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Cannot output a value using QSerialPort

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  • SGaistS SGaist

    How did you test that ?

    As for the call to open: again, always check that it succeeded. You might be trying to use an already opened device or you don't have the rights to open said device. Therefore, add that check before going further.

    J Offline
    J Offline
    jude.bato
    wrote on last edited by
    #25

    @SGaist I have

    Dialog::~Dialog()
    {
        if(arduino->isOpen())
        {
            arduino->close();
        }
        delete ui;
    }
    

    Would this satisfy the QSerialPort::open()?

    Also would I need to use connect? I change that line to just readSerial(); but I'm not able to implement void Dialog::updateVoltage(QString sensor_reading) into if(arduino_is_available)

    jsulmJ 1 Reply Last reply
    0
    • J jude.bato

      @SGaist I have

      Dialog::~Dialog()
      {
          if(arduino->isOpen())
          {
              arduino->close();
          }
          delete ui;
      }
      

      Would this satisfy the QSerialPort::open()?

      Also would I need to use connect? I change that line to just readSerial(); but I'm not able to implement void Dialog::updateVoltage(QString sensor_reading) into if(arduino_is_available)

      jsulmJ Offline
      jsulmJ Offline
      jsulm
      Lifetime Qt Champion
      wrote on last edited by jsulm
      #26

      @jude-bato said in Cannot output a value using QSerialPort:

      Would this satisfy the QSerialPort::open()?

      Of course not, it does not have anything to do with open().

      if(!arduino->open(QSerialPort::ReadOnly)) {
          qDebug() << "Opening serial port failed";
          qDebug() << arduino->error() << arduino->errorString();
      }
      

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

      J 1 Reply Last reply
      5
      • jsulmJ jsulm

        @jude-bato said in Cannot output a value using QSerialPort:

        Would this satisfy the QSerialPort::open()?

        Of course not, it does not have anything to do with open().

        if(!arduino->open(QSerialPort::ReadOnly)) {
            qDebug() << "Opening serial port failed";
            qDebug() << arduino->error() << arduino->errorString();
        }
        
        J Offline
        J Offline
        jude.bato
        wrote on last edited by
        #27

        @jsulm Thank you for your suggestion, I put in your code and I ran it again. This is what I got:1.png I'm so confused why my program isn't working correctly. I have a feeling that my problem has to do with reading from or something with making a connection with Arduino rather than the Serial Port itself.

        Pablo J. RoginaP jsulmJ 2 Replies Last reply
        0
        • J jude.bato

          @jsulm Thank you for your suggestion, I put in your code and I ran it again. This is what I got:1.png I'm so confused why my program isn't working correctly. I have a feeling that my problem has to do with reading from or something with making a connection with Arduino rather than the Serial Port itself.

          Pablo J. RoginaP Offline
          Pablo J. RoginaP Offline
          Pablo J. Rogina
          wrote on last edited by
          #28

          @jude-bato

          First: please don't post screenshots, paste the text itself. It's easier for others to copy/paste/reply to that!

          Device is already open

          Have you seen this message?
          What do you think about that? My bet is that you also have other program (i.e. Arduino IDE) connected to your device...

          Upvote the answer(s) that helped you solve the issue
          Use "Topic Tools" button to mark your post as Solved
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          J 1 Reply Last reply
          4
          • J jude.bato

            @jsulm Thank you for your suggestion, I put in your code and I ran it again. This is what I got:1.png I'm so confused why my program isn't working correctly. I have a feeling that my problem has to do with reading from or something with making a connection with Arduino rather than the Serial Port itself.

            jsulmJ Offline
            jsulmJ Offline
            jsulm
            Lifetime Qt Champion
            wrote on last edited by
            #29

            @jude-bato Exactly what @SGaist was suggesting

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

            1 Reply Last reply
            2
            • Pablo J. RoginaP Pablo J. Rogina

              @jude-bato

              First: please don't post screenshots, paste the text itself. It's easier for others to copy/paste/reply to that!

              Device is already open

              Have you seen this message?
              What do you think about that? My bet is that you also have other program (i.e. Arduino IDE) connected to your device...

