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I'm struggling to get the Eagle Autorouter (Eagle 7.6) to route only the VCC (layer 2) and GND (layer 15) layer on a 4 layer board. I have created a net class for VCC and GND. Now I would like to have a separate "routing pass" for GND and for VCC.

What I want it to do is just add vias on all GND and VCC pads to the respective layer and don't create traces where possible (only for through hole components f.e.). E.g. use the shortest path to the respective layer instead of drawing and connecting traces to the PSU.

I tried setting the cost of all layer but the GND or VCC layer to 99 and the cost of vias to 0 but I always end up with all signals routed, not just the GND signals.

How do I accomplish this?

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  • \$\begingroup\$ RTFM. In this case, do "HELP AUTO". That really should have been obvious. \$\endgroup\$ – Olin Lathrop Aug 24 '16 at 18:35
  • \$\begingroup\$ @OlinLathrop The problem is, I think a sizable proportion of Eagle users don't even know the command line interface exists. \$\endgroup\$ – tcrosley Aug 24 '16 at 19:55
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    \$\begingroup\$ @OlinLathrop Well a lot of googling and looking into the autorouter help articles I found did not say anything about different settings that you can use in the cli version of the autorouter compared to the GUI version or that the command even exists. So no, it was not obvious to me otherwise I wouldn't have asked the question. I'm not a seasoned user of the program and have used the cli to only a small extent so far. \$\endgroup\$ – PTS Aug 24 '16 at 22:15
  • \$\begingroup\$ The auto command also does not solve my issue with the documentation provided by eagle. \$\endgroup\$ – PTS Aug 25 '16 at 14:38
  • \$\begingroup\$ @tcrosley: Then they shouldn't be there. Pearls before swine. The real power of Eagle is in the commands. The GUI is just a wrapper that can be convenient sometimes. It is inexcusable for any Eagle user to at least not be aware of this. \$\endgroup\$ – Olin Lathrop Aug 25 '16 at 15:38
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If you use the command version of the auto router feature, you can specify a signal or signals to be routed, like this:

AUTO ! GND VCC;

More info on this page.

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  • \$\begingroup\$ Thanks that is definitely helpful. How can I specify some rules though? The Eagle help doesn't specify much about what arguments the command can take other than signal names. This works for routing a single net but it trys to avoid vias at all costs and routes on all available layers. Is there a more complete reference to this command other than the Eagle Quick Help? \$\endgroup\$ – PTS Aug 24 '16 at 22:28
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Use the "Fanout" tool instead of the autorouter. With the "Fanout" tool selected, select the "Fanout Signal" button in the top toolbar. Now click on a GND or VCC pad and all of the pads of that net should via to the appropriate plane.

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