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  4. [SOLVED] Qserialport in QT 5.3 running in Android !!!!
Forum Update on Monday, May 27th 2025

[SOLVED] Qserialport in QT 5.3 running in Android !!!!

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  • M Offline
    M Offline
    mr_wallyit
    wrote on last edited by
    #6

    Hello,

    this are the directory for default.
    << QStringLiteral("/var/lock")
    << QStringLiteral("/etc/locks")
    << QStringLiteral("/var/spool/locks")
    << QStringLiteral("/var/spool/uucp")
    << QStringLiteral("/tmp");

    The file system of Android is not standard, we can't write or create /var/, /tmp o write the folder looks in "/etc/locks.

    In the folder /data/ we can write because is the folder where we install the apps. In the the last build 5.3.0 of qserialport i see :
    #ifdef Q_OS_ANDROID
    << QStringLiteral("/data/local/tmp");
    #else

    So, i have tried to move the directory under /data/.
    But this it is big workaround because I have create manually the folders.
    Tomorrow i write the ticket

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    • K Offline
      K Offline
      kuzulis
      Qt Champions 2020
      wrote on last edited by
      #7

      Hmm.. then maybe Android has something other directory to contain an temporary files? This directory(es) are present on Android? Do you know?

      Because I'm not an Android expert..

      Maybe we can just to use an /data directory directly, and to write a lock file there, that not to create additional directories manually.?

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      • P Offline
        P Offline
        projetoslinux
        wrote on last edited by
        #8

        Hi mr_wallyt

        do you have sucess to serial port???
        work for you, for me not,...
        if possible send for my mail your code ???

        thanks for this.

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        • P Offline
          P Offline
          projetoslinux
          wrote on last edited by
          #9

          hi ,
          to create this folders, second mr_wallyt
          //in host with usb cable
          adb shell
          cd ..
          cd ..
          su
          #mount -o remount,rw /
          #mkdir -p /var/lock
          #mkdir -p /var/spool/locks
          #mkdir -p /var/spool/uucp
          #mkdir -p /tmp
          #mkdir -p /data/local/tmp
          #mount -o remount,rw /system
          #mkdir -p /etc/locks

          i have sucess to create folders in android, but not testing serial port...

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          • M Offline
            M Offline
            mr_wallyit
            wrote on last edited by
            #10

            Hello,

            I have created the folder on /data because the user "system " can read and write.
            Sorry but i can't know how upload an image of file system. When driver send byte on the serial port use the folder how semaphore. Have you checked the permission?

            This is a tentative to create the folder automatically in startup. It work correctly when i create the folder on /sdcard/ but don't work with /data/

            @
            QString program = "command";
            QStringList arguments;
            arguments << "mkdir"<< "/sdcard/test"

            QProcess *myProcess = new QProcess;
            myProcess->start(program, arguments);
            myProcess->waitForFinished();;
            @

            I can send source code.
            This code in my Android don't work.
            #mount -o remount,rw /

            @kuzulis
            Maybe we can just to use an /data directory directly, and to write a lock file there, that not to create additional directories manually.?

            We can try.

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            • P Offline
              P Offline
              projetoslinux
              wrote on last edited by
              #11

              Hi mr_wallyt

              thanks for send-me
              I have sucess to compile and install your qserialport
              for armv7

              i compile and testing but not work
              i write sudo chmod 777 for all folders and testing
              $touch a /data/lock etc..
              i have permission
              and when running
              have this message

              Starting remote process.E/SELinux (21549): Function: selinux_android_load_priority [0], There is no sepolicy file
              E/SELinux (21549):
              E/SELinux (21549): Function: selinux_android_load_priority , loading version is VE=SEPF_SM-N900_4.3_F023
              E/SELinux (21549):
              E/SELinux (21549):
              E/SELinux (21549): selinux_android_seapp_context_reload: seapp_contexts file is loaded from /data/security/spota/seapp_contexts

