Driver ((hot)) - Bt-bu1

For persistent issues, download (BCM20702_fw_loader.exe). Run it as administrator, and it will automatically flash the firmware to the device.

Many clone devices use a generic STMicro or Silabs MCU running custom firmware that emulates a Bluetooth controller.

If you have a clone or custom board with the BT-BU1, you can write a out-of-tree kernel module.

If the device is not recognized or is listed as an "Unknown Device" in the Device Manager, you can attempt the following steps to resolve connectivity issues: Update Bluetooth drivers in Windows - Microsoft Support

If the adapter is still not working, try these common fixes:

Run usbmon or Wireshark with USBPcap to see where the device sends its HCI events.

For the smoothest experience pick a BT-BU1 variant with a well-known chipset (Realtek or Broadcom) and confirm vendor driver/firmware support for your OS before purchase; for Linux, prefer devices known to work with the kernel btusb driver and readily available firmware.