Re: gEDA-user: moving slotting to pcb?

[Stefan Salewski <mail@xxxxxxxxxxxx>]

On Sat, 2010-06-26 at 13:18 -0400, DJ Delorie wrote:
> A random thought occurred to me today - why does gschem do slotting at
> all?  Why does it care about footprints and packages?  Would it make
> more sense, from a design flow perspective, to just send the symbolic
> information to pcb and let pcb assign footprints and pinouts?
> 
> That way, gschem does all the symbolic stuff, and pcb does all the
> physical stuff.  It would, of course, mean major changes to pcb to
> handle "elements without footprints yet" and stuff, as well as mapping
> multiple refdes's to single elements.  Probably make power pin
> management more complex too, unless we came up with a new way to
> manage "hidden" pins.
> 
> Anyway, food for thought.
> 

Indeed, I do not like the footprint attribute in symbols too much. One
reason is, that gschem does not really understand the footprint, gschem
can not do sanity checks, i.e. about pin count, and can not display the
footprint for visible inspection.

On the other hand: I think symbols really should have information about
footprints. Consider making a schematic with 100 symbols. Do we want to
select a footprint for each of these in PCB. And again for the next pcb,
with a similar schematic.

Maybe, symbols should contain a set of footprints, which are valid for
that symbol. I.e. DIP8 and SO8 for a OpAmp symbol, and we should have
the possibility to select one of these in PCB program. One may be the
default, but we should have the power to change it in PCB. For
Resistors, symbols may state that all 2 pin footprint match, so we can
select 0805, 0603 ... in PCB.

I think we may need indeed a much closer connection between PCB and
gschem. I.e. in gschem it should be possible to specify attributes for
nets/traces like width, maximum length, impedance... And inside PCB we
should have these information available, i.e. for the autorouter. And:
It should be possible to select a net or pin in PCB and see that net/pin
in the schematic high-lighted -- and vice versa.

I have to admit that I have no idea how we can do that in an efficient
way in the current modular design (separate programs). Of course I like
modular design, but it can make things (like pinswap) much more
difficult.

Best wishes,

Stefan Salewski
 



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