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gEDA-user: An idea: rework design support...

Hi everyone,

I just thought I'd document this idea in order to get some feedback. I
have no time to implement it for the foreseeable future, but it might
provide someone inspiration to get hacking on PCB.

I sometimes find myself working within a particular generation of
prototype board, wanting to modify it in order to chance aspects of the

I'm fairly confident this is a common task, since it is rare that a
prototype will work perfectly first time and NOT require modification,
nor would the designer always send a new spin of the board for
manufacture in order to test modifications which could be tested by

Rework may involve leaving components off the board, fitting blue-wires,
lifting pins or cutting traces. It may also involve adding components
"dead bug" style.

Managing the build state and netlist of a reworked board is tedious
manual work. We should ideally support:

1. Updating schematics with changes (perhaps having a way to grey out or
dot-dash draw omitted components).

2. Forward those changes into PCB

3. Annotate on a "rework" layer (or layers), where modifications take
place to the board.

Rework layers depicting wiring would support curvilinear free-form
routing, where overlaps don't cause short-circuits.

Rework layers depicting cut tracks would probably be a negative layer
overlay on the existing layer.

I'm not quite sure how to implement it (or the UI), but support for
lifting pins would require both annotation of the isolation between a
pad and the component pin, AND a way to target the lifted pin for
addition of a blue-wire route.

Adding support for "dead-bug" components will also be required.

The idea is that the rework layers / annotations be an extra step after
the "as made" board geometry, which augments the connectivity PCB
"understands", and allow the reworked design to match an updated
schematic net-list whilst a link between your on-screen CAD and the
board you have on the desk in front of you.

I don't know of any other software tools which manage rework like this,
but I think it would be an awesome feature for us to support.

Bonus points for ability to spit out a list of rework instructions for a
technician or board assembly house to follow and tick off as they are


Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,

Tel: +44 (0)7729 980173 - (No signal in the lab!)
Tel: +44 (0)1223 748328 - (Shared lab phone, ask for me)

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