Re: gEDA-user: New user question

[sdb@xxxxxxxxxx (Stuart Brorson)]

> At Tue, 4 Jan 2005 21:05:07 -0500 (EST),
> Stuart Brorson wrote:
> > A gschem symbols usually carries a "device" attribute which tells you
> > what the part is generally.  That is, for resistors, the
> > device=resistor, for caps, device=capacitor, for an IC, device=AD8047,
> > say.  Unfortunately, the device attribute is not promoted, meaning
> > that it doesn't become an editable attribute in gschem.
> 
> I was thinking that if every part had a default filename=blah.sym in
> the attributes, that would make it easier to figure out.  It would be
> nice if everything was correctly labeled but even if someone sets up a
> device attribute correctly, the filename may be different.

One issue is that the same file might be used for many different
parts.  The  best examples are the passives, where you use the same
symbol for many different resistors (say), and just change the value
attribute to specify the resistor value.  

This is clear in the case of passives.  However, for other parts, it
might be more involved.  For example, many op-amps come in an eight
pin package with standard pin-outs.  I might want to use two different
op-amps in my design.  I could use teh same symbol and differentiate
between the two using the value attribute.  This requires that I
maintain enough discipline to make sure that I fill out the value
attribute for both.

The problem with using the filename is that it is not very
descriptve.  Moreover, it can even be confusing.  I think we have
resistor-1.sym, resistor-2.sym, and resistor-3.sym.  The only
difference between the three is how they are drawn (one of the three
is teh European box resistor symbol, another is the American squiggle,
and the third . . . . well, I have forgotten.  

That's why I would prefer to somehow display the "device" attribute.
Usually, it has the most to do with what the part actually is, since
folks who build new symbols are required to fill it out.

For you, it may be that the best way to keep track of the parts is to
make sure you fill out the "value" attribute.  Longer term, you might
also incorporate a "DigkKey_Part_No" attribute into your schematic for
each part, if you want to be very specific.  This is easy to do using 
gattrib (shameless plug).

> Along with other usability issues, it would be nice to get off page
> connections to show where nets go but after reading these lists, it
> seems that's still not going to work.  I imagine it would be difficult
> since gschem doesn't seem to have a concept of page numbers in a
> project.

True.  In gschem all netnames are global, so you can do an off-page
connection by just naming the net the same on both pages.  IIRC, Orcad
forces you to use off-page connection symbols, which has never made 
sense to me -- it's just extra work & doesn't clarify anything or
prevent any errors.  Personally, I prefer it the gschem way.  ViewDraw
-- a schematic capture package waaaay superior to Orcad -- does it
this way too, FWIW.  

Stuart