On 08/08/2011 14:35, John Ferrell wrote:
> My objective is to learn what I can about Digital signal processing and
> FFT. My real hobby in retirement is studying. I suspect that if I could
> find the details of the implementation of any PC soundcard I could
> bypass using a PIC at the moment.

Ah I see, the endless pursuit of knowledge..
Regarding the PC soundcard, I did a little research into how easy it was=20
to process and manipulate sound in .Net a while back. Although I only=20
skimmed the surface I discovered implementing the maths, graphics (if=20
necessary) was easy enough, but the ever present problem (with=20
implementing more involved tasks fully on a PC) is that of no=20
access/control of low level processes or timing without some some=20
difficulty.

FFTW (Fastest Fourier Transform in the West) is a useful library to know=20
about:
http://www.fftw.org/
Here is a link on more FFT stuff too:
http://www.jjj.de/fft/fftpage.html
Some useful DSP related info:
http://www.dspguru.com/dsp/links/online-books
http://www.dspguide.com/pdfbook.htm

> The M-Audio card is impressive when used to process the I-Q signals for
> a software defined radio. (Google "softrock").
> It allows a bandwidth in this application of about 190 khz. Latency
> seems to be an issue with any DSP.

I had a look - there seems to be about 3 different sites which the owner=20
is in the process of shuffling about so it was a little confusing!

> If I find the details of its windows or Linux implementation I will
> pursue the M-Audio path. In the meanwhile, I will have to work with the
> PIC A->D->A setup because that is what I can grasp!

That was the problem I mentioned finding above with a "standard" on=20
board sound unit, but I thinking there must be some cards out there that=20
are commonly used for SDF and have the lower levels detailed and usable?
I don't know anything much about SDF (although I'd like to have a go=20
myself if time allows at some point) but I'd imagine the PIC based setup=20
might be a good place to start as you won't have all the quirks of an=20
operating system to worry about, plus you will have a lot more control=20
over timing - maybe grab a dsPIC dev board?
I bet this would be good application for FPGAs/CPLDs if you really want=20
to delve deeper into the DSP logic implementation side.

> I also have a TI Piccolo Stick that may be better suited to the task but
> it looks like a steep learning curve. I am old, my time is limited, both
> short term&  long term!
>
> There is no product to develop, there is no commercial interest on my
> part. There are many commercial products in Amateur Radio that are
> reasonable in cost and awesome in performance. I may never reach the
> desired level of understanding but that is not a problem... the fun is
> in the pursuit!

Sounds like a worthy and enjoyable challenge. Things often turn out=20
quite well when undisturbed by any commercial interests - and indeed as=20
you say, the journey is the reward. I hope you have lots of fun on the way.=
..
 From what you have put forward, maybe you should pursue the option(s)=20
that interest(s) you most, then simply deal with issues as they arise.=20
If there is no deadline or initial specification/solid goal, then (if=20
finance permits) you can forage ahead and change course at a later date=20
if necessary.


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