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HCSR04.cpp
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HCSR04.cpp
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/*
HCSR04 - Library for arduino, for HC-SR04 ultrasonic distance sensor.
Created by Martin Sosic, June 11, 2016.
*/
#include "lib/hcsr04.h"
#include "Arduino.h"
UltraSonicDistanceSensor::UltraSonicDistanceSensor(int triggerPin,
int echoPin) {
this->triggerPin = triggerPin;
this->echoPin = echoPin;
pinMode(triggerPin, OUTPUT);
pinMode(echoPin, INPUT);
}
double UltraSonicDistanceSensor::measureDistanceCm() {
// Using the approximate formula 19.307°C results in roughly 343m/s which is
// the commonly used value for air.
return measureDistanceCm(19.307);
}
double UltraSonicDistanceSensor::measureDistanceCm(float temperature) {
// Make sure that trigger pin is LOW.
digitalWrite(triggerPin, LOW);
delayMicroseconds(2);
// Hold trigger for 10 microseconds, which is signal for sensor to measure
// distance.
digitalWrite(triggerPin, HIGH);
delayMicroseconds(10);
digitalWrite(triggerPin, LOW);
// Measure the length of echo signal, which is equal to the time needed for
// sound to go there and back.
unsigned long durationMicroSec = pulseIn(echoPin, HIGH);
double speedOfSoundInCmPerMs =
0.03313 + 0.0000606 * temperature; // Cair ≈ (331.3 + 0.606 ⋅ ϑ) m/s
double distanceCm = durationMicroSec / 2.0 * speedOfSoundInCmPerMs;
if (distanceCm == 0 || distanceCm > 400) {
return -1.0;
} else {
return distanceCm;
}
}