Hi all, I m using qt-embedded-4.5.3 on my mini2440 with 3.5" LCD. I want to turn off LCD backlight for power management while my qt app is running, after some period of time say 2 min. Also , if someone taps on LCD , then backlight should turn on automatically. I saw /usr/bin/bl , Also , tried echo 0 > /dev/backlight but no use. I also seen "backlight control" topic , but no clues. Any suggestions? Thanks in advance.
Hi, I've twiddled with my kernel a little, so this may not work with your configuration.. But, if your system contains this directory /sys/devices/platform/s3c24xx_led.5/leds/backlight You can do the following to turn off the backlight of the LCD echo 0 > /sys/devices/platform/s3c24xx_led.5/leds/backlight/brightness If the board doesn't have a sys file system (I can't recall of the boards do by default), do the following to see if you can mount /sys somewhere cat /proc/filesystems if there's a line like this nodev sysfs You can then do the following mkdir -p /sys mount -t sys none /sys to get access to the to the /sys/devices/platform/s3c24xx_led.5/leds/backlight/brightness file. Sorry if this doesn't work with your RFS, as I've made lots of changes to mine and don't have the "shipping" RFS handy as a reference. Regards, gene
Hi gene.sally , thank you very much for your solution. It worked !!!! thanks once again.
On the default kernel there is no: /sys/devices/platform/s3c24xx_led.5/leds/backlight so two questions: - how could I enable this in my kernel or - how can I control it without this entry?? It must be possible, as the demo application in qtopia does it, too! Is there any source available for that???
>> ow could I enable this in my kernel This is in the sysfs file system. Check if you have it by doing the following: $ grep sysfs < /proc/filesystems if you get this output: nodev sysfs You can just do a mkdir /sys mount -t sys none /sys If there's no sysfs support, you'll need to rebuild the kernel with sysfs and then mount this file system. If you want to access this directly, without sysfs, you'll need to write some code that changes the state of the GPIO line that handles the backlight. This is line 4 on gpio bank G, so the call from the kernel would be s3c2410_gpio_setpin(S3C2410_GPG(4), 0); to turn off the backlight. But you'll probably want to wrap that in a nice interface that you can reach from userland by creating a simple driver. Regards, gene
Hey All, I tried compiling my kernel to get the support required to turn the backlight LED off however i dont have /sys/devices/platform/s3c24xx_led.5 I do have /sys/class/gpio # ls export gpiochip128 gpiochip192 gpiochip32 gpiochip96 gpiochip0 gpiochip160 gpiochip224 gpiochip64 unexport # But nothing I do changes the LEDs on board or on the LCD. Any ideas? I am running Linux buildroot 2.6.32.2-FriendlyARM #2 Fri Oct 8 17:44:42 WST 2010 armv4tl GNU/Linux
Ok, Just an update for everyone, I found the support in the latest kernel available at; git://repo.or.cz/linux-2.6/mini2440.git Linux buildroot 2.6.32-rc8 #1 Fri Oct 8 21:32:14 WST 2010 armv4tl GNU/Linux Now does anyone know how you can get the screen to issue the echo "0" > /sys/devices/platform/s3c24xx_led.5/leds/backlight/brightness when idle for x minutes and echo "1" > /sys/devices/platform/s3c24xx_led.5/leds/backlight/brightness when you press the screen? Cheers Slampt