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Re: BOM support


On Fri, 30 Jul 2010, Brian F. G. Bidulock wrote:

I have between 500 and 1000 0.1uF X5R 0402 bypass capacitors on
my card.  You are going to have 1000 repetitions of this

Ever considered a dieletric layer in your board (i.e. power layers
*being* the bypass capacitors)? with that kind of
capacitor number it could be economical :D

<component> structure in the file, where the only difference is
the 'ref' attribute in the first line (resplendent with
repetitions of my user-defined fields (manufacturer's P/N,
vendor, vendor's P/N, price, price breakpoint, type,
substitutions, power consumption, thermal resistance) which will
be the same for all 1000 capacitors.  This is going to be about
100,000 lines of XML.  It will be unreadable because I won't be

It was said more than one million times... XML is not actually mean to
be *usefully* readable :P

able to see other components for the capacitors.  Paging through
with an editor will be a pain.

Postprocess it. You'll avoid a sort/merge step which would be
unnecessary in most other scenarios without imposing a projection (IIRC
db theory correctly) in most other scenarios (like the 'by reference'

I think this would be a KISS scenario.

Might I suggest that you consider an already tried and true BOM
format, already specified in XML, such as that from "IPC-2581
includes Ammendment 1," Section 7. (Google:
IPC-2581witham1pub.pdf).  Also talk a look at the Approved
Vendor List in Section 9 of the same document.

*That* would be a good idea. Better use an existing standard than
reinventing the wheel. Too bad you have to pay for most IPC standards :(

You will notice some necessary features such a whether the
component is populated at the refdes or not.  Also, real
electrical properties instead of loosey goosey value field.
Place for both external OEM and internal part numbers.  Full

We have completely arbitrary attribute fields... good luck reconciling
the two structures (we're hitting the R.E/O.O. impendance mismatch, as

The problem with having a BOM that has too little information is
that the assembler will import it into a spread sheet and start
changing it.  Loss of sync between the CAD data, spreadsheet and
CAM system (chip shooters) simply results in rapid and automated
descruction of parts and boards.  Money can be burnt easier (and
maybe even safer) with fire.

In my book the source BOM XML/whatever would be contain *everything*
that kicad knows about the component. Postprocessors would then extract
relevant informations from it, depending on the application.

Lorenzo Marcantonio
Logos Srl