              J Offline
              J Offline
              jude.bato
              wrote on last edited by
              #30

              @Pablo-J-Rogina I have an Arduino Uno connected via USB, that's my original point in making the forum post is because I am unable to capture a voltage in Qt from it. I have it stated in my original post.

              Pablo J. RoginaP 1 Reply Last reply
              0
              • J jude.bato

                @Pablo-J-Rogina I have an Arduino Uno connected via USB, that's my original point in making the forum post is because I am unable to capture a voltage in Qt from it. I have it stated in my original post.

                Pablo J. RoginaP Offline
                Pablo J. RoginaP Offline
                Pablo J. Rogina
                wrote on last edited by
                #31

                @jude-bato said in Cannot output a value using QSerialPort:

                I have an Arduino Uno connected via USB,

                Yes, I assumed that. What you should know, if not aware yet, is that you cannot have two applications (i.e. your Qt app and the Arduino IDE) using the same port simultaneously

                Upvote the answer(s) that helped you solve the issue
                Use "Topic Tools" button to mark your post as Solved
                Add screenshots via postimage.org
                Don't ask support requests via chat/PM. Please use the forum so others can benefit from the solution in the future

                J 1 Reply Last reply
                3
                • Pablo J. RoginaP Pablo J. Rogina

                  @jude-bato said in Cannot output a value using QSerialPort:

                  I have an Arduino Uno connected via USB,

                  Yes, I assumed that. What you should know, if not aware yet, is that you cannot have two applications (i.e. your Qt app and the Arduino IDE) using the same port simultaneously

                  J Offline
                  J Offline
                  jude.bato
                  wrote on last edited by
                  #32

                  @Pablo-J-Rogina So how can I just read voltage from my Arduino Uno in Qt

                  Pablo J. RoginaP 1 Reply Last reply
                  0
                  • J jude.bato

                    @Pablo-J-Rogina So how can I just read voltage from my Arduino Uno in Qt

                    Pablo J. RoginaP Offline
                    Pablo J. RoginaP Offline
                    Pablo J. Rogina
                    wrote on last edited by
                    #33

                    @jude-bato said in Cannot output a value using QSerialPort:

                    So how can I just read voltage from my Arduino Uno in Qt

                    Since you haven't describe your environment/use case so far, I'll assume that you have a program running on the Arduino board, and that program reads some sensor and it outputs such readings via serial.

                    So with that assumption, I expect you to go through something like this:

                    1. Write the Arduino code, and via Arduino IDE deploy it on your Arduino device
                    2. Close the Arduino IDE
                    3. Start Qt Creator and write a Qt application that will read the serial port and display the readings on screen
                    4. Run your Qt application
                    5. Success!

                    Upvote the answer(s) that helped you solve the issue
                    Use "Topic Tools" button to mark your post as Solved
                    Add screenshots via postimage.org
                    Don't ask support requests via chat/PM. Please use the forum so others can benefit from the solution in the future

                    J 1 Reply Last reply
                    2
                    • Pablo J. RoginaP Pablo J. Rogina

                      @jude-bato said in Cannot output a value using QSerialPort:

                      So how can I just read voltage from my Arduino Uno in Qt

                      Since you haven't describe your environment/use case so far, I'll assume that you have a program running on the Arduino board, and that program reads some sensor and it outputs such readings via serial.

                      So with that assumption, I expect you to go through something like this:

                      1. Write the Arduino code, and via Arduino IDE deploy it on your Arduino device
                      2. Close the Arduino IDE
                      3. Start Qt Creator and write a Qt application that will read the serial port and display the readings on screen
                      4. Run your Qt application
                      5. Success!
                      J Offline
                      J Offline
                      jude.bato
                      wrote on last edited by jude.bato
                      #34

                      @Pablo-J-Rogina Thats exactly what I'm trying to do. I read upon this article: https://forum.qt.io/topic/64696/sending-a-data-to-arduino-through-serial-port-using-qt and it is a similar problem to the one I'm having, for some reason Qt is not reading from the Arduino at all. It recognizes it but it's not reading from it. Here is my Arduino IDE code:

                      int offset = 20;
                      
                      void setup() 
                      {
                        Serial.begin(9600);
                      }
                      
                      void loop()
                      {
                        int volt = analogRead(A0);
                        double voltage = map(volt, 0, 1023, 0, 2500) + offset;
                      
