External 24 bit audio codec on BB xM?


has someone here added an external audio codec (24 bit) to an BB xM
and provide some hints?


We implemented an expansion board using the TI PCM1792A top performance 24-bit, 192 kS/s stereo DAC (in mono mode). We used one McBSP for fast I2S and another (!) for 49.152 MHz system clock. The command interface is SPI. All these resources are available in the expansion connector when you read the documentation carefully. We are using C4 but I don’t see any reason why the same tricks wouldn’t work with XM as well. Working in the 24-bit analog space requires the very best opamps you can find - but with them the results are impressive!

Best regards,

I'd be interested in getting a look at the kernel-side drivers
required to implement something like this. Any chance your source is


Once we have our application fully operational, we are ready to open the driver source.
Some of the stuff in it is slightly different from normal…

Our board is now in the final testing and we might offer it to public.
It is a BB-format double sided PCB fitting back-to-back to BB and
only needs what is available from the BB extension connector.
Since we are using premium parts only, the unit price would probably
be around $175.

Let’s keep in contact.

are there any limits to implement Stereo mode?

2010/10/10 Seppo Nikkilä <seppo.nikkila@innovativeideas.fi>

Basically no.

We just went to mono to get another 3 dB of dynamic range.
But PCM1792A can easily be programmed to stereo and since our
output is differential, it is easy to use the outputs as two single-ended
lines for stereo as well. And you still have the exceptional dynamics of
127 dB. Our opamps are 1.1 nV/sqrt(Hz) but in “standard” opamp
SO8 footprint.


Sounds interesting. My goal is to send audio data streams in I2S
format via McBSP3 to an external FPGA using this board:


I've got a number of applications in mind - additional audio streams,
better codecs, hardware DSP and SDR. I've got a few of these things in
the works but they all depend on getting that audio data and I just
haven't hit on the right way to do that yet. A known-working example
would be a big help.


Thanks for your reply.

Any chance that there will be an ADC or codec board as well?