Price of the Freerunner spare parts
andy at openmoko.com
Thu Mar 27 22:21:54 CET 2008
Somebody in the thread at some point said:
> Thanks Kevin,
> I recall asking engineering what would happen if somebody disabled this
> check ( hey its open source) and the general impression was that if the
> charger was not capable of fast charging then you would not have nice
> outcomes. I think the worse case might be if you tried to draw more than
> 500ma from a PC USB. Somebody not in marketing should answer that question.
If you start poking at registers in kernelspace or via /sys you can make
it think it is on a charger and try to pull 1A. But in normal operation
it takes care to look for the special 48K resistor on the ID pin which
is found on the real charger before allowing it. So you have to go
around that check to make trouble.
Every USB host I ever saw has a high side switch and current limit
implemented anyway, if you pull much more than you are allowed (often
simply 500mA) it goes into overcurrent and turns off the tap.
Since we talk about random nonstandard meddling (ie, this isn't the
product's own behaviour) you can just put a bent paperclip in the USB
host socket and do much better than 1A if that wasn't the case :-)
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