QT 6.4.1 Use a SERIAL PORT in a subwindow

Question

I wrote a small program to connect via Serial Port, send strings via LineEdit and receive the response in a TextBrowser. (for testing I use an Arduino which sends back all what it receives as an answer).

I wrote the connection in a class that I named "Serialport". As long as I run it as MainWindow and include and call the class "Serialport" everything works without problems.

But since I want to use it as a sub-window in my program, I want to open and use it in a separate window.

I call the class like this:

// subwindow.cpp
.
.
.

    serialport = new SerialPort(parent);

    connect(ui->pushButtonConnect, SIGNAL(clicked(bool)), this, SLOT(verbinden()));
    connect(ui->pushButtonDisconnect, SIGNAL(clicked(bool)), this, SLOT(trennen()));
    connect(ui->pushButtonSend, SIGNAL(clicked(bool)), this, SLOT(senLinEdit()));
    connect(serialport, SIGNAL(dataEmpfangen(QByteArray)), this, SLOT(beiDatenEmpfangen(QByteArray)));

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.
.

void subWindow::beiDatenEmpfangen(const QByteArray &empfData) 
{
    zwischengespeicherterText += QString::fromLocal8Bit(empfData); //zwischengespeicherterText IS a QString
    qDebug() << zwischengespeicherterText + "\n";

    if(zwischengespeicherterText.endsWith("\r\n"))  //\r\n is my end signal from the Arduion
    {
        zwischengespeicherterText.replace("\r\n", "\n");
        ui->textBrowser->append(zwischengespeicherterText);

        zwischengespeicherterText = "";
    }

}

.
.
.

// mainwindow.cpp

    subWindow sn_vb(this); //
    sn_vb.setWindowTitle("Teste die Serielle Verbindung"); 
    sn_vb.exec();

Now only sending to the SerialPort works I don't receive anything anymore, There must be an error somewhere but I don't understand exactly where it could be.... I can post the code if you wish.

I am a complete newbie and have learned everything I know about videos so far please don't be too angry if I made basic mistakes.

I tryed: I ask ChatGPT hundrets of times, look YT Videos, googled it, ask a Friend who is good in C and C++

I hope that someone can explain to me where my error lies.

Offtopic but you should give Qt's ["new" signal and slot syntax](https://wiki.qt.io/New_Signal_Slot_Syntax) a try. It has the advantage to check connections at compile time (among other things). — Friedrich, Mar 07 '23 at 08:45

score 0 · Accepted Answer · answered Mar 11 '23 at 15:57

I found out how it works,

in my serialport class i add a function called "verbindungCheck" and it connect it again in the right way:

    bool SerialPort::verbindungCheck()
{
    if(m_serial->open(QIODevice::ReadWrite)) {
        // its connected 
        // the following line was missing 
        connect(m_serial, &QSerialPort::readyRead, this, &SerialPort::liesDaten);
        return true;
    } else {
        // something went wrong
        QMessageBox::warning(nullptr, "Error", "Couldn't connect ERROR Line: " + m_serial->errorString());
        return false;
    }
}

and this in the Subwindow.cpp

if(serialport->verbindungCheck()) {
    // Connected
    QMessageBox box;
    box.setText("Connectet sucessfully with: " + ui->comboBox->currentText());
    box.setIcon(QMessageBox::Information);
    box.addButton("OK", QMessageBox::AcceptRole);
    box.exec();
} else {
    // something went wrong
    QMessageBox box;
    box.setText("Connection faild");
    box.setIcon(QMessageBox::Warning);
    box.addButton("OK", QMessageBox::AcceptRole);
    box.exec();
}

Sorry for my bad english I am verry tiered and just want to go to bed.

QT 6.4.1 Use a SERIAL PORT in a subwindow

1 Answers1