From: greene@edisto.mro4.dec.com (Michael Greene)
Newsgroups: rec.models.railroad
Subject: Re: Command-control  14 speeds not enough
Date: 19 Aug 92 11:18:11 GMT
Reply-To: greene@edisto.mro4.dec.com (Michael Greene)
Organization: Digital Equipment Corporation


--In article <4908@blue.cis.pitt.edu.UUCP>, ebe@pitt.edu (Elmer Beachley) writes:
|>Path: ryn.mro4.dec.com!nntpd.lkg.dec.com!news.crl.dec.com!deccrl!decwrl!sdd.hp.com!zaphod.mps.ohio-state.edu!pitt.edu!ebe
|>From: ebe@pitt.edu (Elmer Beachley)
|>Newsgroups: rec.models.railroad
|>Subject: Command-control  14 speeds not enough
|>Message-ID: <4908@blue.cis.pitt.edu.UUCP>
|>Date: Tue, 18 Aug 92 17:38:48 GMT+5:00
|>Sender: news+@pitt.edu
|>Organization: University of Pittsburgh
|>Lines: 41
|>Originator: ebe@unix.cis.pitt.edu
|>
|>
|>Michael:
|>
|>Is your concern over the number of available speeds primarily to enable
|>matching dissimilar units in multi-unit operation, or are there other
|>instances where you see this is important?
|>
|>As far as the prototypes go, the Diesel Cyclopedia from Model Railroader
|>mentions just briefly that "a 4 solenoid throttle control ... provides
|>seven engine speeds above idle, is the most widely used M.U. connection."
|>
|>Possibly some parameters could be added during the programming of the
|>decoder chip to allow different mappings between speed integer and
|>actual input to the motor.  This MAY allow you to tune the performance of
|>different  units for comparable performance.  There are currently
|>parameters to specify acceleration and deceleration and the voltage
|>sent to the motor for speed = 1.
|>
|>On another note, I think the most significant problem with the proposed
|>coding is there is no uniform way for individual extension by multiple
|>vendors.  If you are at all familiar with MIDI (musical instrument
|>digital interface) which is actually not so far removed from this
|>issue (serial, 8-bit interface, ~32kbaud), one of the most important
|>reasons for it's success is the system exclusive feature.
|>
|>Sysex allows each manufacturer to be assigned a unique id, which, when
|>recognized in the byte string basically says:  everything that follows
|>is reserved for MY exclusive use and everybody else should just ignore
|>this junk.  However, all the "important" parts of the MIDI spec, note
|>on, note off, etc. are the same for everyone and provide enough common
|>denominator that it is useful to connect instruments from different
|>vendors and expect reasonable behavior.
|>
|>As technology advances, no one is going to be satisfied with one and two
|>byte commands, right?  Does it really make sense to try to squeeze
|>everything that you can think of today into a couple bytes?  No, but there
|>does have to be enough of a "standard" so you can buy decoders here and 
|>a computer interface somewhere else and expect to see the trains go.
|>
|>Just me two cents,
|>Elmer  ebe@unix.cis.pitt.edu
|>

I believe you are referring to some comments made by a colleague, Jeff Barry.
I posted his comments earlier, at his request, due to the fact that he
did not have immediate news access and was departing on vacation.
I'll will forward your comments to him so that he can reply.

Michael
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Michael Greene                  Phone:     +1 508.467.2149
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Newsgroups: rec.models.railroad