rr_pilot wrote:The eagle autorouter really isn't all that bad, you just need to know how to use it. First thing I do is start by giving the router as many choices as possible.
1) Change the routing direction to '*'
2) Change the routing grid to something appropriete, I have found after many trial and error a routing grid of 0.1 mm with traces from 8mil - 12mil.
For some reason eagles router seems to be alot slower then other routers i've used but with 0.1 mm grid then its not to big of a deal anyways.
I've played around alot with changing the settings in the optimization passes with little change in the overall result. The most effective way of reducing vias in eagle is selecting a appropriete routing grid and the placement of your parts.
Yeah, I really agree with just about everything you said. The autorouter has a lot to think about as it lays traces, rips them up and looks for a better route (although some don't belive that it does this
I noticed the really slow routing on a 0.1mm grid and I do agree that grid has a LOT to do with the effitiancy of the autorouter. I typically route on a 10 mil grid for most projects. Funny thing is, I do all of my measuring and placing in mm, but I always switch over to mils and set the grid to 10. This seems to help.
As for placement of components, you hit the nail on the head. Paying attention to where you place a resistor that is tied to an IC or whatever makes all of the difference in the world. If a cap is tied to two legs of an ST202 and I place them each at opposite ends of the board, you can bet your *** you'll end up with a bunch of vias when the autorouter tries to get from point A to point B. Strategic placing will reduce this sort of thing immensely. I have seen cases where someone had a project with 20 or so caps and resistors and they wanted the board to look nice, so they just lined them all up and pretty. Sure, that looks nice, but now the traces to get from these to all points of the board is now bloated out of whack and you end up with tons of vias, a crowded mess of traces and more than likely noise or other issues introduced into the design.
Play with the autorouter and you'll find you can do many things to make it work better for you.