Re: gEDA-user: Slotting and visible power connections

[Joerg <joergsch@xxxxxxxxxxxxxxxxxxxxx>]

Mark Rages wrote:
> On Tue, Nov 4, 2008 at 7:42 PM, Joerg <joergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:
>> Sorry for asking a lot here lately but I believe others will hit this
>> snag as well and I could not find much info about it, not even via a web
>> search outside geda.seul.org:
>>
>> Often power pins must be made visible. For example if you have to filter
>> the supply for digital parts or opamps separately for each instance. Or
>> if you use a 74HC14 at 5V and another 74HC14 on the same schematic at 3.3V.
>>
>> Those power pins show up on every single slot. Looks quite ghastly on a
>> schematic. So the LM358 dual-opamp was to be my first part made with
>> gEDA. I tried this:
>>
>> Slotdef=2: 5,6,7
>> Slotdef=1: 3,2,8,4,1
>>
>> That butchered it. Connected both outputs to pin 1 and assigned pin 7 to
>> the supply (which should have been the 2nd output). Somehow I'd have to
>> have power pins on slot 1 but none on all the others.
>>
>> Is there a somewhat orthodox way to do this? A method where renumbering
>> at a later point doesn't break refdeses?
>>
> 
> I don't know about renumbering, but the standard way to handle this is
> to use two different symbols with the same refdes.   You could use one
> symbol for each slot in a dual part, with one having power pins
> included.  Or as I do, have a two-pin symbol for the power pins, then
> two instantiations of the LM358 op-amp symbol for the two op-amps.  As
> long as all three have the same reference designator, the netlister
> will do the right thing.
> 

Yes, I thought about that, having generic opamp blocks and scooting a 
pair of "floating" power pins over the first instantiation of a two- or 
four-pack. That is how it's done in Eagle if you don't want to create a 
new symbol (make a part with implicit power explicit). But Eagle keeps 
all that together because it formally belongs to the same part. In 
gschem you'd have to design a separate power pair for pretty much every 
part that has more than one slot. Can be done but kind of messy.

A renumbering script would probably butcher that up.

-- 
Regards, Joerg

http://www.analogconsultants.com/



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