At 04:05 PM 3/28/01 -0500, Bryan Bernesi wrote:

>When I run the autorouter it stops after initializing.
>Is there a way to systematically troubleshoot and find out the reason why 
>the autorouter stops without resorting to maybe this or guess that, trial 
>and error methods?

Mr. Bernisi has already done the most obvious things. I don't use the 
autorouter very much, so I think there will be other users with comments 
and suggestions that are, perhaps, more helpful, but I think this is a good 
prospect for sending the file to Protel if it does not immediately become 
clear that there is some known issue here. What I write below is for the 
desperate or exceedingly curious.

For systematic troubleshooting, there is a generic process I call chunking. 
Take the design and divide it into two parts, each approximately half of 
the design. You can do this on the PCB, since nets are carried by the pads. 
Delete the parts in one half (obviously you are doing this with a copy of 
your design so you can completely screw it up without losing anything). If 
the autorouter now runs, the problem is probably in the half you deleted. 
By extending and following this process recursively, you may be able to 
find, in a few operations, exactly what part or primitive is causing 

Obviously, if you change something and it now routes, what you changed 
almost certainly contains the problem.

Note that if the offending primitive is in a footprint that is used on both 
halves, deleting one-half will not delete it. So one might generically 
delete a whole class of primitives. But leave at least two simple parts, 
like a two bypass capacitors, which might be ideal if they both have the 
same net assignments.

If you end up with two single simple parts, and it still does not route you 
know the problem is not with any of your components. I suppose you could 
try placing something from a regular Protel library.

It might also be a good idea to draw a keepout around the whole board. Yes, 
I know he said that he had created the board with the wizard, but if 
somehow the keepout was not complete, that too might confuse the autorouter.

If the board has a simple rectangle keepout outline that has no openings in 
it, each line terminating at the beginning of the next line, and there are 
only two simple parts with appropriate nets that should route to each 
other, you've checked the net assignments, etc., and it still does not 
route, you probably have a garbaged installation; reinstallation might be 
in order.

But before he goes to all this trouble:

>- I have a single schematic project.
>- I have run ERC, no errors
>- I made my PCB template using the board wizard
>- I have placed all components
>- I have run the DRC, no errors
>- All my layers are set up

There are plenty of little nooks and crannies in this where there might be 
a problem. For example, one might have disabled clearance or other 
important DRC checks, either in the rule dialogs or in the DRC run dialog. 
The layer setups might be unusual in some way. Most of these things will be 
detected most efficiently if the board is sent to Protel or one of us. (I'm 
willing to receive such boards, generally, don't *ever* send one to this 
list, Of course, I will not disclose the design contents to anyone without 
the permission of the sender.)

Abdulrahman Lomax
P.O. Box 690
El Verano, CA 95433

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