Re: gEDA-user: Split ground planes and zero ohm jumpers

[Stephan Boettcher <boettcher@xxxxxxxxxxxxxxxxxx>]

John Griessen <john@xxxxxxxxxxxxxx> writes:

> On 04/07/2011 04:52 AM, Stephan Boettcher wrote:
>> PCB layer groups may be used here.  Put the short on an extra layer, in
>> an extra group.  At checkout time, you can assign the extra layer to the
>> group representing the copper layer that needs shorting.  This is
>> probably a single char in the PCB file header, and can be done with a
>> simple sed script.
>
> I like that idea -- at least until someone figures how to have a starpoint
> symbol and footprint that keeps DRC checking of separate ground planes while
> still having a short there for fabbing purposes.
>
> I'm thinking of two scripts external to pcb, for use with make.  While editing
> a pcb board, I would run DRC and effectively have a non conductive piece
> of trace between separately named ground planes.  When I run make faboutput,
> one script is run to change the non conductive piece
> of trace to copper on a layer, then output RS274-X, the run the other script
> to change the piece of copper on a layer to a non conductive piece
> of trace.
>
> We don't have the concept of non-conductive built into pcb now though,
> so some kind of "ignore for DRC purposes" might do.
>
> There's still a problem with that method though... It won't check for
> proper clearances of the starpoint blob of copper to other copper if it
> is handled by an "ignore for DRC purposes" attribute.

As soon as we have the option to define arbitary layer types, we also
need to be able to define arbitrary DRC rules.  The star-point may be a
footprint with a structure on some non-conductive "shorts" layer, which
will need to be accompanied by a set of design rules in the technology
specs.  The fact that the non-conductive "shorts" layer is implemented
in conductive copper by merging the layer with the bottom copper is
irrelevant, since for netlist purposes it is non-conductive, just like a
"resistor" layer.  Part of the design-rule check is to be perfomed
manually, you'll always need to check your footprints in your library.


-- 
Stephan


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