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Subject: Re: [geda-user] Wilkinson splitter - how to implement and use?
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From: "Dan McMahill (dan AT mcmahill DOT net) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
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Date: Wed, 10 Aug 2016 23:44:44 -0400
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On 8/2/2016 7:33 PM, Larry Doolittle wrote:
> Evan -
>
> On Tue, Aug 02, 2016 at 04:47:05PM -0400, Evan Foss (evanfoss AT gmail DOT com) [via geda-user AT delorie DOT com] wrote:
>> On Mon, Aug 1, 2016 at 6:44 PM, Erich Heinzle (a1039181 AT gmail DOT com)
>> [via geda-user AT delorie DOT com] <geda-user AT delorie DOT com> wrote:
>>> If pcb were modified to honour the flag, I could easily add a "nodrc" flag
>>> as discussed to the non-pad line element outputs of the utility.
>> I think we need something more subtle than nodrc. Having DRC turned
>> off for a specific footprint or any other board area is just as bad as
>> having DRC return bogus warnings/errors.
>
> I agree in general.  For the copper structures wished for to handle
> star grounds and Wilkinson splitters, we actually want the layer
> to exist for DRC purposes, but not for netlist purposes.  So a
> "nonetlist" flag?
>
>> The reality is that these structures are not footprints but functional
>> elements. They have design rules, just very different ones with higher
>> orders of complexity. We can't really have pcb process the full
>> complexity of these rules across the whole domain from DC to daylight
>> (or shorter) because of limitations in processing. It would also
>> require a level of developer time which is far past what pcb-* has
>> right now.
>
> Without diving into a more general capability set, this particular tweak
> _sounds_ simple enough to me.  But my limited experience poking around in
> the internals of the existing pcb code base makes me predict it will be
> difficult to do without breaking somethings else.  Maybe I'll look at
> pcb-rnd and see if that looks any more promising.


This has been on my wish list for a long long time.  A related topic is 
one of wishing for true hierarchical design.  Take something like a 
combline filter.  You have a combination of lumped capacitors along with 
some critically sized and spaced copper lines.  You'd really like to be 
able to group that all together and then only allow it to be moved 
around as a unit.  I supposed a mid ground would be the ability to 
create a group of footprints and traces that stick together even if you 
can't create multiple instances of the same thing.

-Dan