Testing GRBL in Arduino Board (Without the Motors)

Once you make sure your Arduino board is working, the next step is to upload the GRBL software to the Arduino board.

I like to use the “standard” Arduino method to upload code. For that we can use the GRBL library that Protoneer put together: [link]. I copied the following instructions from the Protoneer website:

We have created an Arduino Library of the popular GRBL g-code Interpreter. A great little application that turns your Arduino into a very capable CNC machine.

This library makes it so much easier to install GRBL onto your Arduino. No more issues with making HEX files or trying to find a way to upload the Hex file to your board. Simply install the library and open the right example sketch for your Arduino.

How to install it:

  • Down load the library from GitHub : https://github.com/Protoneer/GRBL-Arduino-Library/archive/master.zip
  • Unzip the library and copy the main folder into the “Libraries” folder in the folder you installed your Arduino software. Eg. C:\arduino-1.0.3\libraries\
  • Rename the folder to “GRBL”. (This will stop the Arduino IDE from complaining about the long folder name)
  • Open up the Arduino IDE.
  • Click on the following menu : File -> Examples – > GRBL (or what ever you renamed the folder to) -> ArduinoUno
  • Upload the sketch to you Arduino UNO board.

If you are interested in the source code, its available at https://github.com/Protoneer/GRBL-Arduino-Library

The GRBL code is 27K in size. The Arduino still has some space (5K) to do “other things”. For now there are no “other things” to do.


Next is to download “GRBL Controller”. This software will allow manual sending GRBL to the Arduino


In order to test the Arduino/GRBL, you need an LED. You can test all the DIRECTION and PULSE pins (pins 2 to 7) by clicking on the arrows in GRBL Controller and observing the LED (it will turn on/off). For the PULSE pins, the LED will be much dimmer than with the DIRECTION because the signal on the PULSE pins is a pulse rather than a continuous level.


Here is LED connected to the X-Axis Direction pin (pin 5). When you click the horizontal arrow in one or the other direction the LED will turn on/off.


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