Re: gEDA-user: How to deal with single/dual parts?

[Andrzej <ndrwrdck@xxxxxxxxxxxxxx>]

On Thu, Nov 19, 2009 at 6:21 AM, Peter Clifton <pcjc2@xxxxxxxxx> wrote:
>
> See this old diagram Peter B and I drew:
>
> http://geda.seul.org/wiki/geda:data_structure_design_discussion?s=data%
> 20structure

That looks perfect to me. In fact it is almost identical to what I use
in pschem. Is there any particular reason for not including this model
in gEDA?

> The core of the diagram (blue and yellow) would apply as a hierarchical
> design / netlist representation _without_ the need for any schematic.
> That was its real purpose - defining the logic required in a
> hierarchical netlist representation.

The good thing about it is that all the tools automatically share the
same logic. Whether you start gschem or gnetlist they
would see the same design.

This also reduces problems with design integrity. Gschem, for example,
doesn't see external design changes until the user forces the
schematic reload (not sure if that has changed in newer versions). The
model you've drawn is essentially an implementation of a MVC pattern,
where schematic editor manipulates the database and the database
automatically updates its views (schematics). That's nothing new
really, all larger EDA tools are built on top of such design databases
(although they often obfuscate their internals).

One problem I see in gEDA, which could make implementation of this
scheme difficult, is that libgeda is rather inflexible. Its
implementation has to be written in C, with all the usual ABI
restrictions. This tends to limit flexibility of the whole tool by
moving too much of the implementation into the compiled part (gnetlist
is a good example). That BTW is the main reason I've chosen to
implement pschem in Python only (could have been Scheme if its
implementations were more robust).

> I can imagine a netlist of a "simulink" type digram being used to define
> a system for simulation - where "nets" represent abstract signals,
> rather than electrical connectivity.

The main reason for using a specialized tool for circuit design (as
opposed to a general purpose vector graphics editor) is that the
specialized tool understands the semantics of the circuit. Can
schematics editor be used for drawing simulink/UML/petri net/...
diagrams? Sure. But it will not be much better in this than e.g.
PowerPoint and probably worse than Visio.

Andrzej


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