              D/OpenGLRenderer(21549): Enabling debug mode 0
              W/Qt (21549): qtudev_p.h:114 (bool resolveSymbols(QLibrary*)): Failed to load the library: udev, supported version(s): 1 and 0
              D/mali_winsys(21549): new_window_surface returns 0x3000
              W/Qt (21549): kernel/qplatformwindow.cpp:380 (virtual bool QPlatformWindow::setKeyboardGrabEnabled(bool)): This plugin does not support grabbing the keyboard
              D/Qt (21549): qserialport_unix.cpp:69 (QString serialPortLockFilePath(const QString&)): 69 qserialport_unix.cpp
              D/Qt (21549): qserialport_unix.cpp:80 (QString serialPortLockFilePath(const QString&)): 80 qserialport_unix.cpp
              W/Qt (21549): qserialport_unix.cpp:103 (QString serialPortLockFilePath(const QString&)): The following directories are not readable or writable for detaling with lock files
              W/Qt (21549):
              W/Qt (21549): qserialport_unix.cpp:105 (QString serialPortLockFilePath(const QString&)): /data/lock
              W/Qt (21549):
              W/Qt (21549): qserialport_unix.cpp:105 (QString serialPortLockFilePath(const QString&)): /data/locks
              W/Qt (21549):
              W/Qt (21549): qserialport_unix.cpp:105 (QString serialPortLockFilePath(const QString&)): /data/spool/locks
              W/Qt (21549):
              W/Qt (21549): qserialport_unix.cpp:105 (QString serialPortLockFilePath(const QString&)): /data/spool/uucp
              W/Qt (21549):
              W/Qt (21549): qserialport_unix.cpp:105 (QString serialPortLockFilePath(const QString&)): /data/tmp
              W/Qt (21549):
              W/Qt (21549): qserialport_unix.cpp:105 (QString serialPortLockFilePath(const QString&)): /data/local/tmp
              W/Qt (21549):
              W/Qt (21549): qserialport_unix.cpp:206 (bool QSerialPortPrivate::open(QIODevice::OpenMode)): Failed to create a lock file for opening the device

              when i connect terminal...

              return for me a android message permission danied OK

              testing to connect ttyGS... ttyS.. ttySAC..
              and use terminal serial port code of tq 5.3

              if possible send for dropbox your complete code to test ???

              message failed to load lib UDEV error, do you have this message ??

              you add permissions in android manifest ???

              your /dev/device use is ttyGS0 ?

              my phone is note3 rooted !!! i have permissions for sudo !!

              Sorry for all questions and thanks for this.

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              • M Offline
                M Offline
                mr_wallyit
                wrote on last edited by
                #12

                Hello,

                i thinks that we are the user "system" when the app run. I don't like create the folder manual, so i have thinks to use the path /sdcard/.

                Please check the directory with ls -l
                @
                QDir dl("/sdcard/Android/data/lock") ;
                if (!dl.exists()){
                dl.mkpath(dl.absolutePath());
                qDebug() << LINE << FUNCTION<< dl.absolutePath();
                }
                @

                If we can create the folder, the driver run correctly. If this work, i can rebuild the driver serial port with this path and add the check on directory.

                Second:
                Download this app, and try if you can open the serial port correctly.

                https://code.google.com/p/android-serialport-api/downloads/list

                My port is different because i use a Point of sales.

                Third
                W/Qt (21549): qtudev_p.h:114 (bool resolveSymbols(QLibrary*)): Failed to load the library: udev, supported version(s): 1 and 0
                I have this warning but work.

                The app "terminal" work and i have changed nothing.

                In the Android manifest i have added this permission:
                android.permission.WRITE_EXTERNAL_STORAGE

                Do you have downloaded this code ?
                https://codereview.qt-project.org/83480

                I tried but the git don't download the class java

                @
                git clone https://codereview.qt-project.org/p/qt/qtserialport refs/changes/80/83480/4 && git checkout FETCH_HEAD
                @

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                • K Offline
                  K Offline
                  kuzulis
                  Qt Champions 2020
                  wrote on last edited by
                  #13

                  2 mr_wallyit,

                  [quote]
                  W/Qt (21549): qtudev_p.h:114 (bool resolveSymbols(QLibrary*)): Failed to load the library: udev, supported version(s): 1 and 0
                  [/quote]

                  It is normal. The QtSerialPortInfo trying to use the udev library as main feature. In case the udev library is not present (e.g. can not to resolve it), then do fallback to the SysFs usage. In case the SysFs is not present (e.g. has no rights to read of the /sys/class/tty directory, or when no such this directory when the SysFs is disabled in Linux kernel), then do fallback to the enumeration of devices in /dev directory.

                  Usually, the Android has no udev, so all ok.

                  [quote]
                  Do you have downloaded this code ?
                  https://codereview.qt-project.org/83480
                  [/quote]

                  This code works only with the USB/Serial devices, so, no any ttyGS… ttyS.. ttySAC.., unfortunately. Has been used the directly I/O with the USB interface (read/write from the USB endpoints and so on), by analogy with the "libusb" on Linux. So, this solution it is an workaround, and can not be go to main QtSerialPort trunk.

                  This code also has a continuation in here: https://codereview.qt-project.org/#change,84338

                  Please read there are comments, maybe you will have other ideas how to re-implement it..

                  You can download this code like:

                  @
                  git clone git://gitorious.org/qt/qtserialport.git
                  cd qtserialport
                  git fetch https://codereview.qt-project.org/p/qt/qtserialport refs/changes/38/84338/2 && git checkout FETCH_HEAD
                  @

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                  • P Offline
                    P Offline
                    projetoslinux
                    wrote on last edited by
                    #14

                    Hi
                    thank you for all
                    thank you mr_wallit and kuzulis

                    i have partial sucess !!

                    testing with terminal example in qt3.0 to recieve serial data in usb

                    for this i create in /sdcard/folders and change in source code and compile this directories in qserial_port_unix
                    its possible create this in execution mode !!

