Re: gEDA-user: How to split one large PCB into two smaller ones

[Stefan Salewski <mail@xxxxxxxxxxxx>]

Am Samstag, den 20.09.2008, 08:30 -0400 schrieb DJ Delorie:
> > Can someone give a more detailed description or a pointer to it?
> > 
> > In the past I have only routed gsch2pcb generated boards, without
> > inserting additional footprints or rat lines.
> 

Thank you for your detailed description -- it is very similar to my own
thoughts.

> That's all I did.  Include all schematics in gsch2pcb,

And you included the connector in the schematics too? I think so.

> name the signals differently for the two sides of the connector.

That is one critical point: I have 10 different voltages and about 30
(slow) signals which should travel from one pcb to the other. Renaming
nets in schematics just to fit pcb layout is really a dirty job.

> If you accidentally leave a signal named the same, you get a rat crossing the
> boundary.
> 
> Note that this may not work for you if you have things like GND or
> VDD, because those will be the same on both boards :-(
> 

I have no VCC, but GND and AGND (and +3.3V, -5V, 1.2V, ...).

> I suppose if you *did* have the nets the same, as long as the closest
> points between boards *are* the connectors, you can use a spare copper
> layer to connect the connectors together

My idea too, but I will mount the two PCBs on top of each other (so I
can use a cheap, compact case) so both connectors are on the same
position on both pcb boards. But maybe it will work also -- maybe I can
move the connector to its final place when all other is done. I will
test it -- my hope was that someone has tested it before me ;-)

> 
> It would be interesting to ponder the idea of PCB knowing that two
> connectors will be "connected" in real life, and letting the path
> following go through them.
> 

Yes this would be very useful.

Last question: My understanding of pcb manual was that it should be
possible to insert additional rat lines in pcb, see

The PCB-20080202 manual (PDF) page 28:

"A common way to use rats nests is to place some elements on the board,
add the rat-
lines, and then use a series of moves/rotates of the elements until the
rats nest appears to
have minimum tangling."

Is this wrong information, or is my understanding wrong? (Tried a long
time to insert rats manually yesterday, seems not be possible.)

My current impression is that the best solution (currently) is to make a
new sheet wich contains the connector and to connect all 40 Signals to
it. Then run gsch2pcb with on group of schematics and this connector
sheet, and run it again with remaining schematics and connector sheet.
So I will get two pcb boards. Problem: There can remain unconnected
signals -- I have to be very carefully. The other disadvantage is that I
have to put all devices of one schematic to one pcb, I can not put some
devices from schematic "LinRegulators.sch" to first pcb and other
regulators to the other. But I think this will be OK for me.

Best regards

Stefan Salewski





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