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• First the PTH version with Pi Pico

  DailyDuino • 05/10/2026 at 11:52 • 0 comments

  A few days ago, I was recommended a video by Moby Pixel on YouTube where he built a custom MIDI macropad for music composition. It looked like a pretty cool project, and I immediately wanted to build one for myself but not for music, but to automate a couple of on-demand tasks for my day job as a software developer.

  I know there are plenty of great, fairly priced macropads available on AliExpress, Tindie, and Lectronz. However, I want to get back into PCB design, as it has been eight years since I last designed a professional board.

  I’m also a huge Halo fan. I want my desk setup to feature a Master Chief color scheme, and I want this new macropad to perfectly match my Master Chief controller holder.

  While I loved the simplicity of Moby Pixel’s design, I couldn’t find a cheap 4×4 mechanical switch PCB to use for prototyping. That inspired me to build my own.

  With this project, I have a few specific goals:

  • Design a PCB where mechanical switches can be directly soldered.
  • Design a PCB with hot-swap sockets for mechanical switches.
  • Design a PCB featuring both hot-swap sockets and RGB LEDs.
  • Explore and experiment with QMK and ZMK firmwares.

  Through these iterations, I will be packing more components onto a 2-layer PCB, evolving the project from a basic USB HID macropad into a fully featured version with Bluetooth, HID, and LED support. Finally, I will be stepping away from Eagle to use EasyEDA for the design to see how it performs.

  The Design

  There are a couple of key differences between Moby Pixel's project and mine. First, he uses a dedicated GPIO pin for every switch, whereas I will be using a keypad matrix. Second, his design integrates both the switches and the microcontroller onto a single PCB. In my version, I will design a separate PCB for the microcontroller. This modular approach will allow me to easily swap out microcontrollers to experiment with different firmwares.

  Schematic

  In the key matrix i added external pull-ups and switch the rows and columns. this is how the schematic looks.

  The bill of materials is pretty simple

  Component	Count
  1N4148 Diode (SOD-123)	16
  Mechanical Switch of your choice	16
  10K Resistor (0603) (optional)	4
  10 Pin 0.1″ Header Pins	1

  PCB Layout

  The PCB is 82.8mm x 82.8mm and i want to keep the distance between the switchers small so that it will ergonomic and low profile.

  Finally, I was happy with my design. It took me a whole of 2 hours to design it and now i have to send it for fabrication. It was pretty easy to order PCBs from easyEDA. I just had to click one button and the PCB design was sent to JLCPCB.com and form there it was very easy and cheap to order the PCBs. I was not sponsored by JLCPCB. *cough *cough please sponsor thanks.

  Assembly

  I soldered the diodes using a soldering iron and it took me 10 minutes to do that. I soldered on the resistor for pull ups but later removed them because i wanted to use the internal pull ups of the RP2040.

  Now for the mounting plate. I designed it using fusion360 and printed it on my 3D printer. The choice of color on this is not so great.

  Next, I snapped the mechanical blue switches into place on the mounting plate and it snapped perfectly into place. Nice.

  Finally I mounted and soldered the PCB in the top mounting plate with the switches.

  Okay, here's where I messed up. I should have also ordered the bottom PCB with a microcontroller but I had to work with what I had on hand for testing the prototype. So, I soldered the Pi Pico i had which has the RP2040 microcontroller.

  I connected the macropad to pi pico using the following pin configuration

  Macro Pad Pins	RP2040 GPIO
  1 (COL1)	GP9
  2 (COL2)	GP8
  3 (COL3)	GP7
  4 (COL4)	GP6
  5 (ROW1)	GP5
  6 (ROW2)	GP4
  7 (ROW3)	GP3
  8 (ROW4)	GP2
  9 (VCC)	—
  10 (VCC)	—

  Now that i have connected everything, I plugged in the Pi Pico to my PC and it showed up as a mass storage device.

  Software

  I had the sweet temptation of writing the software using...

  Read more »

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