Is there any way to access the OC outputs from PoBlocks while running with the Mach4 plugin? I'm trying to simulate a sequence of button presses to control my spindle on a SX2.7 mill.

The control board from the mill does something funny in the button circuit - simply connecting the button leads to 5V/GND doesn't work, but shorting them with a diode does, so the optocouplers should be able to switch them. There's some kind of digital signal going across the buttons.

I've worked out how to use PoBlocks to generate the needed pulses ("press" 1 button 100ms, next button 100ms), but need to use the optocoupled outputs to make it work.

I'd really rather not have to get out the oscilloscope and logic analyzer 

Reverse engineered button/lcd board: