[Tfug] Audio client

[Bexley Hall]

Hi Steve,

> The LPC2468 comes to mind...I wasn't being entirely facetious.  You do

I've been evaluating the AVR32UC3A family.  Seems to be the same
ARM7 core with a different assortment of I/O's (pretty much
what you'd expect for anything ARM-ish, eh?  Since its all
just IP)

> have to put ram & nand flash in your layout if you want to run linux
> on it, however, but it does get you down into the milliwatts
> power/mini size...course you'd have to figure out how to get the
> uaudio driver into the nand chip, which I've never messed with...

I'm disappointed with the I/Os on the AVR part (ditto for the NXP
devices). And, fearful that 64K of SRAM is just not going to fit
well buffering audio.  I guesstimate half goes for regular housekeeping
(pushdown stack, network stack overhead, etc.) so with ~40KB you
can buffer at most 20K 16b samples -- 10K per channel or ~200ms.

So, it might make sense to add SRAM or SDRAM.  :<  This starts
to really hurt when it comes to real estate!   CPU needs PHY.
PHY needs XTAL.  PoE controller and associated magnetics.  RJ45 
and audio connectors.  Power amplifier.  S(D)RAM.  etc.

And, the sampling rate for the AVR part is a fixed divisor off
the system clock (which means you need to be able to tune the
oscillator at runtime).  :<

I'm wondering if a better approach might be to cut things into
tiny modules:
- CPU, S(D)RAM, LDO, XTAL
- RJ45, PHY, XTAL, PoE
- *better* DAC, amp, output connectors

This has the win of being reusable for other things (e.g.,
discard the audio "board" and attach a USB camera and you
have an IP camera; a group of iso-optillators and you have
an HVAC controller, etc.) but it means adding connectors and
complicating assembly (no big deal since this is just
hobbyist stuff).

Thoughts?

Best wishes for coming New Year!
--don