Adventures in Bluetooth 4.0 – Part 1: Initializing a CSR 8510 A10 aka Sitecom CNT-524

I recently bought a Sitecom CNT-524 Bluetooth 4.0 USB dongle, which seems to be based on a Cambridge Silicon Radio reference design, CSR 8510 A10 aka CSR Nanosira. It comes up in some sort of dummy HID mode which does nothing useful, or I couldn’t find what it would do. So I set out to make it work properly.

I started out by looking at what comes up by default when you plug in the device:

Bus 006 Device 023: ID 0a12:100b Cambridge Silicon Radio, Ltd
[361895.944068] usb 6-2: new full-speed USB device number 23 using uhci_hcd
[361896.302190] usb 6-2: New USB device found, idVendor=0a12, idProduct=100b
[361896.302203] usb 6-2: New USB device strings: Mfr=0, Product=2, SerialNumber=0
[361896.302211] usb 6-2: Product: CSR8510 A10
[361896.329542] input: CSR8510 A10 as /devices/pci0000:00/0000:00:1d.0/usb6/6-2/6-2:1.0/input/input53
[361896.329986] hid-generic 0003:0A12:100B.0027: input,hiddev0,hidraw0: USB HID v1.11 Keyboard [CSR8510 A10] on usb-0000:00:1d.0-2/input0
[361896.338126] input: CSR8510 A10 as /devices/pci0000:00/0000:00:1d.0/usb6/6-2/6-2:1.1/input/input54
[361896.338597] hid-generic 0003:0A12:100B.0028: input,hidraw1: USB HID v1.11 Mouse [CSR8510 A10] on usb-0000:00:1d.0-2/input1

As said, the device doesn’t seem to do anything useful in this mode. Maybe it would react to some BT-HID or BT-LE-HID devices automagically?

So I started looking at how to get this device to do something sensible. In the end I caved and booted a virtual Windows7 (the virtual machines from are great for such one-shot exercises), installed the driver (418MByte, sic!) and attached the USB device to the virtual machine. Lo and behold the device disappeared and a new device appeared.

[362349.728136] usb 6-2: USB disconnect, device number 23
[362350.668045] usb 6-2: new full-speed USB device number 24 using uhci_hcd
[362350.845137] usb 6-2: New USB device found, idVendor=0a12, idProduct=0001
[362350.845144] usb 6-2: New USB device strings: Mfr=0, Product=2, SerialNumber=0
[362350.845148] usb 6-2: Product: CSR8510 A10
Bus 006 Device 024: ID 0a12:0001 Cambridge Silicon Radio, Ltd Bluetooth Dongle (HCI mode)

Just what I was looking for and also that device then does have BT-LE (aka Bluetooth Smart) functionality without requiring further exact steps.

# hcitool -i hci1 lescan
LE Scan ...
00:18:33:7A:96:05 (unknown)
00:18:33:7A:96:05 MetaWatch 05
00:17:EA:92:05:E4 (unknown)
00:17:EA:92:05:E4 Biscuit
78:C5:E5:6E:E3:38 (unknown)
78:C5:E5:6E:E3:38 SensorTag

It immediately finds my TI SmartTag, MetaWatch and RedBearLab BLE Mini, all of those are LowEnergy devices.

Having verified that, it’s time to get back to making this work on Linux without the help of a VM. So the next logical step was to find out what exactly happens under Windows, so that I could then reproduce it using the fine usb_modeswitch tool. For that I’ve taken a look at Mark’s blog post and adapted it to my situation.

One of the problems I faced was that the Windows drivers don’t seem to work properly in the Windows XP VM I had. So I resorted to, my anyway preferred tool, Wireshark for sniffing the USB traffic directly on the host Linux machine:

# modprobe usbmon

Then start Wireshark and start listening to the right bus as indicated by e.g. lsusb. In my case that’ bus 6, as you can also see from the previous output. Then attach the USB device to the virtual machine and let the drivers do their work. Verify the device switched. Stop the capture and restart. Rinse, repeat.

Luckily I took a look at the Windows services that were running and found one suspiciously named “CSR Bluetooth Switcher Service” with the telling description of “Allows a Bluetooth device to switch from boot mode to Bluetooth HCI mode“. I then verified, that it does exactly that, by stopping the service and attaching the dongle – It wouldn’t switch to HCI mode until I restarted the service. I still don’t understand why they don’t come up in HCI mode by default…

This allowed to narrow things down to exactly one packet sent from the Laptop to the device:

No.  Time           Source  Destination  Protocol  Length  Info
112  66.328046000   host    14.0         USBHID    73      SET_REPORT Request

