Rpi5 dual HDMI setup?

[doppiaemme]

Hi,

I installed OpenPlotter on a RPi5 and tried to connect two HDMI displays.

The issue I have is that HDMI-2 works, but HDMI-1 doesn't.

Simply connecting to HDMI-1 makes the screen go on power save for no input available.

I've tried removing the SD and NVME and boot it.
In this mode:
HDMI-1 output works but at a very high definition
HDMI-2 output works but at a low (more normal) resolution.

This is telling me the HDMI ports seems to boht phisically work and the screens too.

But then once it boots with a proper image, then it doesn't work.

any clue?

thanks in advance!

M

[doppiaemme]

[UPDATE]
After some troubleshooting, it seems the issue comes from wrong hotplug detection related to the new firmware or KMS.
It seems that the bootloader fails to detect the HDMI EDID profile on HDM1 port (while it works on HDMI2!).
Then when the kernel starts up, it doesn't find this profile and doesn't know what to do with HDMI-1

I found a way to (at least) enable the port, by forcing
video=HDMI-A-1:1280x720@60D

in cmdline.txt

While this brings up the display, it's not an optimal solution, it doesn't recognize all the resolutions of the screen etc. Also I have issues with the mouse pointer.
So further investigations are needed.

[Sailoog]

thanks for reporting, is it reported on Raspberry OS somewhere?

[doppiaemme]

thanks for reporting, is it reported on Raspberry OS somewhere?

No I haven't, and I am not doing it for now as I am not even sure it's a real bug.
For sure the hotplug capabilities in raspberry is poor, but I am getting so weird behaviours even by changing the HDMI cable.

My plan was to use one touchscreen in the cockpit and one down at the chart table, with screen mirroring.
I need to find the right working setup.
but Connecting/disconnecting the screen often and in real time it's something rpi doesn't likes a lot.

Also with the new Wayland instead of X11 setting up screen mirroring is almost impossible. :-(

[doppiaemme]

[UPDATE SOLVED]

Indeed it was not a RPI problem.
it was an HDMI adapter issue.
I am using an adapter (Waveshare Micro HDMI To HDMI Multifunctional Adapter) and it was faulty making the hotplug fail on port 1
Replacing that, it worked!

[Jon on Wildflowers]

[UPDATE SOLVED]

Indeed it was not a RPI problem.
it was an HDMI adapter issue.
I am using an adapter (Waveshare Micro HDMI To HDMI Multifunctional Adapter) and it was faulty making the hotplug fail on port 1
Replacing that, it worked!

Is the touch function carried via the HDMI cable?

[EyeofCy]

[UPDATE SOLVED]

Indeed it was not a RPI problem.
it was an HDMI adapter issue.
I am using an adapter (Waveshare Micro HDMI To HDMI Multifunctional Adapter) and it was faulty making the hotplug fail on port 1
Replacing that, it worked!

Is the touch function carried via the HDMI cable?

I had  thought that too about touch function being controlled over HDMI when touch control wasn't working.  Turns out its the power supply to the monitor that carries the touch signal.  I moved my USB-C power cable from  the wall wart to the USB-C slot of the Raspberry Pi and the touch screen worked straight away.  Good luck!

[doppiaemme]

[UPDATE SOLVED]

Indeed it was not a RPI problem.
it was an HDMI adapter issue.
I am using an adapter (Waveshare Micro HDMI To HDMI Multifunctional Adapter) and it was faulty making the hotplug fail on port 1
Replacing that, it worked!

Is the touch function carried via the HDMI cable?

I had  thought that too about touch function being controlled over HDMI when touch control wasn't working.  Turns out its the power supply to the monitor that carries the touch signal.  I moved my USB-C power cable from  the wall wart to the USB-C slot of the Raspberry Pi and the touch screen worked straight away.  Good luck!

IMHO the touch function is controlled only via USB.
What you have done is indeed connecting the RPI USB to the screen's USB, thus enabling the touch control over USB.
If before you had the screen powered by the external power brick plus the HDMI cable, the USB was not connected.
By powering the screen via USB you ALSO connected the USB, which carries the touch control.