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Date: Fri, 22 Jan 2016 09:49:09 +0100
From: "Nicklas Karlsson (nicklas DOT karlsson17 AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
To: geda-user AT delorie DOT com
Subject: Re: [geda-user] PCB data structures (was: features: layers stack,
 padstack/vias)
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> > The PCB layout has an object of type pcb_layout as the root object, which can contain an arbitrary number of pcb_layer objects--which in turn contain the geometric primitives--and pcb_element objects which aren't associated with a layer.  Objects of type pcb_polygon can have child objects of type pcb_polygon_hole:
> >
> > pcb_layout
> > +- pcb_layer
> >    +- pcb_arc
> >    +- pcb_line
> >    +- pcb_pad
> >    +- pcb_pin
> >    +- pcb_polygon
> >       +- pcb_polygon_hole
> >    +- pcb_rat
> >    +- pcb_text
> >    +- pcb_via
> > +- pcb_element
> 
> Sounds reasonable, and similar to what we have now but with much cleaned up
> naming and hierarchy.

I would say then looking at data layer by layer there are: arc, line, circle, polygon and cutout of these drawing primitives.

Pad/pin/via is a composite of these drawing primitives on different layer, this is the case no matter how they are represented. A hole is equal to a round cut out usually thru all board layers with or without plating. Text is probably also a composite of other drawing primitives.


> > A footprint (element definition) has a pcb_footprint object as the root object which can only contain objects of the types pcb_element_arc, pcb_element_line, pcb_pad, and pcb_pin:
> >
> > pcb_footprint
> > +- pcb_element_arc
> > +- pcb_element_line
> > +- pcb_pad
> > +- pcb_pin

There should probably be: arc, line, circle, polygon and preferably cutout of these primitives. It would be useful with possibility to assign drawing primitives to a layer. Pad, pin and also via is a composite of the drawing primitives even though a short hand notation may be useful. Vias and holes without a pin number are also useful. I guess it should be possible to assign the pin numbers to any of these objects and in such case a pin connection point with arbitrary shape could be done, it would probably only make sense to connect to copper layer but this is probably more of a drc check.

It would be useful with possibility to reference predefined via/pin/pad or connection point from a library.

> When I originally referred to creating a new structure, I had a more humble
> goal in mind:  I just wanted something like PCBType, minus all fields that
> don't go in a pcb file (e.g. the rtree), plus everything not reachable from
> PCBType that does go in a pcb file (e.g. the grid stuff from Settings).
> 
> I've since become even more humble and decided it might be better to just try
> to add a little bit to PCBType such that it consists of a superset of what
> goes in a pcb_file.  This would be a slightl improvement over the existing
> situation (which is that PCBType is neither superset nor identical set).
> 
> I think you have slightly different purpose in mind of creating a foundation
> for a pcb API.  I don't like the idea of an API based off PCBType either,
> but my present goal is a bit more modest than a full API, so I'm not sure
> I want to tackle that at the moment.  It it does materialize I'll be happy
> to use it as a basis for an on-disc format though :).
> 
> Britton

It would also be useful if information with possibility to add information to any of the objects about which sub circuit it belong to. If it is possible to store which sub circuit an object belong to it could be used for example to select all objects belong to a "power supply" even though shape is irregular either for simply moving it or reuse it somewhere else. It would also be useful for multichannel design.


Nicklas Karlsson