Enable - Cambridge Silicon Radio, Ltd Bluetooth Dongle (HCI mode)

text.sh

$ lsusb
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 040: ID 0a5c:21e8 Broadcom Corp. BCM20702A0 Bluetooth 4.0
Bus 001 Device 002: ID 05e3:0608 Genesys Logic, Inc. Hub
Bus 001 Device 044: ID 0a12:0001 Cambridge Silicon Radio, Ltd Bluetooth Dongle (HCI mode)
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

# get the pre-compiled driver
$ wget https://github.com/Realtek-OpenSource/android_hardware_realtek/raw/rtk1395/bt/rtkbt/Firmware/BT/rtl8761b_fw

$ sudo cp rtl8761b_fw /lib/firmware/rtl_bt/rtl8761b_fw.bin

# unplug and replug the device back in

# check dmesg

[Wed Jan 27 21:16:23 2021] usb 1-1: new full-speed USB device number 44 using xhci_hcd
[Wed Jan 27 21:16:23 2021] usb 1-1: New USB device found, idVendor=0a12, idProduct=0001, bcdDevice=88.91
[Wed Jan 27 21:16:23 2021] usb 1-1: New USB device strings: Mfr=0, Product=2, SerialNumber=0
[Wed Jan 27 21:16:23 2021] usb 1-1: Product: USB1.1-A
[Wed Jan 27 21:16:23 2021] Bluetooth: hci1: CSR: Unbranded CSR clone detected; adding workarounds...

# check config

$ hciconfig 
hci1:	Type: Primary  Bus: USB
	BD Address: 00:1A:7D:DA:71:11  ACL MTU: 679:9  SCO MTU: 48:16
	DOWN 
	RX bytes:642 acl:0 sco:0 events:41 errors:0
	TX bytes:2130 acl:0 sco:0 commands:41 errors:0

# check rfkill

$ sudo rfkill
 ID TYPE      DEVICE      SOFT      HARD
  1 wlan      phy0   unblocked unblocked
186 bluetooth hci0   unblocked unblocked
189 bluetooth hci1     blocked unblocked

# unblock

$ sudo rfkill unblock 189

# check

$ sudo rfkill
 ID TYPE      DEVICE      SOFT      HARD
  1 wlan      phy0   unblocked unblocked
186 bluetooth hci0   unblocked unblocked
189 bluetooth hci1   unblocked unblocked

# do a scan

$ sudo hcitool -i hci1 lescan
LE Scan ...
71:5F:E7:16:56:22 (unknown)
71:5F:E7:16:56:22 (unknown)