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How to adjust text brightness and shut off time

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  • How to adjust text brightness and shut off time

    I have a 4.3" LCD cape attached to a BBB. I display text from my program and it is not easy to read because the text is rather dim. How can I make this brighter, please?

    Also, how do I make the display stay on when it is not being used?

    Thank you.

  • #2

    One method is to SSH into the Beaglebone Black
    from your PC , and set the backlight value that way.
    Note this does not persist over restarts, so this
    would need to be entered into a startup script if the
    setting is required to be set each startup.
    That is, Add commands to /etc/rc.local
    At the command prompt, type the following:
    cd/sys/class/backlight/backlight.10/echo 100 > brightness

    Where 100 represents 100%, this can be changed
    to any number from 0 to 100 as required.

    Changing the brightness on Android is simple.
    Navigate to the Settings menu, and to the Display
    option, and then to Brightness. Slide the slider to
    the desired position.

    For disabling the Screen Saver please see this
    forum thread:

    Completely disable screensaver

    Best regards,


    • #3
      Thank you for your quick response. For some unknown reason I was not able to use rc.local to change the brightness or screen blanking. I was however able to stop the screen blanking by adding "optargs= consoleblank=0" to the uEnv.txt file.

      Unfortunately I am still unable to make the text full 100% brightness automatically on boot.

      I can change it manually using your command but that only lasts until the next restart.

      I tried adding it to the /etc/rc.local file and the /boot/uEnv.txt file. Neither work.

      Do you know of any other ways to do this?

      Also, is the brightness controlled by a PWM GPIO? I am wondering if I can set that in either my program or the Device Tree Overlay.

      Thank you for your kind assistance.


      • #4

        You can make the brightness to 100% every time by following this procedure

        1. Create a file named
        using a text editor, type the following

        cd /sys/class/backlight/backlight.11/
        sudo chmod 777 brightness
        echo 100 > brightness

        2. in rc.local
        sudo nano /etc/rc.local

        add the following (take note of the path where you saved use pwd to determine the path

        sh '/home/debian/'

        if /etc/rc.local is not yet executable, use the following
        sudo chown root /etc/rc.local
        sudo chmod 755 /etc/rc.local

        you can test if the script is working by changing the brightness and typing ./

        After making or modifying the files test and reboot

        best regards,


        • #5
          To set brightness to 100

          sudo nano /etc/rc.local

          exec= sudo chmod 777 /sys/class/backlight/banklight/brightness

          exec= echo 100 > /sys/class/backlight/backlight/brightness

          Thank you for your help.


          • #6
            Oddly, the above commands work on one BBB but not the other.


            • #7
              I updated and upgraded the BBB that worked with the above command and it no longer worked.

              cat /etc/dogtag now shows 2016-1-24
              The above commands do not work, however, when i do:
              sudo chmod 777 /sys/class/backlight/backlight/brightness
              echo 100 > /sys/class/backlight/backlight/brightness

              the change persists after reboot.
              I have no idea why.


              • #8

                Depending on the Angstrom or Beagle Bone OS you are using,
                please check the path of the brightness file. On my version of Angstrom,
                the brightness file is located in /sys/class/backlight/backlight.11
                Please take note of the 11 at the end of the backlight folder.
                Please use the cd and ls command to check the folder where the brightness file
                is located.

                Best regards,


                • #9
                  I am running debian and I did check the relevant subdirectories. There was no backlight.11

                  Thank you for asking.