Re: gEDA-user: X-Y placement files

[Dan McMahill <dan@mcmahill.net>]

On Mon, Apr 26, 2004 at 10:40:37PM -0400, Dan McMahill wrote:
> On Mon, Mar 15, 2004 at 09:40:49PM -0800, Matt Ettus wrote:
> > 
> > 
> > Is PCB capable of creating X-Y placement files for pick and place?  The format
> > seems pretty simple.
> > 
> > Thanks,
> > Matt
> > 
> 
> Hi Matt,
> 
> I have mostly implemented this.  Do you have any good data from a
> manufacturer on the exact format they like to see?  It is fairly
> industry standard?
> 
> What I'm doing is having the routine calculate the centroid of the
> pins/pads on the fly so you're not sensitive to where the mark may
> be on the footprint.  The only thing I have left to do is rotation.
> Any suggestions on the algorithm?  Any idea what the standard definition
> might be?  For example, if I have an 8 pin DIP or SOIC, what is the
> angle of this:
> 
> 1  8
> 2  7
> 3  6
> 4  5
> 
> Is that 0 degrees or +90 degrees?
> 
> DJ has suggested an approach that looks which quadrant pin #1 is in
> after you find the centroid and then using a definition like:
> 
> pin #1 quadrant, rotation
> 
> 1, +180 degrees
> 2, +90 degrees
> 3, 0 degrees
> 4, -90 (or should this be written as +270) degrees
> 
> Any thoughts based on real experience as to cases where this will fail?
>
> I suppose (thinking while typing) if pin 1 falls on an axis, I need to
> properly deal (SIP packages, 2 pin packages, etc) and a 1 pin part 
> would always be 0 and a 1 pad part could be 0 or 90 based on aspect
> ratio of the pad.
> 
 
well, I found one.  SMA connectors have pin #1 at the centroid of the part.

I think pin #1 at the centroid is the only case where what I've implemented
totally misses the boat.  Then again, probably not too many parts fall into 
this category.

An excerpt from what I have so far is:

# $Id$
# PcbBOM Version 1.0
# Date: Tue Apr 27 03:16:14 2004 UTC
# Author: Dan McMahill,At Home ,258-8142,
# Title: CA16R001 - PCB BOM
# RefDes, Description, Value, X, Y, rotation, top/bottom
# X,Y in 1/100 mil units.  rotation in degrees.
# --------------------------------------------
C43,"0805","2.2u",282200,298000,0,top
R55,"0603","10k",256000,69600,270,top
J11,"MTA100_8","Amp 640456-8",259000,21000,0,top
R59,"0603","10",265000,90600,270,top
J14,"HEADER8_2","unknown",261000,130000,180,top
R53,"PANASONIC_EXB2HV","EXB2HV201J",391000,142000,90,top
U6,"US8","unknown",244000,87000,180,top
TP21,"TP-40-100","unknown",266000,112000,0,top
C50,"0805","2.2u",256000,89800,270,top
R57,"0603","10k",276000,69600,270,top
R56,"0603","10k",266000,69600,270,top



-Dan

--