Finally, the next installment in my dual-controller saga...
I've been manually connecting/disconnecting power, steppers, and USB for awhile, but since we're out of the deep freeze now I can actually get back to work in the shop. I've since added a USB hub so both boards are connected in with a single cable to my laptop. In addition I finally have completed the "switching" control PCB:
This control will switch the (4) stepper connections and the 24V power switching to the GRBL or ESTL controllers (which get "series'd" thru my E-Stop switch). There's also a 12V linear regulator to power up the wireless AC remote controls that run my dust collection vac and router. I'll snap some additional pics when this is populated up with the components and connectors.
The PCB was designed using Eagle (using just a board design, no schematic) . The CAM was generated using the PCB-GCODE ULP and was cut with 0.03125" and 0.0625" end mills. The drill file was a 2-tool job, and the secret I found was to set both Z heights to 1.5" above the work surface so Carbide Motion would pause retracted high enough to swap bits (the CAM didn't seem to pay attention to the tool-change height). I gauged the first tool against the work surface with a fixed tool protrusion length, and when tool #2 went in, I set it at the same exposed length as tool #1. With slight overdrill depths, this method worked well with Carbide Motion employing multiple tool changes in a single job.