Re: gEDA-user: Busses in gschem

[Steve Meier <smeier@xxxxxxxxxxxxxxxxxxx>]

Philipp,

Standard gshem and gnetlist (gsch2pcb) treat buses as a graphical object
that doesn't influence the final netlist in anyway.

If your design is flat hook up a net segment from a components pin to
the bus. Select the net segment and add a net attribute net=D0 for
example. Some where else do the same from the bus to another components
pin and add a net attribute again net=D0. It is these net attributes
that are responsible for causing the two pins to be part of the same
net. You could even delete the bus and bus rippers and the netlist will
build the same way.

If your not interested in hierarchical schematics ignore the rest of
this email.

However, if you are trying to do something that is hierarchical and
re-uses hierarchical symbols (that have schematics within them) then
this isn't adaquete. And standard geda doesn't support it.

I have a non-standard derivative (fork) of geda that does the hierarchal
buses. My version of gschem is rather buggy and it mostly just allows a
pin to be selected and the pin type can then be changed from a net pin
to a bus pin. The files my version generates also consider busrippers to
be different then complex objects, thus replacing the "C" for complex
with an "S". This however doesn't always work and i have yet to spend
the effort to debug why connecting a net from the left of a bus to the
bus thinks a busripper is a complex and connecting it from the right of
the bus to the bus thinks that the bus ripper is a bussripper. 

The standard gschem could easily be used in conjunction with a text
editor to create hierarchical symbols and schematics. Use the text
editor to identify wich symbol pins are bus pins and use the text editor
to change the "C" of a busripper to an "S". Also check to see that your
busripper symbol is constructed from two pins one being a net pin the
other being a bus pin.

I am in the process of writting some documentation on using my new
netlister that processes my version of geda files. Uhm I also support a
few non-standard attributes, such as hierarchy-disabled, manufacturor,
manufacturor_partnumber, nobom and green. All except the
hierarchy-disabled are used for generating boms.

Steve Meier

On Thu, 2007-03-15 at 17:38 +0100, Philipp Klaus Krause wrote:
> I'm creating my first schematic using gschem (previously I schematics
> were in my head or on paper only and I only used pcb to create the pcb
> layout).
> I've drawn lots of nets when I noticed the button for busses. How do I
> use these (the documentation only states "Buses are very new and there
> are many aspects which are not defined yet, so keep that in mind as you
> uses buses. More to be added here eventually.")? How do I specify bus
> width? When I connect a pin to the bus using a net how do I specify to
> which of the bus lines it connects? Will busses work well with gsch2pcb?
> 
> Philipp
> 
> 
> _______________________________________________
> geda-user mailing list
> geda-user@xxxxxxxxxxxxxx
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