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Serial Port configuration in RHEL

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  • mrjjM mrjj

    @Nimika
    Hi.
    ok. With 5.7 it should just work if you have
    QT += serialport in .pro file.

    -Is there anything to write inside version control or in kit option?
    No. Its just a c++ class.

    Did you try the terminal sample?

    N Offline
    N Offline
    Nimika
    wrote on last edited by
    #5

    @mrjj
    Hello
    Thanks for reply.
    I have added it in my pro file but still can't open it.

    mrjjM 1 Reply Last reply
    0
    • N Nimika

      @mrjj
      Hello
      Thanks for reply.
      I have added it in my pro file but still can't open it.

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

      @Nimika said in Serial Port configuration in RHEL:

      still can't open it.

      Well did u try the Terminal sample and try it there?
      Can it list and see your ports?

      N 1 Reply Last reply
      1
      • mrjjM mrjj

        @Nimika said in Serial Port configuration in RHEL:

        still can't open it.

        Well did u try the Terminal sample and try it there?
        Can it list and see your ports?

        N Offline
        N Offline
        Nimika
        wrote on last edited by
        #7

        @mrjj yeah its working but not showing any serial port which I have installed using my card.
        This is my program and its output----

        #include <stdio.h>
        #include <QObject>
        #include <QtSerialPort/QSerialPort>
        #include <QSerialPortInfo>
        #include <string.h>
        #include <QTextStream>
        #include <QCoreApplication>
        #include <QStringList>
        #include <iostream>
        #include <QDebug>
        
        using namespace std;
        
        
        
        
        
        QT_USE_NAMESPACE
        int main(int argc, char *argv[])
        {
            QCoreApplication a(argc, argv);
        
            // Example use QSerialPortInfo
           foreach (const QSerialPortInfo &info, QSerialPortInfo::availablePorts()) {
                qDebug() << "Name : " << info.portName();
                qDebug() << "Description : " << info.description();
                qDebug() << "Manufacturer: " << info.manufacturer();
        
                // Example use QSerialPort
                QSerialPort serial;
                serial.setPortName("ttyM0");
                qDebug() << "Name:" << serial.portName();
               //serial.setPort(info);
               QIODevice::OpenMode mode = QIODevice::ReadOnly | QIODevice::Unbuffered;
               if(serial.open(mode))
                   qDebug() << "port connected";
               if (serial.isOpen() && serial.isWritable())
               {
               qDebug() << "Serial is open";
               serial.close();
            }
        
            return a.exec();
        }
        }
        

        output is:
        Name : "ttyS0"
        Description : ""
        Manufacturer: ""
        Name: "ttyM0"

        ``

        1 Reply Last reply
        0
        • SGaistS Offline
          SGaistS Offline
          SGaist
          Lifetime Qt Champion
          wrote on last edited by
          #8

          Hi and welcome to devnet,

          Does your user have the rights to access that device ?

          Call ls -la /dev/ttyS0 to see who can access it.

          Your user is likely not in the group that can access the serial port. If that's indeed the case, add your user to that group and logout/login. You should then be able to access the device.

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

          1 Reply Last reply
          2
          • N Offline
            N Offline
            Nimika
            wrote on last edited by
            #9

            how will I get to know wo is accessing that device?
            how can I add the user to the group which you have specified.

            jsulmJ 1 Reply Last reply
            0
            • N Nimika

              how will I get to know wo is accessing that device?
              how can I add the user to the group which you have specified.

              jsulmJ Offline
              jsulmJ Offline
              jsulm
              Lifetime Qt Champion
              wrote on last edited by
              #10

              @Nimika The user using your application needs access right for /dev/ttyS0.
              If you execute the command @SGaist provided you you will see who has access. Check which group is set for that device. Then add yourself to this group (see /etc/group file).

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

              N 1 Reply Last reply
              1
              • jsulmJ jsulm

                @Nimika The user using your application needs access right for /dev/ttyS0.
                If you execute the command @SGaist provided you you will see who has access. Check which group is set for that device. Then add yourself to this group (see /etc/group file).

                N Offline
                N Offline
                Nimika
                wrote on last edited by
                #11

                @jsulm Hey thanks!
                I am getting this after writing the calling function ls -la /dev/ttyS0:
                crw-rw----. 1 root dialout 4, 64 Oct 7 10:35 /dev/ttyS0

                What does it mean?

                jsulmJ 1 Reply Last reply
                0
                • N Nimika

                  @jsulm Hey thanks!
                  I am getting this after writing the calling function ls -la /dev/ttyS0:
                  crw-rw----. 1 root dialout 4, 64 Oct 7 10:35 /dev/ttyS0

                  What does it mean?

                  jsulmJ Offline
                  jsulmJ Offline
                  jsulm
                  Lifetime Qt Champion
                  wrote on last edited by
                  #12

                  @Nimika That means that user root and group dialout have read/write access, nobody else have any access.
                  So you either start your app as root, or (much better) add the user you're using (hopefully not root) to the group dialout.

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

                  1 Reply Last reply
                  0
                  • SGaistS Offline
                    SGaistS Offline
                    SGaist
                    Lifetime Qt Champion
                    wrote on last edited by
                    #13

                    NEVER EVER use root like that. All the more when developing. It's bad practice and doing so you're opening a gaping security hole.

                    Add your normal user to the dialout group and be done with it.

