Doubt with LCD backlight and Linux

LEICIF · 11-23-2009, 04:56 AM

Hello,

Let me introduce myself, my name is John and I am here to look for answers, if is possible.

I have developed a embedded system with Geode LX800 and all works fine.
But now I have a doubt.

If is possible to controlled backlight signal enable from user program???

I have looked for information about it but I dont understand well if it is possible.

Best regards.

uppman · 11-23-2009, 06:34 AM

Hi and welcome to LQ!

You could try one of the following:

Console:

echo "7" > /sys/devices/virtual/backlight/acpi_video0/brightness

In X:

xrandr --output DFP5 --gamma 1:1:1

/Magnus

LEICIF · 11-23-2009, 06:57 AM

Quote:

Originally Posted by uppman

Hi and welcome to LQ!

You could try one of the following:

Console:

echo "7" > /sys/devices/virtual/backlight/acpi_video0/brightness

In X:

xrandr --output DFP5 --gamma 1:1:1

/Magnus

Hello Magnus,

In my laptop works fine, but in my embedded system does not work.
I have supposed that it is possible to access backlight using /dev/fb0, but I can not find any example to handle it.

Anyway, thanks a lot.

uppman · 11-25-2009, 04:07 AM

What kind of graphic adapter is in the embedded system?

You probably need to look in the kernel source/docs to find out how that specific adapter works.

Perhaps you can try this kernel module for Nvidia:

http://aur.archlinux.org/packages.php?ID=25467

There is something called matrox-tools which should work with Matrox cards:

http://viz.aset.psu.edu/ga5in/MediaCenter.html

# apt-get install matrox-tools fbset

tweak contrast, saturation, hue and brightness:

# matrox 0x1e 0xd0
# #matrox 0x20 0xff
# #matrox 0x22 0xff

/Magnus

LEICIF · 11-25-2009, 10:48 AM

Quote:

Originally Posted by uppman

What kind of graphic adapter is in the embedded system?

Hello,

I use GEODE LX800, and It has own graphic adapter.

I have tried to access GPIO signal to handle backlight enable, but I don't if it is a good idea.

Best regards.