How to set a signal before shutdown?

[inger]

Hello!

I'm using qextserialport for sending data. In my program I have no GUI. The progam will automatic start in the background when the PC is started. I need to set RTS low before shutdown the program. The program will be shutdown when the power turn off. In my testprogram I push x-button in Application Output.

Is it possible to catch some shutdownsignal so I can call

CommPort->setRts(0);

CommPort->setRts(0);

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before the PC is shutdown. It is possible to use another connect for a shutdown signal?

My main program is like, I have deleted some code that I think are irrelevant:

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    createDatabaseConnection();
 
    // Initiate all modules
    FlexiBlinkRX flexiBlinkRx;
    FBtoFLTP FBtoFLTP1;
    FilterEngine filterEngine;
    smsThread SMSThread;
 
    SMSThread.start();
 
    // Connect all signals between modules
    FBtoFLTP1.connect       (&flexiBlinkRx, SIGNAL(incommingDataSignal()), SLOT(startTask()));
    filterEngine.connect    (&FBtoFLTP1, SIGNAL(inputToQueueSignal()), SLOT(checkqFilterQueue()));
 
    // Start executing
    a.exec();
 
    SMSThread.quit();
    SMSThread.wait();
 
    flexiBlinkRx.CommPort->setRts(0);
    return 0;
}

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    createDatabaseConnection();

    // Initiate all modules
    FlexiBlinkRX flexiBlinkRx;
    FBtoFLTP FBtoFLTP1;
    FilterEngine filterEngine;
    smsThread SMSThread;
    
    SMSThread.start();

    // Connect all signals between modules
    FBtoFLTP1.connect       (&flexiBlinkRx, SIGNAL(incommingDataSignal()), SLOT(startTask()));
    filterEngine.connect    (&FBtoFLTP1, SIGNAL(inputToQueueSignal()), SLOT(checkqFilterQueue()));
    
    // Start executing
    a.exec();

    SMSThread.quit();
    SMSThread.wait();

    flexiBlinkRx.CommPort->setRts(0);
    return 0;
}

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[Zlatomir]

I think the aboutToQuit signal is what you are looking for.

[ChrisW67]

I think it is pointless. If the power is going off then the state of RTS will surely follow into electrical oblivion.

[inger]

I use external power supply for the unit where I use the signal, because I need 9V. It's the reason why I need to shutdown the RTS-signal.
I have tried the following in main:

flexiBlinkRx.connect    (&a, SIGNAL(aboutToQuit()), SLOT(shutDownRts1()));

flexiBlinkRx.connect    (&a, SIGNAL(aboutToQuit()), SLOT(shutDownRts1()));

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But this seems not to work.
I have put in the sentence together with the other connect-sentences.
Can anybody help me?

[ChrisW67]

Is the slot never called, or the slot called but not working?
Does the code setting RTS require a Qt event loop to process the request?
Can you achieve the same thing by simply putting the RTS code in the flexiBlinkRx destructor?

It may be that Windows (It is Windows right?) is terminating the application forcibly and the aboutToQuit() signal is not sent.

You could try using the QCoreApplication::winEventFilter() to capture the WM_ENDSESSION and/or WM_QUERYENDSESSION message.

[wysota]

Provide the third argument to connect() explicitly.

[inger]

I use Ubuntu Virtual Machine.
The slot is never called.
I have also tried to set the RTS signal in the destructor, but no result.
Wysota: I don't understand what yiou mean. Can you please explain?

[wysota]

Where is the "shutDownRts1" slot implemented?

[inger]

It is implemented in flexiBlinkRx.cpp as a public slot.

[wysota]

Does the aboutToQuit() signal gets emitted at all? How are you testing your code?

[inger]

It seems that the aboutToQuit() signal never gets emitted.
I am testing my code by debugging and running the code.
For stopping the program I push the X-button in the Application window.

[wysota]

Maybe your program crashes instead of quitting?

[inger]

Yes, I think so.

Do you know if I then can catch some signals so I can set the RTS-signal to 0?