[alsa-devel] Driver for daisy-chained AD1938 audio codecs?

Lars-Peter Clausen lars at metafoo.de
Wed Oct 12 11:13:24 CEST 2011

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


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

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