Get Arduino Mega 2560 Grbl Pinout Gallery. I realized that the pinout wasn't the same with grbl for both boards. Each of the 54 digital pins on the arduino 2560 mega can be used as an input or output, using pinmode(), digitalwrite(), and digitalread() functions.

Grblduino Mega Shield V1 The Eccentric Workshop Blog
Grblduino Mega Shield V1 The Eccentric Workshop Blog from i0.wp.com
When cheaper boards are available, why go with arduino mega? Hola amig@s del mundo de instructables ,entusiasta de la mini electrónica y de las maquinitas de control numérico (cnc) apoyadas por arduino, acá les dejo un aporte espero les sirva y les ayude en su desarrollo de sus invenciones. They operate at 5 volts.

Grbl pinout arduino nano v3.0:

Each of the 54 digital pins on the arduino 2560 mega can be used as an input or output, using pinmode(), digitalwrite(), and digitalread() functions. The chip used in arduino 2560. I realized that the pinout wasn't the same with grbl for both boards. Latest verified version of grbl9f2560 from github.