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From: ForthNet@willett.UUCP (ForthNet articles from GEnie)
Newsgroups: comp.lang.forth
Subject: DSP CONFERENCE
Message-ID: <205.UUL1.3#5129@willett.UUCP>
Date: 5 Jan 90 20:44:24 GMT
Organization: Latest Link in ForthNet Chain
Lines: 38


 Date: 01-02-90 (01:18)              Number: 63
   To: CLIFFORD KING                 Refer#: 62
 From: NICK JANOW                      Read: NO
 Subj: DSP CONFERENCE                Status: PUBLIC MESSAGE


 >I am interested in the tools you use to generate coefficients.

 I assume you mean what do I use as a "signal generator".  I wrote some
 tools to build various waveforms, then added some extras, like FM and AM 
 modulation.  It's simply for making an N-point array, since I hadn't
 gotten to the point of running long sequences.

 I use MacFORTH's floating point tools (80 bits) to generate the initial
 values for a sine table, based on the sample length I'm using.  Every
 sine-based signal is then calculated using that table; quickly and
 easily.  The integer trig functions just didn't have the resolution.  I
 went crazy trying to find a bug in the fft program at one point.  The
 problem turned out to be lack of resolution in the original sine table
 (using integer trig).

 For output I have a simple "oscilloscope" or "FFT" window.  It's not at
 all polished, but it's worked well enough for my present needs.

 I haven't used any canned software.  That would defeat the whole purpose 
 of this exercise: education.  It also forces me to write more 4th; also
 good for educational purposes.  Besides, the commercial programs for DSP 
 on the Mac seem rather expensive.

 I'll provide more information if you like.  The n-point fft program is
 available on the BCFB as FFT.MFP (in the Mac section, File area 9). 
 It's only 8k, but it is MacFORTH Plus specific.  Criticism welcome.  :)

 NET/Mail : British Columbia Forth Board - Burnaby BC - (604)434-5886   
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