CC2540

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Revision as of 22:06, 16 November 2016 by Bertrik Sikken (talk | contribs)
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Project CC2540
Cc2540 webee.png
Making the CC2540 BLE dongle work
Status Initializing
Contact bertrik
Last Update 2016-11-16

Introduction

This page is about the CC2540 bluetooth low-energy sniffer dongle and getting it to work with Linux. A nice end result could be that it becomes possible to sniff directly in WireShark with this dongle.

I have such a "WeBee" dongle that can be found for about E15,- on websites like Aliexpress.

It's supposedly a CC2540 (or compatible) dongle, the USB id is 0451:16b3.

Interesting links:

Analysis

USB descriptor

When plugging this stick into a Linux machine, you can see it uses only one bulk endpoint.

Bus 001 Device 009: ID 0451:16b3 Texas Instruments, Inc. 
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass            0 (Defined at Interface level)
  bDeviceSubClass         0 
  bDeviceProtocol         0 
  bMaxPacketSize0        32
  idVendor           0x0451 Texas Instruments, Inc.
  idProduct          0x16b3 
  bcdDevice           90.07
  iManufacturer           1 Texas Instruments
  iProduct                2 CC2540 USB Dongle
  iSerial                 0 
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength           25
    bNumInterfaces          1
    bConfigurationValue     1
    iConfiguration          0 
    bmAttributes         0x80
      (Bus Powered)
    MaxPower              100mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           1
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass    255 Vendor Specific Subclass
      bInterfaceProtocol    255 Vendor Specific Protocol
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x83  EP 3 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               5
Device Status:     0x0000
  (Bus Powered)

USB logs from Windows

This USB device does actually work with Windows:

I've captured a log of the communication over USB while the BLE is capturing bluetooth traffic from some iBeacon, using USB pcap.

In the logs, I cannot see any firmware blobs being downloaded to the stick. Probably the stick comes with a pre-loaded firmware of itself to do the BLE sniffing.

Protocol

In the windows sniffer software, it seems there are only two things communicated:

  • towards the stick: which radio channel to sniff, and some other radio settings
  • from the stick: raw sniffed BLE frames

Configuring the radio

Cc2540 settings.png

This appears to be done using USB control transfers.

Control transfer OUT:

  • request type 0x40
  • request 197 (0xC5)
  • value/index/length 0/4/0
  • no data

Control transfer IN:

  • request type 0xC0
  • request 198 (0xC6)
  • value/index 0/0
  • data: 0x00

Control transfer IN:

  • request type 0xC0
  • request 198 (0xC6)
  • value/index 0/0
  • data: 0x04

Control transfer OUT:

  • request type 0x40
  • request 201 (0xC9)
  • value/index 0/0
  • data: -

Control transfer OUT: to set the radio channel to sniff

  • request type 0x40
  • request 210 (0xD2)
  • value/index 0/0
  • data: 0x27

Control transfer OUT: ???

  • request type 0x40
  • request 210 (0xD2)
  • value/index 0/1
  • data: 0x00

Control transfer OUT: ???

  • request type 0x40
  • request 208 (0xD0)
  • value/index 0/0
  • data: -

Reading BLE frames

Cc2540 packet details.png
Cc2540 wireshark.png

This appears to be done using USB bulk input transfers.

I can see a lot of similarities between the USB log and the BLE sniffer log. The bulk USB data starts off with two bytes indicating the length of the rest of the data.