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Questions relating to designing PCBs
By smbaker
#174937
First of all, I understand that real engineers manually route. I'm not trying to start a debate between using the autorouter and manually routing.

What I am trying to do is to figure out if there is a way around this 'polygons have fallen apart' issue. I design two layer boards. I usually try to put a ground polygon on the bottom layer. It autoroutes successfully, and then as soon as the route is accepted, it decides the polygons have fallen apart. Usually it's just one or two little islands of ground plane that it can't connect. Eagle 5.x I could tell it to autoroute again, and usually the silly program would realize that it does in fact know how to connect those polygons. Since upgrading to Eagle 7.x, that doesn't seem to work for me.

Does anyone know a way to minimize this polygon problem? Sometimes moving a few components around will fix it. Other times, moving a few components will make the problem unexpectedly worse. (unpredictability is the nature of the autorouting algorithm, I get that)

Eagle 7.x is nice in that it will generate 16 routes for me to pick from, but unfortunately I won't know if the polygons have fallen apart until I select one of them.

I've just about given up on using a ground polygon in favor of using a big fat ground trace instead.
User avatar
By Ross Robotics
#174938
Don't lay your ground polygons until you are done routing. Then you will have to use vias to connect your islands.
By smbaker
#174969
Nice. That worked.

I wonder if it would be possible to create a ULP that says:
1) Delete the ground polygon if it exists
2) Autoroute the board
3) Create a ground polygon to the dimension of the board
4) Autoroute the board again.
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By Ross Robotics
#174973
Why would you want to route twice? That doesn't make sense.
By smbaker
#174975
When I draw the polygon after routing the first time, it's just an outline. Once I run it through the second autoroute, it creates the polygon pieces, and connects them to the ground traces.

Is there some other operation (aside from autoroute) that causes a freshly drawn polygon outline to be realized?
User avatar
By Ross Robotics
#174977
Hit this button and see what happens..
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