Discussion
GPIO madness.
Dear Lazyweb, riddle me this: Boot Pi with HDMI monitor attached: works fine. Boot without monitor: all GPIO inputs "flap" about once a second. Plug in monitor: 10 seconds later, inputs start behaving normally. Unplug monitor: remains...
https://jwz.org/b/yk2F
@jwz someone smarter and better paid than me suggests comparing the output of `pinctrl` in state [2] against the output in state [3] (once stable)
@jwz I wonder if it’s a weird memory allocation thing. The video memory and the normal ram are shared. I wonder if the GPIO and Video have some overlapping memory tables. When you connect the monitor it’s all properly allocated, then when you unplug it takes a while for some bit of data to overwrite that memory space. I’m not technical enough or smart enough to test or debug this but it came to mind as I was reading about miners using dummy hdmi to trick anti hash cards.
UPDATE: I have now been informed *NINE TIMES* that HDID dongles exist by people who don't read the replies before commenting with the first thing that popped into their head, don't have an answer to my actual question, but think they know how to Google.
I am blocking every single one of you.
Don't be that guy.
@jwz who can see what on masto confuses the hell out of me, but is there a chance they just can't see those other replies? Like if they're not on the same server?
@Aedius Do not explain Mastodon to me. *plonk*
@jwz Maybe reading via Mastodon, where some replies are not fetched automatically? But yes, once clicking through...
@jwz slim chance this might be related, I encountered this some years ago, a only-when-headless, non-booting Linux (Ubuntu 20), due to kernel config: https://rightsock.blogspot.com/2020/05/intel-compute-stick-wont-boot-without.html?m=1
@jwz Maybe hdmi monitor detection causing the gpios to flap?
You can tell the kernel to just turn off the hdmi sockets entirely in the config.txt I think.
(Googles) Try hdmi_ignore_hotplug=1 in config.txt ?
Let's try a different question: How do I make a Pi4b Debian 12.11 believe that an HDMI monitor is connected even if one is not?
@[email protected] There is fake monitor dongle that you can buy for a few dollars from China.
Example (untested): https://www.aliexpress.com/item/1005007634237816.html
HEY EVERYBODY I HAVE BEEN INFORMED THAT FAKE HDID DONGLES EXIST. SIX TIMES.
@[email protected] And I can't see any of the other posts about fake HDMI dongles. The wonders of federated network in action
@jwz Either
hdmi_force_hotplug=1 (turns the hdmi sockets permanently on) or hdmi_ignore_hotplug=1 (turns them off) in config.txt will do what you want, I think.
@pja No, and no.
@jwz Annoyingly this appears to be out of date advice that doesn't work with the video driver in modern kernels.
I think you're supposed to use raspi-config to select an appropriate dtoverlay maybe? Some suggested configurations here: https://forums.raspberrypi.com/viewtopic.php?t=344322
The fact that things continue working *after I have unplugged the monitor* makes me think that this some kernel initialization or dependency nonsense and perhaps there's some modprobe that could fix it, but I didn't see a smoking gun in lsmod.
@jwz
I think there are HDMI deadplugs. Stupid solution, but maybe the easiest.
@jwz The onluy way I can think of is by using a dummy HDMI plug. Basically a small dongle that you plug into the HDMI port.
@jwz Do you have pull-ups or pull-downs enabled on the GPIO pins. I've forgotten to do that and gone nearly insane a few times.
@[email protected] sonst würde ja niemand die hdmi dongle kaufen, die simulieren, dass ein monitor angeschlossen ist.
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