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  4. [SOLVED]Possible? Multiple QSerialPort Threads Simultaneously Independently
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[SOLVED]Possible? Multiple QSerialPort Threads Simultaneously Independently

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qserialportmultiplethreadsindependentsimultaneouslyterminal
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  • SGaistS SGaist

    Hi,

    How are you creating your QSerialPort objects ?
    Do you haven on sensor per physical serial port ?

    S Offline
    S Offline
    Sen Li
    wrote on last edited by
    #3

    @SGaist
    Hi,

    Here is my QObject for QSerialPort control, with openSerial, closeSerial, and algorithm to control how to read data.
    When I put SenSerialControlAlgorithmObject into a thread, it keeps telling me
    QWinEventNotifier: Event notifiers cannot be enabled or disabled from another thread
    whenever it comes to the openSerial or closeSerial command, and the serial communication doesn't work.

    One Serial Port connects with one MCU to control one sensor.

    #include <QObject>
    #include <QtSerialPort/QSerialPort>
    #include <QTime>
    #include <QElapsedTimer>
    
    class SenSerialControlAlgorithmObject : public QObject
    {
        Q_OBJECT
    public:
        explicit SenSerialControlAlgorithmObject(QObject *parent = 0);
    
        QSerialPort *mySerialPort;
        QByteArray SenMotionByteArray;
        bool motionReadBegun;
        QElapsedTimer *myElapsedTimer;
    
    signals:
        void emitSerialCloseSetting();
        void emitSerialOpenedSetting();
        void emitSerialDataToConsole(QByteArray);
    
        void emitMotionTrackingStart();
        void emitMotionTrackingStop(qint64);
        void emitMotionUpdateSignal(QByteArray SenMotionByteArray, int);
    
    public slots:
        void openSerialPort(Settings mySettingInfo);
        void closeSerialPort();
        void readData();
        void handleError(QSerialPort::SerialPortError error);
    
    private:
        int motionReadBytes, delta_X, delta_Y;
    };
    #endif // SENSERIALCONTROLALGORITHMOBJECT_H
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    • SGaistS Offline
      SGaistS Offline
      SGaist
      Lifetime Qt Champion
      wrote on last edited by
      #4

      How are you putting SenSerialControlAlgorithmObject in a QThread ?

      Interested in AI ? www.idiap.ch
      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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      0
      • SGaistS SGaist

        How are you putting SenSerialControlAlgorithmObject in a QThread ?

        S Offline
        S Offline
        Sen Li
        wrote on last edited by Sen Li
        #5

        @SGaist

        In the constructor in MainWindow of Terminal.
        The MainWindow has ui for Serial Info Setting.

            mySerialThread = new QThread();
        //    SenSerialControlAlgorithmObject ->moveToThread(mySerialThread );
            mySerialThread ->start();
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        • SGaistS SGaist

          How are you putting SenSerialControlAlgorithmObject in a QThread ?

          S Offline
          S Offline
          Sen Li
          wrote on last edited by Sen Li
          #6

          @SGaist
          MainWindow:

          #include <QMainWindow>
          #include <QtSerialPort/QSerialPort>
          #include "SenConsole.h"
          #include "SenSettingsDialog.h"
          #include "SenSerialControlAlgorithmObject.h"
          
          class SenOpticalFlowSensorsMainWindow : public QMainWindow
          {
          private slots:
              void writeData(const QByteArray &data);
              void showDataInConsole(QByteArray data);
          
          signals:
              void emitOpenSerialOrder(SenSettingsDialog::Settings);
          
          private:
              Ui::SenOpticalFlowSensorsMainWindow *myMainWindow_ui;
              SenConsole *mySenConsole;
              SenSettingsDialog *mySenSettingsDialog;
          
              SenSettingsDialog::Settings mySettingInfo;
              SenSerialControlAlgorithmObject *myDefaulSerialObject;
          
              QThread *mySerialThread;
          };
          

          Constructor:

          SenOpticalFlowSensorsMainWindow::SenOpticalFlowSensorsMainWindow(QWidget *parent) :    QMainWindow(parent),
              myMainWindow_ui(new Ui::SenOpticalFlowSensorsMainWindow)
          {
              myMainWindow_ui->setupUi(this);
              mySenConsole = new SenConsole;
              setCentralWidget(mySenConsole);
          ////
              myDefaulSerialObject = new SenSerialControlAlgorithmObject();
          ////
              mySenSettingsDialog = new SenSettingsDialog;
              initActionsConnections();
          
              mySerialThread = new QThread();
          //    myDefaulSerialObject ->moveToThread(mySerialThread );
              mySerialThread ->start();
          }
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          • K Offline
            K Offline
            kuzulis
            Qt Champions 2020
            wrote on last edited by
            #7

            Just do not use the threads if you don't know how to do it.

            S 1 Reply Last reply
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            • K kuzulis

              Just do not use the threads if you don't know how to do it.

              S Offline
              S Offline
              Sen Li
              wrote on last edited by
              #8

              @kuzulis
              So is it impossible to do multi-Terminal in Qt?

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              • SGaistS Offline
                SGaistS Offline
                SGaist
                Lifetime Qt Champion
                wrote on last edited by
                #9

                No it's not impossible, however thread programming is a complex matter where it's very very very easy to shoot yourself in the foot.

                One guess: your actual QSerialPort doesn't have a parent, so when your move myDefaultSerialObject, the serial port itself is not moved.

