Unicorne

unicorne

A unibody Corne: both halves of the Corne v3 key layout on one PCB, each half rotated 16°, with an Azoteq TPS43 trackpad in the middle (it sits on the case, over the nice!nano) and a nice!nano v2 at the top.

Status: layout fixed, schematic done, MX and Choc boards fully routed (DRC: 0 unconnected, 0 copper violations).

Design

• 42 keys (3×6 + 3 thumbs per half), outer pinky columns break off for a 36-key board

• Key spacing, stagger, thumb cluster and LED positions copied from crkbd v3-final (19.0 mm pitch)

• Two board versions with the same placement: Kailh MX hotswap, and Kailh Choc hotswap (fits Choc V1 and V2)

• nice!nano v2 on the top side, components up, USB on the top edge; the edge is notched for the mid-mount USB-C, whose shell drops below the nano's underside

• TPS43 trackpad wired to six bare pads (no FPC, to keep it thin). It sits on the case above the board, so it may cover the nice!nano; its position is the one that brings the halves closest together (higher and it meets the inner columns' top keycaps, lower and the thumb keycaps). It is drawn on F.Fab and User.Drawings only, with no 3D model on the board

• Optional LEDs: 12 SK6812MINI underglow + 42 SK6812MINI-E per key, on their own MOSFET-switched supply. A solder jumper picks the source: the nice!nano's 3.3 V VCC (up to its 1 A regulator), or an external supply up to 5 V on the LED IN pads for full brightness. Never the battery.

• MSK-12C02 battery cut-off switch, through-hole battery pads

• Exposed pads: expansion header (3V3, GND, UART, I2C) and GPIO header (P0.24, P1.00, P0.11)

• Pro Micro mode: a Pro Micro-footprint controller without the nice!nano's three inner pins (P1.01, P1.02, P1.07) works with three solder jumpers bridged, which move those nets to outer pins that aren't the Pro Micro I2C pair:

  Jumper	Net (nice!nano pin)	Bridged to	That pin's other use, lost in this mode
  JP4	COL5 (P1.01)	P0.24	free GPIO / sensor MISO
  JP5	COL6 (P1.02)	P0.11	free GPIO / sensor CS
  JP6	ROW5 (P1.07)	P0.08	UART RX

  I2C (SDA/SCL), the trackpad's RDY, LED data (P0.06) and LED power (P1.00) keep working. Leave all three open with a nice!nano, or two controller pins drive one net. In firmware, point COL5, COL6 and ROW5 at the bridged pins.

The full pin plan and parts list are in mock/index.html (open it in a browser).

Parts list

Everything is hand-soldered. Quantities are for one board; the 36-key build needs 36 of each per-key part.

On the PCB

Optional LEDs

Leave all of these off for a board without lighting.

Off the PCB

Ordering (JLCPCB)

Upload export/jlcpcb/unicorne-mx-jlcpcb.zip or unicorne-choc-jlcpcb.zip (gerbers plus Excellon drills, plated and non-plated separate). Settings:

No assembly: every part is hand-soldered (see the parts list). Regenerate the zips with python3 tools/export_gerbers.py after any board change; it refuses to export a board that fails DRC.

3D

export/unicorne-mx.step and export/unicorne-choc.step are the full boards with parts, for designing a case (rendered previews next to them). Sockets and the Cherry MX and Choc V1 switches are real models; the nice!nano, TPS43, SK6812MINI and MSK-12C02 are size-accurate placeholder boxes from tools/step_box.py. Regenerate with python3 tools/export_3d.py after any board change.

Switch plates

The top plate, as a starting point for a case. Plates are solid (no break lines), so there is one per switch type and size:

Each has the same outline, coordinates and M2 holes as its PCB, a 44.3 x 41.3 mm opening for the TPS43, an opening over the nice!nano that runs out through the top edge (so the USB stays reachable) and a window over the reset switch, both with 0.5 mm clearance. The 36-key plates are cut evenly on both sides where the PCB snaps off its outer columns (on Choc, whose break lines differ by side, at their average), with rounded corners. export/plate/ holds, per plate:

• *-jlcpcb.zip: order as an FR4 board, no copper (the copper layers are included empty so JLCPCB's viewer reads the stack); set the thickness above.
• *.dxf: Edge.Cuts outline in mm, for laser-cut aluminium, steel or acrylic.
• *.step: the plate solid, in the same coordinates as the board STEP files.
• *.png: a render.

Files

Regenerating

# Geometry (needs KiCad's bundled Python for the outline)
/Applications/KiCad/KiCad.app/Contents/Frameworks/Python.framework/Versions/Current/bin/python3 tools/layout.py

# Schematic (overwrites the three .kicad_sch files)
python3 tools/gen_schematic.py

# PCBs (overwrite the board files; placement, outline, holes, silkscreen, no tracks)
# then route them; both steps throw away any hand routing
/Applications/KiCad/KiCad.app/Contents/Frameworks/Python.framework/Versions/Current/bin/python3 tools/gen_pcb.py mx
/Applications/KiCad/KiCad.app/Contents/Frameworks/Python.framework/Versions/Current/bin/python3 tools/gen_pcb.py choc
/Applications/KiCad/KiCad.app/Contents/Frameworks/Python.framework/Versions/Current/bin/python3 tools/krt_route.py mx
/Applications/KiCad/KiCad.app/Contents/Frameworks/Python.framework/Versions/Current/bin/python3 tools/krt_route.py choc
# On MX the plane repair reaches U2 pad 3 (GND, boxed in by LED_DIN) only through a via in the
# pad, which krt_route.py removes, leaving that pad unconnected. The committed board joins it by
# hand: a via at (160.65, 137.45) between pads 3 and 4, a back-layer track to pad 3 and a
# front-layer track to the GND copper.

# LED map for firmware (chain index -> LED, switch, matrix position)
/Applications/KiCad/KiCad.app/Contents/Frameworks/Python.framework/Versions/Current/bin/python3 tools/led_map.py

# Wavy silkscreen on both PCBs (redraws only the waves, leaves the routing alone)
/Applications/KiCad/KiCad.app/Contents/Frameworks/Python.framework/Versions/Current/bin/python3 tools/waves.py

# Switch plates and their exports (reads hole positions from the routed boards)
/Applications/KiCad/KiCad.app/Contents/Frameworks/Python.framework/Versions/Current/bin/python3 tools/gen_plate.py

Licenses

The nice!nano footprint comes from bstiq/nice-nano-kicad under GPLv3; the hotswap footprints from keyswitch-kicad-library under MIT.