ST_HW_HC_SR04

Advanced arduino library for HC-SR04 ultrasonic sensors

Usage

Basic example:

#include <ST_HW_HC_SR04.h>

ST_HW_HC_SR04 ultrasonicSensor(13, 12); // ST_HW_HC_SR04(TRIG, ECHO)

// Get the time the ultrasonic pulses took from the sensor to the blocking object
int hitTime = ultrasonicSensor.getHitTime();

// Calculate the approximate distance in centimeters (as seen in extras/HC-SR04.txt)
int distanceInCm = hitTime / 29;

The getHitTime function will return 0 if the ultrasonic sensor doesn't receive back the packets it sent before the timeout value.

Timeouts

The default timeout value is 5000 microseconds, which sould be enough for approximately 86 centimeters ([5000 / 58] ~= 86.2).

Although I didn't confirm, it is stated in this datasheet (alternate link) that max. range of this sensor is 4 meters (400cm). As so, setting the timeout value to 23200 microseconds (23.2 ms) should be enough for all cases where the object distance is less or equal to 4 meters.

The timeout-related methods of this library are:

// Setters
ultrasonicSensor.setTimeout(unsigned long desiredTimeout);
ultrasonicSensor.setTimeoutToDefaultValue();

// Getters
unsigned long currentTimeout = ultrasonicSensor.getTimeout();

Extra information

Information about how the ultrasonic sensor works is present in the extras/HC-SR04.txt file.