What PolyKybd Adds to QMK
PolyKybd’s firmware is a QMK fork. Layers, tap-hold, combos, unicode input and the rest of the QMK feature set work as documented upstream. This section covers what the fork adds that stock QMK does not have. Most of it exists because the keyboard has 72 displays and 8 MB of flash to look after, and some of it is useful to any RP2040 keyboard.
Pages in this section
Section titled “Pages in this section”| Feature | What stock QMK does | What PolyKybd does |
|---|---|---|
| Firmware update over HID | Update through the bootloader drive, one half at a time | The host streams the image to the running keyboard; both halves stage it, check it, install it and reboot together |
| Firmware signing | Installs whatever is flashed | Checks an Ed25519 signature before installing; your own builds need a keypress on the keyboard |
| Crash handler & watchdog | A fault or hang leaves the board dead until replugged | Records the fault or hang, reboots, and reports it on the next boot |
| The second core | Second core idle | Decompresses overlay images, renders the screensaver (from firmware 1.5.0) and runs DOOM |
| 200 MHz system clock | Default clock | 200 MHz with the core voltage raised to match |
| Split link sync | Syncs matrix, layers and a few feature states | CRC-checked transactions for display state, images, keymap edits, firmware and font packs |
| Main-loop profiler | None | Measures each main-loop pass and where the time goes, readable over HID |
| Community modules | Upstream modules only | Seven reusable modules: core1 launcher, CRC32, RLE, PRC image decoder, Monocypher, OS action chords, LTR-559 driver |
| PRC image decoder | None | Decodes keycap icons coded against a fixed probability table, at about 28 bytes per icon; ships a tool to train a table for your own images |
Covered elsewhere in these docs
Section titled “Covered elsewhere in these docs”- Per-keycap displays and overlays. Each key has its own 72×40 OLED, and the host sends images for the application in focus. See Context-Aware Overlays and Display Graphics & Fonts.
- Font packs in external flash. Glyph bundles live in the 8 MB flash and are updated separately from the firmware. See Font Packs & Resources.
- A version-gated HID command set. More than 40 commands over raw HID, each enabled only on firmware that supports it. The byte layout of every command and the RLE and PRC image encodings are in HID Protocol.
- Keyboard languages and glyph scripts. The legends follow the OS layout, for 160 layouts. See Languages & Unicode Input and Glyph Scripts.
- Trackpad gestures. Decided by PolyKybd’s own firmware rather than the trackpad chip. See Trackpad.
- Ambient-light brightness. An optional LTR-559 sensor sets the display brightness. See Display Brightness.
- Hardware-in-the-loop testing. Firmware pull requests are built, flashed onto real keyboards and tested. See Test Rig & CI.
Smaller additions without their own page
Section titled “Smaller additions without their own page”- Handedness stored in its own flash sector. Stock QMK’s
EE_HANDSkeeps left/right in the emulated EEPROM. QMK’s wear levelling wipes that whole store when it finds it damaged, and a zeroed byte reads as a valid “right”, so a half could boot as the wrong side. PolyKybd writes handedness to a dedicated 4 KB sector that only changes when the side changes. - Board state the host can see within a second. The firmware keeps a counter that goes up whenever a setting changes on the keyboard itself. It rides in the identity reply the host already polls every second, so the host notices with no extra traffic.