One of the weaknesses of a classic spread sheet bom is that there exist many to one relationships that spreadsheets are very bad at. Not unlike me trying to write considering my inherent spelling capabilities.
A symbol could be supported by several equivellent parts from different vendors. A part could be supported by several different packages each with a different package and thus pin locations. A part can have a manufacturor and multiple vendors. Take surface mount resistors. package choises: 1210 0805 0604 0402 etc Value: way to numerous but NOT INFINITE! it would help to have a pull down list not unlike digikey for picking legal values and then a similar pull down list for picking a vendor and then a similar for picking the specific family and thus part number. Thus the idea of having a database that can support these more complex relationships is really apealing. But, after we have been through all of this and we have that completed schematic with selected parts and the completed gerbers at that moment a spreadsheet is very handy for passing on to the purchasing team. Though I think they should have access to the database too so that when they find out that a cap has a 16 weeklead time they can find a pre-selected alternative and not bother me as much. Steve Meier DJ Delorie wrote: >> 10. John Doty is very keen on being able to set up libgeda to >> automatically copy any symbols used to a local symbol store of some >> description. >> > > I like this idea too. > > >> 11. Several people are keen on the idea of changing everything to use a >> separate BOM as a master document. I don't understand what they heck >> they're >> talking about nor how it would work, so I would like them to spell it out >> carefully for stupid people like me. To me, a BOM is a spreadsheet, >> generated from the schematics, containing a list of refdeses and part >> information which is sent to an assembly house so they know which bits to >> put >> where. >> > > Right, that's what a BOM is. In our case, the BOM knows which > physical part is being used, so it can tell PCB what footprint to use, > and what the pin numbering is. That way, the schematics don't need to > know if I've chosen a TO220 or SOT23 regulator, which may have > different pin numberings. It can be told later, but at first it just > knows that the regulator has pins named "IN", "OUT", and "GND". The > BOM decides which physical part is used, so it can tell gschem that IN > is pin 1, OUT is pin 3, and GND is pin 2. > > That way, the only attributes that MUST go in the schematic are those > that are visible in the schematic, like refdes and value. The rest > need not go in the schematic (but may), and can be auto-populated by > the BOM or some parts database. > > So, given all this database, the schematic would say "resistor-1.sym, > 4.7k" and the BOM knows I prefer 0603 Rohm from Digikey, and can fill > in the rest. > > >> Message-Id: <[EMAIL PROTECTED]> >> > > URL? > > > _______________________________________________ > geda-dev mailing list > [email protected] > http://www.seul.org/cgi-bin/mailman/listinfo/geda-dev > > _______________________________________________ geda-dev mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-dev
