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Re: gEDA-user: Google Summer of Code on gEDA Webpages

On Mar 11, 2007, at 3:02 AM, Werner Hoch wrote:

Hi Ben,

On Saturday 10 March 2007 22:47, Ben Jackson wrote:
On Sat, Mar 10, 2007 at 09:53:07AM +0100, Werner Hoch wrote: 
I'm currently drafting a better spice integration into gschem.
Maybe that could be a project, too.


Anyone who is thinking of improving a spice GUI has got to try
Linear Technology's free SwitcherCAD (aka ltspice).  It's the nicest
spice I've ever used.  It's a better schematic entry program than
most, too (and that would include Eagle and gschem).


I've played with LTSpice an hour.

Things I like:
 * the current and voltage probing (visible marks are missing)
 * all entries (simulations and voltage sources) are done with dialog
   widgets and also printed in plain text.
 * changing the model of a diode or transistor
 * the property dialog for each circuit element (right mousebutton)

Things I don't like:
* schematic entry (selecting, moving, ...)
* only one simulation at a time.
This is o.k. for tinkering, but not for real work. I hate it when
using PSpice (schematics) at work. You can't split your workflow into
entry, simulation and postprocessing with it. 

I use LTSpice fairly regularly.

I like the same things Werner likes. I also like the ease of creating new library components. I like how it's easy to specify parasitics for passives (such as ESR for caps, etc).

I am annoyed by the schematic capture. Zoom in and out are not on any reasonable key (how about pgup and pgdwn or + and -?) and its panning algorithm never seems to work right (try placing a symbol off the edge of the screen and it doesn't pan as it should).

I like how the schematics are ASCII, which makes them SCC friendly.

I hate how the libraries must be in the same set location. I haven't figured out a good way of keeping my libraries separate from the LTC libraries, so updates don't fsck up my libraries when I run the program updater.

You can set up the usual Monte Carlo runs, etc etc, and you can run it in batch mode if you like.

Like most people who use some sort of Spice program, I keep the simulation schematic separate from what will be used for layout, for all of the usual reasons: some components on the layout schematic can't be simulated, and some things needed for simulation shouldn't be on the layout schematic.

I don't think LTSpice is an example of "vendor lock-in," except for the obvious, which is that LTC makes their switcher part library models available only with LTSpice. You can't use the models with another simulator, and they won't open up that simulation engine for use with other vendors' devices. LTSpice began as a means to an end -- to get people to buy LT's parts (which are pretty good). The fact that it's a full-featured Spice comparable to the non-free (as in beer) programs is a nifty bonus. And it doesn't suck, unlike National Semiconductor's Web Bench and TI's castrated TINA.

-a


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