Ok, I’ve got a 2.4d board, which is the same as 2.4e. Lacking a picture, I pulled out my board and chased through it.
Interesting trivia, but unrelated:
- A3, which is coolant enable, has a via labeled “A3” over by the cpu (the atmega328 QFP toward the bottom of the board). I don’t know anyone doing gcode controlled coolant, so that’s interesting to be pulled out like that.
- The PWM output is nicely labeled on 2.4d/e. There are 4 pins above the spindle connector, labeled PWM, 5V, GND, and D13. D13 is spindle direction on GRBL 1.1
I have no idea where the spindle “reset” pin goes. So that’s out.
The CPU is arranged on the board like this:
Pin1 is in the bottom right (there’s a dot in the plastic package)
“A0” is the abort/reset pin for GRBL. It’s pin 23. This is where the old e-stop went. It relies on software to abort, which isn’t really that great an idea. If the software is wedged and still outputting steps, this won’t help.
“Reset” which is probably about as good, is pin 29, and on the header above the cpu. At least that’s guaranteed to stop motion.
Honestly, a better thing to do would be to wire the emergency stop to the power for the router and machine (this may be why they dropped the pins.) .
Why stick with the SO3 when CNC router parts has an alternative? Their electronics are a $1500 add on to their machines, they’re not included. If you’d rather do that (which is also Mach3/4 w/ smoothstepper) then I won’t convince you otherwise. If you’re otherwise happy with your mechanicals, and it’s really the emergency stop that’s got you upset, there are a lot cheaper ways to get an emergency stop. If it’s actually about something else, not sure why you bothered to ask about it.
A box like this can get you an e-stop power cut for cheap ($20):