power plug

Andreas Kostyrka andreas at kostyrka.org
Sat Jan 20 14:38:15 CET 2007

* Nikita V. Youshchenko <yoush at debian.org> [070120 13:19]:
> >> How can it charge over USB if it gets full discharged?
> >> AFAIK, USB device is not powered by USB host until it is configured.
> >> So gadged must be operational to charge over usb.
> > 
> > Well, I'm almost certain that my USB mouse has no battery builtin, so
> > I guess USB does provide some minimal power to enable configuration.
> Sure.
> That depends on how usb client hardware is done.
> In your mouse, there is microcontroller that controls usb client
> functionality, and powers itself from usb (yes usb gives some limited
> power - up to 100 mA if I remember correctly - even to client which is not
> configured yet.
> But in case when USB is controlled by Linux USB Gadget driver, central CPU
> must be operational and kernel up and running for USB client functionality
> to work.
That depends upon how clever the USB port hardware is, I'd guess.

> Soft is Linux kernel in my case.
> And yes, it can't charge over usb until it is up.
I know, I've owned an iPaq with GPE once with that characteristic too ;)


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