So the screen from here is working in Kodi now (LCD datasheet / pinout), but it draws a lot of power when the backlight is on (~200mA extra). We want to turn at least the backlight off, leaving the touchscreen active so we can interact and wake it up again. Buuut the LCD has no backlight control which is a pity (would have cost close to nothing). Good thing is: We can easily add it.
UPDATE: This only needs a wire an NO software tinkering, but for the 5″ display you have to take it apart, because the IC is on the back side of the PCB. But this is the most convenient solution! Thanks Antje.
You’ll need a thin wire. Enamel wire works well here. The general idea is the same as in Antjes tutorial. Carefully seperate the screen from the PCB, solder a wire to pin 8+9 of the TFP401 and thread it through to the other side of the PCB.
Now the problem for the 5″ screen is that pin 4 (ENable) of the PT4103 chip controlling backlight power is directly connected to 5V through some vias on the PCB. There’s no good way to cut that connection, so I used a soldering iron with a thin tip and gently lifted pin 4 of the PT4013 up, so it does not touch the PCB anymore. Then solder the wire from the TFP401 to it. That’s it.
Turning the screen on/off in Kodi
For the following instructions, use the home directory of the user you want to run Kodi from. If you make Kodi autostart by editing /etc/default/kodi, this is the user “kodi” (used here), else it is probably the user “pi”.
Now to integrate support for the backlight into Kodi, we need to run those commands when the Kodi screensaver starts or ends. For that we need a service addon called “service.xbmc.callbacks“. Download the script from the releases section and unzip it into /home/kodi/.kodi/addons. Now start Kodi and add those two lines in the addon configuration:
For screensaver starts:
vcgencmd display_power 0
For screensaver stops:
vcgencmd display_power 1
Your backlight should now turn off / on with the screen saver.