Re: gEDA-dev: pcb FAQ: how many layers?

[DJ Delorie <dj-at-NOSPAMdelorie_dot_com>]

> * pcb is limited to exactly 8 copper layers and 2 silkscreen layers ?

False.  The current *default* is to allow up to 16 copper layers,
defaulting to 8, but you can recompile with pretty much any number of
layers you need.

If this question keeps coming up, I'm changing the default to 9 ;-)

As for silkscreen, we have two "known" silkscreen layers, but you can
use other layers for silkscreen if you want.  One of the to-do
projects is to formalize this by assigning types to layers.

> * pcb has no way to make a "mechanical layer" to show the physical
> outline of the board and its dimensions ?

Name the layer "outline" and PCB treats it like a board outline.

> * pcb has no "solder mask" or "paste mask" layer?

PCB doesn't have a *separate* mask/paste layer, but it does produce
mask/paste gerbers.  You can edit the mask opening size on a per-pad
or per-pin basis.

> Is there a "pcb FAQ" somewhere that would answer that sort of
> question?

Not really, other than the gEDA wiki.

> * update the FAQ so it clears up any FUD. Then I can email the URL
> to people who don't know the answers to these questions (or, worse,
> have old, obsolete, no-longer-correct "answers" to these
> questions). So I can say "gEDA actually can handle all these
> things. The FAQ explains how."

That would be good.

> * Any remaining things that gEDA can't currently handle, that are
> preventing people from switching to gEDA, should be added to the
> buglist.

PCB has a "todo" list in the source tree (src/todo) that lists
features we haven't added yet, but want to.  PCB also has a bug
tracker and feature tracker on sourceforge.

> My impression of gEDA was that it wasn't for high tempo professional
> work.

I think we agree that gEDA is a middle-of-the-road toolset.  It's
certainly more than an "intro" or "beginner" level (although it
obviously *can* do beginner projects), but we admit that there's a lot
of "high-end" features that the tools are missing.

But that doesn't stop people from using it for high-end professional
work.  I've seen some boards made with gEDA (sorry, can't publish
them) that are *amazingly* complex.

> Everything is done from mostly command line stand-alone programs -
> like a lot of Unix software.

True.  Some of us were working on integrating everything at one point,
but that work hasn't made it back into the main repositories.

> The PCB program is 8 copper layers, not total layers.

The PCB program *defaults* to two silkscreen layers, one rat (netlist)
layer, two mask layers (not directly editable), and 8 "other"
(i.e. copper) layers (13 total).  You can use the "other" layers for
pretty much anything you want (they just produce gerbers, after all).
Any layer named "outline" becomes a mechanical layer.  Also, you can
add up to 8 more layers (or remove unwanted layers) via the layers
menu, bringing the (default build) total to 21 layers.  A simple
rebuild gets you as many layers as you want, assuming the GUI can
squeeze them all on the screen.  I've tested it with 53 layers, which
worked, but was a bit messy GUI-wise.

> As I recall, there aren't any mechanical layers upon which to do any
> of the dimensioning or commenting you might want.

We support one called "outline" that's used for fab and assembly
drawings.

> Obviously, you can't crossprobe, or do anything that depends on
> functional integration.

True.  Dan was working on some of that, and we also have the
beginnings of DBUS cross-connectivity.

> Nothing you have done under Protel is usable in gEDA - it speaks a
> language all its own.

This is true of many proprietary products.  It's called "vendor
lock-in" ;-)

gEDA at least publishes all its file formats, and supports exporting
(we can export netlists to many proprietary packages, for example).
The trick is to find (1) published specs for proprietary file formats,
and (2) someone willing to write (or pay for) the converters.

With proprietary programs, adding such converters is either (1)
impossible, or (2) at the whim of the owner.

> Likewise, nothing you do in gEDA is portable to any commercial EDA
> package (as far as I know).

Ah, but if a package published an import format, we *can* add
converters.  gEDA's file formats are all DOCUMENTED ascii files, so
it's not gEDA that's stopping you.

> Maintainability is at the mercy of the gEDA developers.

You're thinking of this backwards.  With a proprietary package,
maintainabililty is at the mercy of the owners because you CANNOT
change or fix it at all.  With gEDA, you get all the vendor support
you get from a proprietary program AND you can do it yourself or hire
a contractor to do it for you.

> It's up to you to compile the code if you're not running a Fedora or
> Redhat version for which it has already been compiled.

There are pre-compiled packages for Debian though, and I've seen Dan
produce a Windows installer packge.  We don't have a paid staff, so we
focus on making sure that it *can* "just compile" on most platforms.

> http://www.linuxjournal.com/article/8438 and

This was written by one of the primary gEDA developers.

> http://linuxfocus.org/English/December2004/article355.shtml

This reviews the now-obsolete Xaw version of PCB.  We've made a lot of
progress since then.


_______________________________________________
geda-dev mailing list
geda-dev@moria.seul.org
http://www.seul.org/cgi-bin/mailman/listinfo/geda-dev