                    #ifdef Q_OS_ANDROID

                        << QStringLiteral("/sdcard/data/lock")
                        << QStringLiteral("/sdcard/data/locks")
                        << QStringLiteral("/sdcard/data/spool/locks")
                        << QStringLiteral("/sdcard/data/spool/uucp")
                        << QStringLiteral("/sdcard/data/tmp")
                        << QStringLiteral("/sdcard/data/local/tmp");
                        qDebug() << __LINE__ << __FILE__;
                    

                    #else

                    no more message not LOCK

                    but when i open serial port show message

                    error permission denied OK

                    in debug lines have

                    Debugging starts
                    E/SELinux (15962): Function: selinux_android_load_priority [0], There is no sepolicy file
                    E/SELinux (15962):
                    E/SELinux (15962): Function: selinux_android_load_priority , loading version is VE=SEPF_SM-N900_4.3_F023
                    E/SELinux (15962):
                    E/SELinux (15962):
                    E/SELinux (15962): selinux_android_seapp_context_reload: seapp_contexts file is loaded from /data/security/spota/seapp_contexts
                    D/dalvikvm(15962): Late-enabling CheckJNI
                    D/dalvikvm(15962): GC_FOR_ALLOC freed 187K, 19% free 15034K/18436K, paused 14ms, total 14ms
                    I/dalvikvm-heap(15962): Grow heap (frag case) to 20.069MB for 2359312-byte allocation
                    D/dalvikvm(15962): GC_FOR_ALLOC freed <1K, 17% free 17338K/20744K, paused 18ms, total 18ms
                    D/dalvikvm(15962): Trying to load lib /data/data/org.qtproject.example.serialMaster/lib/libgnustl_shared.so 0x42969fa0
                    D/dalvikvm(15962): Added shared lib /data/data/org.qtproject.example.serialMaster/lib/libgnustl_shared.so 0x42969fa0
                    D/dalvikvm(15962): No JNI_OnLoad found in /data/data/org.qtproject.example.serialMaster/lib/libgnustl_shared.so 0x42969fa0, skipping init
                    D/dalvikvm(15962): Trying to load lib /data/data/org.qtproject.example.serialMaster/lib/libQt5Core.so 0x42969fa0
                    D/dalvikvm(15962): Added shared lib /data/data/org.qtproject.example.serialMaster/lib/libQt5Core.so 0x42969fa0
                    D/dalvikvm(15962): Trying to load lib /data/data/org.qtproject.example.serialMaster/lib/libQt5Gui.so 0x42969fa0
                    D/dalvikvm(15962): Added shared lib /data/data/org.qtproject.example.serialMaster/lib/libQt5Gui.so 0x42969fa0
                    D/dalvikvm(15962): No JNI_OnLoad found in /data/data/org.qtproject.example.serialMaster/lib/libQt5Gui.so 0x42969fa0, skipping init
                    D/dalvikvm(15962): Trying to load lib /data/data/org.qtproject.example.serialMaster/lib/libQt5Widgets.so 0x42969fa0
                    D/dalvikvm(15962): GC_CONCURRENT freed 11K, 17% free 17336K/20744K, paused 5ms+9ms, total 31ms
                    D/dalvikvm(15962): Added shared lib /data/data/org.qtproject.example.serialMaster/lib/libQt5Widgets.so 0x42969fa0
                    D/dalvikvm(15962): No JNI_OnLoad found in /data/data/org.qtproject.example.serialMaster/lib/libQt5Widgets.so 0x42969fa0, skipping init
                    D/dalvikvm(15962): Trying to load lib /data/data/org.qtproject.example.serialMaster/lib/libQt5SerialPort.so 0x42969fa0
                    D/dalvikvm(15962): Added shared lib /data/data/org.qtproject.example.serialMaster/lib/libQt5SerialPort.so 0x42969fa0
                    D/dalvikvm(15962): No JNI_OnLoad found in /data/data/org.qtproject.example.serialMaster/lib/libQt5SerialPort.so 0x42969fa0, skipping init
                    D/dalvikvm(15962): Trying to load lib /data/data/org.qtproject.example.serialMaster/qt-reserved-files/plugins/platforms/android/libqtforandroid.so 0x42969fa0
                    D/dalvikvm(15962): Added shared lib /data/data/org.qtproject.example.serialMaster/qt-reserved-files/plugins/platforms/android/libqtforandroid.so 0x42969fa0
                    I/Qt (15962): qt start
                    D/dalvikvm(15962): Trying to load lib /data/app-lib/org.qtproject.example.serialMaster-1/libserialMaster.so 0x42969fa0
                    D/dalvikvm(15962): Added shared lib /data/app-lib/org.qtproject.example.serialMaster-1/libserialMaster.so 0x42969fa0
                    D/dalvikvm(15962): No JNI_OnLoad found in /data/app-lib/org.qtproject.example.serialMaster-1/libserialMaster.so 0x42969fa0, skipping init

                    1- No JNI_OnLoad found in
                    its normal ???

