README.md

Arduino/ESP8266/ESP32 library for HC-SR04 ultrasonic distance sensor.

This library is used for measuring distance with the HC-SR04, which is an ultrasonic sensor that measures distances from 2 to 400cm. My library features a temperature correction and can utilize one trigger pin with multiple echo pins in parallel. I based this library on two other libraries.

1. https://github.com/Martinsos/arduino-lib-hc-sr04 --> I basically used the temperature calculation
2. https://github.com/gamegine/HCSR04-ultrasonic-sensor-lib --> I basically used the idea of using one trigger and multiple echos. But instead of measuring them in series, I tried to do that in parallel.

Usage

Example

#include <HCSR04.h>

byte triggerPin = 21;
byte echoCount = 2;
byte* echoPins = new byte[echoCount] { 12, 13 };

void setup () {
  Serial.begin(115200);
  HCSR04.begin(triggerPin, echoPins, echoCount);
}

void loop () {
  double* distances = HCSR04.measureDistanceCm();
  
  for (int i = 0; i < echoCount; i++) {
    if (i > 0) Serial.print(" | ");
    Serial.print(i + 1);
    Serial.print(": ");
    Serial.print(distances[i]);
    Serial.print(" cm");
  }
  
  Serial.println("");
  delay(500);
}

Library Options

You can get the distance back in several different units, using these methods:

Method	Unit
measureDistanceM()	Meters
measureDistanceMm()	Millimeters
measureDistanceCm()	Centimeters
measureDistanceIn()	Inches
measureDistanceFt()	Feet
measureDistanceYd()	Yards

You can optionally pass into the method, the current ambient temperature in degrees Celcius for better accuracy.

Examples

float tempC = 22.2222222 // 72 Degrees F
float distance = measureDistanceCm(tempC)

#include <HCSR04.h>

byte triggerPin = 21;
byte echoCount = 2;
byte* echoPins = new byte[echoCount] { 12, 13 };
const double tempC = 22.2222; //72 degrees F
double* distances = new double[echoCount];

void setup () {
  Serial.begin(115200);
  HCSR04.begin(triggerPin, echoPins, echoCount);
}

void loop () {
  HCSR04.measureDistanceMm(tempC, distances);
  
  for (int i = 0; i < echoCount; i++) {
    if (i > 0) Serial.print(" | ");
    Serial.print(i + 1);
    Serial.print(": ");
    Serial.print(distances[i]);
    Serial.print(" mm");
  }
  
  Serial.println("");
  delay(500);
}