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Re: gEDA-user: Light vs heavy gschem symbols?
Your light vs. heavy nomenclature is a reasonable term. Let me give you
some prospective about the issue base on my years of experience with big
bucks PCB design tool suites, mostly Mentor Graphics and some Cadence.
Both use the heavy approach with special database management software to
get the "library" of circuit symbols and footprints correct. In large
companies specific employees are the only ones who can create symbols
and footprints for the dozens if not hundreds of engineers and pcb board
designers. There is a very large economic incentive to have symbols and
footprints correct the first time. Projects die and people get fired
when an expensive pcb comes back from the pcb vendor with footprint
The company "symbol and "footprint" library is its "golden jewel". It's
the key link to design engineering and producing hardware. The general
idea is called "schematic based design". A circuit design engineer
dreams up the latest product on the schematic editor using symbols from
menu choices in the "company approved symbol library". These approved
"released library" symbols have all the attributes and links to all the
analysis and pcb layout tools used in the company. There will always be
a few new components not available in the release library. For these
symbols and/or footprints the engineer creates them from scratch or
modifies existing ones. These are placed in a "development library".
Preliminary circuit designs usually have the majority of components that
have be proven before. The bulk of the effort is in getting the
remaining few moved from the "development library" to the "release
library". Some formal checking, verification and release process
applies. The final transition to the release library is done by the
company "librarian". While this sounds complex, and it is, the goal is
to have that ever growing "golden library".
It seems to me that the concept of a "release library" and a
"development library" could support both the newbies and the more
experience user that wants more freedom. The newbie would be directed
to use "release library" symbols with specific footprint attributes and
the experienced user could do his own with "development library" parts.
Stuart Brorson wrote:
> Light vs. heavy is nomenclature which I just made up. Perhaps there
> are other terms? If so, I don't know what they are. Anyway, this is
> what I mean:
> Gschem currently uses "light" symbols. That is, each symbol in the
> symbol lib has almost no built-in attributes. It is up to the user
> to place the symbol and then add all the attributes he needs manually,
> either using gschem's attribute pop-up or perhaps using gattrib or an
> equivalent program.
> By "heavy" symbol I mean that each symbol in the lib has a bunch of
> attributes already attached to it. In this case, the user just sticks
> the symbol into his design, and he is then ready to netlist without
> further work. Particular attributes which users seem to want built
> into the symbol include "footprint", and spice models. Protel is an
> example of an EDA system with "heavy" footprints.
> The reason for the discussion is that we constantly hear reports from
> newbies that they want better integration between gschem and PCB. A
> common complaint involves the fact that newbies don't want to -- or
> don't know how to -- stick PCB footprint names onto the symbols while
> creating their schematics. I just got a few more in my in-box last
> week, which triggered my Free Dog suggestion.
> It is true that it is not a priori clear what footprint names to stick
> into symbols until you have had some experience with PCB. Nowhere in
> any documentation does it tell you what footprint names go with which
> parts. Indeed, if you use the M4 footprints you've got to look
> through the files themselves to find the footprint names. The newlib
> footprints are a little better since the footprint name is the file
> name. Nonetheless, newbies are often thrown for a loop when it comes
> to putting footprint attributes into the schematic. This is the
> reason I bring the subject up.
> Personally, I like gschem's attribute mechanism just the way it is.
> "Light" footprints provide maximum flexibility to users who know what
> they are doing. Moreover, bulk managing footprints is easy using
> gattrib. On the other hand, Ales had some good ideas about how to
> further simplify the selection of footprint attribs. I thought I
> would share with the teeming Free Dog multitudes a couple of my recent
> e-mails from newbies complaining about footprint attributing. Then
> perhaps we would talk more about various improvements one might make
> to gschem which would be lightweight, but might also make it easier
> for newbies to attribute their designs.
> Any thoughts?
> > Stuart,
> > Could you give us a brief discussion on light vs. heavy gschem symbols?
> > Thanks,
> > Steve Meier
> > Stuart Brorson wrote:
> > >-------------- Free Dog Gathering Announcement ----------------
> > >
> > >The Free EDA Users Group will meet this coming Thursday, June 2nd.
> > >Once again, let's meet at the Starbucks across the street from Quantum
> > >Books on Ames St, between Main St and Broadway. It's about 1 block
> > >away from the Kendall Sq "T" stop. (In Cambridge, MA, USA, of
> > >course.)
> > >
> > >The meeting will be an open and informal working session. Bring your
> > >laptop! Some items on the agenda are:
> > >
> > >* Scilab vs. Octave showdown! (by request)
> > >* More discussion about "light" vs. "heavy" gschem symbols.
> > >* Your favorite issue here!
> > >
> > >Free Dog is an association of like-minded hackers and engineers
> > >interested in free and open EDA tools. We hold monthly meetings at MIT
> > >(and other locations) featuring informal networking, speakers, and
> > >camaraderie. Our goals are to learn more about CAD, engineering and
> > >scientific software, share ideas about our current projects, and --
> > >most importantly -- have fun with like-minded people. We welcome new
> > >members and participants of all ages. Students are particularly
> > >welcome!
> > >
> > >
> > >Date: Thursday, June 2nd, 2005. (*** Note the change of day! ***)
> > >Time: 7:00pm
> > >Location: Starbucks Coffee, 6 Cambridge Center, Cambridge,
> > >MA, USA.
> > >
> > >For more details, please contact me privately at sdb (AT) cloud9 (DOT)
> > >net.
> > >
> > >
> > >