Q: Is possible to modify the inactivity time after that the mobile device disable the display (so also the backlight)?

A: In order to configure the screensaver's timeout (i.e. the inactivity time after that the mobile device disable the display) the user must change the content of a configuration file on the mobile device: for the moment Nylux platform doesn't enable the user to make this setting using a graphic interface such as Screen Setup.
The user must edit (using the Editor utility installed on the Nylux, or using the editor integrated in the ssh communication program) the script /usr/bin/X on the mobile device
In the Nylux's default configuration, this script runs Xfbdev with the followings parameters:

Xfbdev -ac -screen 240x320@90 -keybd keyboard,device=/dev/input/event1 -mouse tslib,,device=/dev/input/event0,rightbutton,samples=20,tolerance=4 -root-ppm /usr/share/pixmaps/xsplash-qvga.ppm

In Xfbdev's startup parameters isn't defined any timeout for the screen-saver, so the platform uses the default timeout, that is 600 seconds (10 minutes).
In order to define a different timeout the user must add to Xfbdev's startup parameters the following option:

-s minutes

followed by the startup parameters already existent.

For example, to setup a timeout of 1 minute, the command line must be:
Xfbdev          -s 1 -ac -screen 240x320@90 -keybd keyboard,device=/dev/input/event1 -mouse tslib,,device=/dev/input/event0,rightbutton,samples=20,tolerance=4 -root-ppm /usr/share/pixmaps/xsplash-qvga.ppm