M66 alternative

Hello...

I try to make scanning laser project.
I add rotating axis (A) with laser attached to arm.

For modulating laser I use streamer component with two bitstream. One is lased enable and other is position index. Now when laser rotates I wait in Gcode with M66 to get falling edge of index to advance Y axis for new arc scan. The trouble is that M66 seems to be userspace component and sometime miss the index. Is there maybe some other alternative to M66?