Mithril

Mithril

A 54-key (27 per side) column-staggered split ergonomic mechanical keyboard with per-key underglow, USB-C on each half, and a dual-MCU design.

Features

• Split — two independent halves connected over TRRS
• MCU — ATmega32U4 on each half (true split, dual-MCU)
• Layout — 4×5 column-staggered grid + outer pinky column + thumb cluster (27 keys/side)
• Switches — MX-compatible, Kailh hotswap sockets (1u plated)
• Lighting — SK6812MINI-E reverse-mount per-key underglow
• Connectors — USB-C on both halves, TRRS jack for inter-half communication
• Case — 3D-printed shell + PCB top plate
• Firmware — QMK (see Firmware) · VIA-compatible

Gallery

PCB & switches	Keycaps on	Underglow

3D render of the panelised PCB:

Repository layout

Mithril/
├── Mithril.kicad_pro          Main PCB project (schematics + layout)
├── Mithril.kicad_pcb
├── Mithril.kicad_sch          Root schematic
├── lefthalf.kicad_sch         Left-half matrix
├── righthalf.kicad_sch        Right-half matrix
├── mcu.kicad_sch              MCU + USB-C + TRRS (half 1)
├── mcu1.kicad_sch             MCU + USB-C + TRRS (half 2)
├── leds.kicad_sch             SK6812 underglow chain
├── Mithril-panneled/          Panelised PCB for fabrication
├── Top_plate/                 Switch top plate (separate KiCad project)
├── Production/                Gerbers, BOM, positions (PCB)
│   ├── Mithril.zip
│   ├── bom.csv
│   ├── positions.csv
│   └── designators.csv
├── case/                      3D-printable case (STEP)
│   ├── caseLeft.stp
│   └── caseRight.stp
├── docs/
│   └── schematic.pdf          Full schematic (all sheets in one PDF)
└── images/                    Photos and renders

Build guide

1. PCB — order from Production/Mithril.zip (or Mithril-panneled/ if your fab requires a panel). The BOM and pick-and-place files are in Production/bom.csv and Production/positions.csv.
2. Top plate — order from Top_plate/production/Top_plate.zip. It is a PCB-as-plate; if you prefer laser-cut acrylic/FR4, export the edge cuts to DXF from KiCad.
3. Case — 3D-print case/caseLeft.stp and case/caseRight.stp. Any filament works; PETG/PLA are tested.
4. Components — source per Production/bom.csv. Notable items:
   • ATmega32U4-AU (QFN-44) × 2
   • SK6812MINI-E reverse-mount LEDs
   • Kailh MX hotswap sockets × 54
   • USB-C receptacle (HRO TYPE-C-31-M-12) × 2
   • TRRS jack (PJ-320A or compatible) × 2
   • 16 MHz crystal + caps × 2, decoupling caps, diodes, resistors per BOM
5. Assembly — solder SMD first (LEDs and MCU support circuitry), then through-hole (sockets, TRRS, reset). Flash QMK before installing the case.

Firmware

QMK PR: qmk/qmk_firmware#26212 (adds keyboards/mithril/rev1/).

• Bootloader: Caterina
• Layout macro: LAYOUT_ortho_4x6_3
• Matrix: 5 rows × 7 cols per half, COL2ROW
• USB: VID 0x8371, PID 0x4D52
• RGB: WS2812 driver, 54 LEDs (27 per half)

Pin mapping (per half, ATmega32U4):

VIA / Vial JSON: not bundled yet.

License

• Hardware (PCB, plate, case) — CC BY-SA 4.0
• Firmware / config — MIT (in the QMK fork)

Credits

Designed by @sanfeps. Inspired by foostan/crkbd and the ZSA Voyager, among other column-staggered ergo splits.