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Re: Raspberry Pi 4 Dual Monitors

Posted: Sun Jul 07, 2019 1:26 pm
by masterofslack
Thanks for that Dave. I won't return them just yet.

After seeing aBUGSworstnightmare's comment, I ran rpi-update. Since then I've rebooted 3 times and cold-booted 3 times. The Pi4 booted up with dual displays each time.

I don't want to give another premature report of success, but the updated firmware seems to have helped.

Re: Raspberry Pi 4 Dual Monitors

Posted: Sun Jul 07, 2019 1:38 pm
by maddogdave
The software update has fixed the issue for me
sudo rpi-update
I also now see how the layout can be tweaked by the positioning of the 2 displays, so that you can overlap or not, hence ignore my comment earlier regarding the interface, which now does exactly what it says on the tin.
Even booting with both my tv’s in standby, the primary display automatically switches on, both are active on the Pi and if I manually power up the second screen it all works exactly as it should.
For me, it’s solved.

Re: Raspberry Pi 4 Dual Monitors

Posted: Sun Jul 07, 2019 8:32 pm
by PeterO
I just did an rpi-update and both my monitors are now waking up from sleep during the boot 8-)
PeterO

Re: Raspberry Pi 4 Dual Monitors

Posted: Sun Jul 07, 2019 10:04 pm
by davidcoton
PeterO wrote:
Sun Jul 07, 2019 8:32 pm
I just did an rip-update ...
Doesn't that imply that the Pi is dead? :lol:

Re: Raspberry Pi 4 Dual Monitors

Posted: Mon Jul 08, 2019 2:57 pm
by cpthomas
Hello!
I've had similar problems and symptoms getting dual monitors working. Two (differently sized) screens would individually work in HDMI-0 on boot, and tvservice would correctly report them, but I couldn't boot with two screens plugged in, and tvservice wouldn't recognise anything plugged into HDMI-1, returning "[E] Invalid device/display ID." instead .

Running sudo rpi-update and then rebooting seems to have fixed it for me too.

Re: Raspberry Pi 4 Dual Monitors

Posted: Mon Jul 08, 2019 3:08 pm
by jamesh
cpthomas wrote:
Mon Jul 08, 2019 2:57 pm
Hello!
I've had similar problems and symptoms getting dual monitors working. Two (differently sized) screens would individually work in HDMI-0 on boot, and tvservice would correctly report them, but I couldn't boot with two screens plugged in, and tvservice wouldn't recognise anything plugged into HDMI-1, returning "[E] Invalid device/display ID." instead .

Running sudo rpi-update and then rebooting seems to have fixed it for me too.
Excellent. This fix is looking good so far. Thanks for trying it out.

Re: Raspberry Pi 4 Dual Monitors

Posted: Tue Jul 09, 2019 12:13 am
by Prince Hal
Still having trouble, even following latest update (and I had to accept changes [--allow-releaseinfo-change] because things went "stable").

I'm using two HDMI monitors, admittedly older, but each works individually in HDMI0 whilst in HDMI1 they each show only the rainbow screen and nothing further. I can even switch the monitors (unplugging and swapping the micro-HDMI cables between HDMI0 and HDMI1) when both are active, and whichever one is plugged into HDMI1 will only show the rainbow splash screen, whereas the one plugged into HDMI0 will immediately show the text screen that comes up on boot. If I run startx, only the screen plugged in to HDMI0 will show the desktop, and that is true even when I hot-swap the cables, as before. I've rebooted many times to the same end.

tvservice -l
2 attached device(s), display ID's are :
Display Number 2, type HDMI 0
Display Number 7, type HDMI 1

tvservice -m DMT -v 2
Group DMT has 18 modes:
mode 4: 640x480 @ 60Hz 4:3, clock:25MHz progressive
mode 5: 640x480 @ 72Hz 4:3, clock:31MHz progressive
mode 6: 640x480 @ 75Hz 4:3, clock:31MHz progressive
mode 8: 800x600 @ 56Hz 4:3, clock:36MHz progressive
mode 9: 800x600 @ 60Hz 4:3, clock:40MHz progressive
mode 10: 800x600 @ 72Hz 4:3, clock:50MHz progressive
mode 11: 800x600 @ 75Hz 4:3, clock:49MHz progressive
mode 16: 1024x768 @ 60Hz 4:3, clock:65MHz progressive
mode 17: 1024x768 @ 70Hz 4:3, clock:75MHz progressive
mode 18: 1024x768 @ 75Hz 4:3, clock:78MHz progressive
mode 21: 1152x864 @ 75Hz 4:3, clock:108MHz progressive
mode 32: 1280x960 @ 60Hz 4:3, clock:108MHz progressive
mode 35: 1280x1024 @ 60Hz 5:4, clock:108MHz progressive
mode 36: 1280x1024 @ 75Hz 5:4, clock:135MHz progressive
mode 42: 1400x1050 @ 60Hz 4:3, clock:121MHz progressive
mode 47: 1440x900 @ 60Hz 16:10, clock:106MHz progressive
mode 51: 1600x1200 @ 60Hz 4:3, clock:162MHz progressive
(prefer) mode 58: 1680x1050 @ 60Hz 16:10, clock:146MHz progressive

tvservice -m DMT -v 7
Group DMT has 2 modes:
mode 4: 640x480 @ 60Hz 4:3, clock:25MHz progressive
(prefer) mode 35: 1280x1024 @ 60Hz 5:4, clock:108MHz progressive


One possible clue is from dmesg, which contains these lines:

[ 0.268375] bcm2708_fb soc:fb: FB found 1 display(s)
[ 0.313537] Console: switching to colour frame buffer device 210x65
[ 0.322196] bcm2708_fb soc:fb: Registered framebuffer for display 0, size 1680x1050

Does this mean the frame buffer software is only seeing one of the displays?

