What is GRBL?
GRBL is free, open source software for controlling the motion of machines that move, that make things, or that make things move, and runs on wide variety of microcontrollers. GRBL is used to power thousands of different CNC routers, lathes, mills, lasers and more. It is essentially the standard for open source CNC machines.
The first version of GRBL was released in 2009 by Simen Svale Skogsrud. It was later picked up and led by Sungeun "Sonny" Jeon Ph.D who evolved it into a highly capable machine control system running on the Arduino family of microcontroller boards. It makes incredibly efficient use of the 8-bit Atmel processors on the Arduinos and is an amazing feat of software engineering to get so much from such a humble processor. Unfortunately GRBL has reached the limits of the Atmel processors. Higher performance is needed and small code space limits the ability to add new features. In addition, the Atmel processors have been dramatically overtaken in capacity, features and performance by newer 32 bit microcontrollers.