4 layers234 × 84 mm
Main panel
google/mozc-devices
Circuit diagrams and firmware source code for Gboard DIY keyboards
234 parts3kApache-2.0
2 layers99 × 99 mm
CobraPad
SnaggingCobra/hackpadCobraPad is a compact 8-key macro pad built around the Seeed XIAO RP2040, with a rotary encoder, SSD1306 OLED display, addressable RGB underglow, and a custom 3D-printed case.
- Size
- 99 × 99 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 39
- Nets
- 34
- Pads
- 117
- Tracks, vias
- 337, 17
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 15 Aug 2026
- Updated
- 17 Sep 2026
Overview
CobraPad is an open-source printed circuit board by SnaggingCobra, from the SnaggingCobra/hackpad repository on GitHub, published under the MIT licence. It is a 2-layer board of 99 × 99 mm with 39 parts on 34 nets, routed with 337 tracks and 17 vias.
It is built around the SK6812MINI-E. Its parts include 16 diodes, 9 switches, 8 capacitors and 2 ICs. It belongs with the lEDs and displays boards of this library.
Main components
1README
README.mdCobraPad
CobraPad is a compact 8-key macro pad built around the Seeed XIAO RP2040, with a rotary encoder, SSD1306 OLED display, addressable RGB underglow, and a custom 3D-printed case. The board and case are treated as the source of truth, and the firmware is mapped directly to the actual KiCad net names and pad assignments.
Overview
- MCU: Seeed XIAO RP2040
- Layout: 2 rows x 4 columns, 8-key matrix
- Extras: rotary encoder with push switch, 128x32 OLED, 8 SK6812MINI-E LEDs
- Firmware: CircuitPython
- PCB: 2-layer custom board, 99 mm x 99 mm
- Case: custom top and bottom enclosure designed for a fitted assembly
Project photos
Overall project / visible build
Schematic
PCB
Case fit / enclosure
Hardware summary
| Component | Quantity | Notes |
|---|---|---|
| Seeed XIAO RP2040 | 1 | Main controller |
| Mechanical switches | 8 | Key matrix |
| Diode (1N4148 or equivalent) | 8 | One per switch |
| Rotary encoder with switch | 1 | EC11-style encoder |
| SSD1306 128x32 OLED | 1 | I2C display |
| SK6812MINI-E RGB LEDs | 8 | Addressable LED chain |
| Decoupling capacitor | 3 | Power filtering |
| Resistor | 1 | Pull-up / support |
| 3D-printed case parts | 1 set | Top and bottom shell |
| M2 hardware | 4+ | Case assembly |
Verified board pin mapping
The firmware in Firmware/circuitpython/code.py is mapped to the board as follows:
| Function | KiCad signal / board net | CircuitPython pin |
|---|---|---|
| Row 1 | PA02_A0_D0 | D0 |
| Row 2 | PA4_A1_D1 | D1 |
| Col 1 | PA10_A2_D2 | D2 |
| Col 2 | PA11_A3_D3 | D3 |
| Col 3 | PB08_A6_D6_TX | D6 |
| Col 4 | PB09_A7_D7_RX | D7 |
| OLED SDA | PA8_A4_D4_SDA | D4 |
| OLED SCL | PA9_A5_D5_SCL | D5 |
| Encoder A | PA7_A8_D8_SCK | D8 |
| Encoder B | PA5_A9_D9_MISO | D9 |
| LED data | PA6_A10_D10_MOSI | D10 |
BOM
The table below is the verified BOM for the current KiCad schematic and board assembly.
| Component | Quantity | Description |
|---|---|---|
| Seeed XIAO RP2040 | 1 | Main microcontroller board |
| Mechanical keyboard switch | 8 | Cherry MX-compatible switches for the key matrix |
| 1N4148 diode | 8 | One diode per switch for matrix protection and flyback suppression |
| SK6812MINI-E RGB LED | 8 | Addressable underglow/lighting LEDs |
| SSD1306 128x32 OLED module | 1 | I2C display for status and output |
| Rotary encoder with push switch | 1 | EC11-style encoder for control input |
| 100 nF decoupling capacitor | 8 | SMD power-filter capacitors used across the board (C1-C8) |
| M2 case mounting hardware | 4 | Screws/standoffs used for the enclosure assembly |
| 3D-printed top shell | 1 | Custom top enclosure cover |
| 3D-printed bottom shell | 1 | Custom bottom enclosure base |
See BOM.csv for the CSV version of the same parts list.
