This laser cutter/engraver from Io Engineering is running a customized version of grblHAL to support PPI (pulses per inch) laser power control. It uses a custom CPLD based PPI controller. PPI allows very fine details to be cut, even in paper! PPI is superior to feed rate based power control because laser power response to PWM is non-linear.
Mechanical: Belt driven.
Motors/Drivers: NEMA 17 Steppers and DM420A drivers.
Control: Customized driver for grblHAL running on a TI TM4C123 based controller board. Galvanically isolated USB interface. Image engraving control is with a second controller supporting up to 127 gray levels with a simple encoding (not GCode based).
Laser: 40W CO2.
Laser Control: Custom CPLD based PPI Controller.