Setting / checking fast charge in /sys/devices/platform/whatever

Andy Green andy at
Fri Jul 25 23:37:43 CEST 2008

Hash: SHA1

Somebody in the thread at some point said:
| On Monday 14 July 2008 21:44, Stroller wrote:
| ...
|> I decided to try forcing the Freerunner to fast-charge, and a little
|> Googling found me the CheckFastCharge-script on the Wiki [3].
|> Reading I find that it checks '/sys/devices/
|> platform/s3c2410-i2c/i2c-adapter/i2c-0/0-0008/chgmode' and that fast
|> charging is indicated by "fast_cccv" there.
|> Presumably this script was written for the Neo1973, however, or a
|> different kernel, as on my Freerunner the location is '/sys/devices/
|> platform/s3c2440-i2c/i2c-adapter/i2c-0/0-0073/chgmode' and it
|> currently says "fast", not "fast_cccv" (or, for that matter, slow or
|> anything like that).
|> So is "fast" the correct syntax for the Freerunner's chgmode?
|> Has it somehow detected that the charger is capable of 500+ mA?
|> Or should I echo "fast_cccv" to that location?
|> What are the correct '/sys/devices/platform/s3c2440-i2c/i2c-adapter/
|> i2c-0/0-0073/chgmode' values for "slow" and no-charge for the
|> Freerunner, please? (using the default factory image)
|> Or is chgmode simply broken on the Freerunner's default factory image?
| Did you actually try this yet, and did it work? I just bought a
| which is supossed to be able to provide over 2A, but the freerunner
will only
| pull 100mA which is annoying.

You can force it to pull up to 1A if you are sure it's OK for your power

"fast" and so on are modes in the charger state machine, they're
different from the actual limits which are enforced earlier in the power
chain pretty much at the USB power inputs to the PMU.

| A related question, the freerunner wil detect a 47k resitor in the
| charger. Is this value measured and available in software somewere? We
| be able to identify other chargers as well and build a database of ID
| resistors and allowed current (assuming other vendors use the same trick).

I don't think it is exposed down /sys at the moment.

- -Andy
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