4.2 DC22 Tri-mode (work in progress)

22-key tri-mode numeric keypad · USB / Bluetooth / 2.4G

Work in progress

The wired (USB) channel is verified on real hardware: enumeration, typing, VIA remapping and saving to flash all work.

The following are not yet verified on hardware, and specs / keymap may still change: Bluetooth (BLE), 2.4G, low power, audio-reactive lighting.

1. Basic specs

Spec	Value	Notes
Keys	22	Direct GPIO, no matrix, no diodes
Layers	4	0 base / 1 FN / 2 lighting (FN2) / 3 user (empty from factory)
Connection	Tri-mode: USB wired / Bluetooth BLE / 2.4G	Bluetooth & 2.4G work in progress
MCU	CH582M (RISC-V4A, 448K Flash / 32K RAM)	In-house firmware (not QMK / ZMK)
Port	Type-C	USB2 path
C2C	Supported
Scan period	1 ms	5 ms debounce
Polling rate		TBD
Latency		TBD
N-Key rollover	Supported	NKRO bitmap report; FN + 7 toggles NKRO / 6KRO
Full keys customizable	Supported	VIA online remap, USB channel only
Lighting	22 per-switch RGB LEDs, bottom	49 effects; audio-reactive needs a PC tool pushing the spectrum
Battery	Built-in Li-ion, Type-C charging	Battery measurement not implemented; reports a fixed 100% over BLE
Sleep timeout		TBD
Kit size / weight		TBD
Firmware platform	In-house CH582 firmware	Not QMK / ZMK
Source code open	WIP	Repo is being cleaned up, not public yet

2. Shortcuts

Factory defaults. All of them can be changed in VIA (see section 6); changes persist across power loss.

2.1 Base layer

Standard numpad: 0~9, ., /, *, -, +, Enter, NumLock, Home, End, PgUp, PgDn, plus one FN key.

2.2 FN layer (hold FN)

Shortcut	Keycode (VIA)	Function	Notes
FN + 1	Mode BT1	Switch to Bluetooth profile 1	Broadcast name czm_dc22_ble1; LED blinks blue, solid once connected
FN + 2	Mode BT2	Switch to Bluetooth profile 2	Broadcast name czm_dc22_ble2
FN + 3	Mode BT3	Switch to Bluetooth profile 3	Broadcast name czm_dc22_ble3
FN + 4	Mode USB	Back to USB wired	LED under P4 stays green for 3 s
FN + 5	Mode 2G4	Switch to 2.4G	Work in progress; LED under P5 stays purple for 3 s
FN + 8	BT Next	Next Bluetooth profile	Equivalent to FN + 1/2/3, cycles through
FN + 6	BT Pair	Bluetooth re-pair	Advertises for 30 s; any host can pair during that window
FN + 7	NKRO	Toggle NKRO / 6KRO	Saved to flash
FN + 0	Battery	Report battery level	Works over Bluetooth; not implemented over USB
FN + .	Bootldr	Enter bootloader (flashing)
FN + PgUp	Reset	Restore the factory keymap
FN + /	Volume -	Media key	Not available over Bluetooth / 2.4G
FN + *	Volume +	Media key	Not available over Bluetooth / 2.4G
FN + -	Mute	Media key	Not available over Bluetooth / 2.4G
FN + +	Play / pause	Media key	Not available over Bluetooth / 2.4G
FN + Enter	Calculator	Media key	Not available over Bluetooth / 2.4G
FN + Home	Previous track	Media key	Not available over Bluetooth / 2.4G
FN + End	Next track	Media key	Not available over Bluetooth / 2.4G

2.3 FN2 lighting layer (long-press P/)

A short press of P/ is divide; holding it for about 0.2 s enters the FN2 layer. The lighting keys deliberately avoid the handiest FN-layer positions P1–P4 — those are reserved for mode switching.

Shortcut	Keycode (VIA)	Function
Long-press P/ then 1	LED +	Brightness +
Long-press P/ then 2	LED -	Brightness -
Long-press P/ then 3	LED Tog	Lighting on / off
Long-press P/ then 4	LED Next	Next effect
Long-press P/ then 0	Battery	Report battery level
Long-press P/ then .	Bootldr	Enter bootloader

3. USB / Bluetooth / 2.4G

In one sentence: cable plugged in means USB; unplug and it returns to the last Bluetooth profile you used; once you switch manually it won't be pulled back.

3.1 Automatic switching

The firmware switches on the VBUS edge — you don't need to press FN + 4 in normal use:

Event	Behavior
Plug in	Switches back to USB immediately and remembers the mode
Unplug while on USB	Returns to the last used Bluetooth profile; profile 1 if Bluetooth was never used
Unplug while not on USB (2.4G)	Stays put

• You can switch to Bluetooth with the cable plugged in: after pressing FN + 1/2/3 it won't be pulled back to USB.
• Powering up with the cable plugged in = USB first: you never boot into Bluetooth and have to press FN + 4.
• VBUS has 20 ms debounce, so plug wobble won't trigger it.

