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Replace STDIN with a Serial port

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  • SGaistS Offline
    SGaistS Offline
    SGaist
    Lifetime Qt Champion
    wrote on last edited by
    #4

    It will offer you an easier more integrated way to get the data from your serial ports. From there you can create and post key events to the event loop and have them processed like it would come from a standard keyboard

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    • E Offline
      E Offline
      Epileftric
      wrote on last edited by
      #5

      From there you can create and post key events to the event loop

      Something like this?

      @
      QSerialPort *keypad= new QSerialPort("/dev/ttyS7", (QObject *)my_gui);
      @

      And that's it? How do I manually connect the signals from the port to my gui?

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      • SGaistS Offline
        SGaistS Offline
        SGaist
        Lifetime Qt Champion
        wrote on last edited by
        #6

        You should rather write a little class that represent that keypad and have the QSerialPort in there. You'll connect that class to your GUI to keep things cleanly separated.

        On a side note, QWidget is a QObject so there's no need to cast. Furthermore, never use c style cast with QObject derived class, use qobject_cast.

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        • mrdebugM Offline
          mrdebugM Offline
          mrdebug
          wrote on last edited by
          #7

          It' very easy to do. I know and use Olimex A20 with serial devices and graphic interaction.
          I suggest you to write a class based on QSerialPort and implement events on special data.
          If you want I can to it for you.

          Which kind of hardware do you use?

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          www.denisgottardello.it
          GMT+1
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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.

              Need programmers to hire?
              www.labcsp.com
              www.denisgottardello.it
              GMT+1
              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.

                  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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                  • 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

                      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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                      • 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.

                          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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                          • 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

                              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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                              • 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

                                    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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