Version: V1.1.1
V1.1.1 — Optimized BLE initialization stability — increased main task stack size for reliable startup.
V1.1.0 — BLE stack rebuilt (Bluedroid → NimBLE), security upgraded to Passkey Entry (6-digit verification code, MITM protection). ⚠ If you encounter compatibility issues, please use V1.0.1 instead.
V1.0.1 — Replaced custom USB/BLE drivers with official ESP-IDF components; added Web flashing page.
V1.0.0 — Initial release. USB keyboard to BLE bridge (Bluedroid), CapsLock/NumLock LED sync, 3-slot device switching (independent MAC), hotkey switching/unpairing, LED status indicator.
Turns a wired USB keyboard into a wireless Bluetooth (BLE) keyboard using an ESP32-S3, with support for up to 3 paired hosts.
- Plug in the USB keyboard → power on → red LED (USB initializing)
- LED changes to blinking purple → board starts BLE advertising
- Search for "Loommii-KB-01" on your computer or phone and pair
- A 6-digit pairing code appears on the host screen
- Type the pairing code on your USB keyboard and press Enter
- LED turns green → pairing successful, ready to use
- To switch devices: press
Scroll Lock + 2(orScroll Lock + 3) to switch to the second/third device, search for "Loommii-KB-02" (or "-03") on that device and repeat steps 3–6
Press Esc at any time during pairing code entry to cancel pairing.
Tested by the author. Devices and systems not listed may still be compatible.
| Keyboard | Host | Result |
|---|---|---|
| Logitech K845 | Windows PC (Intel AX201 Bluetooth) | ✓ |
| Logitech K845 | Android Tablet | ✓ |
| Logitech K845 | Mac Mini M4 | ✓ |
| — | Web flashing page | ✓ |
| Item | Spec |
|---|---|
| MCU | ESP32-S3 series (author uses ESP32-S3-N16R8, approx. ¥20 online) |
- Open https://loommii.github.io/ESP32S3-USB-Keyboard-To-BLE/
- Click "Connect and flash"
- Select the serial port → wait for completion → device reboots automatically
- Wired keyboard to BLE wireless — plug-and-play USB keyboard, Bluetooth connectivity to PC/tablet/phone
- 3-host switching — pair with up to 3 hosts, switch instantly via hotkey
- Independent MAC addresses — each slot uses its own MAC, hosts see them as distinct physical keyboards
- Persistent bonding — auto-reconnects on switch, no re-pairing needed
- CapsLock / NumLock / ScrollLock LED sync — turn off NumLock on the host, the keyboard LED goes out simultaneously
- Keyboard pairing code entry — type the pairing code directly on your USB keyboard, no screen or extra buttons needed
- Hotkey switching & unpairing — Scroll Lock modifier combos, no extra buttons
| State | Color | Description |
|---|---|---|
| USB disconnected | Solid red | USB keyboard not plugged in or not ready |
| Waiting for Bluetooth | Blinking purple | USB ready, BLE advertising, waiting for host |
| Connected | Solid green | USB + BLE both connected, normal operation |
| Pairing code entry | Solid purple | Waiting for user to type the pairing code on the keyboard and press Enter |
| Switching | Solid orange | Device slot switching in progress (reboot pending) |
| Error | Solid red | USB communication error |
Scroll Lock is used as the modifier (press Scroll Lock first, then the action key):
| Hotkey | Action |
|---|---|
Scroll Lock + 1 |
Switch to Slot 1 |
Scroll Lock + 2 |
Switch to Slot 2 |
Scroll Lock + 3 |
Switch to Slot 3 |
Scroll Lock + Esc |
Unpair current device (clear bonding) |
| Slot | BLE Name |
|---|---|
| 1 | Loommii-KB-01 |
| 2 | Loommii-KB-02 |
| 3 | Loommii-KB-03 |
| Item | Details |
|---|---|
| SDK | ESP-IDF v6.0.1 |
| BLE Stack | Apache NimBLE |
| Bluetooth Version | BLE 5.0 (compatible with BLE 4.x and later) |
| Power | Powered via ESP32-S3 USB port (no external supply needed) |
| Indicator | On-board RGB LED, color indicates device state |
Copyright (C) 2026 loommii
This project is licensed under the GNU Affero General Public License v3.0 (AGPL-3.0). See the LICENSE file for the full license text.