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Re: gEDA-user: Multiple footprint methodology?


DJ Delorie wrote: 
Given a part with two or more packages, how should the footprint
mapping be defined in the symbol?

It's not, it's added later through, for example, gattrib.

Yes, I get that. I asked my question poorly. There is an attribute in the symbol that points to the correct pin mapping. I get the concept, but I don't know where all the ascii lives, and how it should be split up across various files.


In the case of the ATMega88, the TQFP-32 version of the part brings
out more I/O than the PDIP-28 version. Soo... choices. 1) Define all
the pins, but don't map them to PDIP-28?  Will net lister issue
warnings? 2) different symbol?  Icky, because you would like to
switch packages without deleting/inserting a symbol.


If it were me, I'd have multiple symbols - one common one for the
common pins, and a set of alternates for the I/O areas that change.
As long as they have the same refdes, the netlister knows how to deal
with them.


Perfect!  Naming convention?  PART-1, PART-2?  Or PART-1, PART-EXTRA-1?

Is there a way to make the "extra" pins have a default tie-off so that you don't need to add the extra symbol in designs that don't use those pins?


I did this for the m32c, which has a "cpu" side and an "I/O" side.
Also for an ethernet chip; one symbol for the cpu side, one for the
network side.  That also lets you put the different sides on different
pages.

ATMega88 is actually one of a family of 3 parts: ATMega48, ATMega88,
ATMega168 which have identical pin-outs but different sizes of
internal memory. Again, if you have a board designed around an
ATMega48 and go "oooooops -- code bloat -- need an ATMega88", then
it would be nice to be able to flip an attribute and get a new BOM.


You just edit the footprint attribute.  We just don't expect the
symbols to "just know" which footprints go with it; this is the common
heavy vs light symbol debate.  We chose light, which means the symbols
know little about how they're going to be used, and you use something
like gattrib to set all the footprints.


That's not my question -- this is the flip side of "same symbol with multiple footprints". This is different BOM callout, but same footprint and same schematic symbol (other than BOM part number). If I name the symbol "ATMEGAx8", can the user simply edit the attribute after insertion and not screw up the downstream tools and any library references?

-dave





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