[Gumstix-users] Problem with audiostix2 recording

[Matt M. <mp...@se...>]

After fighting with my gumstix for a couple days, I've discovered what
appears to be an electrical design problem with my audiostix2
(PCB00012-R791) which I've detailed below.

This may or many not be related to my real problem: I can't seem to
record audio. Running brec results in files with lots of 7Fs and 80s
and no amount of messing with aumix -i or -l seems to help. Any hints?

The electrical strangeness:

If I boot with a mic plugged into line-in with a -mono- mic plug, the
sound drivers refuse to load. With the ALSA drivers from either the
latest release (r1161) or buildroot as of a couple days ago, I get:

pxa2xx_ac97_cold_reset: cold reset timeout (GSR=0x0)
pxa2xx_ac97_read: read error (ac97_reg=7c GSR=0x0)
pxa2xx_ac97_read: read error (ac97_reg=7e GSR=0x0)
AC'97 0 access is not valid [0xffffffff], removing mixer.
soc-audio: probe of soc-audio failed with error -5

With the OSS drivers in root_fs_arm.r734 (2.6.11.gum), the module
simply never finishes loading.

If I boot without the mic plugged in, I can load the drivers and play
audio just fine with the ALSA or OSS drivers.

If I load the modules while a mic with a -stereo- plug is plugged in,
again, I can play audio just fine.

If I plug in or remove the mic while audio is playing, audio playback
stops and I have to unload and reload the drivers for it to work
again. I can hear loud noises while doing this.

If I plug in a connector where left is shorted to right then load the
modules, it also works.

So apparently, shorting ground to the right channel either by using a
mono plug or by connecting a plug while the audio hardware is enabled
causes audio to break. Both of which seem very wrong.

-- 
Mathematics is the supreme nostalgia of our time.