The Pad MIDI keyboard is part of the LEET Synthesizer project. If you haven’t – It is a good idea to read the main post first before continuing with the details below:

This post describes how the pad keyboard works and what you need to build your own.

Description of the Pad

Product guide. Click here to download high-resolution PDF.

Part list:

Component cost is around $6 on eBay October 2020 (will depend on shipping and supplier).

  • 1x 3D printed core 3DPCB
  • 1x Arduino pro micro, or compatible clone (5V version. ATmega32U4) – (~$4)
  • 11x 6x6mm 4pin through hole tact switches – preferably with low activation force (50g / 0.5N) – ($0.2)
  • WS2812 LED-strip with 8 LEDs (60 LEDs/m. I used IP60, white FPC) – ($1.1)
  • 1x 25cm RK wire (containing 24 strands of 0.3mm copper wires) – ($0.1)


  • 3D printer (FFF/FDM with PLA filament)
  • Solder station with a narrow tip
  • Basic tools: needle- and cutting pliers, knife, hot-glue
  • Computer to run Arduino IDE and upload firmware (using a Micro USB cable)

Build it

I have not made a step by step building instruction, but check out the video and illustration below. The build process is very similar to the step by step instruction for the keyboard.

Backside view showing routing of wires.


The pad is literally a smaller version of the LEET keyboard. I rearranged the LEDs and switches, downsized it, rebuilt the 3D model and adjusted the code.

Download project files

All files required for this project are available at this GitHub repository:



This project is open source under MIT License
(Attribution is optional, but appreciated /Johan von Konow ;)

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