Corne¶

42-key split keyboard on nice!nano v2 controllers with 128x32 OLEDs, built with ZMK pinned to v0.3.

Board¶

      ┌─────── OLED 128x32 ───────┐      ┌─────── OLED 128x32 ───────┐
      │ cat·bt·batt·mods·dots·key │      │      cat·batt·link        │
      └───────────────────────────┘      └───────────────────────────┘
      ┌───┬───┬───┬───┬───┬───┐          ┌───┬───┬───┬───┬───┬───┐
      │   │   │   │   │   │   │          │   │   │   │   │   │   │
      │   │   │   │   │   │   │          │   │   │   │   │   │   │
      │   │   │   │   │   │   │          │   │   │   │   │   │   │
      └───┴───┴───┴───┴───┴───┘          └───┴───┴───┴───┴───┴───┘
        ┌───┬───┬───┐                      ┌───┬───┬───┐
        │   │   │   │                      │   │   │   │
        └───┴───┴───┘                      └───┴───┴───┘
      nice!nano v2                        nice!nano v2
       (central)                          (peripheral)

3x6 keys + 3-key thumb arc per half; columns run straight - Tab sits directly above the esc/hyper key. The stagger is vertical only: outer columns sit ~0.3u lower than the middle (like finger lengths), never sideways
Each half runs its own nice!nano v2 with a LiPo cell - the halves talk to each other over BLE (the TRRS jack is unused in this wireless build), and the left half (central) resolves all keymap behavior
Double-tap the reset button on a half to expose the UF2 bootloader (NICENANO volume) - copying an uf2 onto it flashes that half
Only the central (left) firmware changes with keymap edits; the peripheral build is keymap-independent

Structure¶

File	Purpose
`keyboards/corne/west.yml`	West manifest, pins ZMK `v0.3` + the OLED module
`keyboards/corne/corne.keymap`	Keymap - layers, behaviors, combos
`keyboards/corne/corne.conf`	Board config - OLED, sleep, BLE tuning
`keyboards/corne/patches/`	OLED module patches, applied at build time (details)

Layout¶

X→MOD = tap sends the letter, hold acts as the modifier (cross-hand holds only). · = transparent - falls through to the layer below, so home-row mods work through layers.

Base¶

┌─────┬─────┬─────┬─────┬─────┬─────┐   ┌─────┬─────┬─────┬─────┬─────┬─────┐
│ TAB │  Q  │  W  │  E  │  R  │  T  │   │  Y  │  U  │  I  │  O  │  P  │ BSPC│
├─────┼─────┼─────┼─────┼─────┼─────┤   ├─────┼─────┼─────┼─────┼─────┼─────┤
│⎋/HYP│A→SFT│S→CTL│D→ALT│F→GUI│  G  │   │  H  │J→GUI│K→ALT│L→CTL│;→SFT│  '  │
├─────┼─────┼─────┼─────┼─────┼─────┤   ├─────┼─────┼─────┼─────┼─────┼─────┤
│SHFT │  Z  │  X  │  C  │  V  │  B  │   │  N  │  M  │  ,  │  .  │  /  │ ESC │
└─────┴─────┴─────┴─────┴─────┴─────┘   └─────┴─────┴─────┴─────┴─────┴─────┘
               ┌─────┬─────┬─────┐   ┌─────┬─────┬─────┐
               │ GUI │ LWR │SPC/H│   │ENT/H│ RSE │A/GUI│
               └─────┴─────┴─────┘   └─────┴─────┴─────┘

⎋/HYP = tap sends Esc, hold acts as Hyper (Cmd+Alt+Ctrl) - the capslock pattern.

The left outer thumb is a plain Gui - always Cmd, no hold-tap latency.

SPC/H and ENT/H = tap sends Space / Return, hold acts as Hyper. space, space<hold> auto-repeats space, enter, enter<hold> auto-repeats enter; a lone hold past the tapping term fires Hyper (Cmd+Alt+Ctrl) for app shortcuts and window management. A/GUI mirrors it on the right: tap sends Alt, hold acts as Gui.

Double-tap-hold: tap a hold-tap key, then press it again within 250 ms (quick-tap-ms) and hold - the tap fires immediately and auto-repeats. j, j<hold> gives a held j (continuous scroll in the browser) instead of the home-row mod.

