Post #1569283
2026-03-07 16:31 UTC
@tubetime
A client demanded that I use a USB-C connector for something that was not USB at all. I wanted to.put in stuff to negotiate a custom alternate mode, but it would have increased cost slightly. I did get them to allow adding the resistors to the device on the plug side to make it a "debug mode" device, though, and put the funny signals (3V CMOS logic levels) on the SBU (sideband) pins. The device on the jack side would detect that it was debug mode.
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Replies (1)
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@brouhaha@mastodon.social 2026-03-07 16:35
@tubetime The device with the plug wouldn't work on any normal host, and there's no telling what a host will do with a debug mode device, but it _maybe_ wasn't too likely to damage either. Plugging a real USB-C device into the jack wouldn't work but wouldn't harm the either. I still didn't like it. Since behavior of debug mode is unspecified, it shouldn't be used for anything that ships to end users. 2/2