Repository layout
- PCB/CobraPad — KiCad PCB, schematic, and project files
- kicad-libs — custom symbols and library files
- CAD — assembled CAD and mechanical source files
- CAD/Case — case source and generated shell files
- Firmware — CircuitPython firmware and notes
- assets — project screenshots and render images
- production — manufacturing and production outputs
- BOM.csv — project components list
- LICENSE — project license
Production files
The final project includes fabrication and production artifacts in production:
- production/gerbers.zip — PCB fabrication Gerbers and drill files
- production/CobraPad.step — PCB STEP export
- production/CobraPAD_CASE_FINAL_top_cover.step — case top shell
- production/CobraPAD_CASE_Finalbottom_shell.step — case bottom shell
- production/CobraPad_circuitpython.zip — firmware bundle
CAD and enclosure
The assembled CAD model is located in CAD/CobraPAD_All together.step. This file represents the assembled project geometry and includes the designed enclosure plus the PCB in context. The project also includes the editable FreeCAD source file in CAD/Final.FCStd.
Firmware
The active firmware is written in CircuitPython and lives in Firmware/circuitpython/code.py. The companion notes are in Firmware/README.md.
Firmware capabilities
- 8-key matrix scanning
- rotary encoder clockwise / counter-clockwise detection
- encoder push-button input
- SSD1306 display output
- 8-addressable RGB LED support
- USB HID keyboard output
Build / setup notes
- Open PCB/CobraPad/CobraPad.kicad_pro in KiCad.
- Verify the board matches the schematic and intended parts list.
- Flash CircuitPython onto the XIAO RP2040.
- Copy the contents of Firmware/circuitpython onto the CIRCUITPY drive.
- Assemble the PCB, case, encoder, OLED, and LEDs.
- Validate key presses, encoder behavior, display output, and LED animation.
Design notes
- The KiCad PCB and case files are the source of truth for this project.
- The board is intentionally mapped to the specific RP2040 pins used in the hardware.
- The firmware is designed to match the actual board connection map and component placement.
- The project is meant to be a compact, low-profile macro pad with a clean custom enclosure.
Project status
This repository is prepared as a final project archive and submission bundle for the CobraPad macro pad. The current project includes the final PCB source, fabricated production outputs, custom case files, and the CircuitPython firmware.
License
This project is released under the MIT license. See LICENSE.
Parts
39| Qty | Value | Footprint | References |
|---|---|---|---|
| 8 | 100nf | Capacitor_SMD:C_0603_1608Metric | C1, C2, C3, C4, C5, C6, C7, C8 |
| 8 | 1N4148 | Diode_THT:D_DO-35_SOD27_P7.62mm_Horizontal | D1, D2, D3, D4, D5, D6, D7, D8 |
| 8 | SK6812MINI-E | LED_SMD:LED_SK6812MINI-E_3.2x2.8mm_P1.5mm_ReverseMount | D9, D10, D11, D12, D13, D14, D15, D16 |
| 8 | SW_Push | Button_Switch_Keyboard:SW_Cherry_MX_1.00u_Plate | SW1, SW2, SW3, SW4, SW5, SW6, SW7, SW8 |
| 1 | ER_OLEDM0.91_1x-I2C | Display:ER_OLEDM0.91_1x-I2C | U2 |
| 1 | MOUDLE-SEEEDUINO-XIAO | footprints:XIAO-Generic-Hybrid-14P-2.54-21X17.8MM | U1 |
| 1 | RotaryEncoder_Switch | Rotary_Encoder:RotaryEncoder_Alps_EC11E-Switch_Vertical_H20mm | SW9 |
The 35 most common of 39 parts.
Questions
How big is the CobraPad PCB?
It measures 99 × 99 mm and has 2 copper layers, 1.6 mm thick.
What parts does the CobraPad use?
39 parts, built around the SK6812MINI-E. 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 CobraPad KiCad files?
From the SnaggingCobra/hackpad repository on GitHub, at the commit this page was made from: the board is PCB/CobraPad/CobraPad.kicad_pcb and its schematic PCB/CobraPad/CobraPad.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the CobraPad design in my own project?
Its repository publishes it under the MIT licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).
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