USB current limit when phone off

Andy Green andy at
Thu Feb 5 15:25:27 CET 2009

Hash: SHA1

Somebody in the thread at some point said:
| On Thu, Feb 5, 2009 at 15:12, Andy Green <andy at> wrote:
|> So during all these tests we never hook to anything but a "dumb"
|> charger?  The kernel never gets the idea during that session that it
|> could pull 500mA legitimately and somehow wrongly hold on to that idea?
| yes... quite strange...
| I will try to do more tests to be sure of how much it pulls when off.
| And if I can find another charger, I'll try too (or with my computer
| when on vista -no driver-)...
| Maybe this charger is not so dumb... or rather even "dumber" than I
| thought after all ! ;-)  I do no remember with which phone it was
| originally shipped...
| Might be that under certain conditions the phone recognize the
| resistance making it think it is its wall charger....

It's possible, but the CPU is needed to actually go and measure the
special resistor on the charger and then change the USB current limit
mode, it's not like one GPIO or something that might accidentally go to
the wrong level when "off".

I'll see if I can reproduce it here in a little while since it's a very
specific thing you're seeing.

- -Andy
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