Keychron Multiboot Fix

Keychron.md

This also should applies to other keyboard that has this issue.

1. Remove all paired device from both macOS and Windows.
2. Factory reset the keyboard fn1 + J + Z
3. Boot into Windows and pair the keyboard fn1 + Q
4. Boot into macOS
5. Factory reset the keyboard fn1 + J + Z
6. Pair the keyboard in macOS fn1 + Q
7. Once paired, run the following commad sudo defaults read /private/var/root/Library/Preferences/com.apple.Bluetoothd.plist LinkKeys. Enter your macOS login password when asked

You will get the output similar to this

{
    "a4-5e-60-e1-4a-d8" =     {
        "dc-2c-26-dc-25-1f" = {length = 16, bytes = 0x8a428b934874c684c78da8d6350d5e65};
    };
}

• a4-5e-60-e1-4a-d8 is your Bluetooth MAC address.
• dc-2c-26-dc-25-1f is your Keychron MAC address.
• 0x8a428b934874c684c78da8d6350d5e65 is your paired link key (Security Mode 3)

0x8a428b934874c684c78da8d6350d5e65 is in Big Endian, it need to be converted to Little Endian, use this online converter

If done coorrectly, it will look like this 655E0D35D6A88DC784C67448938B428A

Now turn off your Keychron and boot into Windows. In windows, open Registry Editor Win + R and type regedit. Navigate to your BT MAC, Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\BTHPORT\Parameters\Keys\YOUR_BT_MAC. In there, you should be able to find MAC address of your keyboard,you will have to export it File -> Export, save it on your desktop with whatever name that you like.

Open the exported registry in text editor it should look something like this

Now take the converted link key and seperate it into individual byte like this. 65,5E,0D,35,D6,A8,8D,C7,84,C6,74,48,93,8B,42,8A and replace it in the registery like so and save the file.

Until this point, your keybaord should remain off.

Now double click on the registry, when asked, click Yes like so

Double check in the Registry Editor whether the link key is updated or not. Now reboot back into Windows, now you can turn on your keyboard, initial sync will take few second. If you follow this correctly, you should be able to use your Keychron seemlessly with Windows and macOS