From Newsgroup: comp.sys.raspberry-pi

Having some strange trouble getting dual monitors working with my
8GB Pi5. It only wants to use one of them.

Initially, the machine set up with an hdmi monitor on output 0
and an old DVI monitor on output 1. That did all I wanted, giving
sound via the hdmi output and extra screen space on the DVI monitor.

Overnight, the menu bar migrated to the extra monitor and I can't
move it back. The screen configuration utility doesn't recognize
the original monitor, though both monitors display at least some
boot output. At the moment, however, I get:
bob@raspberrypi:~$ xrandr
Screen 0: minimum 320 x 200, current 1920 x 1200, maximum 8192 x 8192
HDMI-1 disconnected primary (normal left inverted right x axis y axis)
HDMI-2 connected 1920x1200+0+0 (normal left inverted right x axis y axis) 519mm x 324mm
1920x1200 59.95*+
1600x1200 60.00
1680x1050 59.88
1280x1024 75.02 60.02
1152x864 75.00
1024x768 75.03 60.00
800x600 75.00 60.32
640x480 75.00 59.94
720x400 70.08
HDMI 1 is recognized when it's alone and works properly, sound and all.
It's a standard 1920x1080 display.

Some months ago a dual display worked fine with a DVI 1600x900 monitor.

I've tried both Wayland setups and X11, all behave the same at least in
regard to what monitors are active.

I believe it's important that the HDMI monitor be primary, in that it's
the only one that can provide audio output

At TNP's suggestion the power supply was replaced, raising the GPIO
rail to 5.45V, so I don't think that's the problem. I've also added usb_max_current_enable=1 to config.txt, but that seems unlikely to
help the monitor recognition. I'll find out after sending this.

Thanks for reading,

bob prohaska

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From Newsgroup: comp.sys.raspberry-pi

bp@www.zefox.net wrote:

Having some strange trouble getting dual monitors working with my
8GB Pi5. It only wants to use one of them.

After much fumbling about, both monitors are recognized and
working as desired. HDMI0 is the monitor providing audio output,
HDMI1 is a DVI monitor providing extra screen space. So far, so good.

Most of the time, HDMI1 isn't needed. However, if I power it off,
the mouse freezes, even if the cursor is visible on HDMI0. Worse
things could happen, but I'd rather not leave it powered on without
need. HDMI1 uses around 60 watts, more than the rest of my hardware
combined. I never tested this with the earlier dual-monitor setup,
a small 1600x900 DVI, so am not certain if the behavior is new or old.

Anybody know of a workaround?

Thanks for reading,

bob prohaska

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From Newsgroup: comp.sys.raspberry-pi

On 24/06/2025 05:28, bp@www.zefox.net wrote:

bp@www.zefox.net wrote:

Having some strange trouble getting dual monitors working with my
8GB Pi5. It only wants to use one of them.

After much fumbling about, both monitors are recognized and
working as desired. HDMI0 is the monitor providing audio output,
HDMI1 is a DVI monitor providing extra screen space. So far, so good.

Most of the time, HDMI1 isn't needed. However, if I power it off,
the mouse freezes, even if the cursor is visible on HDMI0. Worse
things could happen, but I'd rather not leave it powered on without
need. HDMI1 uses around 60 watts, more than the rest of my hardware
combined. I never tested this with the earlier dual-monitor setup,
a small 1600x900 DVI, so am not certain if the behavior is new or old.

Anybody know of a workaround?

Are you running the standard Pixel desktop which by default will now use
the Wayland windowing system instead of X11? If so try switching to X11
using raspi-config and see if that stops the problem.

I'm running the Mate desktop on X11 and don't have any problems with one
or other or both of the monitors disappearing, as they are on HDMI
switches allowing me to mix and match monitors with other systems as
desired.

---druck
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From Newsgroup: comp.sys.raspberry-pi

druck <news@druck.org.uk> wrote:

On 24/06/2025 05:28, bp@www.zefox.net wrote:

bp@www.zefox.net wrote:

Having some strange trouble getting dual monitors working with my
8GB Pi5. It only wants to use one of them.

After much fumbling about, both monitors are recognized and
working as desired. HDMI0 is the monitor providing audio output,
HDMI1 is a DVI monitor providing extra screen space. So far, so good.

