Re: gEDA-user: gEDA, where are the loadable examples?

[sdb@xxxxxxxxxx (Stuart Brorson)]

Hi Guys --

Welcome to gEDA!

> >> Also, in grepping for the chip building blocks I'd need, none of
> >> the 3 main chips '82c55', 'L298' or 'L297' I need seem to be
> >> present.
> >
> >That's simply because none of the existing gEDA users have had a
> > need for these symbols.  What I do in this case if find a symbol
> > that is close to the one I need and modify it.
> 
> Possible, but the 8255 family is almost a cpu in it own right, so I 
> doubt there is anything useable other than its 40 pin 600 mill dip 
> packageing.  And 24 of those 40 pins can input, or output, depending 
> on how its mode register is programmed.  One would have to write 16 
> variations of it and use the one corresponding to the mode byte.  
> That, as they say, makes the cheese a bit more binding.

First, I think you need to distinguish between the device's symbol
and its footprint.  The symbol is the graphic object you place on the
schematic using gschem.  The footprint is the graphic object you place
on the PC board using PCB.

There are plenty of parts with no symbols in gEDA.  This is because
everybody just makes their own symbol for their specific job, and
nobody shares the symbols after that.  It's just human nature --
sharing software is fun, sharing symbols isn't. . . .  go figure.
Anyway, you will probably need to make your own symbol.  

As for the footprint, you will need to run PCB to see if it exists.
If it's a standard symbol, it may exist.  If it's not, then you'll
need to make it.  There is a link to a doc talking about building PCB
symbols on this webpage: 

http://www.brorson.com/gEDA/ 

Also, John Luciani has build a large number of PCB footprints; he put
them on the web for free download here:

http://www.luciani.org/geda/pcb-footprint-list.html

> How is ngspice at simulating analogue circuitry thats supposed to be 
> running in pwm mode?

Probably slow -- it doesn't have the concept of event-driven
simulation, which is very useful for simulating pwm-mode circuits.
Try GnuCap instead.  Or download LTSpice from the Linear Tech website.
It is Windows native (yuck!), but you can also run it under wine. 

Stuart