Refreshing grbl on the LEKN C1 controller

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The LEKN C1 grbl Controller we offer, operates as an Arduino UNO 328p with grbl shield attached. Below you will find the latest firmware version from LEKN – this is available in a zipped (.rar) format.

Download LEKN C1 FIRMWARE V3.2.1 (download the zipped .rar file to your computer and uncompress it)



1. Having installed the proper CH340 USB driver for your operating system, remove the LEKN C1 grbl Controller from your CNC machine (unplugging all stepper motors, limit switches, spindle, power and offline sender connections). Now connect the bare controller to your computer via a suitable USB data cable.

2. Open the Arduino IDE application, select the “Tools” drop down, hover over “Board:” and set the board type to “Arduino Uno”.

Select “ArduinoUNO” as your board type from the “Tools” drop down.

3. Identify the port that your grbl controller is connected to and set this within the Arduino IDE. Select the “Tools” drop down, hover over “Port:” and select the proper port for your device from the expanded list.

Choose the correct port for your connected device.

4. Ensure that the Arduino IDE has the proper grbl library files loaded. To do this, extract the contents of the grbl-1.1h.20190825-C1.rar file downloaded from the LEKN github site, that contains the updated “firmware” for the C1 controller (presently V3.2.1).

5. From within the Arduino IDE menu bar select “Sketch | Include Library | Add .ZIP library…”

Add a library from a folder or .ZIP archive to Arduino IDE

6. Navigate to the folder containing the contents of the (previously extracted) grbl-1.1h.20190825-C1.rar file. Select the “grbl” folder and click “Choose”. Arduino IDE will confirm the upload and addition of the new library files.

Select the folder containing the libraries to upload to Arduino IDE

7. Verify that the grbl libraries are now contained within the “Contributed Libraries” section within the Arduino IDE application. Select “Sketch” from the menu bar drop down, hover over “Include Library” and see that “grbl” now resides under “Contributed Libraries”.

Verify that the grbl library resides under “Contributed libraries” from within the Arduino IDE application.

8. Now from within the Arduino IDE application, go to “File | Open” and navigate to the “grbl” folder within the extracted contents of the .rar file and select “grbl.ino” sketch, then click “Open”.

Select the grbl.ino file from the grbl folder.

9. Upon opening the “grbl.ino” file you will be greeted with this screen below. Note the usage instructions contained in the notes section of the grbl sketch. We’ve already covered these setup points in the previous steps – so the last thing to do is to click the “Upload” arrow at the top left of the sketch window. After clicking upload your LEKN controller will be flashed with the latest firmware release.

Click the “Upload” arrow to flash the controller with the updated grbl “firmware”.

10. After flashing, none of your previous grbl $ settings will be retained. Close the Arduino IDE, then connect your newly flashed LEKN controller to the gcode sender application of your choice (we like OpenBuilds Control). From within the sender application, reset the grbl $ variables to match your (vendor provided) machine specifications. Specifications for NCPRO brand machines can be found by clicking here.

Setup your $ grbl variables, to match your machine specifications.

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