Frame 112: 73 bytes on wire (584 bits), 73 bytes captured (584 bits) on interface 0
    Interface id: 0
    Encapsulation type: USB packets with Linux header and padding (115)
    Arrival Time: Oct  5, 2013 16:43:39.667846000 UTC
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1380991419.667846000 seconds
    [Time delta from previous captured frame: 26.537027000 seconds]
    [Time delta from previous displayed frame: 26.537027000 seconds]
    [Time since reference or first frame: 66.328046000 seconds]
    Frame Number: 112
    Frame Length: 73 bytes (584 bits)
    Capture Length: 73 bytes (584 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    [Protocols in frame: usb:usbhid]
    URB id: 0xffff88008eafd840
    URB type: URB_SUBMIT ('S')
    URB transfer type: URB_CONTROL (0x02)
    Endpoint: 0x00, Direction: OUT
        0... .... = Direction: OUT (0)
        .000 0000 = Endpoint value: 0
    Device: 14
    URB bus id: 6
    Device setup request: relevant (0)
    Data: present (0)
    URB sec: 1380991419
    URB usec: 667846
    URB status: Operation now in progress (-EINPROGRESS) (-115)
    URB length [bytes]: 9
    Data length [bytes]: 9
    [Response in: 113]
    [bInterfaceClass: HID (0x03)]
URB setup
    bmRequestType: 0x21
        0... .... = Direction: Host-to-device
        .01. .... = Type: Class (0x01)
        ...0 0001 = Recipient: Interface (0x01)
    bRequest: SET_REPORT (0x09)
    wValue: 0x0301
        ReportID: 1
        ReportType: Feature (3)
    wIndex: 0
    wLength: 9

0000   40 d8 af 8e 00 88 ff ff 53 02 00 0e 06 00 00 00  @.......S.......
0010   bb 41 50 52 00 00 00 00 c6 30 0a 00 8d ff ff ff  .APR.....0......
0020   09 00 00 00 09 00 00 00 21 09 01 03 00 00 09 00  ........!.......
0030   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
0040   01 05 00 00 00 00 00 00 00                       .........

The device then ACKs this message with a status code of 0 (success) and some last messages, of which the last one cuts off and is thus malformed. 60ms later it is gone. Then the ‘right’ device appears and enumerates.

That’s where I’m currently stuck. I’ve tried to send the bolded payload (or some part/permutation of it) to the device using usb_modeswitch, but for some reason it seems it can’t get to the device endpoint 0x00 that windows uses for this message.

# usb_modeswitch -v0a12 -p100b -W 
-m00 -M 
 Accessing device 016 on bus 006 ...
Getting the current device configuration ...
OK, got current device configuration (1)
Using interface number 0
Error: message endpoint not given or found. Aborting.

I’ve emailed the usb_modeswitch author to see if he sees something obvious that I have missed. After all USB hacking is not my every day pastime.

I’ll write a follow-up blog post once I’ve made progress with this. For the moment I have to begrudgingly resort to waking up a Windows VM for switching the device after plugging it in.

7 thoughts on “Adventures in Bluetooth 4.0 – Part 1: Initializing a CSR 8510 A10 aka Sitecom CNT-524

  1. Pingback: Bluetooth Low Energy dongles with Linux compatibility | Simon Wiesmann

    1. Thomas B. Rücker Post author

      I found out that there is a tool shipped with bluez that should accomplish this instead: hid2hci
      Somehow I am using it wrong though… If anyone figures it out, I’d appreciate to hear about it.

  2. Romain MARIADASSOU (roms)

    Finally I had got it working with (at least) OS X Mavericks and on Linux.

    For the story, CSR8510 A10 chip is a dual-mode chip. On your dongle, and mine (“It Works” – Micro Bluetooth 4.0 USB Adapter from Darty in France), the dongle boot in HID mode by default (VID 0A12 PID 100B). Even with a Linux computer, i could’nt get the dongle to work in HCI mode (Bluetooth mode so – VID 0A12 PID 0001).

    If you have a computer that is running Windows (7 – 64bits for me) you can modify the “initial device bootmode”.

    To change the device bootmode :

    Download the BlueSuite to modifiy “BlueCore Persistent Store” :
    Unplug your Bluetooth dongle
    Install the BlueSuite Software (default options)
    Plug your Bluetooth dongle in another port than previously
    Run CSR BlueSuite 2.5.0 / PSTool as Administrator
    With the first window : Choose Transport = USB then Port = \\.\csr0 and click OK
    In the Filter box, type bootmode then click on the item “Initial device bootmode”
    Note the hex number in case something goes wrong (mine was 0002), then change to 0000
    Click on the Set button then click on the Close button
    Wait some seconds then unplug your Bluetooth dongle.

    Finally, run your OS X or Linux host with the dongle plugged-in and your Bluetooth dongle will now work out of the box 🙂

    With this modification, your Bluetooth dongle, will always start in HCI mode.

    Some information about the dual-mode in Bluetooth USB :

    Hope it will work for you too.


    1. gkr

      well the USB Vendor Command, as described in above link, doesn’t work with the CN524 as this is what hid2hci is using. i implemented the switch using the usb protocol capture from above. would be nice to see what is happening when windows tries to switch the protocol back to hid mode though, before providing the patch to bluez. any help appreciated.

    2. Thomas B. Rücker Post author

      As hid2hci doesn’t support the dongle at this point, this seems to be the best option for a one time change. It does require at least Windows 7 and the original driver installed. Virtual machine works fine if it supports USB forwarding, you just need to make sure to reattach after the driver resets the dongle to HCI mode.