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Digital Filter Potpourri — Parallax Forums

Digital Filter Potpourri

BRBR Posts: 92
edited 2010-04-06 23:04 in Propeller 1
Anybody out there doing DSP on the Prop? Or any kind of digital filtering?

I've been playing around with various digital filters on the prop for a some time now, both as a means to teach myself about DSP and also as a means to learn Spin/PASM. I know what some of you are probably saying...if you want to do DSP, why use a Prop...buy a DSP. Well, although the prop is no DSP, it is capable of some pretty decent signal processing. This humble moving average filter is capable of just under 1M samples/sec in a single cog. Also, the Prop's ease of use and accessibility make it a great platform for learning DSP (an Andy Lindsay lab on this topic would be neat). Finally, there are tons of applications where a little mild digital filtering is useful, especially if it can be done without any extra hardware. If that's not reason enough, how about "I felt like it"?

Looking to the future, it appears that the PropII is going to have something like 20X the DSP capability of the prop 1 (figure 8X the MIPS/cog, plus a MUL instruction, plus CORDIC, plus a bigger bag-o-tricks in the counters). Come to think of it, didn't Chip say the Prop II would have a MAC instruction? If so, make that 25X.

With the above in mind, it seems to me that it would be nice to fill out the Prop's repertoire a bit in the digital filtering and DSP department. So I thought I'd start a thread to see if I could find out what's already out there and what's being worked on relative to DSP and digital filtering on the prop. And maybe pick the brains of a few of gurus out there.

Actually, I'm a bit surprised that there aren't more DSP-related objects in obex or more DSP related threads in the forum. There are a lot of "building block" elements that have come along over time, particularly lately. A few recent ones I can think of:
Just for good measure, here's a link to my favorite DSP reference: www.dspguide.com

In my DSP meanderings, I've implemented a variety of IIR and FIR digital filters on the prop and have attached a few of these for folks to peruse. The "recurse_demo" attachment is an IIR implemented in spin using integer math. The "filters_demo" contains several filters, most of them of FIR. The demos are set up so one can easily try out the various filters. A variety of example filter kernels are provided. Any comments/suggestions welcome.

Post Edited (BR) : 6/26/2010 9:49:23 PM GMT

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