Nominate our 2022 Qt Champions!

Multiple screens on Qt Automotive with iMX6

  • Hello,

    Following Building Your Own Embedded Linux Image, I was able to create a Qt Automotive image and the Neptune demo works fine

    But now I would like to have two screen working together with the Neptune demo.

    I modified my local.conf to remove X11 and wayland in order to work only with EGLFS

    DISTRO_FEATURES_remove = "X11 wayland"

    I also modified my u-boot enviroment variables to set up my two screens (HDMI and LVDS)

    setenv vidargs 'video=mxcfb0:dev=ldb video=mxcfb1:dev=hdmi,1280x1024M@60,if=RGB24 video=mxcfb2:off video=mxcfb3:off fbmem=32M'

    I can see the neptune in my HDMI monitor (fb2) but a black in my LVDS screen (fb0)

    but when I execute:

    cat /dev/urandom > /dev/fb0

    it does work, I can see the random pixels being painted

    But in my app when I execute:

        QList<QScreen *> screens = QGuiApplication::screens();
        printf("Screens = %d\n", screens.count());

    I only get one screen and when I run qtdiag I get the next:

    Screens: 1, High DPI scaling: inactive
    # 0 "" Depth: 16 Primary: yes
      Serial number:
      Geometry: 1920x720+0+0 Available: 1920x720+0+0
      Physical size: 487.68x182.88 mm  Refresh: 62 Hz Power state: 0
      Physical DPI: 100,100 Logical DPI: 100,100 Subpixel_None
      DevicePixelRatio: 1 Pixel density: 1
      Primary orientation: 2 Orientation: 2 Native orientation: 0 OrientationUpdateMask: 0

    It looks like Qt Embedded is only detecting my first screen (fbo)

    Does somebody has had experience with multiple screen working together?
    Am I missing some configuration file?

    My intention was to configre neptune to something like this: Neptune 3 UI - Configuring Screens on Embedded Linux

    My HW is:

    • Apalis iMX6
    • Apalis Evaluation Board
    root@b2qt-apalis-imx6:~# uname -a
    Linux b2qt-apalis-imx6 4.1.44-2.7.5+g18717e2b1ca9 #1 SMP Fri Feb 22 10:41:34 CST 2019 armv7l armv7l armv7l GNU/Linux


  • @Isaias Did you try to set QT_QPA_EGLFS_FB like it's in manual ?

  • Hello @tomasz3dk

    I can run the Qt Neptune demo or other Qt app in one screen or the other, even both at the same time, setting QT_QPA_EGLFS_FB to the correct fb before executing the app

    But my final intention is to modify the Neptune configuration to work something like this Neptune 3 UI - Configuring Screens on Embedded Linux

    It looks like I am missing to set up a configuration for the Qt Embedded Stack to detect both screens but I don't know.

  • Hello everyone
    I have the same problem.
    Please comment if you know how to solve it.

Log in to reply