Raspberry PI - how to use ultrasonic rangefinder with c++ (cpp)?

$ wget abyz.me.uk/rpi/pigpio/pigpio.zip

$ unzip pigpio.zip

$ cd PIGPIO

$ make

$ sudo make install

$ rm pigpio.zip

$ sudo rm -rf PIGPIO

#include <pigpio.h>

#include <iostream>

#include <time.h>

​

#include <stdlib.h>

#include <sys/time.h>

​

​

using namespace std;

​

​

struct timeval tv;

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double getTime()

{

    gettimeofday(&tv, NULL);

​

    return (double)tv.tv_sec + (double)tv.tv_usec * 0.000001;

}

​

// https://en.wikipedia.org/wiki/Speed_of_sound

// https://www.google.com/search?q=343+m%2Fs+to+cm%2Fs&oq=343+m%2Fs+to+cm%2Fs&aqs=chrome..69i57j6.443j0j9&sourceid=chrome&ie=UTF-8

int coefficient = 17150; // it should be selected experimentally - it is half of speed of sound in air in cm/s

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int TRIG = 23; // BCM/GPIO pin number

int ECHO = 24; // BCM/GPIO pin number

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void initializePins()

{

    gpioSetMode(TRIG, PI_OUTPUT);

    gpioSetMode(ECHO, PI_INPUT);

}

​

bool waitValue(int value, int limit = 10000) // use 1000000 to increase measurement distance

{

    for(int i = 0; gpioRead(ECHO) == value; ++i)

    {

        if(i >= limit)

            return false;

    }

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    return true;

}

​

double detectDistance()

{

    gpioWrite(TRIG, 0); // reset rangefinder state

    usleep(500000); // wait for reset state - use 100000 to speedup program

    gpioWrite(TRIG, 1); // hi state runs rangefinder measurement

    usleep(10); // 10 us of hi level is necessary to start measurement - depended on rangefinder model 

    gpioWrite(TRIG, 0); // prepare rangefinder for measurement

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    if(waitValue(0)) // wait until lo level is achieved on echo pin

    {

        double pulseStart = getTime();

​

        if(waitValue(1)) // wait until hi level is achieved on echo pin - hi level duration is proportional to distance

        {

            double pulseEnd = getTime();

​

            double duration = pulseEnd - pulseStart;

            double distance = duration * coefficient;

​

            return distance;

        }

    }

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    cout << "Measurement error!"; 

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    // Troubleshooting:

    // - check correctness of pin connection, 

    // - check supply in case of many devices connected,

    // - check maximal supported distance by rangefinder

​

    return 0.0 / 0.0;

}

​

int main () 

{

    if(gpioInitialise() < 0)

        cout << "PIGPIO initialisation failure!" << endl; 

​

    else

    {

        cout << "PIGPIO initialisation success!" << endl;

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        initializePins();

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        for(int i = 0; i < 100; ++i) // for example: 100 measurements

        {

            double distance = detectDistance();

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            cout << "Distance: " << distance << "cm" << endl;

        }

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        gpioTerminate();

    }

​

    return 0; 

}

$ gcc -o program -lpigpio -lpthread -lrt program.cpp

$ ./program

TEMPLATE = app

CONFIG += console

CONFIG -= qt

​

LIBS += -lpigpio -lpthread -lrt

​

SOURCES += program.cpp