Re: Raspberry Pi 4 Dual Monitors

Posted: Tue Jul 09, 2019 4:01 am
by chipace
PeterO wrote:
Sun Jul 07, 2019 8:32 pm
I just did an rpi-update and both my monitors are now waking up from sleep during the boot 8-)
PeterO
Thank you very much. I updated my firmware and have no problems driving dual monitors. No /boot/config.txt settings needed.

Is there a way to tell which firmware is installed? Is the firmware installed on the SPI flash chip, or is that just for booting?

Re: Raspberry Pi 4 Dual Monitors

Posted: Tue Jul 09, 2019 10:30 am
by tvjon
tvjon wrote:
Thu Jul 04, 2019 8:48 am
I see that arandr has has been updated, along with a firmware fix to re-enable Composite video on RPi3.

...
No change in findings for pure hdmi connections, however...

Is there further information available regarding the "less capable" HDMI1 output?

I eliminated the possibility of a faulty Pi4 by trying the same setup with a different Pi4, in fact a Pi4 with 2Gb ram, with reproducable problems as per my previous post.

So, bearing in mind the "less capable" HDMI 1, I tried 2 different, but same make, Dell monitors which do not have HDMI, but its predecessor, DVI-D, & lo & behold Pi4 boots reliably, & said DVI-D extends the desktop properly.

Moving the icons around in arandr no longer crashes Pi4 using this configuration.

The reverse, with DVi-D in HDMI0, & any available HDMI only monitor in HDMI 1 socket, as reported before the boot text scrolls up the screen & then the Pi4 crashes, no SSH possible.

It would be interesting to see if anyone having dual screen monitors, but unable to boot, could see if such applies to them.

Re: Raspberry Pi 4 Dual Monitors

Posted: Tue Jul 09, 2019 11:08 am
by snowballEarth
I also ran sudo rpi-update and now i no longer get blank screens during noobs raspbian boots

Re: Raspberry Pi 4 Dual Monitors

Posted: Wed Jul 10, 2019 8:18 pm
by andynz
I did the rpi-update yesterday and the second monitor then workined fine. But after an 'apt update upgrade' the unit does not fully boot. I see the 4 Raspberries on the first monitor then blank screens and just the RED LED lit on the Pi4-4G board. If I remove the second monitor connection the boot works fine with single monitor.

I have not tried doing a reinstall, rpi-update and NOT do the apt upgrade yet to confirm it is definitely the apt update that causes the issue.

Oh and BTW, thanks heaps to the Pi developers. You guys have produced a great general workstation with huge potential. I really appreciate what you have created.

Re: Raspberry Pi 4 Dual Monitors

Posted: Wed Jul 10, 2019 8:26 pm
by timg236
andynz wrote:
Wed Jul 10, 2019 8:18 pm
I did the rpi-update yesterday and the second monitor then workined fine. But after an 'apt update upgrade' the unit does not fully boot. I see the 4 Raspberries on the first monitor then blank screens and just the RED LED lit on the Pi4-4G board. If I remove the second monitor connection the boot works fine with single monitor.

I have not tried doing a reinstall, rpi-update and NOT do the apt upgrade yet to confirm it is definitely the apt update that causes the issue.

Oh and BTW, thanks heaps to the Pi developers. You guys have produced a great general workstation with huge potential. I really appreciate what you have created.

It might be worth checking the value of "vcgencmd version" to see whether the 'apt-get update upgrade' potentially downgraded the firmware. The HDMI display fixes in the rpi-update image have been rolled into the next set of apt packages which should be available very soon. Maybe tomorrow if all goes well.

Re: Raspberry Pi 4 Dual Monitors

Posted: Wed Jul 10, 2019 8:42 pm
by andynz
Ah, that makes sense. Many thanks. You guys are fantastic :)

Re: Raspberry Pi 4 Dual Monitors

Posted: Thu Jul 11, 2019 1:53 am
by Prince Hal
Since I was still having trouble with dual monitors, I thought I should retry everything with a clean install of Buster, with the latest update. Sure enough, the dual monitors worked, and I now realise my mistake. I had copied over my old Raspi3B+ config file.

