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From: rstevew@armory.com (Richard Steven Walz)
Subject: Re: MiniBoard without CPU?
Organization: The Armory
Date: Sun, 24 Jul 1994 17:31:11 GMT
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References: <johan.solve-2207941047000001@js_mac.hh.se> <30pe76$jvt@handler.eng.sun.com>
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In article <30pe76$jvt@handler.eng.sun.com>,
Chuck McManis <cmcmanis@Sun.COM> wrote:
>Johan Solve (johan.solve@itn.hh.se) wrote:
>: Is there an equivalient to the MiniBoard 2.0 that doesn't have the HC11
>: CPU? I'm interested in low-cost basic computer control (some motors,
>: lamps, and some input from sensors, to control Lego projects) over the
>: serial port on a Mac, so I don't think I have need for the CPU (no
>
>There is a company called "Fascinating Electronics" that sells something
>called "The Experimenter". This is a board with some motor drivers, parallel
>I/O, and Analog I/O that can be hooked up to a PC or a Mac and driven by
>the serial port. Strangely enough it has a CPU on board (a Signetics
>
>: Am I mixing things up?
>
>Somewhat, there aren't any chips that talk RS-232 directly for control
------------------------------------------
I don't mean to be contrary, but doesn't anybody ever consider using a
parallel port for unenhanced PC I/O??? Is it because it looks harder than
RS-232C to people with a software emphasis??? If so, please tell me, as I
have been interested in adding an article to Zhahai Stewart's Parallel Port
FAQ, which I had a tiny hand in, if he'll have me, and in writing an
article with schematics to show how to expand multiplexed use of that port
to an unbelievable degree. Parallel is more straight-forward, voltage-wise,
and it's actually easier to program for both input and output once you have
the details written up for you about it in code. C functions could easily
be written to handle a host of the housekeeping that might seem so daunting
to you, and preserving printer pass-through is a piece of cake, actually!

It's really a lot easier than trying to send everything on a time
multiplexed single bit at a couple of voltages that are not as easy to get
unless you drag them out from your internal power supply or produce the
+/-12VDC externally! Just adding latches or buffers to a number of lines on
your parallel port is SO much more straightforward, once the few inverted
lines are taken care of and the arbitration of using control outputs for
inputs when they are HI open collector and such as that! And you always
need a UART with serial as well, which takes room and perhaps another
controller outboard!! A parallel rig with a huge number of ports in and out
needs nothing of the kind!! And it transmits at as much as 150K Bytes per
second, even on old XT's!! Please write me and tell me whether this would
be interesting to you on a design, bareboard/kit, or finished product
level. I/O is MUCH easier out of big computers than many have been lead to
believe!!!
-Steve Walz  rstevew@armory.com

