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Replace STDIN with a Serial port

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  • E Offline
    E Offline
    Epileftric
    wrote on last edited by
    #8

    What i'm missing is: should I create a new thread for it to monitor the serial port and create the events? or not?

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    • mrdebugM Offline
      mrdebugM Offline
      mrdebug
      wrote on last edited by
      #9

      In this case I normally use an Object based on QThread to manage the serial device. I normally add to the object the Tcp features, because sometimes the serial device can be attached with a rs232 - tct converter.
      The object has to manage the device and can emit an event at particular situations.
      For example, if you have a usb - rfid reader, when a tag will read, the object emit an event with the read tag code.

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      Skype: mrdebug

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      • E Offline
        E Offline
        Epileftric
        wrote on last edited by
        #10

        So it has to be something like this:

        @
        class Keypad : public Qthread {

        public: 
        Keypad(){
         initialize_serial_port();
         this->start();
        

        }

        private:
        QSerialPort serial;
        void run() {
           while(1) {
               serial.get_stff();
              generate_event_for_gui();
         }
        

        }
        };@

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        • SGaistS Offline
          SGaistS Offline
          SGaist
          Lifetime Qt Champion
          wrote on last edited by
          #11

          Technically, threads are not mandatory at all in this case unless you start heavy processing on the data you received.

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          Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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          • E Offline
            E Offline
            Epileftric
            wrote on last edited by
            #12

            But I don't see where and how to create a loop for the events in the GUI.

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            • SGaistS Offline
              SGaistS Offline
              SGaist
              Lifetime Qt Champion
              wrote on last edited by
              #13

              You already have an event loop after you call app.exec(). Use QSerialPort in asynchronous mode

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              Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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              • E Offline
                E Offline
                Epileftric
                wrote on last edited by
                #14

                but how do I get in that loop!?! That's what I don't get

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                • SGaistS Offline
                  SGaistS Offline
                  SGaist
                  Lifetime Qt Champion
                  wrote on last edited by
                  #15

                  You don't need to get in that loop, once app.exec is called, the loop runs. Events are sent, signals and slots activates when needed etc.

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                  Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                  • E Offline
                    E Offline
                    Epileftric
                    wrote on last edited by
                    #16

                    Yeah.. that's what I'm trying to do now. Since I can't use the serial port in a separated thread.

                    So what now? Do I have to create a signal handler for the serial?
                    I'm quite new to GUIs writing, I'm mainly a microcontroller programmer. Sorry if this are really n00b questions.

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                    • SGaistS Offline
                      SGaistS Offline
                      SGaist
                      Lifetime Qt Champion
                      wrote on last edited by
                      #17

                      I never said it won't work in a separated thread, just that it's really not needed.

                      Something like this:

                      @
                      class KeyPad :: public QObject {
                      Q_OBJECT
                      public:
                      KeyPad(QObject *parent = 0 ) :
                      QObject(parent)
                      {
                      connect(&serialPort, SIGNAL(readyRead()), SLOT(processData()));
                      }

                      bool initialize(const QString &portName)
                      {
                      serialPort.setPortName(portName);
                      // setup port

                      return serialPort.open(QIODevice::ReadWrite); // or ReadOnly if you won't write anything in it
                      

                      }

                      signals:
                      valueChanged(int newValue);

                      private slots:
                      void processData() {
                      data.append(serialPort.readAll());
                      // check if enough data is there
                      // parse data
                      // removed processed data from buffer
                      // emit signal(s)
                      }

                      private:
                      QByteArray data;
                      QSerialPort serialPort;
                      };
                      @

                      I've wrote everything in the "header" for brevity only

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                      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                      • E Offline
                        E Offline
                        Epileftric
                        wrote on last edited by
                        #18

                        @ connect(&serialPort, SIGNAL(readyRead()), SLOT(processData()));@

                        I get it now, I was doing right that as you write! SO that's what gets it in the "main event loop" right?

                        Of course you didn't said it won't work in a separated thread, but I tried just that and it didn't work because of some "can't create new thread issue"

                        THANKS A LOT!!

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                        • E Offline
                          E Offline
                          Epileftric
                          wrote on last edited by
                          #19

                          So I got it, now I can navigate the menues with the serial port as I did with the keyboard. But the only thing that's not working are text entries. Whenever I need to input some text in a QLineEdit widget it doesn't recognizes the input as a keystroke!

                          @
                          void Keypad::SerialPortHandler (void){
                          char buff;

                          serial->read(&buff,1);

                          QKeyEvent *last_key = new QKeyEvent( QEvent::KeyPress, buff , Qt::GroupSwitchModifier, QString(buff) );

                          QCoreApplication::sendEvent(pycgui,last_key);
                          }
                          @

                          I use Qt::GroupSwitchModifier only to differentiate the events I create from the real one so I can manually delete them. But it's not the reason the input is not working!

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                          • SGaistS Offline
                            SGaistS Offline
                            SGaist
                            Lifetime Qt Champion
                            wrote on last edited by
                            #20

                            AFAIK, text input requires a press and a release event

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                            Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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