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

                    N 1 Reply Last reply
                    2
                    • N Offline
                      N Offline
                      Nimika
                      wrote on last edited by
                      #14

                      Thankyou both of you.
                      Please tell me how to add my normal user to the dialout group?
                      What is dialout group?

                      mrjjM jsulmJ 2 Replies Last reply
                      1
                      • K Offline
                        K Offline
                        kuzulis
                        Qt Champions 2020
                        wrote on last edited by
                        #15

                        QIODevice::OpenMode mode = QIODevice::ReadOnly | QIODevice::Unbuffered;

                        Did you read documentation? QIODevice::Unbuffered it is unsupported mode.

                        N 1 Reply Last reply
                        1
                        • K kuzulis

                          QIODevice::OpenMode mode = QIODevice::ReadOnly | QIODevice::Unbuffered;

                          Did you read documentation? QIODevice::Unbuffered it is unsupported mode.

                          N Offline
                          N Offline
                          Nimika
                          wrote on last edited by
                          #16

                          @kuzulis Yeah I made it as comment.

                          1 Reply Last reply
                          0
                          • N Nimika

                            Thankyou both of you.
                            Please tell me how to add my normal user to the dialout group?
                            What is dialout group?

                            mrjjM Offline
                            mrjjM Offline
                            mrjj
                            Lifetime Qt Champion
                            wrote on last edited by mrjj
                            #17

                            @Nimika

                            • Please tell me how to add my normal user to the dialout group?
                              sudo usermod -a -G dialout theuser

                            • What is dialout group?
                              Its a predefined group found in many distros.
                              From old times it was used to allowed modems
                              to make connection etc. ( ie allow the user to connect to the internet :)

                            So often the system has this group and any user in it, have access to /dev/ttySX

                            N 1 Reply Last reply
                            1
                            • N Nimika

                              Thankyou both of you.
                              Please tell me how to add my normal user to the dialout group?
                              What is dialout group?

                              jsulmJ Offline
                              jsulmJ Offline
                              jsulm
                              Lifetime Qt Champion
                              wrote on last edited by
                              #18

                              @Nimika You really should learn how user/groups and access rights management is working on UNIX/Linux.

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

                              1 Reply Last reply
                              1
                              • N Offline
                                N Offline
                                Nimika
                                wrote on last edited by
                                #19

                                @jsulm Actually my system is Red Hat Enterprise Linux based so it is different to use its commands.

                                1 Reply Last reply
                                0
                                • mrjjM mrjj

                                  @Nimika

                                  • Please tell me how to add my normal user to the dialout group?
                                    sudo usermod -a -G dialout theuser

                                  • What is dialout group?
                                    Its a predefined group found in many distros.
                                    From old times it was used to allowed modems
                                    to make connection etc. ( ie allow the user to connect to the internet :)

                                  So often the system has this group and any user in it, have access to /dev/ttySX

                                  N Offline
                                  N Offline
                                  Nimika
                                  wrote on last edited by
                                  #20

                                  @mrjj Thank you !! let me add it now and search whether it will work or not.....

                                  mrjjM 1 Reply Last reply
                                  0
                                  • N Nimika

                                    @mrjj Thank you !! let me add it now and search whether it will work or not.....

                                    mrjjM Offline
                                    mrjjM Offline
                                    mrjj
                                    Lifetime Qt Champion
                                    wrote on last edited by mrjj
                                    #21

                                    @Nimika
                                    Np. as far as I can see it's the same for Red Hat with ttySX access, so there is
                                    tons on google on the topic on allowing user X to read and write to /dev/ttSxxx
                                    stuff.
                                    http://ithelpblog.com/os/linux/bashandscripts/howto-add-user-to-group-on-linux-redhat-rhel-centos-fedora/

                                    1 Reply Last reply
                                    1
                                    • SGaistS SGaist

                                      NEVER EVER use root like that. All the more when developing. It's bad practice and doing so you're opening a gaping security hole.

                                      Add your normal user to the dialout group and be done with it.

                                      N Offline
                                      N Offline
                                      Nimika
                                      wrote on last edited by
                                      #22

                                      @SGaist Can I use serial ports to any user other than root?

                                      mrjjM 1 Reply Last reply
                                      0
                                      • N Nimika

                                        @SGaist Can I use serial ports to any user other than root?

                                        mrjjM Offline
                                        mrjjM Offline
                                        mrjj
                                        Lifetime Qt Champion
                                        wrote on last edited by mrjj
                                        #23

                                        @Nimika
                                        Hi
                                        Any user can be granted access to /dev/X devices.
                                        Often it is done via the dialout group as its already assigned to serial devices such as ttyS0 and
                                        any user that is member of that group can use it.
                                        so often
                                        sudo adduser TheUserName dialout
                                        and and reboot is all that is needed.
                                        Adding user to group might have slightly different syntax on RH but concept and rights are 100% the same.:)
                                        http://websistent.com/fix-serial-port-permission-denied-errors-linux/

                                        N jsulmJ 2 Replies Last reply
                                        0
                                        • mrjjM mrjj

                                          @Nimika
                                          Hi
                                          Any user can be granted access to /dev/X devices.
                                          Often it is done via the dialout group as its already assigned to serial devices such as ttyS0 and
                                          any user that is member of that group can use it.
                                          so often
                                          sudo adduser TheUserName dialout
                                          and and reboot is all that is needed.
                                          Adding user to group might have slightly different syntax on RH but concept and rights are 100% the same.:)
                                          http://websistent.com/fix-serial-port-permission-denied-errors-linux/

                                          N Offline
                                          N Offline
                                          Nimika
                                          wrote on last edited by
                                          #24

                                          @mrjj Thanks let me try it.

                                          1 Reply Last reply
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