Realtek USB Bluetooth Dongle with chip rtl8761b does not work on Linux

This post it to make Realtek Dongle with rtl8761b chipset working under any Linux districution

Symptom

Symptom-1: 

Syslog has below messages

Oct 11 11:54:37 nau20 kernel: [11338.462764] Bluetooth: hci1: RTL: loading rtl_bt/rtl8761b_fw.bin
Oct 11 11:54:37 nau20 kernel: [11338.463293] bluetooth hci1: Direct firmware load for rtl_bt/rtl8761b_fw.bin failed with error -2
Oct 11 11:54:37 nau20 kernel: [11338.463298] Bluetooth: hci1: RTL: firmware file rtl_bt/rtl8761b_fw.bin not found

Symptom-1: 

Blutooth adapter show DOWN

$ hciconfig -a
hci1: Type: Primary  Bus: USB
BD Address: 00:00:00:00:00:00  ACL MTU: 0:0  SCO MTU: 0:0
DOWN 
RX bytes:21 acl:0 sco:0 events:2 errors:0
TX bytes:6 acl:0 sco:0 commands:2 errors:0
Features: 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
Packet type: DM1 DH1 HV1 
Link policy: 
Link mode: SLAVE ACCEPT 

FIX

Your linux distribution does not have firmware for this chipset. Use below command to get Open Sourvce firmware and install it

    cd /tmp
    wget https://raw.githubusercontent.com/Realtek-OpenSource/android_hardware_realtek/rtk1395/bt/rtkbt/Firmware/BT/rtl8761b_config
    wget https://raw.githubusercontent.com/Realtek-OpenSource/android_hardware_realtek/rtk1395/bt/rtkbt/Firmware/BT/rtl8761b_fw
    sudo mv rtl8761b_config /lib/firmware/rtl_bt/rtl8761b_config.bin
    sudo mv rtl8761b_fw /lib/firmware/rtl_bt/rtl8761b_fw.bin

    sudo ls -l /lib/firmware/rtl_bt/rtl8761b_config.bin /lib/firmware/rtl_bt/rtl8761b_fw.bin
    sudo modprobe btusb
    sudo systemctl start bluetooth.service
    hciconfig -a # will show that Bluetooth is up now

Usb adapter should work now!

Reference: 

https://github.com/Realtek-OpenSource/android_hardware_realtek