Path: utzoo!mnetor!uunet!husc6!cmcl2!beta!hc!ames!pasteur!trinity!max From: max@trinity.uucp (Max Hauser) Newsgroups: sci.electronics Subject: Re: Posting schematics... Message-ID: <1944@pasteur.Berkeley.Edu> Date: 30 Mar 88 17:52:20 GMT References: <1059@PT.CS.CMU.EDU> <1332@pasteur.Berkeley.Edu> <1213@cpocd2.UUCP> <1254@PT.CS.CMU.EDU> Sender: news@pasteur.Berkeley.Edu Reply-To: max@trinity.UUCP (Max Hauser) Organization: UC Berkeley Lines: 84 Keywords: schematics EDIF SPICE... Summary: On clarifying objectives; and an example circuit To hear all the exotic ideas that came tumbling forward when this topic first appeared (some of them independently on sci.electronics and comp.lsi, against my entreaty to keep the discussion on sci.electronics where it began), one might infer, first, that everyone wants to use a "format" that is already available to them (no surprise); and, second, that there is no common vision or assumption about just exactly what this format is supposed to DO. Allow me to address this point and then (for now) shut up. Paul Dietz and several respondents seem to have the very specific idea of posting *pictures*, i.e., strictly-graphic information, incidentally about circuits. This of course requires a lot of data and an agreeable format. On the other hand, I feel I have to point out very explicitly what some have touched on briefly: that if your real goal is communicating circuits rather than line drawings, requiring actual graphics is unnecesarily restrictive and it is foolish to limit yourself to that approach. Many readers have for years been conveying circuits to their CAD software without so much as a single line being drawn. Before you dismiss this point because it's not what you had in mind, consider that non-graphical schematics can encapsulate ALL of the real information a reader needs to reproduce the circuit; they can (as those not familiar may not realize at all) be readily readable, easy to compose, and self-explanatory with the aid of comments (inevitable anyway); they require NO software, NO graphics device, and NO agreed format; they contain only essentials (topology, devices and values) and thus require much less net bandwidth than graphics (while reaching a wider audience); and, finally, we will have to use them anyway as a lowest-common-denoinator to back UP any graphics format if we ever want our schematics to be acessible to the (vast majority of) readers who lack graphics devices or software. I have of course appended an example, but my point transcends that: if the real interest is in *circuits* rather than general line drawings, and you want any substantial fraction of your readers to have access to them, then an accessible, non-graphics format is obvious, easy, and necessary. (As one dealing daily with circuit hacking for twenty years, I promise that it doesn't REALLY matter what direction the transistor points in, or whether that wire runs above or below, much as some people may have difficulty imagining a circuit not rendered in their favorite format). I will say that the process is most straightforward with small discrete circuits like audio or RF circuits or small logic; if you need to show a big chip in non-graphic form it becomes a tedious netlist -- but then that situation is not much different with graphics either. That was about circuits per se. Now I am the first to agree that it is also nice to communicate pictures of circuits (as long as we keep in mind that it is a different objective, with greater obstacles). I have no easy fix to offer of the kind Paul is calling for, but I certainly agree with others that they payoff is vastly greater in adopting an established industrial format where all of the hard thinking and mistake-making has already been done (by people who know what they're doing). To this end I reiterate my assertion that in the LONG run we must inevitably adopt something based on EDIF. Unfamiliar as it might be to many, it's on the way IN, and it will probably be a lot more familiar to a lot of you in a few years just in the course of events (just as ASCII is now familiar, for example, although it brought blank responses when it was new). I should not have to mention how much it pays to bank on a universal standard that's on the way IN. Here's a little circuit in the already-nearly-universal SPICE-type syntax (in use already at far more sites than the Usenet reaches, BTW). I'll explain that each line is a device; the first couple of numbers are node numbers that the device is connected to; and the last number is a value. It should be obvious that C's are capacitors and R's are resistors; standard element codes for other common devices exist and could be readily summarized in a single posting, along with some other minor details that, if followed, would permit all of the schematics in this format to be applied directly to SPICE-class circuit simulator programs so that people could evaluate them without even building them. Further comments associated with a circuit will readily clarify it further to human readers. To draw a picture of such a circuit, you start by getting an idea of what's going on, helped out by thoughtful comments; you draw numbered points (nodes) according to where you expect the elements to appear; and then you draw the elements connected to the nodes. The result may look a little awkward on first drawing but hey, it's the complete circuit, and it works! Bridged-T filter; node 0 is gound, 1 is input, 3 is output R1 1 2 4.7 k R2 2 3 4.7 k C1 2 0 100 pF C2 1 3 330 pF Max Hauser / max@eros.berkeley.edu / ...{!decvax}!ucbvax!eros!max