NOTE: The following file is provided as-is WITHOUT warranty.  Use at your own discretion.

Download GRBL binary version 0.8l here: grbl.hex  -- LICENSE FILE

This version is the same as 0.8c which ships on the Arduino Uno in the Shapeoko 2 kit available from Inventables.com except for the following:

• Spindle Speed commands with values from 0 to 255 (e.g. S0, S50, S198, S255) will set a PWM pulse on Arduino pin 11 (effectively producing a 0 to 5 volt analog output).
• Arduino pin 11 is no longer usable for a Z-axis limit switch
• The stepper now uses Timer 0 overflow instead of Timer 2 overflow, so that Timer 2 may be used for the PWM on pin 11.

Note that M3/M4/M5 commands still control Pin 12 (Spindle Enable) and Pin 13 (Spindle Direction).

This has been tested with a Shapeoko 2 on which is mounted a 2 Watt, M140 laser that is driven by a FlexMod P3 driver.  The MOD + of the FlexMod P3 is connected directly to the Arduino Pin 11 to vary laser intensity for producing variable burns (gray shades) when working with software such as PicLaser Lite.

Source code is currently available at https://github.com/alsliahona/grbl and may eventually be included in a branch of the original GRBL code available here: https://github.com/grbl/grbl.

Best wishes with it.

-Andrew Sandoval

31 May 2014