Keyboard Variants

PolyKybd ships in two hardware variants. They run one firmware codebase, so a feature added to the keyboard lands on both at once.

split72 vs split42

	split72	split42
Keys	72	42
Footprint	PolyKybd full-size split	CRKBD / Corne 42-key
RGB matrix	Yes (72 LEDs)	No
Pointing device	Cirque trackpad	No
Status OLED	128×64	128×32
Per-keycap OLEDs	72×40 px monochrome	72×40 px monochrome
Build target	polykybd/split72	polykybd/split42

A split72 half — 36 keys, the 128×64 status OLED (here naming the active layout, Colemak DH), and a rotary encoder fitted in the expansion slot:

The split42 board, which carries 21 keys per half and no RGB or pointing device (KiCad render of the PolyCorne Split42 rev1.0 left side):

Note

split42 was renamed from corne42 in 2026-06. Same hardware, PID and LAYOUT_crkbd; the old corne42 paths are gone. If you see corne42 referenced anywhere, read it as split42.

One shared keymap

All behaviour lives in the keyboard-level poly_keymap.c (compiled for both variants via rules.mk’s SRC): rendering, HID/overlay handling, language selection, idle/suspend, split-sync glue, the firmware-update state machine, and the QMK *_user / *_kb callbacks.

Each variant’s default keymap file is data only — it holds the keymaps[] array, the encoder_map[], and (on RGB variants) the LED config:

keyboards/polykybd/
├── poly_keymap.c                      ← shared logic, both variants
├── split72/
│   └── keymaps/default/keymap.c       ← split72 data only
└── split42/
    └── keymaps/default/keymap.c       ← split42 data only

Variant differences resolve at compile time: polykybd.h includes the active variant header (selected by QMK’s -DKEYBOARD_polykybd_<variant>), and RGB_MATRIX_ENABLE / POINTING_DEVICE_ENABLE guard the RGB and trackpad code paths.

Tip

Because the logic is shared, the two keyboards can’t silently drift apart in language support or features. When customising, edit the per-variant keymap.c for data, and poly_keymap.c for behaviour.

Building a specific variant

The build target selects the variant:

qmk compile -kb polykybd/split72 -km default
# or
qmk compile -kb polykybd/split42 -km default

See Firmware Development for the full toolchain setup.