Re: gEDA-user: More robust support of multi-part symbols.

[igor2 <igor2@xxxxxxxxxxx>]

On Thu, 9 Jul 2009, Dave N6NZ wrote:

>Ben Jackson wrote:
>> On Wed, Jul 08, 2009 at 09:20:54PM -0700, Steve Meier wrote:
>>> Let alone, how at the layout level we can do pin swapping and back
>>> annotation.
>> 
>> I've thought about working on that, because I've dealt with that problem
>> in almost every project I've done with geda/pcb.  I'd love to know how
>> the big boys handle it.  
>
>Often poorly.
>
>> Obviously you can't draw wires in gschem and
>> then swap pins in pcb and expect the wires to be asthetically re-drawn
>> in gschem.  So do you only do it with busrippers and netname attributes?
>
>The first thing to realize is that for large projects, hand placed line 
>corners don't scale.  The in-house CAD systems I've used on large 
>(30-300 engineer) projects had auto-routed drawings.  In some ways, 
>auto-routing a drawing is more of a challenge than auto-routing a PCB, 
>since aesthetics matters as well as connectivity.  An in no case were 
>the drawings "perfect" -- that is to say what a good draftsman would do. 
>But all the systems produced readable drawings, and nobody hand to spend 
>much time making them readable.

gpsim (Free PIC microcontroller simulator) tries to do something similaron
the breadboard feature. The breadboard looks like a schematics, you see
there the PIC being simulated, and if you have external modules (LCD,
rs232 terminal, LED, etc), you see them as well. The netlist is visualized
by drawing black lines between the pins. The lines consist of horizontal
and vertical segments and gpsim tries its best to add as many segments as
required to avoid crossing components or other lines.

Of course it works well only if you have 2..3 boxes and max 6-8 lines :)
I agree that this may be a bit overkill. However, swapping pin numbers may
work for the big box symbols. Maybe we could mark groups of pins in a
symbol, let's say GPIO1, 8 pins is a group, if any two of these are
swapped, just swap the pin number on the schematics. If you swap a GND
with a GPIO1 pin, it won't work, because they are not in the same pin
group. I think something similar may be applied on slots.


Another option is defining net lines with different color in gschem.  If
two pins are swapped, gschem deletes the two net segments connceted to the
pins and draws two new segments simply crossing eachothers with this
different color. This means the user can swap whatever he wants on the PCB
and his schematics becomea haystack with red lines, then he can go and
clean it up when he finished swapping pins on the PCB.

Regards,

Tibor Palinkas




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