Re: gEDA-user: Resistor valuesâ

[Vanessa Ezekowitz <vanessaezekowitz@xxxxxxxxx>]

On Sat, 25 Dec 2010 12:44:54 -0500
John Doty <jpd@xxxxxxxxx> wrote:

> > "Often", perhaps, but not usually.  No matter how you slice it, the most
> > common way to use such a symbol and its corresponding physical
> > representation is as a component on a circuit board or in an IC.
> 
> Maybe for you. But gEDA isn't limited to that kind of flow. I pray that it
> will remain flexible, not specific to any particular kind of flow.

Flexibility and specific applicability are not mutually exclusive, and for the very reasons you are citing here.  Just as you can use gEDA and related tools to create VLSI designs, I can use it to create ordinary circuit boards - but the two capabilities only exist because someone had to add those specific, specialized features.

When I edit an HTML file, I use an editor with syntax highlighting for that language because I find it very handy (provided the colors are readable).  That doesn't mean the text editor is an HTML editor, per se.  If someone were to come along and add syntax highlighting for, say, Python, C, Ruby, or any of the dozens of other languages out there, it wouldn't change the fact that it still highlights HTML, would it?

Now suppose someone else comes along and adds a feature that can optionally turn those highlighting modes into actual edit-assist modes, making the text editor into an actual mini HTML/Python/C/... editor.  What has changed?

> > Stop trying to change the subject - this is not about simulation or VLSI
> > design,
> 
> Yes it is. It is extremely important that gEDA remain the excellent tool
> for these jobs that it is.

Look at the Subject: field in the header of this thread as started by the original poster.  Does it not say "resistor values" ?

> > If the presence of a "value=" attribute is of no use to you, then *ignore
> > it*.  
> 
> If the absence of a value= attribute is a problem for you, attach one. Even
> if it's present, it's likely to be wrong, so you have about the same amount
> of work to do in any case. But getting rid of it is somewhat more work,
> especially in existing schematics that assume its absence.

The point here isn't to get *rid* of useless attributes - the point is to outright ignore them.  

If your setup is such that these "value=" attributes cause problems, I submit that the problem is not in the presence of these attributes, but in your workflow.  You've become accustomed to a certain pattern and have not planned far enough ahead to account for relatively minor changes.

> > The existence of something does not imply the requirement to use it.
> > 
> >> gschem/gnetlist are excellent tools for
> >> schematic capture for VLSI, symbolic analysis, and simulation.
> > 
> > And they will continue to be.
> 
> They won't if the attitude of "I don't care to know about any flow except
> pcb, and all I want is my version of the pcb flow" isn't vigorously opposed.

Nor will they be if you continue with your attitude of "I don't care about any workflow other than VLSI simulation".

The project needs to be able to cater to both as well as it can, even if that means the users need to make minor changes to the way they use it.

> > Maybe in your line of work that can be the case, but I submit that the
> > vast majority of users of these types of tools do not make the same
> > comparisons you do.
> 
> Ah yes, the tyranny of the majority. But I'm here because gEDA is far more
> flexible and productive than the competition. I guess all the other
> gnetlist back end writers contributed for the same reason.

You confuse a request for a feature (or in this case, a request for a modified default) with the desire to eliminate some feature you find critical.  One does not have to imply the other, and a good programmer is more than capable of accomplishing this with most any two such features.

"Tyranny of the majority" is a concept for the politics and philosophy classes, not for software projects.

> > You and I both know that "R1" is not meant to have the same meaning as
> > the "10k" written below it in a schematic, and that's what each of our
> > respective instructors taught.  
> 
> Ah, but in pure symbolic analysis there is no "10k". There are only
> equations like "r1*c1==4*r2*c2".

And your point is?  You're writing formulas with refdes's, not value= entries.

No matter how complicated your resistor formula are - sooner or later, those equations HAVE to boil down to some number of ohms or your circuit isn't going to do what it should.

> I started with vacuum tubes and point-to-point wiring. You can't go from
> there to VLSI without changing a lot of thinking.

Which means you should have the same understanding as I have of the fundamentals of circuit design (though I've gotten somewhat rusty at basic analog stuff).  I assume you do, otherwise this discussion would have no hope of a meaningful resolution.

> >> If you only use gschem/gnetlist to feed pcb, you will have a severely
> >> limited perception of their true capabilities, and the genius behind
> >> their design.
> > 
> > Perhaps you mean "you will have a somewhat narrow need for their true
> > capabilities".
> 
> No, the limited perception is a problem. You propose a change that will
> break a significant subset of my library of schematics because you don't
> see the breadth of gEDA's utility.

No, I mean precisely what I said above - I have a somewhat narrow need for gEDA's true capabilities.  No more, no less.  I don't design VLSI circuits, nor do I use it for plumbing work as I've seen mentioned here, and I don't use PCB for doing home layouts either.  I use gEDA for designing circuit boards.

> > The same could be said for a text editor, if all I ever do with one is
> > work on the HTML for my website rather than write the Great American
> > Novel.
> 
> A nice simple text editor is a good thing. Versatile. A WYSIWYG word
> processor is much less versatile.

How so?  Name me one thing a simple text editor can do that a properly-written WYSIWYG word processor supposedly cannot.

> Ah, the tyranny of the majority again.
> 
> >  All we are proposing here is adding some reasonable, sane defaults for
> > things like "value" - things you can ignore if they aren't useful to your
> > particular work.
> 
> If you add a value= attribute to resistor-1.sym it will break most of my
> symbolic analysis schematics because of the inheritance rules. The presence
> of specific values overrides the default of "use the refdes symbolically".

If you don't set up your work environment so that it can grow along with and adapt to changes in the tools that it uses, you are just begging for trouble.  If your rules get broken by simply adding an attribute that is normally absent, then you need to fix your setup to not depend on it, rather than trying to force the software to leave out the offending attribute.  Anything else is a kludge, and you should know that.

> Again, the right answer is not to change the default library, but to create
> libraries for specific purposes on gedasymbols.

Then I submit that VLSI-specific symbols should be created.  Let the existing symbol library remain generic as it is now, just build up the contents of the individual symbols a little bit - a description here, a datasheet reference there, a default value, even a default footprint where it makes sense.

-- 
"There are some things in life worth obsessing over.  Most
things aren't, and when you learn that, life improves."
http://starbase.globalpc.net/~ezekowitz
Vanessa Ezekowitz <vanessaezekowitz@xxxxxxxxx>


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