Control the backlight of your Raspberry pi display
I bought myself the official pi display for my raspberry-pi. My intention was to use the combo as a homebridge/homekit server in my camping van. Therefore the power consumption should be as low as possible.
The most potential for saving power is of course the display. So, I've set the screensaver to Blank. Unfortunately the backlight of the display kept on sucking the battery of my bus although the screensaver was active.
Since I could not find a screensaver-option to do the trick ... I consulted google and found out that I was able to control the backlight like this
sudo sh -c 'echo 1 > /sys/class/backlight/rpi_backlight/bl_power'
sudo sh -c 'echo 0 > /sys/class/backlight/rpi_backlight/bl_power'
Curiously, echo'ing a 1 to bl_power turns the display off. Echo'ing a 0 turns it on. But hey, that was enough information to knit something on Linux (instead of Windows as I'm used to).
First we add everybody's read/write access to the device-anchor to get rid of the need to use sudo
echo 'SUBSYSTEM=="backlight",RUN+="/bin/chmod 666 /sys/class/backlight/%k/bl_power"' | sudo tee -a /etc/udev/rules.d/backlight-permissions.rules
Then we copy the file screensaver-backlight.pl of this repository to our folder /usr/bin and assign execute access
sudo chmod a+x /usr/bin/screensaver-backlight.pl
Finally we enable the auto-execution of the perl-script by modifying the autostart config-file located beyond our home folder
cd ~/.config/lxsession/LXDE/
nano autostart
We add a new entry @screensaver-backlight.pl & somewhere behind the entry of xscreensaver
Reboot the pi afterwards. That's it - now the backlight turns on/off together with screensaver's blank screen. If you want to apply above steps on your own raspi you should be aware to do this at your own risk.
MIT License