[gta02-core] Footprint editor

[Werner Almesberger]

In the next phase of the gta02-core project, we'll need component
footprint drawings. (Kicad calls them "modules".)

Unfortunately, KiCad's module editor lacks automation and its output
is difficult to review. Since reviews are crucial for our project,
I've written a footprint editor that captures more of the design
process and lets one annotate the footprint with measurements taken
directly from the data used in the construction.

The program lives in http://svn.openmoko.org/trunk/eda/fped
To build it, simply

  svn co svn co http://svn.openmoko.org/trunk/eda/fped
  cd fped
  make

To view and edit an SC89 example footprint, run

  ./fped sc89.fpd

The reference from which the footprint was copied:

  http://www.nxp.com/acrobat/packages/footprint/FOOTPRINT-SC75-SC89-REFLOW.pdf

There are two ways of generating footprints: through the GUI or by
writing a description and then processing it with fped. Also a
combination of both approaches is possible. The following example
shows off some of the language features:

http://svn.openmoko.org/trunk/eda/fped/qfn.fpd

A detailed description can be found in the README.

Fped isn't quite finished yet. It still has several rough edges and
doesn't support round pads or pads with a custom solder paste layout
(e.g., for the central pad in QFN components) yet. I'll add these
things in the next few days. It also crashes sometimes, so save
often ;-)

We can already use it to make simple components that don't need these
advanced features, i.e., bipolar packages, SOT-style packages, and
most of the electromechanical parts.

- Werner