Avery Fineman wrote:
You CAN realize a lowpass
function in DSP but the TI chip inputs probably needs some sort
of hardware lowpass filtering...?

An anti-alias filter at the very least! The TI chip in question is actually
a microcontroller rather than a DSP; I chose that based on desiring a low
power design and only requiring one chip rather than two (although I'd grant
you that there are some, e.g., SO-8 package serial interface ADCs out there
that almost don't count as another chip...) and, uh, because I already have
experience with it from other projects. It can sample up to ~200ksps, but I
was shooting for a much lower rather (perhaps some 20-50 ksps) since there
isn't much number crunching 'oomph' available. (I.e., no multipy-accumulate
instruction. In fact, no hardware multiplier at all! :-) I'll build the
mind-numbingly fast DSP monster receiver that can pull a signal 10dB beneath
the noise floor and turn it into CD quality audio once I get the simple ones
working.)

Here's a good hint on melding hardware with software using DSP:

"Scientist's and Engineer's Guide to Digital Signal Processing,"
by Stephen W. Smith, PhD, California Technical Publishing.

How very interesting -- I actually have a copy of that with from Analog
Devices (under a slightly different name); I always figured it was some
third party and not the application engineers at Analog Devices that wrote
it. Now I just have to crack the thing open...

Good luck on that.

It should be up and running within a month here.

I've seen it claimed in text, but no details, that a quasi-lock could
be obtained via voice, working on the harmonics of speech tones.
I'm not going to buy that until I see a demo.

I figured that's what they might have had in mind. Seems like a lot of
effort to avoid sending a pilot tone (but then again, what else to use the
aforementioned DSP for... oh, wait... fancy digital modulation schemes...
ok...)

---Joel