Most of the time, HDMI1 isn't needed. However, if I power it off,
the mouse freezes, even if the cursor is visible on HDMI0. Worse
things could happen, but I'd rather not leave it powered on without
need. HDMI1 uses around 60 watts, more than the rest of my hardware
combined. I never tested this with the earlier dual-monitor setup,
a small 1600x900 DVI, so am not certain if the behavior is new or old.

Anybody know of a workaround?

Are you running the standard Pixel desktop which by default will now use
the Wayland windowing system instead of X11? If so try switching to X11 using raspi-config and see if that stops the problem.

I'm using the default X11 setup for now.

I'm running the Mate desktop on X11 and don't have any problems with one
or other or both of the monitors disappearing, as they are on HDMI
switches allowing me to mix and match monitors with other systems as desired.

Your HDMI switch is likely a big difference. No switch in my setup,
the monitor stays plugged into the Pi5 HDMI port. All I'm turning off
is the power switch on the monitor.

Thanks for writing!

bob prohaska

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From Newsgroup: comp.sys.raspberry-pi

bp@www.zefox.net wrote:

After much fumbling about, both monitors are recognized and
working as desired. HDMI0 is the monitor providing audio output,
HDMI1 is a DVI monitor providing extra screen space. So far, so good.

Here's another weird "feature" 8-)

When the Pi5 dual monitor setup first started up and worked the popup
help menus displayed by mousing over the icons on the top menu bar
appeared close to the icon and cursor, as normal. This is under the
default pixel/x11 windowing system.

Now, roughly a week later, mousing over the menu items (displayed
on HDMI0) reveals the popups, but on HDMI1, which doesn't even have
a menu bar displayed. Invoking the Screen Configuration application
shows the correct monitor identification, so the Pi isn't confused
about which screen is which.

Still, there's a sort of emphasis on HDMI 1 for things like unblanking.
If the host has blanked both screen and the mouse moves, the first to
light up is HDMI1. I expected it to be HDMI0, since that's the primary
monitor. Didn't check this until now, so can't if it's new or old.

As it happens, for space reasons I've placed the "extra" monitor to the
left of the "main" monitor. The default arrangement was clearly to add
the second monitor to the right of the first monitor so it was necessary
to manually correct the arrangement. It appears that somewhere in the
software a vestigal default position has not been overridden by Screen Configuration.

Thanks for reading,

bob prohaska

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From Newsgroup: comp.sys.raspberry-pi

On 24/06/2025 22:49, bp@www.zefox.net wrote:

Your HDMI switch is likely a big difference. No switch in my setup,
the monitor stays plugged into the Pi5 HDMI port. All I'm turning off
is the power switch on the monitor.

The desktop behaves exactly the same way when the switch changes inputs
as when the monitor is physically turned off.

Incidentally the EDID can still be read from a switched off monitor
using power supplied via the HDMI interface.

---druck
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From Newsgroup: comp.sys.raspberry-pi

On 26/06/2025 15:00, bp@www.zefox.net wrote:

When the Pi5 dual monitor setup first started up and worked the popup
help menus displayed by mousing over the icons on the top menu bar
appeared close to the icon and cursor, as normal. This is under the
default pixel/x11 windowing system.

Now, roughly a week later, mousing over the menu items (displayed
on HDMI0) reveals the popups, but on HDMI1, which doesn't even have
a menu bar displayed. Invoking the Screen Configuration application
shows the correct monitor identification, so the Pi isn't confused
about which screen is which.

Menu bar? Do you mean the panel? It is normally only set to be visible
on one monitor.

Still, there's a sort of emphasis on HDMI 1 for things like unblanking.
If the host has blanked both screen and the mouse moves, the first to
light up is HDMI1. I expected it to be HDMI0, since that's the primary monitor. Didn't check this until now, so can't if it's new or old.

The primary monitor is only used for placement of things such as panels.
The order of it unblanking is purely down to how long it takes each
monitor to detect the signal and come out of sleep mode. Even with two seemingly identical monitors they don't both come on at exactly the same
time.

As it happens, for space reasons I've placed the "extra" monitor to the
left of the "main" monitor. The default arrangement was clearly to add
the second monitor to the right of the first monitor so it was necessary
to manually correct the arrangement. It appears that somewhere in the software a vestigal default position has not been overridden by Screen Configuration.

All saved coordinates for windows are from the origin of the left most
screen, so if that is the one you use optionally windows are going to
move around.

Until I got identical home and work monitor setups, I wrote a Python
program to move them to their expected position on differing number and
sizes of monitors when the laptop was in each location.

---druck
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