2 layers19 × 76 mm
Sub
google/mozc-devices
Circuit diagrams and firmware source code for Gboard DIY keyboards
15 parts3kApache-2.0
2 layers
Pax button
rubiconRiver/pax-buttonicaBig glowing turn buttons for Twilight Imperium 4: web app, phone buttons, ESP32 firmware and an open button standard
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 15
- Nets
- 18
- Pads
- 61
- Tracks, vias
- 60, 0
- Pours
- 3
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 20 Sep 2026
- Updated
- 31 Oct 2026
Overview
Pax button is an open-source printed circuit board by rubiconRiver, from the rubiconRiver/pax-buttonica repository on GitHub. It is a 2-layer board with 15 parts on 18 nets, routed with 60 tracks and 0 vias.
Its parts include 3 resistors, 3 connectors, 1 capacitor, 1 IC and 1 diode. It belongs with the ESP32 and RISC-V boards of this library.
README
hardware/pcb/README.mdThe button's carrier board
A 70 mm round, two-layer board that every part of a button solders onto, so the only loose wires left are three to the LED ring and two to the batteries.
Revision 0.2. Status: designed, rule-checked, never manufactured. (v0.1, the first one ordered, is the same board without R2/R3 and the number box, and with C1 nearer the middle; it works the same.) KiCad's design-rule check passes with no violations and nothing unconnected. No board has been made, and the ESP32 module's footprint was drawn from published dimensions, not from a module in hand. Order a small batch and test one before building six.
What's on it
| Ref | Part | Notes |
|---|---|---|
| U1 | ESP32-C3 SuperMini | Top of the board, USB-C at the rim. A spare solder hole sits beside every pin, so anything the module can do is reachable later: extra buttons, a speaker amp, battery sensing. |
| SW1 | MX-style keyboard switch | Dead centre. Any Cherry-MX-compatible switch, 3-pin or 5-pin. One side to ground, the other to the 5th pin on the module's power side. |
| J1 | Battery, 4 × AA NiMH | A 5.08 mm screw terminal, or just solder the holder's leads into the holes. + is on the left. |
| D1 | 1N5817 diode | Reverse-polarity protection. Stripe to the right (marked K). |
| C1 | 1000 µF capacitor | Near the rim, below the LED connector, where it clears both the 8-LED and the 50 mm 12-LED ring. Stripe (negative) away from the + mark. |
| R2, R3 | 100 kΩ × 2, optional | A battery gauge: they halve the battery voltage for the ESP32 to read. Fit both and set BATTERY_PIN in the firmware (the fourth pin on the 5V side, usually 4); the test bench and the game then show each button's battery. Leave them off and nothing changes. |
| J2 | LED ring | 5V · DIN · G. Solder the ring's three wires straight in, or fit a pin header. |
| R1 / JP1 | 330 Ω, optional | JP1 is a jumper that is already bridged on the bare board, so with R1 left empty everything works. To use the resistor: fit R1 and cut the thin link between JP1's two pads. |
| J3 | Three ground holes | For the other leg of any extra buttons. |
| H1–H4 | M3 mounting holes | On a 46 × 38 mm rectangle. |
| Back | "No." box | Somewhere to write which button this is. |
The ground is a copper pour on both sides. There is no copper under the module's antenna.
Two things the board deliberately does not assume
- Which way the module's GPIO numbers run. Sources disagree on whether the five pins after 3V3 are labelled 4-3-2-1-0 or 0-1-2-3-4. The switch goes to the fifth pin on the 5V side. Read the number printed beside that pin on your module and put it in
firmware/button/config.has the first entry ofBUTTON_PINS. The LED data line goes to GPIO10, which everyone agrees on. - That your module isn't mirrored. Looking down on the module with USB-C at the top, 5V should be the top pin on the right. If yours has 5V on the left, solder the module to the back of the board instead; flipping it swaps the rows back. Check before you solder: it's printed on both sides of the board too.
Assembly
Step by step in docs/HARDWARE.md: diode, ESP32 (on its pin strips, USB off the edge), switch, capacitor, battery leads, LED ring.
Ordering (JLCPCB, PCBWay and similar)
Upload pax-button-v0.2-gerbers.zip. The preview should show a round board with a square switch outline in the middle. Then:
- 2 layers · 70 × 70 mm · quantity 5 or 10 (usually the same price)
- 1.6 mm thick · green solder mask (other colours can add days) · HASL finish · 1 oz copper
- Fastest courier they offer (DHL Express or similar). Expect duty, GST and a brokerage fee at the door.
Regenerating it
The whole board is produced by a script, so changes are reviewable text:
/Applications/KiCad/KiCad.app/Contents/Frameworks/Python.framework/Versions/Current/bin/python3 make_board.py
kicad-cli pcb drc pax-button.kicad_pcbpax-button.kicad_pcb opens in KiCad 9 or later if you would rather edit it by hand.
Parts
15| Qty | Value | Footprint | References |
|---|---|---|---|
| 4 | MountingHole_3.2mm_M3 | MountingHole_3.2mm_M3 | H1, H2, H3, H4 |
| 2 | 100k (optional) | R_Axial_DIN0207_L6.3mm_D2.5mm_P5.08mm_Vertical | R2, R3 |
| 1 | 1000uF 16V | CP_Radial_D8.0mm_P3.50mm | C1 |
| 1 | 1N5817 | D_DO-41_SOD81_P10.16mm_Horizontal | D1 |
| 1 | 330R (optional) | R_Axial_DIN0207_L6.3mm_D2.5mm_P7.62mm_Horizontal | R1 |
| 1 | BATTERY 4xAA NiMH | TerminalBlock_Phoenix_MKDS-1,5-2-5.08_1x02_P5.08mm_Horizontal | J1 |
| 1 | ESP32-C3 SuperMini | U1 | |
| 1 | GND x3 | PinHeader_1x03_P2.54mm_Vertical | J3 |
| 1 | LED RING | PinHeader_1x03_P2.54mm_Vertical | J2 |
| 1 | MX switch | SW_Cherry_MX_1.00u_PCB | SW1 |
| 1 | bypass R1 | SolderJumper-2_P1.3mm_Bridged_Pad1.0x1.5mm | JP1 |
Questions
What parts does the Pax button use?
15 parts. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Pax button KiCad files?
From the rubiconRiver/pax-buttonica repository on GitHub, at the commit this page was made from: the board is hardware/pcb/pax-button.kicad_pcb. PCBKit opens the board in the browser, with nothing to install.
Can I use the Pax button design in my own project?
Its repository states no licence, so its author keeps all rights: ask rubiconRiver before reusing the design.
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