[Gta04-owner] QtMoko v48 - Sound

NeilBrown neilb at suse.de
Wed Oct 3 07:51:36 CEST 2012


On Sun, 30 Sep 2012 19:35:50 +0200 Gilles Filippini
<gilles.filippini at free.fr> wrote:

> Gilles Filippini a écrit , Le 17/09/2012 18:02:
> > Radek Polak a écrit , Le 17/09/2012 16:41:
> >> /sys/class/hwmon/hwmon0/device/in7_input seems to work now ok (i get 24 and 26 
> >> values now).
> > 
> > Thank you Radek!
> > 
> > Without any jack plugged in, /sys/class/hwmon/hwmon0/device/in7_input
> > reports values from this set: 26, 29, 31, 34. By far 29 most of the time.
> 
> I've checked these values again, and it appears they were wrong. They
> are actually:
> * around 1058 when *no* headset is plugged in.
> * randomly between 41 and 393 when headset is plugged in.

The value is only meaningful when the /dev/input/jack device is open.  When
it is not open, the mic-bias voltage is not present so it will always
register an open circuit, which is what you see.

The best way to test it is to run
   evtest /dev/input/jack
in one window, and 
   watch cat /sys/class/hwmon/hwmon0/device/in7_input
in another.

I've never seen a number over 1000.  This seems to suggest some sort of short
in your hardware.  When there is no headset present, the circuit should be
open and no current should reach the current detector.

Having a random value is also very strange.  Small amounts of randomness is
certainly expected, but deviations much more than about 30 are hard to
explain.  You are getting 10 times that.

I can only conclude that there must be something odd with your hardware.  I
cannot suggest what it might be, or how you might find out.

NeilBrown



> 
> The values I reported previously (around 29) are obtained only when I
> disable the jack device with
>  # rm -f /dev/input/event4
> before launching qtmoko, and stay the same when the headset is plugged in.
> 
> Thanks,
> 
> _g.
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> Gta04-owner at goldelico.com
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