                Interested in AI ? www.idiap.ch
                Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                • SGaistS SGaist

                  No it's not impossible, however thread programming is a complex matter where it's very very very easy to shoot yourself in the foot.

                  One guess: your actual QSerialPort doesn't have a parent, so when your move myDefaultSerialObject, the serial port itself is not moved.

                  S Offline
                  S Offline
                  Sen Li
                  wrote on last edited by Sen Li
                  #10

                  @SGaist

                  QWinEventNotifier: Event notifiers cannot be enabled or disabled from another thread

                  I appreciate your guessing, however the application output reminder is telling something failed in another thread, which means the command of

                      if (mySerialPort->open(QIODevice::ReadWrite)) {//Here is when the hint comes out
                          emit emitSerialOpenedSetting();
                          syncNumMotionsCount = 0;
                          SenMotionByteArray.clear();
                          debugError = false;
                      } else {
                          emit emitSerialOpenErrorSetting(mySerialPort->errorString());
                      }
                  

                  failed in another thread instead of main thread.

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                  • S Offline
                    S Offline
                    Sen Li
                    wrote on last edited by
                    #11

                    Although it is not allowed to open/close QSerialPort in a new thread, I can open/close it in the main thread, and push it into the new thread after it is opened.

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                    • K Offline
                      K Offline
                      kuzulis
                      Qt Champions 2020
                      wrote on last edited by
                      #12

                      Although it is not allowed to open/close QSerialPort in a new thread,

                      It is not true. There are no differences in from what a thread to do open/close. A main things is that the QSerialPort should be moved into another thread before than opened/closed/read/write on it and so on. Besides, this should be called in that thread to which the QSerialPort was moved (not from the main thread or any others).

                      And I do not understand what is reason to use a more than one thread.. Because you can handle a data from the several serial ports (sensors) from the one main thread "simultaneous".

                      S 1 Reply Last reply
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                      • K kuzulis

                        Although it is not allowed to open/close QSerialPort in a new thread,

                        It is not true. There are no differences in from what a thread to do open/close. A main things is that the QSerialPort should be moved into another thread before than opened/closed/read/write on it and so on. Besides, this should be called in that thread to which the QSerialPort was moved (not from the main thread or any others).

                        And I do not understand what is reason to use a more than one thread.. Because you can handle a data from the several serial ports (sensors) from the one main thread "simultaneous".

                        S Offline
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                        Sen Li
                        wrote on last edited by
                        #13

                        @kuzulis

                        That is also what I do not understand.

                        However, the truth is:
                        QWinEventNotifier: Event notifiers cannot be enabled or disabled from another thread

                        and how will you explain this when it comes to open/close QSerialPort?

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                        • S Offline
                          S Offline
                          Sen Li
                          wrote on last edited by
                          #14

                          It seems that, there is no way to push the Object, which contains QSerialPort, back to main thread and then close QSerialPort.

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                          • K Offline
                            K Offline
                            kuzulis
                            Qt Champions 2020
                            wrote on last edited by
                            #15

                            That is also what I do not understand.

                            What do you don't understand?

                            I once again will repeat: simply don't use the threads, if no reason for this! (in your case there are is no any reason)

                            QWinEventNotifier: Event notifiers cannot be enabled or disabled from another thread

                            Obviously, you do something wrong: all methods of QSerialPort shall be called from the same thread in which an QSerialPort lives.

                            It seems that, there is no way to push the Object, which contains QSerialPort, back to main thread and then close QSerialPort.

                            WTF?

                            S 1 Reply Last reply
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                            • K kuzulis

                              That is also what I do not understand.

                              What do you don't understand?

                              I once again will repeat: simply don't use the threads, if no reason for this! (in your case there are is no any reason)

                              QWinEventNotifier: Event notifiers cannot be enabled or disabled from another thread

                              Obviously, you do something wrong: all methods of QSerialPort shall be called from the same thread in which an QSerialPort lives.

                              It seems that, there is no way to push the Object, which contains QSerialPort, back to main thread and then close QSerialPort.

                              WTF?

                              S Offline
                              S Offline
                              Sen Li
                              wrote on last edited by Sen Li
                              #16

                              @kuzulis
                              I don't understand what's wrong with my codes; it doesn't work anyway to open/close QSerialPort in a new thread.

                              I made it in main thread, no problem without putting the Serial Communication Control in a new thread; however, is that possible to do multiple serial threads?

                              Two reasons to do threads:

                              1. To make it as fast as possible;
                              2. Learn my bug in programming: I do not want to encounter the same bug again.
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                              • SGaistS Offline
                                SGaistS Offline
                                SGaist
                                Lifetime Qt Champion
                                wrote on last edited by SGaist
                                #17

                                @Sen-Li

                                Threads are not always the way to make a program go faster. In some cases performance can be worse with threads. Qt's asynchronous nature allows to avoid usage of thread for most of the cases and generally serial port can be handled in the GUI thread without problem.

                                Interested in AI ? www.idiap.ch
                                Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                                S 1 Reply Last reply
                                0
                                • SGaistS SGaist

                                  @Sen-Li

                                  Threads are not always the way to make a program go faster. In some cases performance can be worse with threads. Qt's asynchronous nature allows to avoid usage of thread for most of the cases and generally serial port can be handled in the GUI thread without problem.

                                  S Offline
                                  S Offline
                                  Sen Li
                                  wrote on last edited by
                                  #18

                                  @SGaist

                                  Thank you very much for your tips!
                                  I probably should give up on the serial thread. It is beyond my ability to play with that problem.

                                  1 Reply Last reply
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