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

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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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