Re: gEDA-user: Driving the netlist from PCB (instead of gschem)

[Rick Collins <erudite999@xxxxxxxxx>]

At 10:36 AM 9/28/2008, you wrote:
> On Sun, 2008-09-28 at 09:46
> -0400, Rick Collins wrote:
>
> > Personally, I favor the idea of a unified data base for both layout
> > and schematic.  So far no one seems to agree with this
> idea.  I 
> > recently found out that IPC has a standard file format for layout
> > information.
>
> IPC-2581?

I believe that is the one.  But when I did some searching, what I
found was confusing and seemed rather splintered, with multiple aborted
efforts.  There is also something related that is XML based.  I
got the impression that the standard was pulled and is being updated to
use an XML format.  


> It would be
> intersting to know how many manufacturers / CAD / CAM
> vendors actually support that format.

My understanding is *none*.


> Lack of existing
> support is no reason to be behind the times, but it
> would be good to know if this is actually going to get used in the
> industry or not. I've not heard of many board houses wanting ODB-X
> instead of Gerber (for example), and ODB-X was a predecessor of this
> standard.
>
> If we're at a juncture in the future where we're considering
> designing
> or adopting a new file-format, adopting something like this natively
> would be a possibility - IFF it could serve all our requirements, and
> /
> or be extended sufficiently. (XML formats have an advantage
> here).

That is actually what I am thinking, an internal native format. 
Yes, the little info I could find on this seems to show a very flexible
format that does not actually specify the lowest level detail, leaving
that up to the vendor, but again, I am not clear on it all. 

I found this out when discussing the possibility of both schematic and
layout sharing a single, common format to facilitate forward/backward
data transfer.  I'm not sure if this standard would help with that
or not.   But it does clearly include all aspects of
manufacturing data.  That alone is a big benefit.  


> If it is just about
> making this an optional export format, there is
> probably no point coding anything until someone needs it, or has a
> desperate desire to code that support.

True.  The part I don't get is that this was not some standards body
trying to force something down vendor's throats.  The vendors are
the ones on the panel creating the standard!  


> If this format is
> suffieicently good at describing layouts without
> loosing information, it may be that it meets resistance from
> vendors.
> They don't seem to _want_ text-based output to contain enough
> information to migrate between CAD vendors. Funny
> that.

Yeah, I have heard that.  But customers have a way of pushing
vendors to do some things that they may not want to.  It just
depends on who is willing to push harder and who presents the more
unified front.  Right now I get the impression that most layout
designers would rather "fight than switch".  But if the
fabrication industry insists on using a format like this for CAD output,
then anyone can write an import utility for their CAD system.  In
the end there is not much point in maintaining a proprietary
format.  

Maybe the vendors want to emasculate the standard to prevent using it as
a design exchange format. 


> I heard this is why
> ODB-X wasn't well adopted, possibly from someone on
> this list.

I've heard that too.  Bruce Parham posting at FreePCB.com seems well
informed on this.  I think he is the one who told me. 

Rick



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