1. Firmware not loading.

   dmesg | grep -i bluetooth
   
   bluetooth hci0: Direct firmware load for brcm/BCM20702A1-0b05-17cb.hcd failed with error -2

2. Download Windows driver from ASUS.
   http://dlcdnet.asus.com/pub/ASUS/wireless/USB-BT400/UT_USB_BT400_6516000.zip
3. Extract and open Win32\bcbtums-win7x86-brcm.inf
4. Find Product Name (BT400).

   %AsusBT400.DeviceDesc%=RAMUSB17CB,          USB\VID_0B05&PID_17CB       ; 20702 standalone

5. Find section for "RAMUSB17CB".

   ;;;;;;;;;;;;;RAMUSB17CB;;;;;;;;;;;;;;;;;
    
   [RAMUSB17CB.CopyList]
   bcbtums.sys
   BCM20702A1_001.002.014.1315.1347.hex
    
   [RAMUSB17CB.NTX86]
   Include=bth.inf
   Needs=BthUsb.NT
   FeatureScore=F0
   CopyFiles=RAMUSB17CB.CopyList
    
   [RAMUSB17CB.NTX86.hw]
   AddReg=RAMUSB17CB.NTX86.hw.reg
    
   [RAMUSB17CB.NTX86.hw.reg]
   HKR,,LowerFilters, 0x00010000, "bcbtums"
   HKR,,%RAMPatchFileName%,0x00000, "BCM20702A1_001.002.014.1315.1347.hex"
   HKR,,%RemoteWakeEnabled%,0x00010001,1
   HKR,,%DeviceRemoteWakeSupported%,0x00010001,1
    
   [RAMUSB17CB.NTX86.Services]
   needs=BthUsb.NT.Services
   AddService=bcbtums,,BCBTUMS_Service_Inst, BTWSECFL_EventLog_Inst

6. Note .hex file referenced: BCM20702A1_001.002.014.1315.1347.hex.
7. Download hex2hcd.
   https://github.com/jessesung/hex2hcd/
8. Convert hex to hcd.

   ./hex2hcd BCM20702A1_001.002.014.1315.1347.hex BCM20702A1-0b05-17cb.hcd

9. Copy to location found via dmesg in Step 1.

   cp BCM20702A1-0b05-17cb.hcd /lib/firmware/brcm/

10. Reboot (or modprobe -r btusb; modprobe btusb).

ht: http://askubuntu.com/questions/605075/how-to-use-a-bluetooth-headset-mic-in-ubuntu