Thanks for your reply, and your timeThe latest "bullseye" and "Bookworm" releases use the KMS video driver.
The KMS driver seems less forgiving when the EDID data from the monitor is bad, nonexistant, or malformed.
If you get no display:
probably, your PI OS cannot figure out the EDID data from the monitor, and as such, cannot figure out what resolution to set. (so it sets none)
there have been many reports of "failed video output" which boil down to bad or non-existant EDID data from the monitor. This is an issue more often with the new KMS driver in Bullseye and Bookworm.
note: many HDMI adapters do not pass data in both directions, and can be the cause of no EDID Data. It is recommended to get the proper cable, and not use adapters.
- check your HDMI cabling and EDID status:
power off your PI
remove the SD card
power on the pi.
- you should get the diagnostic display as shown below. Pay attention to the EDID data status (the last line... below says EDID OK)
no-card1.jpg
if not, may be your cabling or (an adapter?)
however, you can set the resolution manually:
in /boot/cmdline.txt (add to the front/end of the line, NOT a new line)
-- IMPORTANT NOTE: for Bookworm, the file is at /boot/firmware/cmdline.txt !!
video=HDMI-A-1:1024x768@60D
(or whatever resolution you want)
I have determined that the issue is definitely the OS (specifically Debian 12 - Bookworm)I realise now that i had edited the original post but hadn't submitted it!
as i have been able to get the monitor working (albeit at the wrong resolution) by flashing the legacy version of raspOS (debian 11 - Bullseye)to my card.
cabling is not the issue, as all cables work on other machines and monitors.
the switches are not an issue, and are essential, as i have five computers on my desk, and having individual monitors for each would be impossible, also i get the same issue when connecting direct to the monitors.
This problem has cost me at least 8 hours, and it's still not fixed
Statistics: Posted by Mczakk — Sun Jan 28, 2024 4:23 pm