Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uunet!microsoft!brianw
From: brianw@microsoft.UUCP (Brian WILLOUGHBY)
Newsgroups: comp.sys.apple
Subject: Re: Oscilloscopes
Message-ID: <10048@microsoft.UUCP>
Date: 22 Dec 89 03:34:34 GMT
References: <0.net.apple@pro-lep> <5862@wpi.wpi.edu> <1935@psuhcx.psu.edu> <6210@wpi.wpi.edu> <741@batman.moravian.EDU>
Reply-To: brianw@microsoft.UUCP (Brian WILLOUGHBY)
Organization: Microsoft Corp., Redmond WA
Lines: 37

> An apple can be made to do digital sampling up to about 5 or 10 =Hz,
> acting like a scope, but that's too slow for the kind of work I'm doing
> (10-20 MHz).  Even so, if a few people mail to me to say they're interested
> I'll post plans for a sampling card with software. 

I don't know if I've mentioned this before (and I also don't know whether you
mean kHz or MHz), but I built my own custom A/D and D/A cards that are capable
of 40 kHz sampling AND display, with scope-style auto-level edge-triggering
display, with simultaneous average level and peak/peak hold VU display.  This
was at 1 MHz.  At 3.58 MHz TransWarp'd speeds, its unbelievable.  No, I'm not
offering to build these for everyone (like another poster offered).

A much better (read: useful) approach would be to have banks of RAM on a card
devoted to storing incoming signals as digital values.  Then the Apple could
spend full time displaying the data while the card automatically did the
sampling and storage.  Most digital storage scopes run at sampling rates that
are about 8 times faster than DRAM access speeds.  The trick here is to have
eight independent banks of RAM with staggered access.  By cycling through the
banks one at a time, each bank sees accesses at 1/8 the sampling rate.  I read
about this technique in EDN (I think), and the design would be much simplified
by utilizing the Apple ][ power supply and CPU.

Has Apple Co. ever acknowledged the awesome number of Apple ][ computers used
in scientific research labs for data acquisition?  Every time I turn around in
a college campus lab, I see an Apple ][ Plus or //e with wires attached all
over the  place - hooked to monstrous machinery or measuring equipment.  If
Apple would recognize what I feel is a market equal to the so-called
"Education" market, then their emphasis would necessarily shift to performance
as it can be used for engineering applications.  BTW, this kind of shift in
focus would make me very happy - since I basically use my Apple ][ Plus as a
home sound lab tool.

Brian Willoughby
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