@NeilFerreri1 @LarryM Thank you again…
When I updated to the latest GRBL (1.1f), I used the Arduino IDE, but I’ve used the HexUploader before, too; I don’t fully understand how one might be preferred over the other.
What I’d really like is to have spindle speed controllable both by the hardwired potentiometer, as well as controlled by g-code. If this seems too difficult, I would prefer hard-wired control. And to resurface my original concern, right now spindle on/off is non-functional, it’s always on when plugged in, and speed is controllable only by the potentiometer. I made my machine in 2014, so all of the original Shapeoko2 hardware instructions are in place, which is why my spindle is on D12.