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	Fri, 16 Oct 2015 09:58:29 -0700 (PDT)
Date:	Fri, 16 Oct 2015 18:58:25 +0200
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] Is someone working on a PCB autoplacer?
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On Fri, 16 Oct 2015 16:47:17 +0200
Stefan Salewski <mail AT ssalewski DOT de> wrote:

> Maybe I missed that, but there was so much traffic on this list in the
> last months that I was able to read only a very small fraction.
> 
> An autoplacer has the advantage, that it may be useful also for people
> who wants to do manual routing. And for autorouting it is an important
> component. Another point is, that even a bad autoplacer is useful for
> initial part distribution, so all the arguments people have against
> autorouter are not valid for autoplacers. And development may still be
> some fun. For an autoplacer some support by schematics tool would be
> really useful, for example grouping of elements: An OpAmp with its two
> resistors and two bypass capacitors should build a group, indicating
> that these components belongs together. This is important for the bypass
> capacitors, because their pins both belong to very large nets, gnd and
> power, so location is not determined by net. For signal paths, nets
> should include generally only two or very few pins/pads, so that placer
> can use that information to place components at the correct initial
> position. Another point is, that it would be useful when footprint files
> would contain a bounding box for occupied area -- pads, pins and silk
> may be used for that, but exact box may be better, maybe not only a
> rectangular box, but a polygon or circle.

There are cases then an exact box is better and I used it myself. In particular components usually are smaller than the pads. It have nothing directly to do with this but to make components use little space I usually try to put silkscreen below component.

I wrote a few rows about it a short while ago. I think automatic steps was something like this:
  1. Identify decoupling capacitors.
  2. Place decoupling capacitor.
  3. Make a group of component together with decoupling capacitors.
  4. Place groups.
A decoupling capacitor could be defined as the smallest value capacitors connected to the power lines and there is one for each power line. If a button is pressed for each step some manual intervention would be possible. In paricular you may want to place connecers, buttons and LEDs before place groups. It is probably also very common to only work with selected components then a small change is made.

Nicklas Karlsson

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