                    2-my phone is rooted and add manifest.xml to write sdcard.
                    how to execute in sudo ?

                    3- other git examples not work for me !!!

                    thanks..for this

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                    • P Offline
                      P Offline
                      projetoslinux
                      wrote on last edited by
                      #15

                      3- other git examples not work for me !!!

                      change permission in host machine
                      sudo chmod 777 -R /libs/armeabi-v7a/

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                      • M Offline
                        M Offline
                        mr_wallyit
                        wrote on last edited by
                        #16

                        Hello,
                        " JNI_OnLoad found" i see the warning in the my project.
                        If you receive the bytes you can open the serial port,
                        Are you sure, that are you sending the commands correctly?
                        Because all device have the specific syntax, i thinks that if you can receive you can send

                        I don't know how you we open the app with permission "sudo", but i have found how open by shell.

                        @
                        adb shell am start -n org.qtproject.example/org.qtproject.qt5.android.bindings.QtActivity

                        @

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                        • P Offline
                          P Offline
                          projetoslinux
                          wrote on last edited by
                          #17

                          ok thanks
                          mr_wallyit

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                          • K Offline
                            K Offline
                            kuzulis
                            Qt Champions 2020
                            wrote on last edited by
                            #18

                            In addition, seems, there are "way":https://groups.google.com/forum/#!topic/pico-sam9g45/dNt1FJCX6ik to open the serial port with the user permissions.

                            Need to setup permissions to desired serial port, e.g. do it in "init.rc" file, e.g.:

                            @chmod 0666 /dev/ttyS0@

                            Of course, to changing of this file required the root rights, unfortunately. But it can be done once for all non-USB serial ports "integrated" on Your device and do no worry in future.

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                            • M Offline
                              M Offline
                              mr_wallyit
                              wrote on last edited by
                              #19

                              Hi kuzulis,

                              good research.

                              Thanks

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                              • P Offline
                                P Offline
                                projetoslinux
                                wrote on last edited by
                                #20

                                After several weeks I found out why qtserialport not run on any android

                                1 - Root is necessary
                                2 - Android Kernell should be compiled with the option enabled serial port, as well as some needed to install libusb and having to recompile the source code Kernell!!

                                Much work!!
                                Anyone know another method??

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                                • M Offline
                                  M Offline
                                  mr_wallyit
                                  wrote on last edited by
                                  #21

                                  Hello,

                                  I have tried qserialport on industrial pos (point of sales),so i thinks the kernel has enabled serial port and libusb, because i can use the serial port.

                                  In the Qt 5.3 we have bluetooth,
                                  Why Don't we use bluetooth?

                                  @
                                  http://www.brainboxes.com/product/bl-830/bluetooth-to-rs232-serial-adapter-1-port-female
                                  @

                                  I don't have tried, but i thinks that work because android uses protocol bluetooth with adapter than it convert the signal in rs232.

                                  What do you thinks?

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                                  • P Offline
                                    P Offline
                                    projetoslinux
                                    wrote on last edited by
                                    #22

                                    Thanks mr_wallyit

                                    i testing but not have any example whit serial com over bluetooth

                                    looking this

                                    http://qt-project.org/forums/viewthread/41978/

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                                    • M Offline
                                      M Offline
                                      mr_wallyit
                                      wrote on last edited by
                                      #23

                                      Dear projetoslinux,

                                      if we use a adapter, the protocol between smartphone and the adapter is bluetooth, the conversation rs-232 is done by converter.

                                      e.q. in qt:
                                      /opt/qt/Examples/Qt-5.3/bluetooth$ ls
                                      btfiletransfer
                                      picturetransfer
                                      scanner
                                      btchat
                                      btscanner
                                      pingpong

                                      I thinks that the pingpong is a type of communications network client - server. I like this idea but adapters bluetooth are very expensive for me, i search a economic device on ebay. I need a lot of time for try.

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                                      • P Offline
                                        P Offline
                                        projetoslinux
                                        wrote on last edited by
                                        #24

                                        Hi mr_walyit

                                        im a testing in embedded android solutions and work fine, but in my cell phone, not work, in next week i compile phone kernel. adapters is most expensive !!! and dont resolve portability
                                        thanks...

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                                        • M Offline
                                          M Offline
                                          mr_wallyit
                                          wrote on last edited by
                                          #25

                                          Hello,

                                          Have you compiled Kernel?

                                          My best regards

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