Bluetooth Keyboard and Mouse switcher

This script is based on some of many variations of bluetooth keyboard emulation in Python. I tied to get it to a usability level at which I can use it to act as a K(V)M switch replacement. Some of the feaures introcuded:

• Support multiple connected bluetooth devices and hotkeys for switching between them
• Handle mouse input emultion
• Reconnect to paired devices
• Handle any number of input devices as the emulated events source (with hot-swapping)
• Handle keyboard LEDs

Installation

Tested on Rasbperry Pi OS 10 on Rasperry Pi 3B+ and Zero W.

Install required system packages

sudo apt install git python3-dbus python3-pyudev python3-evdev

Download this repository

git clone https://github.com/nutki/bt-keyboard-switcher

Disable bluetooth input device client

As far as I can tell there is no way for the defult bluetooth daemon in Rasperry Pi OS to be input device client and server at the same time. This means the client service has to be turned off first to accept connetions.

Rasperry Pi OS 10 uses systemd to start the bluetooth service and the only way to disable the input plugin is to use a command line option. This means modifying /lib/systemd/system/bluetooth.service line:

ExecStart=/usr/lib/bluetooth/bluetoothd

to:

ExecStart=/usr/lib/bluetooth/bluetoothd --noplugin=input

And for the change to take an immediate effect:

sudo systemctl daemon-reload
sudo systemctl restart bluetooth

Disable mouse event throttling (optional)

Raspberry Pi OS throttles the mouse event rate at the HID level. This is not compatible with some mice (including Microsoft Sculpt ergonomic mouse I own) which causes mouse pointer lag. It is safe to disable it if you don't use grphical interface as this script does its own mouse movement event throttling anyway. To do so modify /boot/cmdline.txt adding the usbhid.mousepoll=0 option.

Usage

• Start the script

cd bt-keyboard-switcher
sudo ./keyboardswitcher.py

• Note this script will take over all input devices connected, so it is not possible to normally stop it if you run it from the local console. To switch to local input passthrouh press LCtrl + F12.
• Press LCtrl + Esc (on a keyboad physically connected to Raspberry Pi) this will make Raspberry Pi discoverable as "Pi Keyboard/Mouse".
• Pair any BT clients (tested with iOS, Android, Windows 10, and Ubuntu Linux)
• To switch between connected devices you can press LCtrl + F1, LCtrl + F2, etc. This will also trigger connect attempt if a previously paired device got disconnected.
• Paired device information is stored in the keyboardswitecher.ini file, which can be edited to reassign the device order or remove a paired device.