/*
hc-sr04.c
Raspberry Pi driving the HC-SR04
to compile : cc hc-sr04.c -o hc-sr04 -lwiringPi
*/
#include <stdio.h>
#include <stdlib.h>
#include <wiringPi.h>
#define trigPin 8
#define echoPin 7
int pulseIn(int pin, int level, int timeout)
{
struct timeval tn, t0, t1;
long micros;
gettimeofday(&t0, NULL);
micros = 0;
while (digitalRead(pin) != level)
{
gettimeofday(&tn,
NULL);
if (tn.tv_sec >
t0.tv_sec) micros = 1000000L; else micros = 0;
micros += (tn.tv_usec -
t0.tv_usec);
if (micros > timeout)
return 0;
}
gettimeofday(&t1, NULL);
while (digitalRead(pin) == level)
{
gettimeofday(&tn,
NULL);
if (tn.tv_sec >
t0.tv_sec) micros = 1000000L; else micros = 0;
micros = micros +
(tn.tv_usec - t0.tv_usec);
if (micros > timeout)
return 0;
}
if (tn.tv_sec > t1.tv_sec) micros =
1000000L; else micros = 0;
micros = micros + (tn.tv_usec - t1.tv_usec);
return micros;
}
int main (int argc, char **argv) {
int i,j,k,l,m;
long duration, distance;
if(wiringPiSetupGpio() == -1) return 1;
pinMode(trigPin,OUTPUT);
pinMode(echoPin,INPUT);
digitalWrite(trigPin, LOW); // Added this
line
delayMicroseconds(2); // Added this line
digitalWrite(trigPin, HIGH);
delayMicroseconds(10); // Added this line
digitalWrite(trigPin, LOW);
duration = pulseIn(echoPin, HIGH, 1000000);
printf("duration=%d\n",duration);
distance = (duration/2) / 29.1;
printf("distance=%d cm\n",distance);
}
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