Re: gEDA-user: uEDA .. was .. Re: Heavy Symbols and such

[Peter Clifton <pcjc2@xxxxxxxxx>]

On Sat, 2007-12-08 at 08:52 +0900, John Doty wrote:
> Right now, we, by default, reference light symbols in a common  
> library, and then attach attributes to them. That's wrong, too: if  
> I'm going to use a bunch of, say, OP220's in a design, I want all of  
> them to have the same package and temperature spec. So, right now, I  
> want to reference an editable heavy symbol here. I want neither the  
> library symbol nor a bunch of separate embedded instances (hear that  
> Peter? At best, your scheme gives me a separate instance per page. No  
  ^________ (I assume you mean Peter B, but I'm sure we've both
               discussed embedding stuff in the past).
> good in a multipage schematic). But maybe the heavy symbol approach  
> isn't right either.

At the risk of sounding like a broken record, I was a proponent of the
embedding scheme to be used for a self-contained transfer. If there is
an option to store a cache of symbols in the .sch file, then handing
someone the .sch file gives them something they can open without any
broken symbol errors. No one ever said that was replacing the database /
directory on disk where those symbols originate from.

> Right now, the mechanics of browsing the libraries for a graphic,  
> copying that to your project library, rescanning symbols to make it  
> visible (arrrggh!), and then finally picking and placing it and going  
> down into it to fix it up are clumsy. But if you don't do that, you  
> may be in trouble down the road when you need to change a footprint  
> or something. Or when somebody "fixes" a common library symbol in the  
> next release.

Sounds like a royal pain. File a feature-request (or email here) how you
want it to work, so any future work on the library system can refer to
it. I can't immediately see how to implement it in a "gEDA" way (e.g. to
retain flexibility about where that symbol might be copied to for your
project).

I do appreciate that a per-project symbol store is the way to go for
designs like you're making here, and that it would be nice to provide
some short-cut way to working with that flow.

> The place where this all comes together is the BOM: that's where all  
> of the non-graphical information about the parts is. But right now,  
> we derive that from the graphics. That's wrong, too: the graphics  
> should represent graphical aspects of the design. Symbols and their  
> connections. But the graphics are an inefficient place to control and  
> edit the textual aspects of the design.

I must say, I like the suggestions about a BOM centric design, but I see
this as another view onto the underlying ECAD database or data
structures.

I can't imagine starting a project, and listing every decoupling cap
before I use it.. but I can imagine a view (gattrib on steroids) which
can be used to edit this information.

> Another thing to cogitate on is textual netlist input. In the old  
> Viewlogic days, I sometimes made text files that were pin maps for  
> connectors. Pin number to net name. I had awk scripts that could  
> merge them with Viewlogic's text netlist format, and also make tbl/ 
> troff pages for documentation. Very handy. But in gEDA we have many  
> different netlist output formats, and the only netlist input format  
> is .sch.

Agree... this would be very nice to have. It might even help the
back-anno problem.....

My take on this (theory only as yet), is that gschem needs a rats-nest
"mode", where it imports some notion of the "truth" from another tool,
PCB, text-input netlist etc.., and gives you the opportunity to frob
your schematic until it matches. "Congratulations your schematic matches
the input netlist". (I see that paperclip on screen again in my head!)

I'd include "rat-parts", e.g. symbols / sub-circuits which should exist,
but aren't on the page, and in the same vein, I'd like to see
"rat-parts" in PCB, e.g. a "folder" of footprints to drop down which
"should" be on the board, but aren't yet.

Best wishes,

-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,
Cambridge
CB3 0FA

Tel: +44 (0)7729 980173 - (No signal in the lab!)



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