                        voltage /= 100;
                        Serial.print("Voltage: ");
                        Serial.print(voltage);
                        Serial.println("V");
                      
                        delay(500);
                      }
                      

                      I've tried doing you recommendation but I'm having difficulties with Qt and grabbing information off Arduino.
                      Picture of Arduino working properly

                      1 Reply Last reply
                      0
                      • J Offline
                        J Offline
                        jude.bato
                        wrote on last edited by
                        #35

                        I am testing the hardware and I see that when I use the Arduino IDE or the Qt code they both work the same way and allow for a reading to happen I believe it is something to do with the GUI that I have designed that would allow for the values to be shown I will try and change it up and see if anything happens. I've been reading many many forum posts and it seems that my code is fine because it compiles and it works the same way when running the board through the IDE.

                        Pablo J. RoginaP 1 Reply Last reply
                        0
                        • J jude.bato

                          I am testing the hardware and I see that when I use the Arduino IDE or the Qt code they both work the same way and allow for a reading to happen I believe it is something to do with the GUI that I have designed that would allow for the values to be shown I will try and change it up and see if anything happens. I've been reading many many forum posts and it seems that my code is fine because it compiles and it works the same way when running the board through the IDE.

                          Pablo J. RoginaP Offline
                          Pablo J. RoginaP Offline
                          Pablo J. Rogina
                          wrote on last edited by
                          #36

                          @jude-bato I don't know why I didn't yet suggested to check with some Qt examples, anyway. What if you try building and running:
                          Command Line Reader Async Example (no GUI, just to test you are able to receive data from Arduino...)
                          Terminal "Terminal shows how to create a terminal for a simple serial interface by using Qt Serial Port."

                          Upvote the answer(s) that helped you solve the issue
                          Use "Topic Tools" button to mark your post as Solved
                          Add screenshots via postimage.org
                          Don't ask support requests via chat/PM. Please use the forum so others can benefit from the solution in the future

                          J 1 Reply Last reply
                          1
                          • Pablo J. RoginaP Pablo J. Rogina

                            @jude-bato I don't know why I didn't yet suggested to check with some Qt examples, anyway. What if you try building and running:
                            Command Line Reader Async Example (no GUI, just to test you are able to receive data from Arduino...)
                            Terminal "Terminal shows how to create a terminal for a simple serial interface by using Qt Serial Port."

                            J Offline
                            J Offline
                            jude.bato
                            wrote on last edited by
                            #37

                            @Pablo-J-Rogina I ran the example and the Application Output I got was:

                            16:00:11: Running steps for project creaderasync...
                            16:00:11: Configuration unchanged, skipping qmake step.
                            16:00:11: Starting: "C:\Qt\Tools\mingw730_32\bin\mingw32-make.exe" -j8
                            C:/Qt/Tools/mingw730_32/bin/mingw32-make -f Makefile.Debug
                            mingw32-make[1]: Entering directory 'C:/Qt/Examples/Qt-5.12.6/serialport/build-creaderasync-Desktop_Qt_5_12_6_MinGW_32_bit-Debug'
                            mingw32-make[1]: Nothing to be done for 'first'.
                            mingw32-make[1]: Leaving directory 'C:/Qt/Examples/Qt-5.12.6/serialport/build-creaderasync-Desktop_Qt_5_12_6_MinGW_32_bit-Debug'
                            16:00:12: The process "C:\Qt\Tools\mingw730_32\bin\mingw32-make.exe" exited normally.
                            16:00:12: Elapsed time: 00:01.
                            

                            Example Output
                            I'm not sure of the result this is a little foreign to me.

