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Control backlight
#1
Hey there,

Controlling the backlight of the official raspberry pi screen is easy enough on raspbian, but it looks like it's different on openplotter.

The file and folder to use in the link do not even exist and you don't have write permission:
https://raspberrypi.stackexchange.com/qu...en-display
Same with the python code.

Anybody figured it out?
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#2
(2018-10-31, 05:00 PM)NaturalBornCamper Wrote: Hey there,

Controlling the backlight of the official raspberry pi screen is ready enough on raspbian, but it looks like it's different on openplotter.

The file and folder to use in the link do not even exist and you don't have write permission:
https://raspberrypi.stackexchange.com/qu...en-display
Same with the python code.

Anybody figured it out?

Hi,

controlling the backlight is very easy:

https://github.com/linusg/rpi-backlight

Open Terminal, type:
sudo nano /etc/udev/rules.d/backlight-permissions.rules

Add this to make access permanent:
SUBSYSTEM=="backlight",RUN+="/bin/chmod 666 /sys/class/backlight/%k/brightness /sys/class/backlight/%k/bl_power"

Install backlight-lib:
sudo pip install rpi_backlight

From now you can run  'sudo rpi-backlight' and it will ask for the brighness.
Or 'sudo rpi-backlight-gui' to get a graphical slider.

I am using an IR remote control and have changed the key-binding to call
the rpi-backlight-gui. Works very nice!

Type:
sudo nano ~/.config/openbox/lxde-pi-rc.xml

Insert after <!--keybindings for LXPanel -->:

<keybind key="your keyboard key here">
<action name="Execute">
<command>sudo ripi-backlight-gui</command>
</action>
</keybind>

To find out the Scancodes of your keyboard/RC, type:
xev

Use strg+c to quit xev.

Cheers,
Chris
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#3
Hey there, thanks for the answer!

I have seen that python project repo on the same link I sent, but it's not working for me, I suppose for the same reason that the file in the first answer is missing. OpenPlotter seems to be set differently.

Here's some error output when trying rpi-backlight:

Code:
pi@openplotter:~ $ sudo rpi-backlight --power
Traceback (most recent call last):
 File "/usr/local/bin/rpi-backlight", line 11, in <module>
   sys.exit(cli())
 File "/usr/local/lib/python2.7/dist-packages/rpi_backlight.py", line 160, in cli
   print(get_power())
 File "/usr/local/lib/python2.7/dist-packages/rpi_backlight.py", line 72, in get_power
   return not int(_get_value("bl_power"))
TypeError: int() argument must be a string or a number, not 'NoneType'


Code:
pi@openplotter:~ $ sudo rpi-backlight --brightness 100
Traceback (most recent call last):
 File "/usr/local/bin/rpi-backlight", line 11, in <module>
   sys.exit(cli())
 File "/usr/local/lib/python2.7/dist-packages/rpi_backlight.py", line 151, in cli
   set_brightness(args.brightness, args.smooth, args.duration)
 File "/usr/local/lib/python2.7/dist-packages/rpi_backlight.py", line 83, in set_brightness
   max_value = get_max_brightness()
 File "/usr/local/lib/python2.7/dist-packages/rpi_backlight.py", line 62, in get_max_brightness
   return int(_get_value("max_brightness"))
TypeError: int() argument must be a string or a number, not 'NoneType'


Code:
pi@openplotter:~ $ sudo rpi-backlight-gui
Unable to init server: Could not connect: Connection refused
Unable to init server: Could not connect: Connection refused
Segmentation fault
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