We are facing a problem where we have a HDMI screen, connected to the Verdin iMX8M Plus, that goes sleep after 30 seconds of no signal input. When this happens, it takes roughly 5 seconds that the screen backlight is fully powered off. After this time, it turns back on and the cycle repeats again.
We use this to control the HDMI output.
echo on > /sys/class/drm/card0-HDMI-A-1/status
echo off > /sys/class/drm/card0-HDMI-A-1/status
We have connected the HDMI screen to my laptop and replicated the test. We disabled the screen in windows the screen showed no signal out. after 30 seconds it went to sleep and the backlight turned off. This worked as expected.
One clue we found is that this specific screen briefly disapears from windows display settings. roughly 2 to 3 seconds. but reapeared again and the backlight stayed off.
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From the description of the issue you are facing, I understood that the HDMI screen is having its backlight cyclically activating even though you set the status of the HDMI to off (via /sys/class/drm/card0-HDMI-A-1/status). Is that right?
Also, the expected behavior (keeping the backlight off) works when connecting the same HDMI screen to your laptop.
I see you are using Torizon OS 5.7.2. Have you tried using a newer version of Torizon OS? E.g. 6.7.0 (Download Links | Toradex Developer Center)? What is the outcome?
Are you using native HDMI or you are using DSI-HDMI? If you used one, could you please test on the other?
And just for completeness, what are you using on your Laptop? Windows? Linux? Which version? Which distro (in case of Linux)?
That’s also correct. When the screen is connected to my laptop and we disable the output in the display settings of windows 10, than after 30 seconds the screen goes into sleep mode and the backlight turns off. It doesn’t turn on again until we enable the output in the display settings.
We tried a 5 months ago to upgrade to 6.3.x, but we ran into problems with our device trees not working or the software not booting at all. So we decided to stop the upgrade.
A second problem would be that we have devices already in the field. Upgrading Torizon for us that mens that we factory reset the device when upgrading Torizon. This is something we want to avoid.
I can give it try but this might take a lot of time to figure out.
We use the native HMDI. We are unable to switch to DSI HDMI since we use our own carrier board. The carrier board doesn’t have DSI HDMI, only native HDMI.
I use windows 10 on my laptop. I also use a Intel Nuc with Ubuntu 20.04 distro for development.
Actually, by using Torizon OS, you can leverage Torizon Cloud to update your devices (OS and/or application) on field using online or offline approach:
By using Torizon Cloud it is quite easy to deploy new version of OS and/or your application on the field with security and robustness.
If you have interest, you can try it for free. Just check the torizon.io website
Regarding the HDMI display, since you are using the native HDMI, isn’t it possible that you should control the card0-HDMI-A-2 instead of card0-HDMI-A-1?
You can actually check which HDMI output you are using before manipulating its status:
When connecting the HDMI monitor to the native HDMI of Verdin iMX8MP on Dahlia, card0-HDMI-A-2 became connected instead of card0-HDMI-A-1. So echoing off to card0-HDMI-A-2’s status disabled the display. I could wait several minutes and the HDMI monitor never activated itself. It only became active after echoing on to card0-HDMI-A-2’s status.
So I could not reproduce the behavior your are facing.
