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How implement serial delay

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  • B Offline
    B Offline
    bask185
    wrote on last edited by
    #1

    I have a send function and now I need a delay of 2 ms after I send a byte. If I send quicker than these 2 ms the receiving end will miss the data.

    void MainWindow::send(QString c)
    {
        serial->write(c.toLatin1());
        QString cAsHex = QString("%1").arg(c, 0, 16);
        qDebug()  << cAsHex << " >>";
    }
    

    I was wondering what the most efficient way would be to do this. I don't know whether I can use some fancy serial function of which I don't know about yet or if I should pause the entire application using a QThread delay.

    It is not big deal if the program freezes temporarily.

    jsulmJ 1 Reply Last reply
    0
    • B Offline
      B Offline
      bask185
      wrote on last edited by bask185
      #5

      This

      void MainWindow::send(QString c)
      {
        QTimer::singleShot(2, this, SLOT(timeOut()));
        timer = true;
      
        serial->write(c.toLatin1());
        QString cAsHex = QString("%1").arg(c, 0, 16);
        qDebug()  << cAsHex << " >>";
        while (timer == true) {;}
      }
      
      void MainWindow::timeOut()
      {
          timer = false;
      }
      

      is not working. The idea is that timeOut gets called 2ms after a byte has been send so the program can escape the while loop.

      Why is this not working??

      EDIT:
      does not matter I used a different approach with a timer object and ->start(2) and -> stop() functions. This works ;)

      jsulmJ 1 Reply Last reply
      0
      • B bask185

        I have a send function and now I need a delay of 2 ms after I send a byte. If I send quicker than these 2 ms the receiving end will miss the data.

        void MainWindow::send(QString c)
        {
            serial->write(c.toLatin1());
            QString cAsHex = QString("%1").arg(c, 0, 16);
            qDebug()  << cAsHex << " >>";
        }
        

        I was wondering what the most efficient way would be to do this. I don't know whether I can use some fancy serial function of which I don't know about yet or if I should pause the entire application using a QThread delay.

        It is not big deal if the program freezes temporarily.

        jsulmJ Offline
        jsulmJ Offline
        jsulm
        Lifetime Qt Champion
        wrote on last edited by
        #2

        @bask185 Just use QTimer

        https://forum.qt.io/topic/113070/qt-code-of-conduct

        B 1 Reply Last reply
        4
        • mrjjM Offline
          mrjjM Offline
          mrjj
          Lifetime Qt Champion
          wrote on last edited by
          #3

          And what ever you do, please dont use QThread delay. :)

          1 Reply Last reply
          4
          • jsulmJ jsulm

            @bask185 Just use QTimer

            B Offline
            B Offline
            bask185
            wrote on last edited by
            #4

            @jsulm said in How implement serial delay:

            @bask185 Just use QTimer

            Thank you. I will try it out ;)

            @mrjj said in How implement serial delay:

            And what ever you do, please dont use QThread delay. :)

            You cannot say something like that if you don't provide the 'why' argument with it. This is just like saying: "never use global variables" or "always use 'private' and 'public'".

            If I say: "jump in the ditch", how likely will it be that you will actually do it? But if I say: "Jump in the ditch, because there is a person drowning in it" than it is more likely that you will actually jump in the ditch. I said in the OP that it would not be a big deal if my program would freeze temporarily during a data transfer so I am not even remotely getting why I should not use a QThread delay??? If my push buttons would be disabled, it would actually be better because no user can accidently send a 'false' byte.

            mrjjM 1 Reply Last reply
            0
            • B Offline
              B Offline
              bask185
              wrote on last edited by bask185
              #5

              This

              void MainWindow::send(QString c)
              {
                QTimer::singleShot(2, this, SLOT(timeOut()));
                timer = true;
              
                serial->write(c.toLatin1());
                QString cAsHex = QString("%1").arg(c, 0, 16);
                qDebug()  << cAsHex << " >>";
                while (timer == true) {;}
              }
              
              void MainWindow::timeOut()
              {
                  timer = false;
              }
              

              is not working. The idea is that timeOut gets called 2ms after a byte has been send so the program can escape the while loop.

              Why is this not working??

