Re: gEDA-user: Library of gnucap and ngspice compatible models?

[al davis <ad252@xxxxxxxxxxxxxxxx>]

On Tuesday 15 September 2009, asomers@xxxxxxxxx wrote:
> I, and judging from the mailing lists and forums many others,
> are frustrated by the difficulty of finding spice models that
> are compatible with open-source circuit simulators. 

Yes.  It's a problem.  It's the kind of problem that will 
require constant attention to keep it up.

> Common 
> replies are "you don't need that level of detail" or "find a
> model library buried in the vendor's website, pick a model
> for a part similar to yours, then alter any lines containing
> X and replace .subckt Y with a reference to your Z".  But
> that's annoying, especially for users who are new to these
> simulators.

I confess ....

"Find a model ... alter any ...."    I admit telling people 
that.  I don't like it, but that's all we have.

"you don't need that level of detail" ...  When I said that, I 
can see that the asker is buried in complexity and needs to 
simplify.  It's a different problem.  There is a problem with 
teachers that show simulation as draw the picture, push a 
button, and scope-like picture magically comes out.  When I was 
teaching, I tried to do better, but it's a real battle.

> So my question is, should I make a new project which is a
> library of models to use with open source simulators?  I
> think that there is a need for such a thing, but would it be
> a good idea? 

I think the best approach is a wiki, a way to get tarballs from 
the wiki, a way to search, and simple way to access it inspired 
by the way Linux distros install from their repository.  The 
more I think about it, the more it looks like what Linux and 
BSD distros are doing with applications.

Make a plan for how it is organized, begin to populate it, and 
invite others to help.  There is lots of space on the Gnucap 
wiki.

It's not just Spice models.  There will never be a significant 
number of "Gnucap models".  Rather, Gnucap needs to read 
standard models, and models designed for other simulators and 
other uses.  Looking forward, Verilog-AMS, VHDL-AMS, and 
System-C are becoming more popular.  Looking back, there are 
lots of IBIS models.

There is also different meanings of "model".  To some, it is a 
spice ".model" statement or subcircuit.  To others, it is the C 
code with the actual model equations.  It's really models that 
depend on other models, which may or may not already be there.

> Licensing should not be a problem; most vendors 
> license their models to permit redistribution. 

Licensing really is a problem.  It goes the whole range from 
freely redistributable to available only after signing a 
nondisclosure agreement.  If you look at any of the Linux 
distros, you will see ways of dealing with it.

> Would it be 
> better to incorporate these into some existing project than
> to start a new one?

I think you need to start a new one.  I have space for you at 
gnucap.org.



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