How To Build a Custom Macropad

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2025-05-20 | By Zach Hipps

License: See Original Project 3D Printing Solder / Desoldering

Last year, my teammate, Ian, dropped some serious knowledge in a custom keyboard class ‎I attended, and I was hooked. I saw the light, and that light was a grid of customizable ‎buttons. Sure, you could buy a kit, and sure, DigiKey even sells macropad kits, but where's ‎the fun in that? If you thought I was just going to buy a kit, you clearly haven't been paying ‎attention. ‎

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A macropad is basically a custom mini keyboard on steroids. You can assign any shortcut ‎or keypress that you want to any button. Are you a creative type? Think brush sizes and ‎filters at your fingertips. Are you an engineer? Well, we can program those complicated CAD ‎keyboard shortcuts that have you twisted like a pretzel to one button press!‎

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I am an engineer, and Fusion 360 and KiCad are the software I use the most. I wanted to ‎speed up my workflow, so Ian and I sat down and sketched out a schematic. First up, we ‎needed to choose the microcontroller. We landed on the RP2040, specifically the Seeed ‎Studio Xiao RP2040 module for its flash, GPIO pins, and the fact that it has a built-in USB-C ‎connector. Now, the RP2040 has plenty of GPIO, but we did not want to limit ourselves. We ‎added an I/O expander because the more buttons, the merrier. Then, we started adding the ‎key switches. We landed on a 4x5 matrix, giving us 20 buttons and because knobs are fun ‎to turn, we added two rotary encoders. Next up, we thought about lighting because what's a ‎macropad without RGB LEDs? We went with SK6812s, reverse-mounted for ease of ‎assembly. Finally, because we're always about going the extra mile, we added a linear ‎potentiometer.‎

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After some schematic cleanup, Ian worked his magic on the PCB board layout. Let me tell ‎you, it was a thing of beauty. We even threw in an I2C Qwiic connector for an OLED display ‎because I like having options. I went to DigiKey to place an order for all the parts I would ‎need for this project.‎

While I waited for the PCBs, I did a little experimenting with the Seed Studio Xiao RP2040 ‎and the Arduino IDE. I found a library from Adafruit, and it turns out that reading key ‎presses is surprisingly simple. It emulates a keyboard by using the HID (Human Interface ‎Device) protocol, and in no time, you're typing numbers with a test key switch. Cool, right?‎

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When the PCBs arrived, they looked great. I set up my workstation, used the stencil to apply ‎solder paste, and got to work placing the SMD components. KiCad's Interactive BOM plugin ‎made component placement a breeze. After placing all the parts, I slid them into my DIY ‎reflow oven, which I had built in a previous video. After the reflow was done, it was time for ‎testing. I began using tweezers and Vial’s IDE to test each set of button pads since I still ‎needed to solder on the key switches. That's where things got interesting. The buttons ‎tested great until rows four and five; that is where things went south. It turns out pull-down ‎resistors are important. A few of them were misaligned from the reflow oven. After a little ‎soldering iron fix, I was back in business with fully working buttons.‎

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Next up, I needed to install the key switches. The world of key switches is a rabbit hole. ‎There are so many different types of key switches. I went with some general-purpose ones, ‎but the options are endless. Before I could solder on the key switches, I needed to work on ‎the case. The case will help align the key caps, so they don’t end up getting soldered crooked ‎and looking wonky. I fired up Fusion 360 and designed one to be 3D-printed. While I was ‎designing my case, I realized that my OLED display didn’t fit where I had planned for it to go ‎between the two rotary knobs. I decided to make it an optional add-on at the top of the ‎enclosure in case I decided later that I didn’t want to use it.‎

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After the case finished printing, I hand soldered all the key switches, rotary knobs, and ‎linear potentiometer. Now, it was time for keycaps. Because I could, I 3D printed them in ‎multicolor, with icons for each shortcut I wanted. Who has a good enough memory to ‎remember what each button does without labels?‎

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Then, the moment of truth: time for programming the firmware. You have options when ‎programming macropads. You could just use open-source software QMK, which would be ‎great if you were mass-producing macropads or didn’t plan on changing firmware often. ‎Since I want to edit the keys and adjust the settings on the fly, I landed on Vial, which is a ‎QMK GUI, and I started assigning shortcuts. Fusion 360 shortcuts, to be precise. And then, ‎because I always need a Byte Sized Engineering special touch, I added a special button ‎feature. A button that... well, you'll have to watch the video to find out.‎

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But seriously, this macropad is a game-changer. It's all about customization, about making ‎your workflow faster and smoother, and if you're not dancing by the end, you're doing it ‎wrong.