Sunday, 9 February 2020

Raspberry Pi screen blanking

I have a Raspberry Pi 4b running Raspbian 4.

After 10 minutes the screen blanks an it is very hard to get it to return: even plugging in a keyboard and mouse and using them doesn't restore the display. Here are some of my findings:

"xset s activate" recreates the problem.

X11 is a client/server Windows Manager.
Raspbian 4 is running Pixel, a derivative of LXDE.

You can see the default display manager with:

cat /etc/X11/default-display-manager
/usr/sbin/lightdm

"sudo service lightdm restart" doesn't fix it.

Accessing the X11 tools differs if you use SSH out of the box from the local terminal connected directly to the Pi. For example I was getting errors such as xset:  unable to open display ""

Also:
echo $DISPLAY
returns :0.0 on the local terminal

but it returns a blank line on SSH unless you turn on X11 forwarding on the Putty console, then it displays:
locahost:10.0

X11 also has security controls.
"xhost +" disables the controls and allows everyone to access it.

References
https://raspberrypi.stackexchange.com/questions/2059/disable-screen-blanking-in-x-windows-on-raspbian




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