<![CDATA[RPI4 Dual Monitor blanking]]>Started a new project with a dual monitor setup using a pi4. Connected via DVI as there is no HDMI (only display port, thanks HP).

Monitors are in portrait mode & MM is setup in single instance configuration using this post as a template (linky)

The latest version of Bullseye seems to have stopped “vcgencmd display_power 0” from working , it no longer blanks the display and just responds with display_power=1. This appears to be due to a change to the KMS driver.

Googling give me this as an alternative

xrandr --output HDMI-1 --off

It does work & switches the screens off (separate commands for HDMI-1 & HDMI-2) however, using

xrandr --output HDMI-2 --off
xrandr --output HDMI-1 --off

to switch off and

xrandr --output HDMI-1 --rotate right --auto
xrandr --output HDMI-2 --rotate left --right-of HDMI-1 --auto

Puts them back in the right place . Sometimes.
About 1 in every 10 off/on cycles the righthand display ends up on HDMI-1 & HDMI-2 shows the desktop. CTRL W puts it back in the right place, but that’s really annoying & I don’t want to reset the MM every time as it looks ugly whilst repopulating.

Has anyone found a more reliable method to blank the displays & return MM back to the correct displays?

]]>https://forum.magicmirror.builders/topic/17885/rpi4-dual-monitor-blankingRSS for NodeThu, 11 Jun 2026 19:40:52 GMTWed, 05 Jul 2023 09:14:39 GMT60<![CDATA[Reply to RPI4 Dual Monitor blanking on Tue, 14 Nov 2023 19:16:10 GMT]]>For anyone having this issue:

Change the kms driver to the fake one by editing /boot/config.txt

change

dtoverlay=vc4-kms-v3d

to

dtoverlay=vc4-fkms-v3d

Reboot & display will now switch on/off using

vcgencmd display_power 0
vcgencmd display_power 1

I’ve not noticed any problems using the fake driver but I’m not using anything 3D (your results may be different)

]]>https://forum.magicmirror.builders/post/112517https://forum.magicmirror.builders/post/112517Tue, 14 Nov 2023 19:16:10 GMT<![CDATA[Reply to RPI4 Dual Monitor blanking on Tue, 14 Nov 2023 19:11:11 GMT]]>@grantc66

For anyone having the same issue:

Another solution is to edit /boot/config.txt & change to the fake kms driver

dtoverlay=vc4-kms-v3d

to

dtoverlay=vc4-fkms-v3d

reboot & then

vcgencmd display_power 0
vcgencmd display_power 1

work as they used to do.

I’ve not noticed any negative effect from using the fake one but I’m not using any 3D effects (your results may vary).

]]>https://forum.magicmirror.builders/post/112515https://forum.magicmirror.builders/post/112515Tue, 14 Nov 2023 19:11:11 GMT<![CDATA[Reply to RPI4 Dual Monitor blanking on Sun, 09 Jul 2023 19:36:47 GMT]]>@grantc66
There are ways to move windows to a specific screen on the bash. But it is complicated.
Maybe one of the solutions in this thread solves your problem.

]]>https://forum.magicmirror.builders/post/110187https://forum.magicmirror.builders/post/110187Sun, 09 Jul 2023 19:36:47 GMT<![CDATA[Reply to RPI4 Dual Monitor blanking on Sun, 09 Jul 2023 10:33:50 GMT]]>After nearly a week of trying different things, short of removing the KMS driver or reverting to Buster, the only method I could come up with was to use the xset screensaver.

Set the timeout to 3 minutes
xset -display :0 s 180
and do
xset -display :0 s reset
to wake it up on motion.

It’s not elegant but without any cec control of the monitor it appears to be my only solution, unless anyone has a method to get xrandr to keep electron on the correct monitor.

]]>https://forum.magicmirror.builders/post/110175https://forum.magicmirror.builders/post/110175Sun, 09 Jul 2023 10:33:50 GMT<![CDATA[Reply to RPI4 Dual Monitor blanking on Fri, 07 Jul 2023 15:18:16 GMT]]>@wishmaster270 Thanks for the suggestion. Unfortunately not a timing issue.

Adding a delay didn’t change the behaviour. ☹️

]]>https://forum.magicmirror.builders/post/110157https://forum.magicmirror.builders/post/110157Fri, 07 Jul 2023 15:18:16 GMT<![CDATA[Reply to RPI4 Dual Monitor blanking on Thu, 06 Jul 2023 18:44:57 GMT]]>@grantc66 Hi,

it may be a timing issue.
Maybe a sleep 1 between the two xrand commands helps.

]]>https://forum.magicmirror.builders/post/110154https://forum.magicmirror.builders/post/110154Thu, 06 Jul 2023 18:44:57 GMT