              EDIT:
              does not matter I used a different approach with a timer object and ->start(2) and -> stop() functions. This works ;)

              jsulmJ 1 Reply Last reply
              0
              • B bask185

                @jsulm said in How implement serial delay:

                @bask185 Just use QTimer

                Thank you. I will try it out ;)

                @mrjj said in How implement serial delay:

                And what ever you do, please dont use QThread delay. :)

                You cannot say something like that if you don't provide the 'why' argument with it. This is just like saying: "never use global variables" or "always use 'private' and 'public'".

                If I say: "jump in the ditch", how likely will it be that you will actually do it? But if I say: "Jump in the ditch, because there is a person drowning in it" than it is more likely that you will actually jump in the ditch. I said in the OP that it would not be a big deal if my program would freeze temporarily during a data transfer so I am not even remotely getting why I should not use a QThread delay??? If my push buttons would be disabled, it would actually be better because no user can accidently send a 'false' byte.

                mrjjM Offline
                mrjjM Offline
                mrjj
                Lifetime Qt Champion
                wrote on last edited by
                #6

                @bask185

                Fair enough, please don't use QThread delay for any kind of pausing in a main thread as it also strangulate the
                event/signal processing and can lead to all sort of odd behaviors. Its simply a wrong solution to the requirements.

                Your buttons are not really disabled, they simply not getting the click event ( or some might) so using
                delay is just bad design in 99% of all cases in regards to the main thread.
                To disable, there is a function for just that.

                1 Reply Last reply
                3
                • B bask185

                  This

                  void MainWindow::send(QString c)
                  {
                    QTimer::singleShot(2, this, SLOT(timeOut()));
                    timer = true;
                  
                    serial->write(c.toLatin1());
                    QString cAsHex = QString("%1").arg(c, 0, 16);
                    qDebug()  << cAsHex << " >>";
                    while (timer == true) {;}
                  }
                  
                  void MainWindow::timeOut()
                  {
                      timer = false;
                  }
                  

                  is not working. The idea is that timeOut gets called 2ms after a byte has been send so the program can escape the while loop.

                  Why is this not working??

                  EDIT:
                  does not matter I used a different approach with a timer object and ->start(2) and -> stop() functions. This works ;)

                  jsulmJ Offline
                  jsulmJ Offline
                  jsulm
                  Lifetime Qt Champion
                  wrote on last edited by
                  #7

                  @bask185 Well, this just cannot work as your while loop blocks the event loop which breaks signals/slots.
                  Why did you put the loop there?

                  void MainWindow::send(QString c)
                  {
                    QTimer::singleShot(2, this, SLOT(timeOut()));
                    serial->write(c.toLatin1());
                    QString cAsHex = QString("%1").arg(c, 0, 16);
                    qDebug()  << cAsHex << " >>";
                  }
                  
                  void MainWindow::timeOut()
                  {
                      // Here send the rest of the data
                  }
                  

                  https://forum.qt.io/topic/113070/qt-code-of-conduct

                  1 Reply Last reply
                  3
                  • J.HilkJ Offline
                    J.HilkJ Offline
                    J.Hilk
                    Moderators
                    wrote on last edited by
                    #8

                    I would suggest something like this:

                    //Member variables:
                    QTimer *timer;
                    QList<QString> dataToSend;
                    
                    /*Timer event*/
                    timer = new QTimer(this);
                    connect(timer, &QTimer::timeout, timer, [=]{
                         if(dataToSend.size() > 0){
                             send(dataToSend.first());
                             dataToSend.removeFirst();
                        }
                        if(dataToSend.isEmpty())
                            timer->stop();
                    });
                    
                    /*Start send*/
                    ...
                    dataToSend.append(newData);
                    if(!timer->isRunning())
                        timer->start(2);
                    

                    Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


                    Q: What's that?
                    A: It's blue light.
                    Q: What does it do?
                    A: It turns blue.

                    1 Reply Last reply
                    1
                    • B Offline
                      B Offline
                      bask185
                      wrote on last edited by bask185
                      #9

                      I now use:

                      void MainWindow::send(QString c)
                      {
                      
                        timer->start(2);
                      
                        serial->write(c.toLatin1());
                        QString cAsHex = QString("%1").arg(c, 0, 16);
                        qDebug()  << cAsHex << " >>";
                        while (Timer == true) {;}
                      }
                      
                      void MainWindow::timeOut()
                      {
                          Timer = false;
                          timer->stop();
                      }
                      

                      and it works like a charm

                      1 Reply Last reply
                      0

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