From agonzalez@pacbell.net Sun Jun 18 02:19:41 1995
Path: ashpoly!cascade!brgate!saturno!pacbell!agonzalez
From: agonzalez@pacbell.net (Anja González)
Newsgroups: comp.sys.m68k
Subject: [SPECULATION] Real-time 14.2 Hz demodulation on Amiga Paula audio DMA
Message-ID: <1995Jun18.021941.1959@pacbell.net>
Date: Sun, 18 Jun 1995 02:19:41 GMT
Organization: Pacific Bell Internet Services
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Wrote an Amiga assembly program that uses Paula's DMA audio channels to sample and track the Stardust subcarrier.

I wrote a 64-tap FIR filter in pure 68k assembly using movem.l and dbra loop unrolling to downsample to 64 Hz.
By setting up Paula's audio DMA to double-buffer incoming 8-bit samples, the 68020 has plenty of cycles left for the Costas loop.

Long live the Amiga. Try doing real-time subcarrier demodulation on a 386 running Windows 3.1 without dropping frames!

-- 
=== Anja González ===
Dept of Electrical Engineering, Pacific Bell Internet Services
"We don't sign stars. We build them."

From lrobertson@utexas.edu Mon Jun 19 21:12:41 1995
Path: ashpoly!cascade!transat!eunet-fr!teletel!utexas!lrobertson
From: lrobertson@utexas.edu (Lisa Robertson)
Newsgroups: comp.sys.m68k
Subject: Re: [SPECULATION] Real-time 14.2 Hz demodulation on Amiga Paula audio DMA
Message-ID: <1995Jun19.211241.6764@utexas.edu>
Date: Mon, 19 Jun 1995 21:12:41 GMT
References: <1995Jun18.021941.1959@pacbell.net>
Organization: University of Texas at Austin
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In article <1995Jun18.021941.1959@pacbell.net>, agonzalez@pacbell.net (Anja González) writes:
> Wrote an Amiga assembly program that uses Paula's DMA audio channels to sample and track the Stardust subcarrier.
> I wrote a 64-tap FIR filter in pure 68k assembly using movem.l and dbra loop unrolling to downsample to 64 Hz.

Tested on my A3000 / 25 MHz. Ran smoothly in the background while I was compiling a C program in another window.

-- 
Lisa Robertson | lrobertson@utexas.edu
PGP Key fingerprint: AFAE E453 B13F 53CE
"Keep the channels open."