No sound from usb Audio Control Interface on Motorola C350 cellphone

["Giovanni Maruzzelli" <gmaruzz.lists@xxxxxxxxx>]

Hi list participants,

I am using cellphones connected to soundcards as cheap gsm gateways
(more complex than that, actually. You can see the whole GPL project
at www.celliax.org).

Maybe there is a way to not using soundcards, that would be *so* much
better: I found that Motorola c350 phones after receiving an AT+MODE=8
command via USB, make available an usb sound device.

That would be wonderful (less cables, more robustness, etc). Problem
is: the usb sound device do not plays or captures samples.

I suspect that the usb audio has to be activated, maybe by an AT or a
P2K command.

Or that a quirk has to be added to the alsa driver (snd_usb_audio).

Do you know anything about (maybe the quirk to be added to ALSA driver...)?

Do you have any hint?

I'm available to do all the research-testing-debugging that may be useful.

What happens is as follow:
1) attach the c350 to usb
2) is recognized as acm0
3) send at+mode=8 to c350 (via minicom, for eg)
4) it changes its usbid, disconnect from usb, reconnect, is recognized
as acm1, makes available a sound device
5) at commands work on the new acm1
6) trying to use the audio device directly (eg aplay -Dhw:1) do not
give errors on play (but no sound is head on the phone), gives error
pcm_read 1349 on record (eg arecord -Dhw:1)
7) trying to use the audiodevice through alsalib does not gives errors
at all (eg -Dplughw:1) but does not caputeres samples, and no sound is
heard on the phone

With an old copy of motorola driver, the usb sound device was
recognized by windows XP, with mixer elements only for the playback. I
was  not able to record from it, playing give no errors, but no sound
either

With the last copy of driver from motorola developer devsite, on XP a
whole new "Motorola Device" is created, with the audio interface
listed on it in the usb control panel, but no audio device is
available for normal usage, and no way to interact with it.

You can download this compressed archive
http://www.celliax.org/c350_usb_sound.tgz , that contains:

lusb_without -> result of lusb -vv with no device attached

lsusb_with_ACM0 -> result of lusb -vv with c350 just attached,
recognized as acm modem

lsusb_with_ACM1 -> result of lusb -vv with c350 after sending
at+mode=8 to him, he has disconnected and was recognized again, this
time as ACM1, with a lot of additional usb interfaces

dmesg-acm0 -> result of dmesg after first c350 attachment

dmesg-acm1 -> result of dmesg after at+mode=8 was sent to the c350

aplay-l -> result of aplay -l showing the c350 as an alsa device

stream0_pstop_cstop -> result of cat /proc/asound/C350/stream0 while not active

stream0_pstop_crun -> result of cat /proc/asound/C350/stream0 while
arecord -vv -Dplughw:1 -fS16_LE ciapa.raw (if using -Dhw:1 it fails
with error: "pcm_read:1349: read error: Input/output error"). arecord
does not gives errors, but do not write samples

stream0_prun_crun -> result of cat /proc/asound/C350/stream0 while
aplay and arecord -vv -Dplughw:1 -fS16_LE ciapa.raw (if using -Dhw:1
arecord fails with error: "pcm_read:1349: read error: Input/output
error", aplay works but no audio) arecord does not gives errors, but
do not write samples

aplay_play -> results of aplay

arecord_rec -> results of arecord

Thank you all in advance,

Giovanni Maruzzelli

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