The Simplest DIY Macro Keypad: Pro Micro + 4x4 Matrix (16 Programmable Keys)

Project Overview

The Simplest DIY Macro Keypad: Two components, zero soldering decisions, one library — a 4x4 matrix keypad plugs straight into an Arduino Pro Micro's GPIO row and becomes a 16-button USB macro pad for OBS scene switching, editing shortcuts, or any hotkey-hungry app.

• Time: ~30 minutes
• Skill level: Beginner
• What you will build: A programmable USB keypad that types Ctrl+Alt+Shift+F-key combos (or anything else) at the touch of a button.

Parts List

From ShillehTek

• Pro Micro ATmega32U4 (Pre-Soldered) — the ATmega32U4 does native USB HID, so your computer sees a real keyboard
• 4x4 Membrane Matrix Keypad — 16 buttons on an 8-pin ribbon

External

• Micro-USB cable

Note: This build only works on boards with native USB support like the ATmega32U4 (Pro Micro, Leonardo). A classic Uno or Nano can't emulate a keyboard — the Pro Micro is the trick that makes it two-component simple.

Step-by-Step Guide

Step 1 — Plug the Keypad Into the Pro Micro

Goal: Complete the entire wiring in one move.

What to do: The keypad's 8-pin connector plugs directly onto the Pro Micro's GPIO 2–9 row — no breadboard, no jumper spaghetti. Orient it so the keypad's leftmost wire lands on GPIO 2, and the hardware is finished.

Expected result: Done wiring. Really.

Step 2 — How the Matrix Works (Optional Theory)

Goal: Understand how 8 pins read 16 buttons.

What to do: The four row pins are outputs and the four column pins are inputs. The Arduino drives each row high in turn while reading the columns; when a pressed button connects a live row to a column, the row/column pair identifies exactly which key it was. The Keypad library handles all of this scanning for you.

Expected result: Matrix scanning demystified (or skipped — your call).

Step 3 — Install the Library and Flash the Code

Goal: Turn key presses into keyboard macros.

What to do: In the Arduino IDE, install the Keypad library by Mark Stanley and Alexander Brevig from the Library Manager, grab the sketch from the author's GitHub, select Arduino/Genuino Micro as the board, and upload. The core of the sketch:

#include <Keypad.h>
#include <Keyboard.h>

const byte ROWS = 4;
const byte COLS = 4;
char keys[ROWS][COLS] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};
byte rowPins[ROWS] = {2, 3, 4, 5};
byte colPins[COLS] = {6, 7, 8, 9};

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

void sendMacroCommand(uint8_t key) {
  Keyboard.press(KEY_LEFT_CTRL);
  Keyboard.press(KEY_LEFT_ALT);
  Keyboard.press(KEY_LEFT_SHIFT);
  Keyboard.press(key);
}

void loop() {
  char key = keypad.getKey();
  if (key) {
    switch (key) {
      case '1': sendMacroCommand(KEY_F1); break;
      case '2': sendMacroCommand(KEY_F2); break;
      // ...one case per button, F1-F12 plus a-d
    }
    Keyboard.releaseAll();
  }
}

Expected result: Each button now types a unique Ctrl+Alt+Shift+F-key combo — combinations nothing else on your system uses.

Step 4 — Bind the Buttons in OBS

Goal: Put the pad to work as a stream deck.

What to do: In OBS, open Settings → Hotkeys, click the field for the action you want (switch scene, mute mic, start recording), then press a key on your macro pad — OBS records that combo as the trigger. Repeat for every scene and toggle you use.

Expected result: One-touch scene switching and source toggling in OBS.

Step 5 — Make It Yours

Goal: Go beyond F-keys.

What to do: Any button can type any sequence: swap a sendMacroCommand() call for Keyboard.press(KEY_LEFT_CTRL); Keyboard.press('c'); and you have a copy key (Ctrl+V for paste); use Keyboard.print("your text") to type whole snippets. Editing shortcuts, game binds, a one-button "thank you for the follow" — 16 keys, your rules.

Expected result: A fully custom macro pad tailored to your daily workflow.

Conclusion

This is the rare project where the bold claim holds: two parts, one plug-in connection, one library, and you own a 16-key programmable macro pad. It's a perfect first HID project — and a genuinely useful desk tool you'll keep using long after the novelty wears off.

Want the exact parts used in this build? Grab them from ShillehTek.com. If you want help customizing this project, check out our IoT consulting services.

Credits

All photos and images in this tutorial are credited to Brian Lough on Hackster.io. The original guide by Brian Lough served as the reference for this ShillehTek version. We thank him for his excellent work in the maker community.