The A/D chip is an Analog Devices 7928. It can do 2 mega-samples per second, multiplexed across 8 inputs. The USB audio interface is provided by my firmware code, assisted by the AVR AT90USB647 micro which has some low-level USB support.

HTH.

Cameron.

Alex Austin wrote:

By Codec, I think he's asking about the A/D chip. For example, the TI PCM2902E is a stereo USB audio codec.

• Alex Austin

(651) 238-9273

"...and then I visited Wikipedia ...and the next 8 hours are a blur."

On Thu, May 28, 2009 at 8:30 AM, Cameron Stone <camerons.lists@cse.unsw.edu.au mailto:camerons.lists@cse.unsw.edu.au> wrote:

Daniel Mack wrote:
> On Thu, May 28, 2009 at 11:47:34AM +1000, Cameron Stone wrote:
>> I've got a USB microphone application that I want to sample at
256000 8
>> bit samples per second so I can listen to bats. I know that my device
>> can get close to that rate, but alsa seems to restrict sampling
rates to
>> 192kHz.
>
> Just out of curiosity - which microphone and what kind of codec
are you
> using for such frequencies?

I don't know which microphone but I can find out if you're interested. I
do know that its sensitivity starts at 10kHz, if that helps.

There is no codec used. I'm using Type I (uncompressed PCM) because it's
being powered by an AVR running at 16MHz and there's not enough clock
cycles to encode the samples.

Cameron.
_______________________________________________
Alsa-devel mailing list
Alsa-devel@alsa-project.org <mailto:Alsa-devel@alsa-project.org>
http://mailman.alsa-project.org/mailman/listinfo/alsa-devel