Re: gEDA-user: Metric PCB footprints using 1mil grid

[Wojciech Kazubski <wk0@xxxxx>]

For m4 parts, look for those that have dimensions (especially pin spacing) specified by big numbers and then divided by 100 or 1000. This significantly reduces the accumuluation of pin spacing errors. M4 has integer arithmetics, so the resulting pin positions are rounded to 1mil.

Wojciech Kazubski

> As I mentioned in an earlier mail, the QFP208_28 footprint I used for
> my board I later found to have 1mil spacing depsite being in the .01mil
> format.  Since it's a metric footprint (0.65mm pitch) the pins vary in
> both width and spacing along each row.  This isn't fatal, certainly, but
> it's not ideal.
> 
> I was considering how to detect this problem automatically.  I would be
> fairly easy to identify parts with 1mil accuracy which also have 'several'
> pins in a row with varying pitch and/or width.  It could be done in a
> script, or within PCB.
> 
> Would anyone be interested in seeing this detected automatically somehow?
> I was thinking about flagging it in the element picker, but that's not
> typically how elements get into a PCB.  It could also be part of the
> DRC, or it could be a separate report.
> 
> -- 
> Ben Jackson AD7GD
> <ben@xxxxxxx>
> http://www.ben.com/
> 
> 
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