[alsa-devel] UAC2 clock selector for AudioBox 1818VSL

[louis at museresearch.com]

Hi Daniel,
  Thanks for the quick reply. I am able to set the clock on my Mac, though
I do need to do further tests and make sure that the sync is actually
reliable there. The setting is available from the built-in, standard OS X
audio setup application "Audio MIDI Setup".

There should be a S/PDIF clock signal going to the digital inputs on the
device. Some of the other controls such as per-channel mute also appear to
work. I've also attached the lsusb output (attachment stripped for the
mailing list).

There are some other details that may be relevant, but I didn't want to
make my initial post too long/confusing because these extra details may
end up just being a red herring: Each mixer element name (as seen in
amixer) is prefixed with "AudioBox 1818 VSL Clock Selector" even if it is
not a clock selector. I am confident though that the control I've been
playing with is the clock selector because it lists the different clock
types as options. I also see this when I plug the device in or load the
ALSA driver:

ALSA sound/usb/mixer.c:342 cannot get ctl value: req = 0x83, wValue =
0x201, wIndex = 0xa00, type = 4
ALSA sound/usb/mixer.c:846 10:0: cannot get min/max values for control 2
(id 10)
ALSA sound/usb/mixer.c:342 cannot get ctl value: req = 0x83, wValue =
0x200, wIndex = 0xa00, type = 4
ALSA sound/usb/mixer.c:846 10:0: cannot get min/max values for control 2
(id 10)
ALSA sound/usb/mixer.c:342 cannot get ctl value: req = 0x83, wValue =
0x201, wIndex = 0xb00, type = 4
ALSA sound/usb/mixer.c:846 11:0: cannot get min/max values for control 2
(id 11)
ALSA sound/usb/mixer.c:342 cannot get ctl value: req = 0x83, wValue =
0x200, wIndex = 0xb00, type = 4
ALSA sound/usb/mixer.c:846 11:0: cannot get min/max values for control 2
(id 11)

Amixer reports the control at numid=2 to be a boolean, but because of the
naming bug I can't see what the control really is. I'm assuming this isn't
relevant, but I'm including it here anyway.

Louis

> On 06.09.2012 22:20, louis at museresearch.com wrote:
>> Hi!
>>   I'm attempting to get the "Clock Selector" mixer control to work with
>> the PreSonus AudioBox 1818VSL (a UAC2 device).
>>
>> The control shows up in amixer as an enumerated value, but I don't seem to
>> be able to set it (I've tried amixer, alsactl, and setting it
>> programmatically). The possible values are correct (listing Internal
Clock, S/PDIF Clock, and ADAT Clock as possible options); It just
doesn't
>> appear to take my setting, by which I mean amixer doesn't update the
settings, I still have the occasional click when the sampling rates
match
>> over S/PDIF and I attempt to use external sync. No error is returned.
>>
>> After digging around USB specs and ALSA's usb/mixer.c and being unfamiliar
>> with both the USB audio spec and the inner workings of ALSA, I thought
it'd be best to ask the list about this: How would I check to see if
ALSA
>> is asking the device to change clock source at all?
>
> Hmm. A clock selector is handled like any other control entity on the
hardware. Some thoughts:
>
> - Are you able to control other settings like the volume?
>
> - It's fairly common for devices to not accept a new clock source
setting if they can't lock to the external source within some time. Did
you connect anything to the digital inputs?
>
> - Are you able to control that setting with the native Mac OS X driver?
(IOW, without installing a 3rd-party driver)
>
> Also, please send the output of "lsusb -v" for that device.
>
>
> Daniel
>

-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: lsusb_1818vsl.txt
URL: <http://mailman.alsa-project.org/pipermail/alsa-devel/attachments/20120907/c3850b9c/attachment-0001.txt>