car charger

Joel Newkirk freerunner at
Sun Oct 12 03:50:29 CEST 2008

On Sat, 11 Oct 2008 16:38:20 -0700, Michael Shiloh <michael at>
> Joel Newkirk wrote:
>> On Fri, 10 Oct 2008 09:05:09 -0700, Michael Shiloh
> <michael at>
>> wrote:
>>> David Garabana Barro wrote:
>>>> On Friday 10 October 2008 12:50:57 Cédric Berger wrote:
>>>>> Ok, thanks...
>>>>> Would be interesting if by chance you could check between the ID pin
>>>>> and ground if you have a resistance close to 4.7Kohm ...?
>>>> I will look at it, and post the results.
>>> Anxiously awaiting your measurements.
>>> If there is no 4.7K resistor, I'd move this discussion to the kernel 
>>> list. We should not be charging at 1A if we do not see this resistor.
>> The cig lighter adapter I got is just a USB port, (the ID pin doesn't
> exist
>> there) just jack in the USB<->MiniUSB cable.  I get the same readings
> below
>> on AC, on PC, and on DC.  If I force charging to 500mA or 100mA then
> they
>> reflect that.
>> root at iota:~# cat
>> /sys/devices/platform/s3c2440-i2c/i2c-adapter/i2c-0/0-0073/chgmode
>> fast
>> root at iota:~# cat
>> /sys/devices/platform/s3c2440-i2c/i2c-adapter/i2c-0/0-0073/charger_type
>> charger 1A mode 1A
> If I understand you correctly, this sounds like a bug.
> Let me confirm:
> 1. Disconnect your FreeRunner from any power source.
> 2. Power cycle (to clear any previous state).
> 3. Connect the FreeRunner to a PC USB port. We know these source at most 
> 500mA.
> 4. Display (and report) chgmode.
> Thanks,
> Michael

OK, here's the final results.  I've flashed the kernel since my previous
post in this thread, currently uname -a shows "Linux 2.6.24
#1 PREEMPT Fri Sep 26 14:13:25 EST 2008 armv4tl unknown".  After shutting
down and restarting:

with nothing connected, I get:
chgmode: play-only
charger_type: charger 1A mode 1A

Connected to PC:
chgmode: fast
charger_type: charger 1A mode 500mA

Connected to included wall charger:
chgmode: fast
charger_type: charger 1A mode 1A

Connected to cheapo car lighter-to-USB adapter:
chgmode: fast
charger_type: charger 1A mode 1A

(of course since the car charger provides 1000mA this is what I want it to
do, but I realize it shouldn't be doing it without intervention)


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