Rpi 4 and two monitors

[sdetweil]

well, I finally got it to work , note I have two displays that support 4k, 3840x2160, so my screen pos is double yours

in /boot/config.txt

[pi4]
# Enable DRM VC4 V3D driver on top of the dispmanx display stack
dtoverlay=vc4-fkms-v3d
max_framebuffers=4

and in /boot/cmdline.txt
add cma=384M to the end of the line, like this…

plymouth.ignore-serial-consoles cma=384M

then you must power down and back up for these changes to be applied

found here
https://retropie.org.uk/forum/topic/24436/drm_ioctl_mode_create_dumb-failed-cannot-allocate-memory/9

I was getting the DRM cannot allocate memory error

MagicMirror/run-start.sh line for chromium

chromium-browser -noerrdialogs -kiosk --user-data-dir='Default' --window-position=0,0 -start_maximized  --disable-infobars --app=http://localhost:$port  --ignore-certificate-errors-spki-list --ignore-ssl-errors --ignore-certificate-errors 2>/dev/null

MagicMirror2/run-start.sh line for chromium

chromium-browser --disable-bundled-ppapi-flash -noerrdialogs -kiosk -start_maximized  --window-position="3840,0" --disable-infobars --app=http://localhost:$port  --ignore-certificate-errors-spki-list --ignore-ssl-errors --ignore-certificate-errors  --user-data-dir='Test2'  # 2>/dev/null

this boots up and both MM start via pm2 and display on separate screens, with different content (modules in different positions)

here is a screenshot of my dev system connected to both MM servers at the same time
(the displays are two hdmi ports on the same TV, so I can’t show them physically at the same time)

[NathTheDude]

@sdetweil - nice 2 x 4k’s.

So, I did what you mentioned in your last post but unfortunetly I am in the same issue. I wonder if your problem was more to do with 2 x 4k’s which is perhaps different to mine? I am not sure.

[NathTheDude]

@sdetweil - if you comment out the chromium line in the run-start.sh does this cause you any issues/errors?

[sdetweil]

@NathTheDude no… you could just change config.js to serverOnly:true, then it won’t try to start chrome

[sdetweil]

@NathTheDude I started by doing

cd MagicMirror
node serveronly 

note no npm start needed, will run til you ctrl-break out

then tried multiple tries to get chrome on the second display…
(it works manually if the position is mispelled!)

then once it worked reliably,
i killed the server instance
then I used pm2 to stop/start that instance til I got that to work.

note that I had to use
–disable-bundled-ppapi-flash
on the second instance as it collided with the 1st…

[krocaq]

@sdetweil

@saljoke
Hi. Thats right. i only use 1 Pi4 to serve both displays via 2 MM instances. first the originally MagicMirror directory and the second in a MagicMirror2 directory. Both powered up via PM2 and turned off and on via PIR sensor.

The config looks like this:

language: “de”,
logLevel: [“INFO”, “LOG”, “WARN”, “ERROR”],
timeFormat: 24,
units: “metric”,
electronOptions: {fullscreen:true, x:1920},

1920 is the resolution witdh of the main display.

Very easy to handle and good for the electrical consumption

[sdetweil]

@krocaq see my comment here , you can do it with ONE directory
https://forum.magicmirror.builders/topic/17239/two-display/2?_=1663555322286