Re: gEDA-user: autorouter enhancements: net characteristics

[Harry Eaton <bumpelo@xxxxxxxxx>]

>  Stefan Salewski <mail@xxxxxxxxxxxx> wrote:
>
> I wonder if the PCB autorouter should be more closely bound to the
> gschem schematics. For example, in the schematics we may specify
> priority of nets (fast signals, power, ...), trace width or clearance
> for net segments. Maybe by attributes? I have no idea how commercial EDA
> software handles this.

This is the point of  "(6) use routing styles in the netlist to have
per-net routing styles."
It doesn't provide "priority" (whatever that is), but it allows you to
specify a routing style for each net which includes trace width,
clearance, and via parameters. This is a feature that pcb's
netlist-file format (and auto-router) has supported for many years
now.

It makes sense for the gschem netlist generator to support it; I'm
supposing from your comment that it doesn't already. That is not the
fault of the autorouter, it came first.

One major drawback at the moment is that all of the net is expected to
have the same characteristics, so if for example you make a "power"
net style that is 20 mils wide with 15 mil clearance, it won't be able
to connect to a fine-pitch part because the constraints can't be met
due to the part characteristics, but it will route what it can. If you
manually create "breakouts" that the autorouter can connect to without
violating constraints, it can then make the connections. Be sure that
any such breakouts have either vertically or horizontally oriented
lines or a via where you want the connection made because the
autorouter will not connect to any diagonal copper.


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