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Date:	Mon, 31 Aug 2015 13:20:33 +0200
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To:	"Markus Hitter (mah AT jump-ing DOT de) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
Subject:	Re: [geda-user] back annotation proposal (RFC)
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On Mon, Aug 31, 2015 at 11:54:30AM +0200, Markus Hitter (mah AT jump-ing DOT de) [via geda-user AT delorie DOT com] wrote:
> Am 31.08.2015 um 11:16 schrieb Nicklas Karlsson:
> 
> > I do not get everything but for pin and gate swapping ideally there
> > should be no need for back annotation.
> 
> Good point!
> 
> For simple elements like resistors the definition should be "pin 1 or pin 2, but not both" or "pin 1 or pin 2, but not the same as the other pin".

Fro simple elements like this, why not have an attribute called
"symmetric_dipole"?

This would be set for non-polarized capacitors, most inductors (not all,
conical inductors are not symmetric) and (all?) resistors. I don't know
of any asymmetric 2 contact resistors, but they might exist.

This causes a problem for pcb ratsnest, because of combinatorial
explosion when trying to decide which pins to swap on symmetric dipoles,
maybe a popup menu to control swapping would be better. But for these
components I fail to see the need for back-annotation to schematics;
I'm just a bit fed-up of rotating passive dipoles by 180° when laying 
out PCB with many such components, especially since if often implies
adjusting the orientation and position of the refdes (when it's not
hidden).

> For elements with slots it should be "pin 1 of the same slot as pin 2 and pin 3". Looks like pin mappings need more logic than just '='.
> 

There are cases where you can do gate (slot) swapping but 
no pin swapping, as with 74125 and 74126, or flip-flops like 7474.


    Gabriel

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