Here is the Arduino Due ino file. I tend to do overkill with the comments as I usually work on lots of projects and need the notes to jog my memory when I come back to them…I use a wide monitor and the comments tend to fill the screen 
I hope this helps you get talking with Mach3…I also included the brain files and a macro file for my pendant, the brain files need to be edited/viewed through Mach3.
I haven’t looked at the code in quite a while, but I can probably answer questions.
Pendant-Testing.ino (54.5 KB)
PendantButtons1.brn (9.2 KB)
PendantButtons3.brn (6.0 KB)
PendantButtons2.brn (9.2 KB)
M1000.m1s (1.9 KB)