Regarding Projector Programming using QT

Prath

@jsulm Could you please help me with the syntax for checking the error. I am completely new in using this.

jsulm

@Prath You know how to connect a slot to a signal?
https://doc.qt.io/qt-5/signalsandslots.html

Prath

Yeah @jsulm . We have to connect this signal [signal]void QSerialPort::errorOccurred(QSerialPort::SerialPortError error) to the slot right?

Is this correct?
void MainWindow::errorReport(QSerialPort::SerialPortError error)
{
if(error!=0)
qDebug()<<"ERROR:"<<endl<<error; // nothing printed
}

connect(this->Serial,SIGNAL(error(QSerialPort::SerialPortError)),this,SLOT(errorReport(QSerialPort::SerialPortError)));

jsulm

@Prath said in Regarding Projector Programming using QT:

Is this correct?

Signal is https://doc.qt.io/qt-5/qserialport.html#errorOccurred not error. Just check the documentation.

Prath

I think it is correct @jsulm. We are catching the signal using the slot and then displaying the signal.

JonB

@Prath
You wrote

connect(this->Serial,SIGNAL(error(QSerialPort::SerialPortError)),this,SLOT(errorReport(QSerialPort::SerialPortError)));

Where you have SIGNAL(error(QSerialPort::SerialPortError)) @jsulm is expecting SIGNAL(errorOccurred(QSerialPort::SerialPortError)). If what you have works, we do not understand how.

If you are writing new code and would change over to the new signal/slot syntax you would presumably receive a compile-time error.

Prath

Sorry for the delay guys. I tried again with the code and couldn't retrieve anything from the serial port regarding the errror.
I got the attached error:-

SGaist

Your MainWindow class does not have such a signal, it's one from the QSerialPort.

Prath

Didnt get you @SGaist .
Could you please help me with the syntax

Prath

When I click on the push button the function on_pushButton_clicked is called and then I call the Qserialport to check the error. I think the code is written correctly.

What's your take?

jsulm

@Prath said in Regarding Projector Programming using QT:

What's your take?

Your connect is wrong: MainWindow does NOT have signal error(QSerialPort::QSerialPort), this signal is in QSerialPort, so not in "this" but in "serial".

And please do not post screen-shots, copy paste your code...

JonB

@jsulm , @Prath

this signal is in QSerialPort, so not in "this" but in "serial".

Is this a case where changing to new-style signal/slot syntax would generate an error for the wrong "context" variable? Or, would testing the return result from the connect() or from https://doc.qt.io/qt-5/qmetaobject-connection.html#operator-bool in code tell the user if the connection has failed because of the wrong context?

jsulm

@JonB Yes, new connect syntax would help here, unless MainWindow has a signal with exact same signature :-)

Prath

Guys can we send two commands to two serial ports concurrently using QT?

SGaist

If you mean use several QSerialPorts at the same time in one application then yes, no problem with that. If you mean something else, please give more details.

Prath

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