pulseIn(pin, value, timeout)
Measures the length of a pulse in microseconds. This function starts measuring when the specified input value (HIGH or LOW) is read. If value is HIGH for example, pulseIn() waits for the pin to go HIGH, starts timing, then waits for the pin to go LOW and stops timing.
Parameters
pin - The GPIO pin number.
value - HIGH or LOW. The start input value to begin measuring.
timeout - In microseconds.
Returns
The length of the pulse in microseconds or 0 if no complete pulse was received within the given timeout.
Example
// Ultrasonic sensor HC-SR04 read
#include "Arduino.h"
// Ultrasonic Vcc pin to 5V
#define trigPin 23 // Ultrasonic Trig pin to GPIO23
#define echoPin 24 // Ultrasonic Echo pin <--^^1k^^--> GPIO24 <--^^2k^^--> GND
// Ultrasonic GND pin to GND
void setup() {
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
}
void loop() {
long long duration, distance;
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
digitalWrite(trigPin, HIGH);
delayMicroseconds(100);
digitalWrite(trigPin, LOW);
duration = pulseIn(echoPin, HIGH, 1000);
distance = (duration/2) / 29.1;
printf("duration = %d, Distance = %d \n", duration, distance);
delay(500);
}