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Date: Sat, 17 Dec 2016 11:35:55 +1300
From: "Lilith Bryant (dark141 AT gmail DOT com) [via geda-help AT delorie DOT com]" <geda-help AT delorie DOT com>
Subject: Re: [geda-help] Orientation of components in X-Y (centroid) files
To: geda-help AT delorie DOT com
References: <cc0d85d7-870f-23a6-c212-1ff753a30df4 AT mochima DOT com>
In-Reply-To: <cc0d85d7-870f-23a6-c212-1ff753a30df4@mochima.com> (from
	moreno+geda-help AT mochima DOT com on Sat Dec 17 10:02:33 2016)
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Reply-To: geda-help AT delorie DOT com

On 2016-12-17 10:02:33 AM, Carlos Moreno wrote:
> Hi,
> 
> How do we define the angle (the orientation) in the X-Y or centroid
> file?  In particular, what is the convention / reference angle for 0
> degrees?
> 
> I understand that from the point of view of the coordinates system,
> zero degrees means along the x-axis.   However, from the point of
> view of the component, what is zero degrees?
> 
> I would assume there are some universal conventions;  for example,
> for IC's, I suspect that zero degrees means the chip with pin 1 to
> the top-left corner  (does it indeed?).  But for example, for a 0805
> surface-mount component --- does zero degrees mean width = 08
> and height = 05, or vice-versa?  And in general, what is the rule?
> 
> 
> Though I guess this is a question that the specific PCB manufacturers
> should answer, I haven't gotten a straight answer from them, so I
> figure you guys may share some insights based on your experience
> with manufacturers?

I made some changes a few years back, so it attempts to match the following
spec:

http://i.screamingcircuits.com/docs/understanding-the-centroid-file-r2-2.pdf

In practice, I've never had a manufacturer spit back anything I've sent them.
I suspect they get a wild mix of messed up files, and components in tapes on random
angles,  so they just eyeball everything and just go ahead and fix whatever is grossly
wrong.