Time from HIGH to LOW

arthuki

Hey everyone,

I have a project with a LM555 timer and need to calculate how much time it takes for an input to go from LOW to HIGH and then to LOW again.

Basically, I want to know the period of a square wave generated by the LM555 timer.

I did it with Arduino using the function Pulseln. But I need to do this using a Beaglebone and programming in C++ (Using QtCreator).

I create this code but it is not working:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QElapsedTimer>
#include "SimpleGPIO.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::on_pushButton_clicked()
{

       QElapsedTimer tempo;
       qint64 nanoSeg = 0;
       QString seg;

       unsigned int PINO = 60;   // GPIO1_28 = (1x32) + 28 = 60
       gpio_export(PINO);    // The LED is in pin 60
       gpio_set_dir(PINO, INPUT_PIN);   // The LED is an INPUT

     //  unsigned int valor = LOW;



       if(gpio_get_value(PINO)==HIGH){

           tempo.start();

       }

       while(gpio_get_value(PINO)==HIGH){
            ui->textEdit_2->setText("HIGH");
       }

       while(gpio_get_value(PINO)==LOW){

       }

       nanoSeg = tempo.nsecsElapsed();

       seg = QString::number(nanoSeg);  // Converte o inteiro 'nanoSeg' em string 'seg'
       ui->textEdit->setText(seg);

}

It compiles alright and when I run it I don't get an error messages, it just crashes.

I have already checked and the libraries are OK. The problem I think is with the while functions. Do you guys have any ideia of what might be the problem?

Thank you in advance.

? Offline

Hi! You start with the following:


       if(gpio_get_value(PINO)==HIGH){

           tempo.start();

       }

So with some bad luck (everytime you come here and gpio_get_value(PIN0) is low) your timer doesn't get started. And in that case, nsecsElapsed's behaviour is undefined.