gEDA-dev: footprint cleanup

[Dan McMahill <dan@xxxxxxxxxxxx>]

I wrote a script which goes through all of the m4lib footprints and 
instantiates them one at a time.  There are currently no m4 syntax 
errors and in the generated footprints there are 28 with pcb syntax 
errors.  This is out of 2039 total (1.37 %).  Note that this doesn't 
mean all of the footprints have the correct dimensions, just that most 
of them can be loaded by pcb.

I'm planning on doing some cleanup to either fix or remove the 28 which 
have pcb syntax errors.  Currently the ones with errors are:



ACYmP -- polarized axial lead part with pin-to-pin spacing of 'm'
RCYmP -- polarized radial lead part with pin-to-pin spacing of 'm'
BREm  -- bottom lead rectangular part with pin-to-pin spacing of 'm'

and one other which I will delete.


My question is, is there anyone around who has familiarity with any 
standards (do they even exist?) for naming these parts?  It seems that 
the naming convention we have here (documented at 
http://geda.seul.org/wiki/geda:scg) is insufficient.  In particular, 
consider the axial lead parts.

- how does one specify the drill size?
- how does one specify the width of the part (dimension perpendicular to 
the main axis of the part)?

In the case of the radial lead part,

- how does one specify the drill size?
- how does one specify the diameter of the part?

And in the BREm parts

- how does one specify the drill size?
- how does one specify the length of the part (dimension along the major 
axis
- how does one specify the width of the part?


I don't want to just blindly fix the pcb syntax errors in these 
footprints when it seems that there is a highly probablility of them not 
being quite right in terms of mechanical dimensions.

http://landpatterns.ipc.org/IPC-7351Table3-15September2005.pdf has 
naming conventions for surface mount.

Unless someone knows of a real standard for these through hold 
footprints I'd suggest we change to:

ACYm  -> ACYmPdDw{,P}  where m = pin pitch, d = pin diameter (not hole 
size but pin size), w=width (perpendicular to axis), P for polarized. 
For example ACY400P25D200P (yeah I know, it is _long_) would be a 400 
mil pin spacing, 25 mil pin diameter, 200 mil wide polarized part.

RCYm -> RCYmPdDo{,P} where m = pin pitch, d = pin diameter, o = outer 
diameter of the part, P for polarized.  So a RCY200P25D400P would be a 
200 mil pin spacing, 25 mil pin diameter, 400 mil component diameter, 
polarized.

BREm -> BREmPdDwXl{,P} where m = pin spacing, d = pin diameter, w = 
dimension of the part perpendicular to the major axis, l = dimension of 
part along major axis, P for polarized.  BRE200P25D150X300 has 200 mil 
pin spacing, 25 mil pin diameter, 150 mil x 300 mil package size and is 
non polarized.

Any comments?

Now comes the question of what set of values to put into the standard 
library.  Clearly I don't support putting in packages in 1 mil 
increments for these.  Anyone know of any standards which might give 
some real clue as to what sizes are actually used?

Thanks
-Dan
(who hasn't used leaded parts like this in about 20 years)






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