[SOLVED] Dual monitor on RPi4

louigi600 · 07-04-2021, 02:57 AM

Ok here's my confg.txt attached

Desiderius · 07-05-2021, 08:34 AM

Finally it works !

The guilty was my HDMI cable ! Apparently something is broken inside it and it does not send ( or receive ) EDID data !

Changing the cable for a new one makes the operation work as expected : I have the same screen on the Diskio Pi screen and my desktop computer screen !
Sorry for the trouble !

Desiderius · 07-09-2021, 08:49 AM

I have now the two displays together as expected but there are a few problems remaining.

When I put :

<CODE>
dtoverlay=vc4-fkms-v3d
max_framebuffers=2
</CODE>

in my config.txt

I have two problems with KDE 5 :

- My System Settings window appears but totally black

However, it is active : when I click inside it, I see the item underneath and can change it but I find something particular it is very difficult

- In VLC, all the videos are disturbed with many interferences ( although the sound is good )

I guess this a problem with the video driver "vc4-fkms-v3d" ; all the other applications are running fine. Effectively, if I delete the two items in config.txt and reboot, the two problems have disappeared.

Is there another video driver I could try that works with dual displays ?

Desiderius · 07-09-2021, 10:15 AM

I have found the right driver !!!!

Replace "dtoverlay=vc4-fkms-v3d" with "dtoverlay=vc4-kms-v3d" and everything is working fine in KDE 5 !!

Desiderius · 07-12-2021, 07:52 AM

Using "dtoverlay=vc4-kms-v3d" resolves many problems :

- Systems settings black screen and VLC videos disturbed work now normally

- But also quality of the image on a computer screen ( now pure and bright versus very pixelated )

- But also using a video projector ( before there was no image; now the image is clear on the wall screen )

The last thing remaining is that with the old driver I had the image on both screens ( Diskio Pi screen and external screen ); Now with this new driver, I have only the image on the external screen and no more on the Diskio Pi screen.

I have tried to launch xrandr but it comes into an error and only sees one screen !

Code:

 xrandr: Failed to get size of gamma for output default
Screen 0: minimum 1920 x 1080, current 1920 x 1080, maximum 1920 x 1080
default connected primary 1920x1080+0+0 0mm x 0mm
   1920x1080      0.00*

I saw that @louigi600 had the same problem at beginning : how do you solve it ?

Quote:

Originally Posted by Desiderius

I have found the right driver !!!!

Replace "dtoverlay=vc4-fkms-v3d" with "dtoverlay=vc4-kms-v3d" and everything is working fine in KDE 5 !!

Desiderius · 07-13-2021, 08:28 AM

Finally I have found how to have both "clean" displays between the screen of Diskio Pi and an external screen

Selecting "dtoverlay=vc4-kms-v3d-pi4"; I have displays on both screens and it is clear !

Quote:

Originally Posted by Desiderius

Using "dtoverlay=vc4-kms-v3d" resolves many problems :

- Systems settings black screen and VLC videos disturbed work now normally

- But also quality of the image on a computer screen ( now pure and bright versus very pixelated )

- But also using a video projector ( before there was no image; now the image is clear on the wall screen )

The last thing remaining is that with the old driver I had the image on both screens ( Diskio Pi screen and external screen ); Now with this new driver, I have only the image on the external screen and no more on the Diskio Pi screen.

I have tried to launch xrandr but it comes into an error and only sees one screen !

Code:

 xrandr: Failed to get size of gamma for output default
Screen 0: minimum 1920 x 1080, current 1920 x 1080, maximum 1920 x 1080
default connected primary 1920x1080+0+0 0mm x 0mm
   1920x1080      0.00*

I saw that @louigi600 had the same problem at beginning : how do you solve it ?

glorsplitz · 07-13-2021, 08:42 PM

I got same thing from xrandr in post #20 with two monitors connected, seems louigi600 and Desiderius figured it out, thanks!

Now that we're talking dual monitors on rpi4, anyone got any slackwareARM desktop backgrounds for these monitors?

Quick search didn't find any, I don't feel quite right using a slackware background on my slackwareARM rpi4.

louigi600 · 08-11-2021, 04:30 PM

I'm for really simple desktop (fluxbox) so background is not my thing but just google for a desktop background ... I'm sure you will find one that inspires you.