@mrsolis93
This is what I use. This is slightly different to the above code the max output is set to 1.00 as lightburn outputs from 0-1 when smoothie hardware is selected.
What laser are you using?
I had to invert and convert the ppm signal from 3.3 to 5v for my diode laser.
G00 G17 G21 G54
G90
M307 H3 A-1 C-1 D-1 ; Disable Heater output on H3
M452 P3 S1 R1.00 F2000 ; Enable Laser mode, on output 3 (heater 3), with max intensity being 1.00, and a PWM frequency of 2000
M571 P3 F200 S0
M3
Mike