Build your own 9-key handwired macropad and a great first soldering project
Difficulty
Beginner
Time
2–3 hours
Steps
6 stages
Every file for this build is up on GitHub, the plates, the case and the firmware
Our GitHubPrefer to see it happen? Here is the full walkthrough of this build and how the finished board actually works. Follow along with the written steps below.
Gather everything below before you start and the whole build goes a lot smoother. The printable parts are on GitHub, so you only need to buy the hardware.
No Case // The Sandwich
There is no case in this build. Our boards are a sandwich, a 3D printed top plate and a 3D printed bottom plate with the whole handwired matrix pressed in between, held together by screws at the corners. That is deliberate. Handwiring goes wrong in ways a beginner or a STEM maker cannot always predict, and a sealed case turns every loose joint into an afternoon of surgery. Undo the screws, lift the top plate, and the entire matrix is in front of you, ready to fix and bolt back together.
| Component | Qty | Specification |
|---|---|---|
| MX-compatible switches | 9 | Any MX switch works |
| Pro Micro ATmega32U4 | 1 | Programmed via Arduino IDE |
| Hookup wire (24 AWG) | ~2m | Two colors recommended |
| 3D Printed Plates (STLs provided) | 2 | Top + bottom, PLA, 0.2mm layer height |
| Keycaps (1u × 9) | 9 | Any MX-compatible keycaps |
| M2 screws (4mm) | 4 | Clamp the two plates together |
| Soldering iron + solder | 1 set | Any soldering iron works for this build |
01
Soldering iron
02
Solder
03
Wire strippers
04
Flush cutters
05
Tweezers
06
Computer with Arduino IDE installed
Work through these in order. Anything you need to download along the way, the plates, the case and the firmware, is already waiting for you on GitHub.
01
Step 1 of 6
The MonkiiPad3x3 STL files are on GitHub, so grab the top and bottom plates there and print them both in PLA. Use 0.2mm layer height, 20% infill. No supports needed. The top plate has nine switch cutouts in a perfect 3×3 grid; the bottom plate screws on underneath to close the sandwich.
02
Step 2 of 6
Snap all 9 switches into the plate, they should click in firmly with no wobble. The MonkiiPad3x3 is a diodeless matrix, so there are no diodes to add, each switch wires straight into the row/column grid.
Pro Tip
Check that no switch pins are bent before pressing them in, because bent pins cause hard to trace matrix issues.
03
Step 3 of 6
Run a wire across each of the 3 rows, soldering directly to one pin of each switch in that row. Strip a small window at each joint, solder, and move to the next. Three rows = three wires.
Pro Tip
Use one color for row wires and another for column wires to avoid confusion.
04
Step 4 of 6
Run a wire down each of the 3 columns, soldering to the top pin of each switch. Three columns = three wires. These must never touch the row wires.
05
Step 5 of 6
Connect each of the 3 row wires and 3 column wires to GPIO pins on the Pro Micro. The reference firmware uses rows on pins 7, 8, 9 and columns on 4, 5, 6. Note down every connection, tuck the wiring neatly, lay the bottom plate over the back of the assembly, and secure the sandwich with M2 screws. Press keycaps onto the switches.
06
Step 6 of 6
The MonkiiPad3x3 sketch is on GitHub, or printed in full further down this page. Open it in the Arduino IDE, set the rowPins and colPins arrays to match your wiring, then upload to the Pro Micro. Open a keyboard tester and all 9 keys should register. Hold key 1 for ~1.5s to toggle between number mode and macro mode (arrows, copy/paste, delete). Want a different layout? The Keymap Editor will build the sketch for you.
Pro Tip
Install the Arduino keyboard HID library before compiling, the sketch depends on it. The exact includes are at the top of the sketch on GitHub.
The full Arduino sketch for this build. Open it in the Arduino IDE, match the pins to your wiring, and upload. There is no need to copy it off this page, the same sketch is sitting on GitHub with the rest of the repo.
#include <Keyboard.h>
const int colPins[3] = {4, 5, 6};
const int rowPins[3] = {7, 8, 9};
bool macroMode = false;
unsigned long pressStart = 0;
const unsigned long holdTime = 1500;
void setup() {
for (int c = 0; c < 3; c++) {
pinMode(colPins[c], INPUT_PULLUP);
}
for (int r = 0; r < 3; r++) {
pinMode(rowPins[r], OUTPUT);
digitalWrite(rowPins[r], HIGH);
}
Keyboard.begin();
}
void loop() {
for (int r = 0; r < 3; r++) {
digitalWrite(rowPins[r], LOW);
delayMicroseconds(30);
for (int c = 0; c < 3; c++) {
if (digitalRead(colPins[c]) == LOW) {
// SPECIAL LOGIC FOR KEY 1
if (r == 0 && c == 0) {
pressStart = millis();
while (digitalRead(colPins[c]) == LOW) {
if (millis() - pressStart > holdTime) {
macroMode = !macroMode;
while (digitalRead(colPins[c]) == LOW);
delay(200);
goto skipKey;
}
}
// short press
Keyboard.write('1');
delay(20);
goto skipKey;
}
// NORMAL MODE
if (!macroMode) {
char numbers[3][3] = {
{'1','2','3'},
{'4','5','6'},
{'7','8','9'}
};
Keyboard.write(numbers[r][c]);
}
// MACRO MODE
else {
if (r == 0 && c == 1) Keyboard.write(KEY_UP_ARROW);
else if (r == 1 && c == 0) Keyboard.write(KEY_LEFT_ARROW);
else if (r == 1 && c == 1) Keyboard.write(KEY_DOWN_ARROW);
else if (r == 1 && c == 2) Keyboard.write(KEY_RIGHT_ARROW);
else if (r == 2 && c == 0) { // Ctrl+C
Keyboard.press(KEY_LEFT_CTRL);
Keyboard.press('z');
delay(10);
Keyboard.releaseAll();
}
else if (r == 2 && c == 1) { // Ctrl+V
Keyboard.press(KEY_LEFT_CTRL);
Keyboard.press('y');
delay(10);
Keyboard.releaseAll();
}
else if (r == 2 && c == 2) { // Delete
Keyboard.write(KEY_DELETE);
}
else {
Keyboard.write('1');
}
}
while (digitalRead(colPins[c]) == LOW);
delay(20);
skipKey:;
}
}
digitalWrite(rowPins[r], HIGH);
}
}
Want a different keymap?
Lay out your own keys, layers and macros in the browser, then download a sketch already wired for this board. No editing C by hand.
Everything is on GitHub
Every 3D printing file, every firmware sketch and every build guide we have written lives in one repository, and all of it is free to download and free to change however you like. The plate and case files are there, so is the Arduino code for each board, the wiring diagrams and the PCB designs.
Stuck on a step, got a tip, or just finished your build? Drop it in our form. We read every single one and it helps us make the guide better.
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