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From:	geda AT psjt DOT org (Stephan =?utf-8?Q?B=C3=B6ttcher?=)
To:	"Rob Butts \(r.butts2\@gmail.com\) \[via geda-user\@delorie.com\]" <geda-user AT delorie DOT com>
Subject:	Re: [geda-user] How to define for an exposed pad to connect to 3 pins/pads
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Date:	Wed, 11 Jul 2018 15:39:02 +0200
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	(Rob Butts's message of "Wed, 11 Jul 2018 08:58:50 -0400")
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"Rob Butts (r DOT butts2 AT gmail DOT com) [via geda-user AT delorie DOT com]"
<geda-user AT delorie DOT com> writes:

> I believe Stephan's solution is what I'm looking for.  My only confusion is
> the "3" in net = GND:3  How does that tie into the net= GND:1?

The '3' is the pin number.

A symbol instance in a schematic can have any number of net= attributes
of the form:

  net=«NETNAME»:«PIN»

This is typically used for power pins.  I try to avouid that.  I use
expicit, visible net= attributes for grounded mounting holes a lot.

Here we talk about a symbol with pins 1 and 2 where nets are drawn, and
the footprint has an additinal pin 3, where you need to attach a net to.

You can construct a complete netlist in gschem format with pin-less
symbols, with refdes= and net= attributes attached.

NB, I was wondering about corner cases.  Say, a symbol has atttributes

 net=GND:7
 net=VCC:14

In the schematic I promote one of them, and add a third

 net=V33:14
 net=nOE:1

Is there a formal rule that ensures that the net=GND:7 in the symbol is
accepted, but the net=VCC:14 is not?  Or do I need to always promote all
net= attibutes if I attache any to the symbol instance?

Stephan

>
> On Wed, Jul 11, 2018 at 8:55 AM, Rob Butts <r DOT butts2 AT gmail DOT com> wrote:
>
>> Yes, I believe so.
>>
>> On Tue, Jul 10, 2018 at 6:52 PM, John Griessen (john AT ecosensory DOT com) [via
>> geda-user AT delorie DOT com] <geda-user AT delorie DOT com> wrote:
>>
>>> On 07/10/2018 05:06 PM, Dave McGuire (mcguire AT neurotica DOT com) [via
>>> geda-user AT delorie DOT com] wrote:
>>>
>>>>   In the
>>>> schematic, I use a standard resistor, which has two pins, 1 and 2.  The
>>>> DPAK PCB footprint has pin 3, which is what gave me trouble.
>>>>
>>>
>>>
>>> I say, "There is no on-the-fly way to do that in the GUI."  [John folds
>>> arms resolutely]
>>>
>>> "It's handled like DJ said:"
>>>
>>> "treat the exposed pad like any other pin/pad, give it a
>>> pinnumber (make one up) and expose it in the schematic symbol."
>>>
>>> Then connect in gschem and output a new netlist, or import from gschem.
>>>
>>> And now Stephan comes up with this!
>>>
>>> "On 07/10/2018 05:33 PM, Stephan Böttcher wrote:
>>> > The footprint has three pins, the schematic symbol only two.  Add a net=
>>> > attribute to the symbol instance to tell where the third pin shall
>>> > connect to
>>> >
>>> >    net=GND:3"
>>>
>>> Sounds like what you were wanting.
>>>
>>>
>>>
>>

-- 
Stephan

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