                            Looking back on my code I figured something out. When I have

                             if(arduino_is_available)
                                {
                                    qDebug()<<"Found the port \n";
                                    arduino->setPortName(arduino_uno_port_name);
                                    arduino->open(QSerialPort::ReadOnly);
                                    arduino->setBaudRate(QSerialPort::Baud9600);
                                    arduino->setDataBits(QSerialPort::Data8);
                                    arduino->setFlowControl(QSerialPort::NoFlowControl);
                                    arduino->setParity(QSerialPort::NoParity);
                                    arduino->setStopBits(QSerialPort::OneStop);
                                    QSerialPort::connect(arduino, &QSerialPort::readyRead, this, &Dialog::readSerial);
                                } else {
                                    qDebug()<<"Could not find the correct port \n";
                                    QMessageBox::information(this,"Serial Port Error", "Could not open the serial port");
                                }
                            

                            I also have:

                            void Dialog::updateVoltage(QString sensor_reading)
                            {
                                ui->voltagelcdNumber->display(sensor_reading);
                            }
                            

                            which is never called. And when I tried to call it in the previous code I get the error:

                            too few arguments to function call, expected 1, have 0
                            

                            If I am able to implement the update voltage into my previous code I believe it will work. My issue now is how am I supposed to get around this error. When I hover over it, it says it requires a QString, I have tried everything to try and get around this error.

                            Pablo J. RoginaP 1 Reply Last reply
                            0
                            • J jude.bato

                              @Pablo-J-Rogina I ran the example and the Application Output I got was:

                              16:00:11: Running steps for project creaderasync...
                              16:00:11: Configuration unchanged, skipping qmake step.
                              16:00:11: Starting: "C:\Qt\Tools\mingw730_32\bin\mingw32-make.exe" -j8
                              C:/Qt/Tools/mingw730_32/bin/mingw32-make -f Makefile.Debug
                              mingw32-make[1]: Entering directory 'C:/Qt/Examples/Qt-5.12.6/serialport/build-creaderasync-Desktop_Qt_5_12_6_MinGW_32_bit-Debug'
                              mingw32-make[1]: Nothing to be done for 'first'.
                              mingw32-make[1]: Leaving directory 'C:/Qt/Examples/Qt-5.12.6/serialport/build-creaderasync-Desktop_Qt_5_12_6_MinGW_32_bit-Debug'
                              16:00:12: The process "C:\Qt\Tools\mingw730_32\bin\mingw32-make.exe" exited normally.
                              16:00:12: Elapsed time: 00:01.
                              

                              Example Output
                              I'm not sure of the result this is a little foreign to me.

                              Looking back on my code I figured something out. When I have

                               if(arduino_is_available)
                                  {
                                      qDebug()<<"Found the port \n";
                                      arduino->setPortName(arduino_uno_port_name);
                                      arduino->open(QSerialPort::ReadOnly);
                                      arduino->setBaudRate(QSerialPort::Baud9600);
                                      arduino->setDataBits(QSerialPort::Data8);
                                      arduino->setFlowControl(QSerialPort::NoFlowControl);
                                      arduino->setParity(QSerialPort::NoParity);
                                      arduino->setStopBits(QSerialPort::OneStop);
                                      QSerialPort::connect(arduino, &QSerialPort::readyRead, this, &Dialog::readSerial);
                                  } else {
                                      qDebug()<<"Could not find the correct port \n";
                                      QMessageBox::information(this,"Serial Port Error", "Could not open the serial port");
                                  }
                              

                              I also have:

                              void Dialog::updateVoltage(QString sensor_reading)
                              {
                                  ui->voltagelcdNumber->display(sensor_reading);
                              }
                              

                              which is never called. And when I tried to call it in the previous code I get the error:

                              too few arguments to function call, expected 1, have 0
                              

                              If I am able to implement the update voltage into my previous code I believe it will work. My issue now is how am I supposed to get around this error. When I hover over it, it says it requires a QString, I have tried everything to try and get around this error.

                              Pablo J. RoginaP Offline
                              Pablo J. RoginaP Offline
                              Pablo J. Rogina
                              wrote on last edited by
                              #38

                              @jude-bato said in Cannot output a value using QSerialPort:

                              I'm not sure of the result this is a little foreign to me.

                              Sorry but it's evident that you don't read the documentation...
                              When running the command line example, please check the arguments it needs...

                              Upvote the answer(s) that helped you solve the issue
                              Use "Topic Tools" button to mark your post as Solved
                              Add screenshots via postimage.org
                              Don't ask support requests via chat/PM. Please use the forum so others can benefit from the solution in the future

                              1 Reply Last reply
                              2
                              • mrjjM Offline
                                mrjjM Offline
                                mrjj
                                Lifetime Qt Champion
                                wrote on last edited by
                                #39

                                Hi
                                Why not try the same
                                https://doc.qt.io/qt-5/qtserialport-terminal-example.html
                                as @Pablo-J-Rogina linked to ?
                                Its a littel serial comm GUI that can easy open a serial port and
                                read and write to it.
                                Very good for testing out if the Arduino responds as expected.

