Project 2 - Measuring distance of an object using ultrasonic sensor (HC-SR04)

#define F_CPU 8000000UL
#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include <string.h>
#include <stdlib.h>
#include "LCD_16x2_H_file.h"/* Include LCD header file */

#define Trigger_pin PA0 /* Trigger pin */

int TimerOverflow = 0;

ISR(TIMER1_OVF_vect)
{
TimerOverflow++; /* Increment Timer Overflow count */
}

int main(void)
{
char string[10];
long count;
double distance;

DDRA = 0x01; /* Make trigger pin as output */
PORTD = 0xFF; /* Turn on Pull-up */

LCD_Init();
LCD_String_xy(1, 0, "Ultrasonic");

sei(); /* Enable global interrupt */
TIMSK = (1 << TOIE1); /* Enable Timer1 overflow interrupts */
TCCR1A = 0; /* Set all bit to zero Normal operation */

while(1)
{

PORTA |= (1 << Trigger_pin);/* Give 10us trigger pulse on trig. pin to HC-SR04 */
_delay_us(10);
PORTA &= (~(1 << Trigger_pin));

TCNT1 = 0; /* Clear Timer counter */
TCCR1B = 0x41; /* Setting for capture rising edge, No pre-scaler*/
TIFR = 1<<ICF1; /* Clear ICP flag (Input Capture flag) */
TIFR = 1<<TOV1; /* Clear Timer Overflow flag */

/*Calculate width of Echo by Input Capture (ICP) on PortD PD6 */

while ((TIFR & (1 << ICF1)) == 0); /* Wait for rising edge */
TCNT1 = 0; /* Clear Timer counter */
TCCR1B = 0x01; /* Setting for capture falling edge, No pre-scaler */
TIFR = 1<<ICF1; /* Clear ICP flag (Input Capture flag) */
TIFR = 1<<TOV1; /* Clear Timer Overflow flag */
TimerOverflow = 0; /* Clear Timer overflow count */

while ((TIFR & (1 << ICF1)) == 0); /* Wait for falling edge */
count = ICR1 + (65535 * TimerOverflow); /* Take value of capture register */
/* 8MHz Timer freq, sound speed =343 m/s, calculation mentioned in doc. */
distance = (double)count / 466.47;

dtostrf(distance, 2, 2, string);/* Converting distance into string */
strcat(string, " cm ");
LCD_String_xy(2, 0, "Dist = ");
LCD_String_xy(2, 7, string); /* Print distance on LDC16x2 */
_delay_ms(200);
}
}