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Subject:	[geda-user] Board DRC
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From:	John Doty <jpd AT noqsi DOT com>
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Date:	Thu, 22 Oct 2015 14:31:26 -0600
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On Oct 22, 2015, at 1:53 PM, DJ Delorie <dj AT delorie DOT com> wrote:

>=20
>> There should be exactly one short at the star ground point. If
>> algorithm calculate their lines meet at the edge end point have to
>> checked in some way.
>=20
> Or if a particular bit of copper could be tagged as "star point" or
> something, the algorithm could know that it should be the edge of
> multiple nets, and verify it.
>=20
> I'm just thinking, our DRC isn't designed to handle these types of
> problems, but a new DRC might, and give us other benefits too.
>=20

I spent the morning in a video meeting reviewing a complicated layout =
from a geda-gaf->Allegro flow. The issues were far beyond the things =
discussed in this (thoroughly mutated) thread. We have segmented =
grounds, but not star connections. Star connections only work well if =
you can neglect inductive coupling. And then there ware other things: I =
was able to say at one point =93Don=92t worry about crosstalk between =
signals X and Y: they crosstalk so badly in the sensor that any =
conceivable crosstalk on the board will be negligible.=94

So, it=92s complicated. I found myself wishing for a tool that would =
show concentrations of AC magnetic field. As far as I know, Allegro =
can=92t handle these issues: humans have to pay attention.

I don=92t think a tool that works from the top down can ever do this =
stuff well. You need a bottom-up model of a circuit board to even start =
to think about how to analyze how your layout really works. Pcb has no =
such foundation, which is the root of the frustration it causes for a =
reductionist like me.

John Doty              Noqsi Aerospace, Ltd.
http://www.noqsi.com/
jpd AT noqsi DOT com



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