GTA02 USB and battery current profile

Werner Almesberger werner at openmoko.org
Sun Mar 9 14:56:37 CET 2008


Felipe Balbi wrote:
> But you're misusing id pin. This is a huge hardware issue and should be
> solve asap. Id pin should generate an interrupt to the otg transceiver
> for it to switch between host and peripheral roles.

I don't know much about OTG, but our documentation says that OTG gives
us either ID open or ID very low-ohm, so we should be able to detect
that resistor "in the middle", no ?

> Instead of hardcoding 500mA current draw in the config descriptors, you
> should add 2 sets of them:
> 1. drawing 500mA
> 2. drawing 100mA

Hmm, that's what we usually do. I'll check later if we're also
consistent there.

> BTW, really precise resistor you got:-p
> 1% tolerance, wow. That must be kinda difficult to find :-p

Hmm, now that you mention it, 48k is indeed hard to find. Gotta check
what it really is - maybe plain good old 47k. That would be available
even with +/-0.1% accuracy :)

- Werner




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