3.2 What happens when switching

• USB and Bluetooth are never connected at the same time. Switching to Bluetooth while plugged in makes the USB keyboard disappear from the host (the keyboard detaches from the bus); switching back re-enumerates.
• Before switching, the keyboard releases every held key, so you never end up with a stuck repeating key.
• VIA only works on the USB channel — over Bluetooth / 2.4G the device doesn't exist on the host. Press FN + 4 to return to USB before remapping.

3.3 Status LED

There is no dedicated status LED; the per-switch LED under the relevant key is used instead (deliberately dimmed, indication only):

Event	LED	Pattern
Switched to Bluetooth / not yet connected	Under the matching number key (FN+1 → the 1 key)	Blinks blue until connected (no timeout)
Bluetooth connected	Same	Solid for 1.5 s, then back to the effect
Bluetooth dropped	Same	Back to blinking blue
Back to USB	Under the 4 key	Solid green for 3 s
Switched to 2.4G	Under the 5 key	Solid purple for 3 s

"Connected" gets its own solid blink on purpose: "stopped blinking" and "the indicator gave up" look identical, so users can't tell from a non-blinking LED whether they are actually connected.

4. Bluetooth

4.1 Three pairing slots

The keyboard remembers 3 hosts, one per slot. A slot is not "the Nth device you paired" — the three slots are independent:

• Switching to a slot broadcasts with that slot's name: czm_dc22_ble1 / czm_dc22_ble2 / czm_dc22_ble3;
• Bonding info is stored in the keyboard (survives power loss), so reconnecting the same computer needs no re-pairing — switching to that slot reconnects automatically;
• Whichever slot is active shows as connected on that host; the other two show as disconnected.

⚠ Work in progress: switching slots only changes the broadcast name — directed reconnect to a specific host isn't implemented yet, so any already-paired host may connect. Per-slot directed reconnect waits on the "slot ↔ host address" table.

4.2 Pairing a new host

1. Hold FN and press 1 / 2 / 3 to pick a slot — the LED under that number key starts blinking blue;
2. In your computer's / phone's Bluetooth settings, find czm_dc22_ble1 (or 2 / 3) and connect;
3. The LED goes solid for 1.5 s and returns to the effect — connected, ready to type.

4.3 Re-pairing

FN + 6: the keyboard advertises "anyone can connect" for 30 seconds. Useful for a new computer or when bonding info got messy. If no host connects within 30 s, advertising stops (saves power and keeps the keyboard out of other people's Bluetooth lists).

4.4 Known limitations

• Media keys don't work: volume / playback / calculator do nothing over Bluetooth. The stack's keyboard service has no consumer report; adding it means changing the HID report descriptor, scheduled after the basic channels are verified on hardware.
• Idle disconnect: Bluetooth disconnects after 60 seconds of idle to save power; any key press reconnects.
• Never verified on hardware: everything above comes from the firmware code; the first hardware run may still need changes.

5. 2.4G wireless

Work in progress. FN + 5 currently only switches the channel and lights the purple LED once — it produces no input; RF transmit and the USB receiver aren't done.

6. Remap with VIA

1. Connect the keyboard to the computer with a Type-C cable and press FN + 4 to make sure you're on the USB channel (VIA only works over USB);
2. Open usevia.app (or via.micah.vip);
3. Load this keyboard's JSON, then remap.

Keymaps are stored in the keyboard — they survive power loss and moving to another computer. FN + PgUp restores the factory keymap.

Besides regular keycodes, the VIA picker also offers this keyboard's own functions (VIA names):

VIA name	Function
Mode USB	Switch to USB wired
Mode BT1 / BT2 / BT3	Switch to Bluetooth profile 1 / 2 / 3
BT Next	Next Bluetooth profile
BT Pair	Bluetooth re-pair
Mode 2G4	Switch to 2.4G (work in progress)
NKRO	Toggle NKRO / 6KRO
Battery	Report battery level
LED Tog / LED + / LED - / LED Next	Lighting on-off / brightness up-down / next effect
Bootldr	Enter bootloader
Reset	Restore the factory keymap

7. Lighting

• 22 per-switch LEDs, 49 effects; brightness / effect / speed / hue / saturation are all saved across power loss;
• Effects are switched in the FN2 layer (long-press P/);
• Audio reactive (listed as Audio Reactive in the effect list) is driven by a spectrum pushed from the PC — there is no microphone on the keyboard, so a PC tool has to run once; USB channel only.

8. Firmware

Work in progress: the firmware is being cleaned up and there is no public download yet. For firmware or usage questions, join the QQ group 677654482 (files are shared there).

For common flashing and remapping issues, see the FAQ.

9. Known limitations

Item	Status
USB wired	✅ Verified on real hardware (enumeration / typing / VIA / saving)
Bluetooth BLE	⚠ Code complete, not verified on hardware; media keys unusable; no per-slot directed reconnect
2.4G	⚠ Skeleton; RF transmit and receiver missing
Low power / sleep	❌ Not implemented
Battery measurement	❌ Not implemented (reports a fixed 100% over BLE)
Audio reactive	⚠ Needs a PC tool, not verified on hardware
VIA remap	✅ Works over USB; not over Bluetooth / 2.4G