DSP etc

[Bob Bruhns]

Hello Doug,

Frank G. introduced me to your book (Digital Audio Processing), and it's great!  I got myself a copy on Amazon.com, and posted a review.  I have been hacking with WavEd to do special AM demodulation.  No results with that yet; I'm afraid I'm still stuck in 6502 and DSP56002EVM mode.

Speaking for myself, I say welcome, but how did you avoid getting a ham ticket all these years???

  Bob, WA3WDR

> C-Lab wrote:
> 
> Hello,
> 
> I recently "caught the bug" after visiting with Frank G
> this Thanksgiving, and am interested in participating/helping,
> that is, if you guys will tolerate a non-ham.  I suppose I
> could be called a pro, instead, because I did indeed design
> interesting DSP-radio things for "the government" some
> 20+ years ago -- back when one did this with wire-wrapped
> TRW multipliers and homebrew cpu's in general.  It's a lot
> easier these days!  Since then, I formed a company that
> does DSP consulting work.
> 
> We do embedded DSP (mainly using the TI stuff) and windoze
> programming (from drivers on up, we _DO_ Windows) for
> a living here at our solar powered facility in Floyd, VA.
> We also do general embedded uP stuff, mainly using PIC
> uP's for lots of interesting things.
> 
> Here, we actually have enough room to make a for-real antenna
> at LF if we wanted to do it, and there's no powerlines for
> at least 1/3 mile in any direction...could be interesting!
> I can of course turn off any locally generated electrical noise,
> since *I* am the power company for these 30 acres.
> Last time I hooked up a SW receiver it was pretty nice.
> 
> I was impressed enough with Frank's setup to get started
> duplicating it, all the stuff is on order and on the way,
> or will be very soon.  (Someone needs to make that
> cool antenna a kit item and sell it!!!  What a pain to
> chase all that stuff down!)
> 
> It did seem to me that the DSP on the tentec was in need
> of assistance.  There are a number of possibilities I'm looking
> into for helping it along.  Most of them would include tapping
> the signal off at the low IF before the builtin DSP sees it,
> since there you have some room to work and do more interesing
> stuff.  I note that the higher quality pc soundcards (the only
> type worth it, the normal SB clones have serious built-in birdie
> troubles, due to "nearest neighbor" builtin resampling and
> other bad design jokes) now support 48k sample rates....
> 
> My company also makes a DSP card that will support just about
> any serial a/d out there as long as you provide the timing signals --
> the board just has a sync serial port that can go 10+mbits.
> 
> One approach would be simply to ditch their dsp card and replace it
> either with code on the PC/soundcard, or another dsp card
> with some for-real horsepower.  This latter could be done
> such that the radio remained back-compatable with existing
> control programs, but would allow for smarter control
> programs to tell it to do "more interesting" things.  By adding
> autobaud software it would be easy to tell if the control
> program was original (1200 baud) or something "new",
> (some faster baud rate, gheesh) for example.
> 
> Plans include adding modes (costas loop "am stereo", nbfm
> fsk psk etc etc etc) and some *good* noise removal using some
> DSP tricks we've learned over the last 20 years of "practicing".
> Better (and maybe adaptive) filters are of course obvious
> and also easy to do.
> 
> For those PC-averse, or who want to be able to use laptops
> which aren't all that fast, we could roll a for-real DSP board
> to replace the existing one in the ten-tec.  In fact, we have
> at the moment a "DSP core" design that we use for proto work
> that would make it easy to test embedded code.  It lives in
> an ISA slot, and has "everything" you could think of for doing
> DSP -- 4 ch of a/d,d/a...half a meg of dword-wide static ram,
> 64megs flash, 5 serial ports (one is 5 mbit) and so forth and
> so on.  Oh yeah, it has a 150 mhz TI 'C33 on it, which we
> find is a bit faster than a top of the line pentium for DSP -- it
> does several things per cycle instead of the other way 'round.
> And it runs my opsys, not windoze, so nothing is wasted.
> 
> Our main customer rolled this up to our specs and we use
> it for prototyping for their designs which can then be put
> into production fast by simply removing the stuff that project
> didn't need.  Yes, there are windoze drivers (and all types of
> windoze too, not just the 9x/dos variants) and plenty of
> debugging tools we've written over the years.
> 
> I'm not sure what your main needs/desires are, but I'm planning
> on doing this anyway, and would of course be glad to share
> it with all.  (It gets boring doing things like Voice over IP etc
> for a living...telephones!)  I also have some interest in spread
> spectrum (hopping)...if the tentec can't switch fast enough,
> do you suppose guys would be willing to get "a couple"
> and hook them up so the switching time could be hidden?
> 
> (Some of my other hobbies include astronomy and benchrest
> shooting, and there, people will spend the dough to get
> what they want, no question at all.)
> 
> Not sure what resume I'd give, but you might look up my book,
> Digital Audio Processing (Doug Coulter) on Amazon.com
> for a hint.  It might even be worth buying for the "free" code
> which includes a complete windows wavefile editor with
> lots of nice windoze programming examples and plenty of
> reusable DSP code (C++ and asm).  Heck, if about 10,000
> more people buy it, the publisher might even have to write
> me a check someday...but I doubt it.  Or if you can stand
> a HUGE download, I can send you the code.  But you'd
> want the text to know how to get in there and tinker
> with it I think.
> 
> What I'll probably do first is write some "shell" software
> that just gets the pc soundcard going and
> 
> // "your dsp code goes here"
> 
> more or less.  (most of the initial dsp code can be swiped
> from waved, the book's "example" program)  I can wrap this in an
> appwizard for devstudio so as to make it easier to share.
> 
> (Most experienced programmers know better than to cut of their
> own nose to spite Bill's face - the M$ tools are the best out
> there, like it or not, and most computers run windoze, again,
> like it or not.  Heck, guess I'll just never be politically correct.)
> 
> Since the details of getting control of and using a soundcard
> are arcane enough to be daunting for most, I think this
> might be best?  DSP and dealing with "chunked" streams
> are tough enough for most people without that other overhead.
> 
> Oops, another thing I should do is put in some for-real serial
> port(s) support, another non-trivial windoze thing if you need
> any speed and/or control.
> 
> Comments?  I'd love to hear from you guys.  The phone number
> is good most times, as I both live and work here, but of course
> during normal business hours, I'm "at work" and can't talk long.
> 
> 
> Doug Coulter, owner
> C-Lab
> c_lab@msn.com
> 540-763-3753