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Date: Thu, 22 Oct 2015 08:59:07 -0400
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Subject: Re: [geda-user] A lesson from gnet-makefile
From: "Evan Foss (evanfoss AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
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On Thu, Oct 22, 2015 at 2:30 AM, Larry Doolittle
<ldoolitt AT recycle DOT lbl DOT gov> wrote:
> Guys -0
>
> On Thu, Oct 22, 2015 at 02:03:43AM +0000, Evan Foss (evanfoss AT gmail DOT com) [via geda-user AT delorie DOT com] wrote:
>> On Thu, Oct 22, 2015 at 1:49 AM, DJ Delorie <dj AT delorie DOT com> wrote:
>> > It would be great if you could just connect two
>> > nets like that and have the system remember the topology long enough
>> > to DTRT in layout.  But in gEDA, this type of connection only results
>> > in an error.
>>
>> Well I was approaching that with the stuff I was talking about in the
>> other thread but I realized there were fundamental issues with it.
>> This is kind of why I was thinking about star grounds. Really this is
>> a type of star topology.
>
> I don't think this failing is unique to gEDA.  I just had a
> board laid out in PADS (schematic in gschem), and some analog
> stuff had to be left hand-wired, non-design-rule-checked, because
> of this exact issue.  Just like in PCB, there seemed to be no way
> to communicate to the layout tool that two nets are supposed to
> touch in a defined spot, but be independent.
>
> I think it's easy enough to create a "star" component in gschem;
> getting a layout tool to deal with it seems harder.  I've heard
> of hacks involving extra layers to make it happen in PCB.  The
> team of PADS experts (not sure if a smiley face belongs there or
> not) couldn't even imagine a way to make it happen for that tool.
> Other than adding a bunch of zero Ohm resistors, which I rejected.

What if you want to make a star with more than 2. I feel like we ether
need a progamatically generated star symbol or a way to recognize when
someone has drawn a star.

The issue that hit me was if you have a multipage design or something
more involved and you use a star how do you know even with a more
involved netlist format where the star.

There are also issues with PCB and it's understanding of this.

>   - Larry


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