Bluetooth Passthrough

Since, Dolphin has the ability to passthrough a Bluetooth adapter for emulated Wii software. This gives emulated Wii software full control of a Bluetooth adapter, which, provided a decent, working adapter, notably allows pairing Wii Remotes to Dolphin, third-party Wii Remote support, working Wii Remote audio and more accurate connectivity.

Limitations

 * The functionality and quality of the connections heavily depend on the quality of the adapter.
 * Even though most adapters work fine in passthrough mode, the only perfect adapter is the Wii's Bluetooth module (so far).
 * Save states can be used with some limitations.
 * Because Bluetooth Passthrough Mode skips Dolphin's emulated Bluetooth and Wii Remote code entirely, it is not possible to mix passthrough mode and emulated/real/hybrid Wii Remote. This means that netplay, TAS input, input display, etc. cannot work.

Linux
A udev rule has to be installed so Dolphin can use a Bluetooth adapter without having to get root privileges.

SUBSYSTEM=="usb", ATTRS{idVendor}=="YOURVID", ATTRS{idProduct}=="YOURPID", TAG+="uaccess"

Dolphin should be able to automatically unload the USB Bluetooth kernel module (assuming you have permission to; you typically need to be in the  group). If not, unload it with.

Windows
Download and open Zadig as Administrator, then:
 * 1) In the "Options" menu in Zadig, make sure "List All Devices" is enabled.
 * 2) Look through the devices for the device to passthrough.
 * 3) On the right column, select "libusbk" then click "Replace Driver". Select "Yes" to modify the system driver.

If you run into problems after doing this, such as an "LIBUSB_ERROR_NOT_FOUND" error when trying to use the adapter with Dolphin, downloading and installing the latest x64 usbdk driver could help.

macOS
There is currently no way to use this feature on versions newer than 10.9, because Apple removed the ability to unload the Bluetooth kernel module.

A potential solution would be to force the OS to ignore the adapter with a codeless .kext, but this hasn't been tried yet.

Android
This feature is not supported on Android.

Using passthrough mode in Dolphin
In Dolphin, open the Controller Configuration dialog, then select the "Passthrough a Bluetooth adapter" option in the Wii Remotes section.

While a game is running:
 * Wii Remotes can be synced and paired to Dolphin by using the Sync button.
 * All saved Wii Remote pairings can be reset by using the Reset button. This will also disconnect all currently connected Wii Remotes.

Sync button hotkey
It is possible to use the "Press Sync Button" hotkey as an alternative to the buttons in the controller configuration dialog.

You will need to map "Press Sync Button" to a key or combination of keys. This can be done within Dolphin by left clicking on the "Hotkey Settings" tab under "Options" to bring up the appropriate configuration menu. You must then left click on the "Wii and Wii Remote" tab and left click on the box for "Press Sync Button" to map this hotkey.

"Press Sync Button" is designed to work just like the Wii's red sync button:
 * Pressing the hotkey will trigger a sync.
 * Holding the hotkey for 10 seconds will clear all saved pairings.

Forcing a specific adapter
If you need to use a specific adapter, instead of using the first Bluetooth adapter that is found, you can force Dolphin to use it by editing Dolphin's configuration file (Config/Dolphin.ini). In the BluetoothPassthrough section, set "VID" and "PID" to your adapter's vendor ID and product ID. These values should be converted from hex to decimal, for example a VID of "057E" should be inputted as "1406".

"Failed to open Bluetooth device: LIBUSB_ERROR_ACCESS"
This error means that Dolphin doesn't have permission to use the Bluetooth adapter.

If on Linux, make sure the udev rule is set up correctly.

"Failed to open Bluetooth device: LIBUSB_ERROR_NOT_SUPPORTED"
On Windows, this typically means that the libusb/WinUSB driver was not installed for the adapter.

"Failed to detach kernel driver for BT passthrough"
Dolphin tried to automatically unload the Bluetooth USB kernel module and failed to. Unload the module manually before starting a game to avoid this issue.

Wii Remotes do not stay paired after closing the game
This means that your adapter is likely broken and does not remember Wii Remote link keys properly. Use a different adapter to avoid this issue.

This may also happen if your SYSCONF is corrupted or if you changed to a Dolphin version which doesn't have BT passthrough. If your adapter is listed as working with pairing or if you're sure it supports pairings (by having checked the HCI command replies), you can try deleting Wii/shared2/sys/SYSCONF and Wii/btdinf.bak.

Black screen on boot
Games send a reset command to the Bluetooth adapter when they start and wait for it to be acknowledged. If you are getting a black screen for a long time (more than 10 seconds), your adapter may be stuck in a broken state and is unable to respond to any commands. Unplug the adapter and try again.

No usable adapter found
This can happen with some adapters. You'll need to force your adapter to be used.

Adapter test results

 * Unknown. Not enough information to classify.
 * Incompatible. Does not work or has significant limitations.
 * Partially compatible. Works well in most cases, but there may be some issues.
 * Fully compatible. Works well in all cases and will give the same experience as a Wii Bluetooth adapter.

Stability
 * [1] May stop working after HCI resets (stopping, resetting emulation or going back to the system menu).
 * [2] Has issues with games which send a lot of commands (including New Super Mario Bros. Wii and The Legend of Zelda: Skyward Sword before you get in game).
 * [3] Starts having lag issues after ~30 minutes. Reconnecting the Wii remote is required.
 * [4] May stop working after HCI resets on Windows, works fine on Linux and macOS.
 * [5] Randomly stop working on Windows, works fine on Linux and macOS.

Pairing
 * [6] Has issues reconnecting multiple Wiimotes.
 * [7] Limited to 1 remote.

Other
 * [8] Doesn't expose its internal Bluetooth adapter, can't be used with Bluetooth Passthrough in any capacity.