Cannot output a value using QSerialPort

[Simon sun]

Maybe this statement doesnot work.
QObject::connect(arduino, SIGNAL(readyRead), this, SLOT(readSerial()));
Maybe the “readyReady” function lack of “()”,or you can try set breakpoint in slot readSerial() to ensure the slot is performed.

[Christian Ehrlicher]

@Simon-sun said in Cannot output a value using QSerialPort:

Maybe the “readyReady”

Not maybe - it does.

Use the new signal/slot syntax to avoid such errors.

[jude.bato]

Thank you for the replies although I'm not 100% sure how I would implement this. Is there code I need to add, or even take away?

[Christian Ehrlicher]

Your connect statement is simply wrong and if you would have checked the return value you would have seen it by yourself. See https://wiki.qt.io/New_Signal_Slot_Syntax for the new signal/slot syntax

[jude.bato]

I just need to receive from the serial port, with the new syntax it requires a sender, &sender function which I cannot use / don't need

[jude.bato]

I changed QObject::connect(arduino, SIGNAL(readyRead), this, SLOT(readSerial())); to QObject::connect(arduino, 0, 0, 0, Qt::ConnectionType()); and I got the same output

[Pablo J. Rogina]

@jude-bato said in Cannot output a value using QSerialPort:

he new syntax it requires a sender, &sender function which I cannot use / don't need

Please please take some time to read the link suggested for @Christian-Ehrlicher and try to understand the concepts of signal & slot under Qt

Tip 1 : sender is a Qt object, and is the sender of a signal; an object that under some conditions will emit (send) a signal
Tip 2: your sender is arduino object

[jude.bato]

I was reviewing the link and with trial and error I began trying to implement the new syntax. Saying that, part of the QObject::connect requires const char *signal which I have no idea what that means.

[jude.bato]

Reading on the new syntax I updated my Qt version as a troubleshooting method and put in QObject::connect(arduino, &QSerialPort::readyRead, this, &Dialog::readSerial); and the Application output is no member named 'connect' in 'QDebug'. I'm very lost

[jsulm]

@jude-bato Please show the code where you call connect()

[jude.bato]

@jsulm QObject::connect(arduino, SIGNAL(readyRead), this, SLOT(readSerial())); This is where connect should be called, but with the new syntax I very confused on how I can connect and read from Arduino into Qt

[SGaist]

Hi,

You signal specification is still wrong in the connect statement.

In any case, as already requested several times: please post the current code you are using.

[jsulm]

@jude-bato Why do you post again your old connect() call (which is wrong because the signal is missing brackets - readyRead())?
Please post the code where you call connect() with new syntax (without SIGNAL/SLOT) and not just the connect() call itself but also the surrounding code...

[jude.bato]

QObject::connect(arduino, &QSerialPort::readyRead, this, &Dialog::readSerial); This is the code line that I have integrated in my current project, I'm just not sure how to convert it to the new syntax. I was using the old code because in the original question I wanted to specify where I was talking about. I know it was wrong and I changed it already. The problem I'm having is with the new syntax.

[jsulm]

@jude-bato And with that code line you get "no member named 'connect' in 'QDebug'"?

[Pablo J. Rogina]

@jude-bato said in Cannot output a value using QSerialPort:

This is the code line

If you're looking for some help in the forum please make others' life easier.
Why is so difficult to show some code snippet of yours? not just ONE line.
Come on, some context helps understand what might be going on with your issue.

[jude.bato]

This is the code snippet, its in my dialog.cpp file

if(arduino_is_available)
    {
        qDebug()<<"Found the port \n";
        arduino->setPortName(arduino_uno_port_name);
        arduino->open(QSerialPort::ReadOnly);
        arduino->setBaudRate(QSerialPort::Baud9600);
        arduino->setDataBits(QSerialPort::Data8);
        arduino->setFlowControl(QSerialPort::NoFlowControl);
        arduino->setParity(QSerialPort::NoParity);
        arduino->setStopBits(QSerialPort::OneStop);
        connect(*arduino, Dialog::readSerial(updateVoltage()),this,readSerial()); //too few arguments to function call, expected 1, have 0
    } else {
        qDebug()<<"Could not find the correct port \n";
        QMessageBox::information(this,"Serial Port Error", "Could not open the serial port");
    }
}

and the read serial code I have:

void Dialog::readSerial()
{
    QStringList buffer_split = serialBuffer.split(",");
    if(buffer_split.length() < 3)
    {
        serialData = arduino->readAll();
        serialBuffer = serialBuffer + QString::fromStdString(serialData.toStdString());
        serialData.clear();
    } else {
        serialBuffer = "";
        qDebug() << buffer_split << "\n";
        parsed_data = buffer_split[1];
        voltage_value = (parsed_data.toDouble()) - 0.1;
        qDebug() << "Voltage: " << voltage_value << "\n";
        parsed_data = QString::number(voltage_value,'g',4);
        Dialog::updateVoltage(parsed_data);
    }
}

[SGaist]

Hi,

One thing that is missing: you don't check that the open call is successful. You should add that.

[Pablo J. Rogina]

@jude-bato said in Cannot output a value using QSerialPort:

connect(*arduino, Dialog::readSerial(updateVoltage()),this,readSerial());

Again, please read the documentation regarding signal and slots. You may want to try this article as well.

Tip: a typical connect sentence has 4 elements, try to identify such elements within your code...

Dialog::updateVoltage(parsed_data);

Do you know why you're calling an static method here?

[jude.bato]

@SGaist I believe I do

bool arduino_is_available = false;
    QString arduino_uno_port_name;
    foreach(const QSerialPortInfo &serialPortInfo, QSerialPortInfo::availablePorts()){
        if(serialPortInfo.hasProductIdentifier() && serialPortInfo.hasVendorIdentifier()){
            if((serialPortInfo.productIdentifier() == arduino_uno_product_id) && (serialPortInfo.vendorIdentifier() == arduino_uno_vendor_id)){
                arduino_is_available = true;
                arduino_uno_port_name = serialPortInfo.portName();
            }
        }
    }

    if(arduino_is_available)
    {
        qDebug()<<"Found the port \n";
        arduino->setPortName(arduino_uno_port_name);
        arduino->open(QSerialPort::ReadOnly);
        arduino->setBaudRate(QSerialPort::Baud9600);
        arduino->setDataBits(QSerialPort::Data8);
        arduino->setFlowControl(QSerialPort::NoFlowControl);
        arduino->setParity(QSerialPort::NoParity);
        arduino->setStopBits(QSerialPort::OneStop);
        QObject::connect(arduino, SIGNAL(readyRead), this, SLOT(readSerial())); //I know this is wrong, this is what I'm trying to fix
    } else {
        qDebug()<<"Could not find the correct port \n";
        QMessageBox::information(this,"Serial Port Error", "Could not open the serial port");
    }
}