QSerialPort

[mvsri]

Hey there,
I have been working with the QSerialPort, Here is the code

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

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

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

void MainWindow::on_pushButton_connect_clicked()
{
    serial = new QSerialPort(this);
    connect(serial, SIGNAL(readyRead()), this, SLOT(serialRead()));
    serial->setPortName("COM7");
    serial->setBaudRate(QSerialPort::Baud115200);
    serial->setParity(QSerialPort::NoParity);
    serial->setStopBits(QSerialPort::OneStop);
    serial->setFlowControl(QSerialPort::NoFlowControl);
    serial->open(QIODevice::ReadWrite);
}

void MainWindow::on_pushButton_write_clicked()
{
    QString Result = ui->lineEdit->text();
    QString request = "\x02"+QString("003")+ QString("%1").arg(Result.toInt(),7,10,QChar('0')) +"\r";
    const QByteArray requestData = request.toUtf8();
    serial->write(requestData);
    qInfo() << "Data Write";
}

void MainWindow::serialRead()
{
    qInfo() << "Serial Read Data: " << serial->readAll();
}

and mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QDebug>

#include <QSerialport>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private slots:
    void on_pushButton_connect_clicked();

    void on_pushButton_write_clicked();

    void serialRead();

private:
    Ui::MainWindow *ui;
    QSerialPort *serial;

};

#endif // MAINWINDOW_H

The code us working fine, the only problem is when i send something using serial->write(), it loop's itself in the Pushbutton_write() function.
Is there any way i can use serial->write() only once when i click the pushbutton.

[artwaw]

I'd suggest throwing out to qDebug content of request and requestData.

[jsulm]

@mvsri said in QSerialPort:

it loop's itself in the Pushbutton_write() function

That's not clear. Can you show what exactly you're doing there?

[mvsri]

@jsulm
i meant once i clicked on the pushbutton_write, i get continuous qInfo() in Application Output

void MainWindow::on_pushButton_write_clicked()
{
    QString Result = ui->lineEdit->text();
    QString request = "\x02"+QString("003")+ QString("%1").arg(Result.toInt(),7,10,QChar('0')) +"\r";
    const QByteArray requestData = request.toUtf8();
    serial->write(requestData);
    qInfo() << "Data Write:  " << requestData;
}

According to the logic of the above code when i press PushButton the code should write the data and print the data only once.

Although what happens is as soon as i press PushButton the whole on_pushButton_write_clicked() function goes into loop(like repeating the pushbutton fucntion itself)by sending write data using serial->write() and printing the qInfo() in Application Output.

[jsulm]

@mvsri Maybe you connected on_pushButton_write_clicked() to some other signal?

[Christian Ehrlicher]

@mvsri said in QSerialPort:

"\x02"+QString("003")

Since \x02 is no valid QString char I would not use QString here in the first place. You will get problems sooner or later with this.

[J.Hilk]

@mvsri I would try to define the slot by hand and explicitly call the QObject::connect to connect signal and slot.

The connectSlotByName meta-method is known to behave not exactly consistent 😄

[mvsri]

@jsulm NO i haven't connected it to any other signal, infact if you could check the mainwindow.cpp you can see that i haven't connected it.

[aha_1980]

@mvsri

Then please comment all the code within MainWindow::on_pushButton_write_clicked() and just add a qDebug() << "on_pushButton_write_clicked"; in it.

If you click the button once, you should see that message also one time. Does that work?

Regards

[mvsri]

i used QObject::connect to connect signal and slot and it solved the problem.

Thank you for the help!

[aha_1980]

@mvsri

Glad you figured it out. So please mark this topic as SOLVED too. Thanks!

[Marco Flad]

@mvsri please can you paste the code or explain more how QObject::connect .

[aha_1980]

@Marco-Flad

Please see here: https://doc.qt.io/qt-5/signalsandslots.html