_BUNGLE_SIZE){
         curPulse = 0;
         isPause = 1;
         OCR1A = 0;
      }
   
   }
}

void  main()
{

   initIO();
   initPWM();
   
   PORTA = 0x00;
   OCR1A = PULSE_DUTY_VAL; 
   
   sei();
   while(1)
   {
      _delay_ms(1);
      // Wait for a meaningful result...
      if(mayMeasure){
      
         // Check results...
         if(PINB & (1 << TSOP)){
            PORTA &= ~(1 << STATUS_LED);
         }else{
            PORTA |= (1 << STATUS_LED);
            _delay_ms(500);         
         }
      }
   } // while(1)
}