6 Jul
2011
6 Jul
'11
9:45 p.m.
Date: Wed, 6 Jul 2011 23:39:14 -0400
From: mcguire at neurotica.com
To:
Subject: Re: free-open source PCB autorouter software development
On 7/6/11 7:03 PM, Andrew Lynch wrote:
With comments to the translation issue, and autorouters:
Cooper and Chyan succeeded with their generic autorouter SPECCTRA by getting the major PCB
EDA companies to adopt and contribute to their translation interface; a key part is the
.DSN and .SES in and out formats. A layout package can only export a DSN, pre-route, and
can only import a SES, post-route.
With this limitation, it was adopted by all EDA companies. Otherwise, SPECCTRA could have
become the pirenial hub-spoke system of EDA translation, and make all systems
interoperable with a neutral database. Once you exported a DSN, why not allow a layout
system to read it back in? Export from ORCAD a DSN, and import it into PADS / Expedition
or your flavor of the month.
You've missed the point entirely. Yes, gEDA
includes a PCB layout
tool (PCB) which includes an autorouter. However, they are closely
coupled and if you want to use the PCB autorouter you must start with
gEDA EDA tool set and stay with it.
This is not correct! While there is a well-developed integrative
path between PCB and the gEDA suite, it is NOT necessary to do all of
your schematics in gEDA in order to use PCB, nor is it necessary to use
PCB for your board layouts if you use gEDA for schematics/BOM/etc.
The program "PCB" is only very loosely associated with gEDA.
Different authors/maintainers, different lineage, different original
platforms (PCB started out as a program for the Atari ST many moons ago,
if memory serves) etc etc.
There is no import/export
capability so if you use KiCAD, FreePCB, EAGLE,
etc then you are out
of luck. This is the "lock in" which plagues the whole EDA
technology because there are few if any interchange standards. There
is no way to import/export PCBs in/out of gEDA AFAIK, at least from
KiCAD. I can't tell if gEDA supports Specctra import/export
necessary to use FreeRouting.net but doesn't appear so.
There's very little import/export functionality in stuff like this
because there are no standard formats. gEDA's file format is purely
text-based and was designed to be easily parsable, so if one can
decipher the desired target format it should be possible to write an
exporter.
-Dave
--
Dave McGuire
Port Charlotte, FL From an autorouting perspective, the translation
problem is greatly simplified as it only knows copper shapes and layers, along with net
names; it has no knowledge of the PCB database and related part and non electrical
information.
Cooper and Chyan are probably now bartenders in the Bahamas, they sold SPECCTRA to Cadence
years ago. There are a few of us who truly know how to drive it - realizing that first of
all it is not an autorouter, but a statistical constraint solver. it creates copper
spaghetti at first, then resolves the constraints (a .DO file) with successive passes,
increasing a 'tax' (don't do this) table to find a solution. I have done a
hundred or more boards with this system with signals at GHz rates, diff pairs, crosstalk
control, and they all worked straight out of the box.
Do not discount the SPECCTRA autorouter, and the funny 90 degree bends and pad escapes,
the boards work just fine.