Troubleshooting • Re: how to force hdmi signal output with pi5?

if you disconnect monitor, Can you probe the hdmi signal on the port with logic analyzer?

you wont get anything, due to how hdmi works

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the source (rpi) will pull one side of the differential pair low

the sink (display) has pullup resistors, and measures the difference

with no display, you have no pull-up, and both lines will register as low

Thanks for your detailed reply. That means hdmi source working like opendrain gpios, so I should to provide the Vcc power to probe its signal. But I find some hdmi circuits picture which the source also provides 3.3v pullup, maybe there are some different versions of hdmi source designs.

Statistics: Posted by dsds — Mon Mar 25, 2024 7:23 am

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