TVZ Mechatronics Team / HCSR04

A distance measurement class using ultrasonic sensor HC-SR04.

Dependents:   Esercitazione4_4 HC-SR04 Group10_slave Oled_Gus ... more

The purpose of this library is to encourage students to develope their own classes. Instructions how to follow the development of this library for ultrasonic distance measurement are given here.

HCSR04.cpp

Committer:
tbjazic
Date:
2015-12-07
Revision:
4:aae70f15357f
Parent:
3:9a7899cf5e3a
Child:
6:cf3e4e307d15

File content as of revision 4:aae70f15357f:

#include "mbed.h"
#include "HCSR04.h"

HCSR04::HCSR04(PinName echoPin, PinName triggerPin) : echo(echoPin), trigger(triggerPin) {
    init();
}

void HCSR04::init() {
    /** configure the rising edge to start the timer */
    echo.rise(this, &HCSR04::startTimer);
    
    /** configure the falling edge to stop the timer */
    echo.fall(this, &HCSR04::stopTimer);
    
    distance = -1;      // initial distance
    minDistance = 2;
    maxDistance = 400;
}

void HCSR04::startTimer() {
    timer.start(); // start the timer
}

void HCSR04::stopTimer() {
    timer.stop(); // stop the timer
}

void HCSR04::startMeasurement() {
    trigger = 1;
    wait_us(10);
    trigger = 0;
    wait_us(23660); // just enough time to measure 400 cm
    timer.stop(); // just in case echo fall did not occur
    distance = timer.read() * 1e6 / 58;
    if (distance < minDistance)
        distance = minDistance;
    if (distance > maxDistance)
        distance = maxDistance;
    timer.reset();
}

float HCSR04::getDistance_cm() {
    startMeasurement();
    return distance;
}

float HCSR04::getDistance_mm() {
    startMeasurement();
    return distance * 10;
}

void HCSR04::setRanges(float minRange, float maxRange) {
    if (minRange < maxRange) {
        if (minRange >= 2) 
            minDistance = minRange;
        if (maxRange <= 400)
            maxDistance = maxRange;
    }
}

float HCSR04::getMinRange() {
    return minDistance;
}

float HCSR04::getMaxRange() {
    return maxDistance;
}