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  1. #1
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    Screen too bright in pCP

    Hello
    I am running pCP on a Pi 1 with a 5.5 inch av screen connected to the Pi 1 av output. The screen is a car reversing camera screen and is working very well but is too bright. There is no facility on the screen to adjust the brightness. Is there any way to reduce the screen brilliance a bit. I am using Jivelite with HD skin 640x480.
    Any help would be appreciated.
    Thanks
    diode84

  2. #2
    Senior Member kidstypike's Avatar
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    Quote Originally Posted by diode84 View Post
    Hello
    I am running pCP on a Pi 1 with a 5.5 inch av screen connected to the Pi 1 av output. The screen is a car reversing camera screen and is working very well but is too bright. There is no facility on the screen to adjust the brightness. Is there any way to reduce the screen brilliance a bit. I am using Jivelite with HD skin 640x480.
    Any help would be appreciated.
    Thanks
    diode84
    On a 7" official pi screen you can adjust screen brightness > Settings > piCorePlayer. Not sure about your 5" screen though.

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  3. #3
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    No it says no official Raspberry Pi display found.

  4. #4
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    I suspect that is not possible via simple configuration.
    I just had a look at the official list of items for config.txt for the composite display and saw nothing that gives controls over that.

    Might be possible with tricks in a display driver ... but pCP does not use X etc so not sure that there will be an easy way to achieve this.

    Are there any adjustable controls on the screen itself?
    Paul Webster
    http://dabdig.blogspot.com
    Author of "Now Playing" plugins covering Radio France (FIP etc), KCRW, Supla Finland, ABC Australia, CBC/Radio-Canada and RTE Ireland

  5. #5
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    If no technical solution available, you get screen dimming films (neutral density type filter) that can be stuck on the display.

    example https://www.amazon.co.uk/dp/B009WTOGFK/ref=dp_cerb_3 - different size are available.

  6. #6
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    Quote Originally Posted by Paul Webster View Post
    I suspect that is not possible via simple configuration.
    I just had a look at the official list of items for config.txt for the composite display and saw nothing that gives controls over that.

    Might be possible with tricks in a display driver ... but pCP does not use X etc so not sure that there will be an easy way to achieve this.

    Are there any adjustable controls on the screen itself?
    No nothing at all, its very basic.

  7. #7
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    Quote Originally Posted by bpa View Post
    If no technical solution available, you get screen dimming films (neutral density type filter) that can be stuck on the display.

    example https://www.amazon.co.uk/dp/B009WTOGFK/ref=dp_cerb_3 - different size are available.
    That could be the solution although I was a bit concerned for the life of the screen itself. I will hook it up to my bench PSU and see if it works on reduced voltage.

  8. #8
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    Reducing the voltage to the screen did not work as it broke up and went off at about 10v. If the official Pi screen has this facility in Jivelite for a 5.5 inch screen I may consider that.

  9. #9
    Senior Member chill's Avatar
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    If there's a command line utility to control the brightness for your particular display, then Jivelite can probably make use of this. As well as the built-in support for the Official Raspberry Pi displays, Jivelite can now support screen brightness control via a more generic approach. This approach was added to support the Pirate Audio boards, and relies on the use of a separate script file.

    If there's a script file called lcd-brightness.sh in /home/tc then Jivelite will attempt to use this if it determines that there's no Official display attached. The job of this script file is to adjust the brightness in response to some standard calls from Jivelite. The script below shows how this done for the Pirate Audio boards, where PWM control of GPIO 13 is used for the brightness, using the 'pigs' command line utility.

    Code:
    #!/bin/sh
    
    #========================================================================================
    # Script to call a command line utility to adjust LCD brightness
    # Written for the Pirate Audio display that uses PWM on GPIO 13 to adjust brightness,
    # so the pigpio command 'pigs' can be used.
    # Adjust this script to use whatever command line utility suits your display.
    #----------------------------------------------------------------------------------------
    #
    # $1 is the only passed parameter
    # If $1 is ""  then do nothing
    # If $1 is "C" then return Current brightness
    # If $1 is "M" then return Maximum brightness
    # If $1 is "R" then set the Range maximum to $rmax (100 is useful, so that increments are %)
    # If $1 is "F" then set to Full (maximum) brightness
    # If $1 is a number then set the brightness to this value
    #
    #----------------------------------------------------------------------------------------
    #
    # To use the 'pigs' utility 
    # pigs GDC 13     : returns the current brightness value
    # pigs PRG 13     : returns the maximum brightness (not really needed when PRS is used
    #                   to set the maximum to 100 - we could simply return 100)
    # pigs PRS 13 100 : sets the brightness range to 0-100
    # pigs PWM 13 100 : sets the maximum brightness
    # pigs PWM 13 0   : turns off the LCD backlight
    #
    #----------------------------------------------------------------------------------------
    
    	g=13		# gpio pin for backlight control
    	rmax=100	# range maximum
    
        case $1 in
        	"" )							# empty string - do nothing
        		exit 1
        		;;
        	"C" | "c" )						# get current value
        		pigs GDC $g
        		;;
        	"M" | "m" )						# return maximum possible brightness
        		pigs PRG $g
        		;;
        	"R" | "r" )						# set maximum brightness range
        		pigs PRS $g $rmax
        		;;
        	"F" | "f" )						# set full brightness 
        		pigs PWM $g $rmax
        		;;
    	    *[!0-9]*) 						# string containing non-numbers - do nothing
    	    	exit 1
    	    	;;
        	* )								# everything else.  Assume only numbers at this point
        		bright_val=$1
        		# add some checking that $bright_val is in range 0-rmax (TBD)
        		pigs PWM $g $bright_val
        esac
    I don't expect that PWM control of GPIO 13 will be suitable for your screen, so this script won't work for you, but if you can find a command line utility that controls your screen's brightness then you might be able to write your own lcd-brightness.sh script file to use that utility.

  10. #10
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    Key thing here is that this screen is connected via the composite socket not the HDMI or GPIO or DSI so it would have to be something that would work for an old fashioned (pre HDMI) TV-style ... unless there is something in the screen that can be wired up to a GPIO which seems not to be the case here.
    Paul Webster
    http://dabdig.blogspot.com
    Author of "Now Playing" plugins covering Radio France (FIP etc), KCRW, Supla Finland, ABC Australia, CBC/Radio-Canada and RTE Ireland

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