Mail Archives: geda-user/2015/06/29/13:52:07
On Mon, 2015-06-29 at 10:54 -0600, John Doty wrote:
> On Jun 29, 2015, at 9:44 AM, Stefan Salewski <mail AT ssalewski DOT de> wrote:
>
> > On Mon, 2015-06-29 at 10:47 -0400, Jason White
> > (whitewaterssoftwareinfo AT gmail DOT com) wrote:
> >> Stefan, I think the easiest solution to net grouping attributes such as
> >> "Power", "Analog", or "Digital" is to allow for each net to be displayed
> >> with a different color.
>
> The file format already supports line colors and styles. I have always
> thought it would make more sense to represent nets and busses with
> lines that have attached attributes than to have primitives for these.
> What we have now is a factoring error. Not too serious, but a barrier
> to the future.
>
gschem file format supports line colors and styles. But for nets only
color index is available currently:
N 53500 61600 53000 61600 4
And my fear is that many colors and styles for nets are really confusing
when displayed all the time. It may be OK when we generally use plain
color/style for all nets, but when we query "show high current +5V nets"
then these are shown in a special color and style. But I am not sure, we
have to test that in real live, and that is some works...
> >
> > Yes, that is generally the first idea. Problem is, that we may not have
> > enough different high contrast colors. We may have analog and digital
> > ground, analog and digital power and ground, high speed signals,
> > impedance controlled traces, short traces i.e. for bypass capacitors and
> > much more. We discussed about all that about 4 years ago, when I started
> > work on my Peted editor. I think one idea was to not add direct
> > properties to nets, but net classes like "HighSpeed" which may be mapped
> > to 50 Ohm with 2 inch maximum length.
>
> It would be another factoring error to build in too much meaning to
> attributes at the schematic editor level. A lot depends on downstream
> flow. Geda-gaf supports many downstream tools. Simulation needs
> different network attributes than layout does. In geda-gaf, the
> netlister carries the responsibility for assigning semantics to the
> primitives. Making the editor aware of semantics detracts from its
> flexibility.
>
That is generally true, you told us that some years ago, and it is a
fine excuse to let gschem as it is. Unfortunately, some years ago
sch2pcb was really stupid. It transfered footprints from schematics to
PCB board, all stacked on top of each other, and gave us only net
connect information. That is really a mess for larger boards. We loose
too much information: Which bypass capacitor is for which OpAmp? Which
trace is for high current. The layouter guy has to manually recover this
information. One simple improvement is grouping elements -- for example
all components close to an OpAmp on schematics should be placed as a
group on PCB too. And there should be an option in PCB program to
highlight all elements of this group, so that we can check if they are
placed well.
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