Dual monitors on Pi5

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

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

I'm using the default X11 setup for now.

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

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

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

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

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.

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