Protoneer cnc shield with laser

Im going crazy trying to figure out how to turn a laser on and off with a protoneer cnc shield, using grbl and gcode. My homebuilt laser engraver is working great except I cant turn laser on and off between burning each letter. I would have thought I could use the spindle enable pinout, tried m3 m4 m45 with no change to voltage on spindle enable pin.

I cant figure how you thought anyone on the Forum could help you based on such a small amount of information.

...R

I am using arduino uno with a protoneer cnc shield v3.0. running grbl 9

waynek:
I am using arduino uno with a protoneer cnc shield v3.0. running grbl 9

I sorta figured that.

The problem is that you are assuming someone here is familiar with all the details that that implies.

I wonder if someone on one of the many CNC Forums would be better able to help you.

...R

Please at least post the shield you're using- a link to the product page at least.