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cvpcb fileformats and BOM enhancement proposal


cvpcb has a GUI and is focused on footprint assignments. Reference
designators and footprints need to be assigned in the schematic editor
then show up in the netlist. I would propose that instead of having
cvpcb produce an updated netlist, it update the schematic file instead.
This would eliminate the need to write a back annotation tool to
update the schematic for board turnon or manufacturing reference.
There already is a placeholder (F2) of the component for the foot
print in the sch file and the footprint currently can be assigned in
EEschema by editing each component instance and it will show up in
the netlist. It also would be handy while creating a schematic to
include the footprint in the add component cache along side the name.

Adding a vendor part number (VPN) field (F3?) would enable an improved
BOM listing. This field would be optional and would show up in the
BOM if present. The advantage of a VPN nails down a symbol and
footprint. Selection of a VPN defines a specific footprint while the
schematic symbol could look like anything the schematic designer likes
as long as the pinout is consistant. A VPN enables future creation of
a project (or board) only BOM (or library) and could reference a
larger company wide parts library (or database). Without this each
designer potentially re-invents a symbol/footprint library for each

part # symbol sect footprint ref manufacture description
--------- ------ -- -------- --- ----------- -----------
DM74LS00N 7400 A DIP14 (or N14A) U1
DM74LS00M 7400 B SMP14 (or M14A0 U2
54LS00W 7400 A W14B (or CFP14) U3
Note: this is 3 separate parts and need separate ref designators
(Using similiar but different parts can happen)
Parts with multiple sections only count as one part in the BOM with
a shared footprint, the section letter would not be listed. The
manufacture, description, inventory could be added to a future,
separate parts database, selector, navigator....

The bottom line is the schematic should be the master controlling
document...need to swap parts, pins or change footprint? - update
the schematic and re-generate the netlist.

A more complicated parametric example:

Digi-Key Part Number FC0603-50BFTR-ND
Manufacturer Part Number FC0603E50R0BTBST1
Symbol: R
Description RES 50 OHM 125MW .1% 0603 SMD
Manufacturer Vishay/Thin FIlm
Resistance In Ohms 50.0
Power (Watts) 0.125W
Tolerance 1/8W ±0.1%
Lead Style Surface Mount (SMD - SMT)
Case 0603 (1608 metric)
Packaging Tape & Reel (TR)
Composition Thin Film
Voltage - Working *
Temperature Coefficient *
Quantity Available 1
Minimum Quantity 1
Unit Price USD 0.91000
here there are many resistors with a common shared symbol and footprint

As a designer why do I want to deal with all this?
Ans: To make sure the correct parts are ordered, your board is
built right, it will work properly and save the company money
by ordering common parts in quantity from a qualified vendor.

Frank Bennett

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