                                J 1 Reply Last reply
                                1
                                • mrjjM mrjj

                                  Hi
                                  Why not try the same
                                  https://doc.qt.io/qt-5/qtserialport-terminal-example.html
                                  as @Pablo-J-Rogina linked to ?
                                  Its a littel serial comm GUI that can easy open a serial port and
                                  read and write to it.
                                  Very good for testing out if the Arduino responds as expected.

                                  J Offline
                                  J Offline
                                  jude.bato
                                  wrote on last edited by
                                  #40

                                  @mrjj @Pablo-J-Rogina I ran both examples and since this is my first Qt project I'm not exactly sure what I'm looking for. I have attached my results.
                                  Simple Terminal
                                  I know that my Arduino works already because I have tested it in the Arduino IDE as well as when I am debugging my code. I already know that everything works, my issue is just being able to display it. That second example is similar to what I want to do expect having my own GUI. Many thanks for all the responses thus far!

                                  Pablo J. RoginaP 1 Reply Last reply
                                  0
                                  • mrjjM Offline
                                    mrjjM Offline
                                    mrjj
                                    Lifetime Qt Champion
                                    wrote on last edited by
                                    #41

                                    Hi
                                    Ok super. so it works.
                                    You are not showing complete code so hard to guess.
                                    QSerialPort::connect(arduino, &QSerialPort::readyRead, this, &Dialog::readSerial);
                                    This looks fine

                                    So in
                                    Dialog::readSerial

                                    you call updateVoltage( yourbuffer )

                                    Or when is that called ?

                                    Im not sure where "too few arguments to function call, expected 1, have 0" comes
                                    but it sounds like you called updateVoltage without its qstring.

                                    J 1 Reply Last reply
                                    1
                                    • J jude.bato

                                      @mrjj @Pablo-J-Rogina I ran both examples and since this is my first Qt project I'm not exactly sure what I'm looking for. I have attached my results.
                                      Simple Terminal
                                      I know that my Arduino works already because I have tested it in the Arduino IDE as well as when I am debugging my code. I already know that everything works, my issue is just being able to display it. That second example is similar to what I want to do expect having my own GUI. Many thanks for all the responses thus far!

                                      Pablo J. RoginaP Offline
                                      Pablo J. RoginaP Offline
                                      Pablo J. Rogina
                                      wrote on last edited by
                                      #42

                                      @jude-bato said in Cannot output a value using QSerialPort:

                                      I'm not exactly sure what I'm looking for

                                      If guessing, to write a Qt app that can connect to your Arduino device and display information sent from it via the serial port.

                                      So your next steps would be to use the Simple Terminal example as a reference to check what you need to do in order to open the port, check for errors, how to connect signal and slots, etc.

                                      Upvote the answer(s) that helped you solve the issue
                                      Use "Topic Tools" button to mark your post as Solved
                                      Add screenshots via postimage.org
                                      Don't ask support requests via chat/PM. Please use the forum so others can benefit from the solution in the future

                                      1 Reply Last reply
                                      2
                                      • mrjjM mrjj

                                        Hi
                                        Ok super. so it works.
                                        You are not showing complete code so hard to guess.
                                        QSerialPort::connect(arduino, &QSerialPort::readyRead, this, &Dialog::readSerial);
                                        This looks fine

                                        So in
                                        Dialog::readSerial

                                        you call updateVoltage( yourbuffer )

                                        Or when is that called ?

                                        Im not sure where "too few arguments to function call, expected 1, have 0" comes
                                        but it sounds like you called updateVoltage without its qstring.