For the benefit of others who may face the same issue, please be aware that the new Raspbian adds a few lines to config.txt in the /boot partition that are necessary for dual monitors. Maybe they are in the documentation, but I didn't notice. They are:

[pi4]
# Enable DRM VC4 V3D driver on top of the dispmanx display stack
dtoverlay=vc4-fkms-v3d
max_framebuffers=2


So if you are having trouble with dual monitors on your shiny new Raspi 4B, make sure you have the above lines in your config.txt file.

Re: Raspberry Pi 4 Dual Monitors

Posted: Thu Jul 11, 2019 6:20 pm
by andynz
Sorry I didn't check the "vcgencmd version" but did a "rip-update" again after I had done an apt upgrade and dual monitor worked fine so as suggested it was just a catch up on the apt packages required.

Re: Raspberry Pi 4 Dual Monitors

Posted: Thu Aug 08, 2019 5:42 pm
by mob-i-l
I have two 1280x1024 screens connected to my Raspberry Pi 4 B with 4 GB RAM. The monitors are connected via HDMI to DVI-D connectors. What is the best amount of GPU memory to use with this? Now I have 128 MB, but that is perhaps unnecessarily high.

Re: Raspberry Pi 4 Dual Monitors

Posted: Thu Aug 08, 2019 6:26 pm
by 6by9
mob-i-l wrote:
Thu Aug 08, 2019 5:42 pm
I have two 1280x1024 screens connected to my Raspberry Pi 4 B with 4 GB RAM. The monitors are connected via HDMI to DVI-D connectors. What is the best amount of GPU memory to use with this? Now I have 128 MB, but that is perhaps unnecessarily high.
The new driver allocates memory from the kernel cma heap, not gpu_mem. Gpu_mem is now only used by the camera and codecs, therefore 64M is sufficient for most use cases, with higher values only being required for heavy camera use cases or 4k hevc decode (libreelec does this for you)

Re: Raspberry Pi 4 Dual Monitors

Posted: Sun Sep 15, 2019 2:55 am
by SnowsongWolf
Admittedly I'm fairly new to Raspberry Pi and Linux in general.

I have both HDMI monitors working, however the pi is simply cloning framebuffer 0. How do I get individual framebuffers for each monitor? I'm using Raspbian buster lite (using the rpi to drive large LCD eyes for a costume).

Re: Raspberry Pi 4 Dual Monitors

Posted: Sun Sep 15, 2019 4:53 am
by SnowsongWolf
Nevermind, finally figured it out. I had to disable the optional driver loaded in the [rpi4] section of /boot/config.txt

Re: Raspberry Pi 4 Dual Monitors

Posted: Sat Oct 05, 2019 9:52 am
by majenko
I am just trying to get dual monitors working on my Pi 4. Following hints above I used the edid from my primary monitor to even get to see the second monitor and its resolutions. Now I have the second monitor "working" in that the Pi sees it and configures the right resolution - and it even turns it on... kind of...

But the display is flashing on and off, and it's comprised of red vertical lines and noise all over it.

* https://photos.app.goo.gl/RzU2YKcwRSWmgh1D7

The first screen is perfect - I'm posting this using it right now. Swapping the cables around makes everything reverse, so it's not the monitor (which i have been using for years in a triple-head setup on my main PC).

It strikes me as a timing problem that can be cured in software, but I don't have the diagnostic tools to work on low-level HDMI problems.

Code: Select all

xrandr:

Screen 0: minimum 320 x 200, current 3360 x 1050, maximum 7680 x 7680
HDMI-1 connected primary 1680x1050+1680+0 (normal left inverted right x axis y axis) 408mm x 255mm
   1680x1050     59.95*+
   1280x1024     75.02    60.02  
   1440x900      74.98    59.90  
   1280x960      60.00  
   1152x864      75.00  
   1024x768      75.03    70.07    60.00  
   832x624       74.55  
   800x600       72.19    75.00    60.32    56.25  
   640x480       75.00    72.81    66.67    59.94  
   720x400       70.08  
HDMI-2 connected 1680x1050+0+0 (normal left inverted right x axis y axis) 408mm x 255mm
   1680x1050     59.95*+
   1280x1024     75.02    60.02  
   1440x900      74.98    59.90  
   1280x960      60.00  
   1152x864      75.00  
   1024x768      75.03    70.07    60.00  
   832x624       74.55  
   800x600       72.19    75.00    60.32    56.25  
   640x480       75.00    72.81    66.67    59.94  
   720x400       70.08  
   

tvservice -l: 
2 attached device(s), display ID's are : 
Display Number 2, type HDMI 0
Display Number 7, type HDMI 1

tvservice -s -v 2:
state 0x6 [DVI CUSTOM RGB full unknown AR], 1680x1050 @ 60.00Hz, progressive

tvservice -s -v 7:
state 0x6 [DVI CUSTOM RGB full unknown AR], 1680x1050 @ 60.00Hz, progressive
Anything else I can try (I have tried tweaking every option I can find, including drive, boost, pixel format, all to no avail. All I can do is change the colour from red to pink...)?

Re: Raspberry Pi 4 Dual Monitors

Posted: Tue Oct 08, 2019 5:31 pm
by majenko
Update: two new matched 24" iiyama monitors, and still the problem persists. HDMI1 is perfect. HDMI2 is just garbage.