Question

Without using a Timer function, write a program to read the distance from the HC-SR04 ultrasonic sensor and display the distance on the C12832 lcd.

*please refer the HC-SR04 datasheet for the operation of the ultrasonic sensor, and mbed website for C12832 library and Timer function

Answer 1

#include <avr/io.h>
#include <MrLcd/MrLCDmega32.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include <stdlib.h>

static volatile int pulse = 0;
static volatile int i = 0;

int main(void)
{
  int16_t count_a = 0; 
  char show_a[16];
  Initialise();
  DDRD = 0b11111011;
  _delay_ms(50);

  Initialise();

  GICR |= 1<<INT0;
  MCUCR |= 1<<ISC00;

  sei();
 
  while(1)
  { 
    PORTD |= 1<<PIND0;
    _delay_us(15);

    PORTD &= ~(1<<PIND0);
    count_a = pulse/58;

    Send_A_String("Distance Sensor");
    GoToMrLCDLocation(1,2);
    Send_A_String("Distance=");
    itoa(count_a,show_a,10);
    Send_A_String(show_a);
    Send_A_String(" ");
    GoToMrLCDLocation(13,2);
    Send_A_String("cm");
    GoToMrLCDLocation(1,1);
  }
}

ISR(INT0_vect)
{
  if(i == 0)
  {
    TCCR1B |= 1<<CS10;
    i = 1;
  }
  else
  {
    TCCR1B = 0;
    pulse = TCNT1;
    TCNT1 = 0;
    i = 0;
  }
}