┌─────┬─────┬─────┬─────┬─────┬─────┐   ┌─────┬─────┬─────┬─────┬─────┬─────┐
│ TAB │  1  │  2  │  3  │  4  │  5  │   │  6  │  7  │  8  │  9  │  0  │ BSPC│
├─────┼─────┼─────┼─────┼─────┼─────┤   ├─────┼─────┼─────┼─────┼─────┼─────┤
│BTCLR│ BT1 │ BT2 │ BT3 │ BT4 │ BT5 │   │  ←  │  ↓  │  ↑  │  →  │ TAB │  ·  │
├─────┼─────┼─────┼─────┼─────┼─────┤   ├─────┼─────┼─────┼─────┼─────┼─────┤
│SHFT │  ·  │  ·  │  ·  │  ·  │  ·  │   │  ·  │  ·  │  ·  │  ·  │  ·  │  ·  │
└─────┴─────┴─────┴─────┴─────┴─────┘   └─────┴─────┴─────┴─────┴─────┴─────┘
               ┌─────┬─────┬─────┐   ┌─────┬─────┬─────┐
               │ GUI │  ·  │ SPC │   │ ENT │  ·  │ ALT │
               └─────┴─────┴─────┘   └─────┴─────┴─────┘

Raise (hold RSE) - symbols¶

┌─────┬─────┬─────┬─────┬─────┬─────┐   ┌─────┬─────┬─────┬─────┬─────┬─────┐
│ TAB │  !  │  @  │  #  │  $  │  %  │   │  ^  │  &  │  *  │  (  │  )  │ BSPC│
├─────┼─────┼─────┼─────┼─────┼─────┤   ├─────┼─────┼─────┼─────┼─────┼─────┤
│CTRL │  ·  │  ·  │  ·  │  ·  │  ·  │   │  -  │  =  │  [  │  ]  │  \  │  `  │
├─────┼─────┼─────┼─────┼─────┼─────┤   ├─────┼─────┼─────┼─────┼─────┼─────┤
│SHFT │  ·  │  ·  │  ·  │  ·  │  ·  │   │  _  │  +  │  {  │  }  │  |  │  ~  │
└─────┴─────┴─────┴─────┴─────┴─────┘   └─────┴─────┴─────┴─────┴─────┴─────┘
               ┌─────┬─────┬─────┐   ┌─────┬─────┬─────┐
               │ GUI │  ·  │ SPC │   │ ENT │  ·  │ ALT │
               └─────┴─────┴─────┘   └─────┴─────┴─────┘

OLED¶

Both halves carry 128x32 OLEDs driven by zmk-nice-oled, fetched via west at build time. Left (central) screen: bongo cat whose speed follows typing, BT profile number, battery, modifier symbols, layer dots + the glyph of the last pressed key. Right (peripheral) screen: looping cat animation, battery, connection icon - layer/BT/mod state never crosses the split link, so a peripheral can only show what it knows locally.

The three dots are the layer indicator (centered in the visible strip - the 68x160 module canvas maps onto the 128x32 display through a 90° rotation, so only a 32px slice of canvas X is on-screen); the number by the BT icon is the active Bluetooth profile; the glyph column shows the last pressed characters - shift-aware, rolling history that clears after 2s idle.

Patches¶

keyboards/corne/patches/ carries diffs against the OLED module: layer dots, bongo cat speed, pressed-key display. Plain patches = cannot work here - stdenv applies them before west fetches the module - so the flake applies them in postConfigure, after the module sources land in the build tree. A zephyrDepsHash bump that changes the patched lines upstream fails the build loudly at git apply and the patch needs a refresh.

Build¶

nix build .#corne           # result/zmk_{left,right}.uf2
nix run .#flash-corne        # interactive flash (Linux)
nix run .#update             # bump west deps, prints the new zephyrDepsHash

ZMK stays pinned by west.yml (v0.3); the west deps are locked by zephyrDepsHash in keyboards.nix
zmk-nix rides nixpkgs stable - Zephyr 3.5's build scripts predate python 3.14's pkg_resources removal in unstable's setuptools
Bumping ZMK: edit west.yml, run nix build .#corne, paste the new got: hash from the mismatch error into keyboards.nix

Flash (nice!nano v2)¶

Double-tap the reset button - the half mounts as a USB drive (NICENANO)
Copy the matching .uf2 from result/ (local build) or the CI firmware artifact:
- left half -> zmk_left.uf2
- right half -> zmk_right.uf2
The half reboots automatically once the file is copied

The halves must run matching firmware versions to talk to each other - flash both back-to-back and expect the keyboard dead in between.

ZMK Studio¶

Both halves build with the studio-rpc-usb-uart snippet and CONFIG_ZMK_STUDIO=y, so the keymap can be tweaked live over USB with ZMK Studio without reflashing. The unlock combo is pressing TAB + Q together.

Note

Studio edits are runtime-only. Lasting changes go in keyboards/corne/corne.keymap.