                                        J Offline
                                        J Offline
                                        jude.bato
                                        wrote on last edited by
                                        #43

                                        @mrjj This is the full code:

                                        #include "dialog.h"
                                        #include "ui_dialog.h"
                                        #include <iostream>
                                        #include <QSerialPort>
                                        #include <QSerialPortInfo>
                                        #include <string>
                                        #include <QDebug>
                                        #include <QMessageBox>
                                        
                                        Dialog::Dialog(QWidget *parent) :
                                            QDialog(parent),
                                            ui(new Ui::Dialog)
                                        {
                                            ui->setupUi(this);
                                            ui->voltagelcdNumber->display("0.00");
                                            arduino = new QSerialPort(this);
                                            serialBuffer = "";
                                            parsed_data = "";
                                            voltage_value = 0.0;
                                        
                                            bool arduino_is_available = false;
                                            QString arduino_uno_port_name;
                                            foreach(const QSerialPortInfo &serialPortInfo, QSerialPortInfo::availablePorts()){
                                                if(serialPortInfo.hasProductIdentifier() && serialPortInfo.hasVendorIdentifier()){
                                                    if((serialPortInfo.productIdentifier() == arduino_uno_product_id) && (serialPortInfo.vendorIdentifier() == arduino_uno_vendor_id)){
                                                        arduino_is_available = true;
                                                        arduino_uno_port_name = serialPortInfo.portName();
                                                    }
                                                }
                                            }
                                        
                                            if(arduino_is_available)
                                            {
                                                qDebug()<<"Found the port \n";
                                                arduino->setPortName(arduino_uno_port_name);
                                                arduino->open(QSerialPort::ReadOnly);
                                                arduino->setBaudRate(QSerialPort::Baud9600);
                                                arduino->setDataBits(QSerialPort::Data8);
                                                arduino->setFlowControl(QSerialPort::NoFlowControl);
                                                arduino->setParity(QSerialPort::NoParity);
                                                arduino->setStopBits(QSerialPort::OneStop);
                                                QSerialPort::connect(arduino, &QSerialPort::readyRead, this, &Dialog::readSerial);
                                                //ui->voltagelcdNumber->display(sensor_reading); Here is where I'm haveing trouble
                                            } else {
                                                qDebug()<<"Could not find the correct port \n";
                                                QMessageBox::information(this,"Serial Port Error", "Could not open the serial port");
                                            }
                                        }
                                        
                                        Dialog::~Dialog()
                                        {
                                            if(arduino->isOpen())
                                            {
                                                arduino->close();
                                            }
                                            delete ui;
                                        }
                                        
                                        void Dialog::readSerial()
                                        {
                                            QStringList buffer_split = serialBuffer.split(",");
                                            if(buffer_split.length() < 3)
                                            {
                                                serialData = arduino->readAll();
                                                serialBuffer = serialBuffer + QString::fromStdString(serialData.toStdString());
                                                serialData.clear();
                                            } else {
                                                serialBuffer = "";
                                                qDebug() << buffer_split << "\n";
                                                parsed_data = buffer_split[1];
                                                voltage_value = (parsed_data.toDouble()) - 0.1;
                                                qDebug() << "Voltage: " << voltage_value << "\n";
                                                parsed_data = QString::number(voltage_value,'g',4);
                                                Dialog::updateVoltage(parsed_data);
                                            }
                                        }
                                        
                                        void Dialog::updateVoltage(QString sensor_reading)
                                        {
                                            ui->voltagelcdNumber->display(sensor_reading);
                                        }
                                        

                                        sensor_reading is private and initialized in QString

                                        @Pablo-J-Rogina I have tested it in the simple terminal and it works, as well as working in the Arduino IDE

                                        1 Reply Last reply
                                        -1
                                        • mrjjM Offline
                                          mrjjM Offline
                                          mrjj
                                          Lifetime Qt Champion
                                          wrote on last edited by mrjj
                                          #44

                                          Hi

                                          Some notes

                                          You call setBaudRate, setDataBits etc AFTER you open port. that is wrong.
                                          must be before open!
                                          All of them. Open goes last.
                                          Actually you can :)

                                          You do not check if
                                          arduino->open(QSerialPort::ReadOnly);
                                          fails.
                                          like
                                          if ( ! arduino->open(QSerialPort::ReadOnly) ) {
                                          QMessageBox::information(this,...report error);
                                          return;
                                          }
                                          see @jsulm post !

                                          So does it ever enter into void Dialog::readSerial() ?

                                          1 Reply Last reply
                                          2

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