Thanks Mike for your response. I'm aware of myFocuserPro/2 project. As a matter of fact, I'm building one now (solderless version), and ordered PCBs to create the smaller footprint PCB version.
My question was about using GRBL as the Arduino code instead of myFocuserPro firmware. The reason I liked GRBL is that it is somewhat standard project used by many ready made hardware and components for other purposes (e.g. building your own 3D printer or engraving machine, ... etc). IMO the advantages IMO are the ability to build very quickly from online ordered components including the PCB's for less than $20 (including small NEMA17 200 step motor), serial port control commands are VERY simple, and the ability to control y default up to 4 motors (or maybe 3) which is useful for other projects or even for the focuser if we wanted to add control to the coarse knob.
It worked beautifully for me, and I wonder if someone started or have INDI or ASCOM interface as this code was out there for a long time...