On 2/6/11 9:09 AM, Elvis Dowson wrote:
> I've got LCD backlight brightness control working with a custom
> beagleboard design, with the LCD backlight pwm control signal connected to
> OMAP3503's gpt9_pwm_evt timer.
>
> GPIO 96 is connected to the LCD LED enable pin for controlling the on/off for
> the LCD backlight.
>
> I also see a bl_power file in /sys/class/backlight/beagleboard/ folder.
>
> # ls /sys/class/backlight/beagleboard
> uevent
> subsystem
> bl_power
> brightness
> actual_brightness
> max_brightness
> boost
> pwm_fq
> min_duty
> power
>
> I want to be able to fully turn the LCD backlight on and off. How do I map
> GPIO 96 to bl_power?
>
> Right now, if I blank the LCD using the following command, it gives me a white
> screen, but the backlight doesn't turn off
>
> $ echo 1 > /sys/class/graphics/fb0/blank
Elvis:
The following script should be instructive:
device="/sys/devices/platform/pwm-backlight.0/backlight/pwm-backlight.0"
power="${device}/bl_power"
brightness="${device}/brightness"
max="${device}/max_brightness"
usage () {
echo "Usage `basename ${0}` [[ --enable | --disable ] | --max | [
brightness ]]"
exit ${1}
}
get_brightness () {
cat ${brightness}
}
set_brightness () {
echo ${1} > ${brightness}
}
max_brightness () {
cat ${max}
}
disable_backlight () {
echo 1 > ${power}
}
enable_backlight () {
echo 0 > ${power}
}
if [ $# -eq 1 ]; then
if [ "${1}" = "--enable" ]; then
enable_backlight
elif [ "${1}" = "--disable" ]; then
disable_backlight
elif [ "${1}" = "--max" ]; then
max_brightness
else
set_brightness ${1}
fi
else
get_brightness
fi
Best,
Grant
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