Driver for daisy-chained AD1938 audio codecs?

Driver for daisy-chained AD1938 audio codecs?

[Steve Strobel]

I am considering a Blackfin DSP hardware design which would need eight
channels of audio input/output. I haven't been able to find a single
audio codec with more than six input channels, so I am looking at
daisy-chaining AD1938 codecs as described on page 19 of its datasheet
[1].

In the past I worked on a prototype that used two AD1938 chips on
separate SPORT interfaces. It worked, but having to deal with two ALSA
sound devices made the software relatively complicated (error
recovery, synchronization, etc). It would be nice if all of the
channels appeared as a single ALSA device.  I believe that
daisy-chained AD1938 chips would work that way, but I haven't found an
ALSA driver for that configuration.
Does such a driver already exist?  Any suggestions for making one?
Thanks for any input.
Steve
[1] - http://www.analog.com/static/imported-files/data_sheets/AD1938.pdf
-- 
Steve Strobel
Link Communications, Inc.
1035 Cerise Rd
Billings, MT 59101-7378
(406) 245-5002 ext 102
(406) 245-4889 (fax)
WWW: http://www.link-comm.com
MailTo:steve.strobel@link-comm.com

Driver for daisy-chained AD1938 audio codecs?

[Steve Strobel]

I am considering a Blackfin DSP hardware design which would need eight
channels of audio input/output. I haven't been able to find a single
audio codec with more than six input channels, so I am looking at
daisy-chaining AD1938 codecs as described on page 19 of its datasheet
[1].

In the past I worked on a prototype that used two AD1938 chips on
separate SPORT interfaces. It worked, but having to deal with two ALSA
sound devices made the software relatively complicated (error
recovery, synchronization, etc). It would be nice if all of the
channels appeared as a single ALSA device.  I believe that
daisy-chained AD1938 chips would work that way, but I haven't found an
ALSA driver for that configuration.

Does such a driver already exist?  Any suggestions for making one?
Thanks for any input.

Steve

[1] - http://www.analog.com/static/imported-files/data_sheets/AD1938.pdf


--
Steve Strobel
Link Communications, Inc.
1035 Cerise Rd
Billings, MT 59101-7378
(406) 245-5002 ext 102
(406) 245-4889 (fax)
WWW: http://www.link-comm.com
MailTo:steve.strobel@link-comm.com

Re: Driver for daisy-chained AD1938 audio codecs?

[Lars-Peter Clausen]

On 10/11/2011 06:04 PM, Steve Strobel wrote:
> I am considering a Blackfin DSP hardware design which would need eight
> channels of audio input/output. I haven't been able to find a single
> audio codec with more than six input channels, so I am looking at
> daisy-chaining AD1938 codecs as described on page 19 of its datasheet
> [1].
> 
> In the past I worked on a prototype that used two AD1938 chips on
> separate SPORT interfaces. It worked, but having to deal with two ALSA
> sound devices made the software relatively complicated (error
> recovery, synchronization, etc). It would be nice if all of the
> channels appeared as a single ALSA device.  I believe that
> daisy-chained AD1938 chips would work that way, but I haven't found an
> ALSA driver for that configuration.
> Does such a driver already exist?  Any suggestions for making one?
> Thanks for any input.
> Steve
> [1] - http://www.analog.com/static/imported-files/data_sheets/AD1938.pdf


Hi,

the existing driver should work fine, at least for daisy-chained ADCs.
Just setup the number of TDM slots using snd_soc_dai_set_tdm_slot. You'll
need to register one of the codecs as primary codec and the other as an
auxdev in your snd_soc_card structure.

- Lars