Re:iPhone 15 and iPhone 15 Plus
by OJFord on Tuesday September 12, 2023 @09:41PM
(#37491158)
I suppose hypothetically you could have data capability built in to the power negotiation pairs, so that it wasn't possible to offer charging without also some amount of data... but quite some complexity to add as a trade-off, not an obvious choice.
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Conveniently, that's actually the case. A USB-C port should provide no power if there's nothing plugged in, and that's sensed by the data connection pairs. However, to support A-C adapters, you can fake it through the normal connection there.
This is why some things that have a C port won't charge on a C-C cable, but will on a A-C cable, because they don't actually talk to say they need power, but the A port will provide some power regardless, but a C port won't.