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        Tue, 27 Sep 2016 08:34:10 -0700 (PDT)
Date: Tue, 27 Sep 2016 17:34:05 +0200
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Subject: Re: [geda-user] Possible paths of gnetlist development
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Yes gschem have all the flexibility neeeded then it come to attributes, just have to figure out how to best use them in a standardardized way.


On Tue, 27 Sep 2016 09:54:27 -0400
John Doty <jpd AT noqsi DOT com> wrote:

> 
> On Sep 26, 2016, at 10:26 AM, al davis <ad252 AT freeelectron DOT net> wrote:
> 
> > On Mon, 26 Sep 2016 09:05:21 -0400
> > John Doty <jpd AT noqsi DOT com> wrote:
> >> 1. Use attributes for rather than special backend-dependent symbols
> >> like spice-subcircuit-LL.
> > 
> > I agree.
> > 
> > Likewise, backends should not have anything symbol-specific.
> 
> There’s nothing symbol-specific in gnetlist. A back end can’t even find out which symbol(s) a “package” corresponds to. But spice-subcircuit-LL.sym has the attribute device=spice-subcircuit-LL, which the SPICE back ends recognize. The problem here is that the layout back ends think this is an actual component.
> 
> > 
> > and all backends should support attributes, in a consistent way.
> > 
> 
> The trouble here is that gEDA supports an open-ended variety of flows, and one size does not fit all. Every gnetlist back end uses the footprint attribute, but what should you put in it? The names from your layout tool’s library? The gEDA convention (http://wiki.geda-project.org/geda:pcb_footprint_naming_conventions, mischievously presented as a pcb convention)? If you use the gEDA convention, do you alias the footprints in the library to match, or do you automatically translate? A lot depends on the size of the project, the tools employed, and the skills and preferences of the designer(s). I’ve used every one of these approaches for one project or another.
> 
> If you’re simulating with SPICE, you’ll want your numeric value attributes to be SPICE numbers. Fortunately, procurement folks find this usable in a BOM. But for a different flow, you might want something different.
> 
> Then, there are attributes for specific back ends. Some of the standard library symbols have pins and class attributes for Allegro. The class attribute is probably not useful for any other flow, but I find pins useful for DRC (http://www.gedasymbols.org/user/john_doty/tools/check-pincount.html).
> 
> 
> John Doty              Noqsi Aerospace, Ltd.
> http://www.noqsi.com/
> jpd AT noqsi DOT com