[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

Re: gEDA-user: Light vs heavy gschem symbols?

At one point I had suggested an intermediate database that mapped all
the symbols, footprints, and other attributes together into instances
of parts.  So, you could pick "2-in NAND gate" in gschem, and later
narrow it down to a specific NAND gate package, either by footprint or
vendor part number, with gschem "knowing" what the range of options
are based on its database.  PCB would use the same database to further
narrow it down, perhaps, resulting in (eventually) a BOM.

So this big database would have fields for vendor, part number, gschem
symbol, "value", pcb footprint, and notes.  Better would be one
file/directory per vendor, to avoid duplicating that field all over
the place.  After you pick a symbol, gschem would know what the list
of possible footprints are, and once you pick one, it would know the
list of possible part numbers and/or vendors.  Etc.

The problem is that there's a lot of variation involved.  We have a
couple of resistor symbols, which do we put in the database?  Eagle,
IIRC, has symbol classes - and I've seen others do this too.  You'd
add a "resistor symbol" and one pops up.  You can change this to some
other type of resistor symbol, but it's still a resistor symbol.  The
database maps "resistor symbol" to a range of through and SMD
footprints, like AX-300-25 or SMD-0603.  You pick SMD-0603.  Now it
can give you a list of vendor part numbers, values, whatnot to choose
from.  You choose the "22.1k" value.  Now there's a smaller list of
vendor part numbers to choose from.  You pick Digikey P22.1KHCT-ND.

But my point is that it shouldn't be up to gschem or pcb individually
to keep track of this information; it's something that needs to be
shared by both and used by both equally, because the information is
used to bridge the two.

Anyway, just food for thought.