Fast charging and the resistor trick

[Andy Green]

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Somebody in the thread at some point said:
|> | How do I have to design the USB endpoints on the device, so the
Freerunner
|> | does charge with 1A? Or do I need the 47k Ohm resistor if the FR is in
|> | host  mode?
|>
|> Only the 47K resistor is looked for to see if a charger is around.
|
| How does the FR knows he can charge with 1A while connected to my
computer?

What the charging limit is set to is separate to the USB power input
limit.  The USB power input limit comes first.

So you should have a USB power input limit of 500mA when enumerated on
your PC, whatever the separate charging limit is set to doesn't change
anything so long as it is >= 500mA.  It will never be able to get more
power than the USB power input limit (minus the power needed to run the
device) anyway.

- -Andy


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