This device supports Bluetooth 4.0, but is backwards compatible with Bluetooth 3.0, 2.1, and 2.0.

HSP/HFP headset profiles do not work, they require proprietary firmware: mention in pulseaudio docs, user's detailed comment .

A2DP profile works fine (headphone functionality only).

lsusb -v

Bus 007 Device 002: ID 0b05:17cb ASUSTek Computer, Inc. Broadcom BCM20702A0 Bluetooth
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass          255 Vendor Specific Class
  bDeviceSubClass         1 
  bDeviceProtocol         1 
  bMaxPacketSize0        64
  idVendor           0x0b05 ASUSTek Computer, Inc.
  idProduct          0x17cb Broadcom BCM20702A0 Bluetooth
  bcdDevice            1.12
  iManufacturer           1 Broadcom Corp
  iProduct                2 BCM20702A0
  iSerial                 3 5CF3708FFF77
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength          218
    bNumInterfaces          4
    bConfigurationValue     1
    iConfiguration          0 
    bmAttributes         0xa0
      (Bus Powered)
      Remote Wakeup
    MaxPower              100mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           3
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      1 
      bInterfaceProtocol      1 
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x81  EP 1 IN
        bmAttributes            3
          Transfer Type            Interrupt
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0010  1x 16 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x82  EP 2 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x02  EP 2 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               1
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       0
      bNumEndpoints           2
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      1 
      bInterfaceProtocol      1 
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x83  EP 3 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0000  1x 0 byteshttps://www.freedesktop.org/wiki/Software/PulseAudio/Documentation/User/Bluetooth/#hspproblem:audioissilentorskipping
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0000  1x 0 bytes
        bInterval               1
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       1
      bNumEndpoints           2
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      1 
      bInterfaceProtocol      1 
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x83  EP 3 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0009  1x 9 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0009  1x 9 bytes
        bInterval               1
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       2
      bNumEndpoints           2
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      1 
      bInterfaceProtocol      1 
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x83  EP 3 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0011  1x 17 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0011  1x 17 bytes
        bInterval               1
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       3
      bNumEndpoints           2
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      1 
      bInterfaceProtocol      1 
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x83  EP 3 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0019  1x 25 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0019  1x 25 bytes
        bInterval               1
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       4
      bNumEndpoints           2
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      1 
      bInterfaceProtocol      1 
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x83  EP 3 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0021  1x 33 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0021  1x 33 bytes
        bInterval               1
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       5
      bNumEndpoints           2
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      1 
      bInterfaceProtocol      1 
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x83  EP 3 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0031  1x 49 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0031  1x 49 bytes
        bInterval               1
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        2
      bAlternateSetting       0
      bNumEndpoints           2
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass    255 Vendor Specific Subclass
      bInterfaceProtocol    255 Vendor Specific Protocol
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x84  EP 4 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0020  1x 32 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x04  EP 4 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0020  1x 32 bytes
        bInterval               1
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        3
      bAlternateSetting       0
      bNumEndpoints           0
      bInterfaceClass       254 Application Specific Interface
      bInterfaceSubClass      1 Device Firmware Update
      bInterfaceProtocol      1 
      iInterface              0 
      Device Firmware Upgrade Interface Descriptor:
        bLength                             9
        bDescriptorType                    33
        bmAttributes                        5
          Will Not Detach
          Manifestation Tolerant
          Upload Unsupported
          Download Supported
        wDetachTimeout                   5000 milliseconds
        wTransferSize                      64 bytes
        bcdDFUVersion                   1.10
Device Status:     0x0000
  (Bus Powered)

hwinfo

05: USB 00.1: 0000 Unclassified device
  [Created at usb.122]
  Unique ID: 4m7i.GCgRyhKh3y1
  Parent ID: BSFT.gkSaZmjGyhD
  SysFS ID: /devices/pci0000:00/0000:00:1d.1/usb7/7-1/7-1:1.1
  SysFS BusID: 7-1:1.1
  Hardware Class: unknown
  Model: "ASUSTek Broadcom BCM20702A0 Bluetooth"
  Hotplug: USB
  Vendor: usb 0x0b05 "ASUSTek Computer, Inc."
  Device: usb 0x17cb "Broadcom BCM20702A0 Bluetooth"
  Revision: "1.12"
  Serial ID: "5CF3708FFF77"
  Driver: "btusb"
  Driver Modules: "btusb"
  Speed: 12 Mbps
  Module Alias: "usb:v0B05p17CBd0112dcFFdsc01dp01icFFisc01ip01in01"
  Driver Info #0:
    Driver Status: btusb is active
    Driver Activation Cmd: "modprobe btusb"
  Config Status: cfg=new, avail=yes, need=no, active=unknown
  Attached to: #9 (Hub)

dmesg

[  273.713778] NET: Registered protocol family 31
[  273.713778] Bluetooth: HCI device and connection manager initialized
[  273.713781] Bluetooth: HCI socket layer initialized
[  273.713783] Bluetooth: L2CAP socket layer initialized
[  273.713787] Bluetooth: SCO socket layer initialized
[  273.741189] usbcore: registered new interface driver btusb
[  273.853511] Bluetooth: hci0: BCM: chip id 63
[  273.854443] Bluetooth: hci0: BCM: features 0x07
[  273.870493] Bluetooth: hci0: BCM20702A
[  273.871420] Bluetooth: hci0: BCM20702A1 (001.002.014) build 0000
[  273.871498] bluetooth hci0: firmware: failed to load brcm/BCM20702A1-0489-e052.hcd (-2)
[  273.871507] bluetooth hci0: Direct firmware load for brcm/BCM20702A1-0489-e052.hcd failed with error -2
[  273.871513] Bluetooth: hci0: BCM: Patch brcm/BCM20702A1-0489-e052.hcd not found