Xref: utzoo sci.electronics:2463 comp.lsi:363
Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!pasteur!trinity!max
From: max@trinity.uucp (Max Hauser)
Newsgroups: sci.electronics,comp.lsi
Subject: Re: Posting schematics...
Message-ID: <1332@pasteur.Berkeley.Edu>
Date: 8 Mar 88 18:27:34 GMT
References: <1059@PT.CS.CMU.EDU>
Sender: news@pasteur.Berkeley.Edu
Reply-To: max@eros.UUCP (Max Hauser)
Followup-To: sci.electronics
Organization: UC Berkeley EECS department
Lines: 81
Keywords: schematics
Summary: Great idea; let's discuss it

In article <1059@PT.CS.CMU.EDU> phd@SPEECH1.CS.CMU.EDU (Paul Dietz) writes:
>A recurring problem in this news group is the need to post readable
>schematics. ASCII circuit representations are just too painfull to
>create, and are quite inflexible.
>
>WE NEED A STANDARD FOR EXCHANGE OF SCHEMATICS!!!!!!!!!!!
>
>Optimally, any standard would have interfaces on many standard
>hardware configurations. (Mac, PC's, Xwindows, GKS, UNIX Plot, etc.)
>Also, for those stuck with standard, non-graphics terminals, a human
>readable form should be generated as a side effect.
>
>Proposal: If I get sufficient feedback, I will start posting schematics
>in binhexed MacPaint format. For you Macintosh hackers, this is a familiar
>format. I've also heard rumor that various PC programs read MacPaint files.


I think this is one of the most constructive ideas I have seen on the
Usenet in a while, and I applaud Paul for proposing it. I do also
think it could bear some further discussion, since the de-facto schematic
representation that emerges may be with us for a while and it would be
a pity to foreclose future flexibility or upward compatibility.

I have included comp.lsi in the primary distribution here since some of its
readers will also have insights on this issue. It is not a new problem;
it comes up also with CAD tools for schematic capture and storage, for
example, although these products are usually proprietary and the designers
have little incentive to create a broadly-readable format. Nevertheless
there are bound to be some readers with experience in mail-compatible 
schematic representation.

I don't know anything about MacPaint, except that a lot of readers who
will be interested in schematics do not have access to it. Is the proposal
to store the schematics in a purely graphic form? If so, is MacPaint the
most widely accessible? Can non-Macintosh users still take advantage of
schematics rendered that way? Perhaps there is some other format to which
a variety of different displays, including MacPaint, can interface or 
translate easily, just as (closer to my own experience) there are two or
three nearly-universal standard formats for graphic representation of
integrated-circuit layouts.  I am just throwing out ideas here; the
prospect of a widely-translatable intermediate representation, if possible
one that already exists, is the first.

I am aware of the emerging IEEE Electronic Design Interchange Format 
(EDIF), although I know nothing about it. Does any reader know if EDIF
relevantly addresses the issue of schematic communication?

Paul rejects "ASCII circuit representations," and I don't know exactly
what he means there -- I infer something like SPICE circuit format,
where you number the nodes in a circuit and then list each component
with its node numbers and specifying information:

   Q6  5  7  12  2N3906
   C2  10 0 47pf

Is it not worth discussing this as a pragmatic schematic representation?
Although it might at first seem unnatural, it (1) is extremely compact;
(2) is inherently ASCII and thus immediately accessible, at once, and 
unambiguous, to everyone even without graphics terminals (the rules are
straightforward and readily summarized); (3) potentially useful as an 
intermediate form that can be rendered automatically as a graphical 
schematic, through software; and most important, (4) not only something 
of a de-facto standard among many professionals already, with tools 
written to support it, and therefore plenty of software to tap into and
people available to answer questions, but in particular, instantly 
compatible with SPICE-class circuit simulators, which are in public 
domain and already exist at far more sites than the Usenet reaches. 

A SPICE node-based circuit representation may seem unnatural if you are
unused to it, but with just a little experience it is quite as easy to 
write down as a graphic schematic, and arguably easier to enter on a 
computer. And of course there is the huge advantage that the file can
come off the Usenet and plug directly into all manner of simulators, 
verifiers, optimizers and other circuit software (much of it even 
PC-compatible), discussion of which could easily flourish along with 
the exchange of schematics.

I'm not completely sold on that format myself, but I offer it for
consideration as I don't know of a purely-graphical schematic format
that would reach nearly as many readers. 

Max Hauser / max@eros.berkeley.edu / ...{!decvax}!ucbvax!eros!max