Playing with Bluetooth Smart devices on Fedora

So I have a few Bluetooth Smart (AKA BT Low Energy or BT-LE) devices including a BeeWi SmartClim Smart Temperature & Humidity Sensor, a TI SensorTag2 and a Runtasic Orbit activity tracker. I thought I’d see if I could connect to them with something other than their proprietary apps that run on my phone and get anything useful out of them.

To do this I installed a Fedora 23 minimal image on a micro SD card for BeagleBone Black, inserted a CSR USB Bluetooth 4.0 dongle and powered it up. Once I’d completed the first boot wizard and logged in I installed the bluetooth command line utility packages with a “sudo dnf install -y bluez bluez-libs”. You don’t need to use a BeagleBone, you can use any ARM device or even a standard laptop which supports Bluetooth 4+ with BT-LE support.

Now that we have a device running we’re ready to start to play.

First lets see if our system sees our bluetooth dongle:

$ sudo hcitool dev
Devices:
	hci0	AA:BB:CC:DD:EE:33

Then lets scan for any Bluetooth Smart devices that are in range:

$ sudo hcitool lescan 
LE Scan ...
A1:B2:C3:D4:E5:F6 (unknown)
A1:B2:C3:D4:E5:F6 CC2650 SensorTag
A9:B8:C7:D6:E5:F4 (unknown)
A9:B8:C7:D6:E5:F4 BeeWi SmartClim

Now create a connection to the device we discovered:

$ sudo hcitool lecc A1:B2:C3:D4:E5:F6
Connection handle 3586

In the bluez package gatttool is a tool we can use to interact with Bluetooth Smart devices. We can use gatttool in interactive mode to send commands to out previously scanned device address:

sudo gatttool -b A1:B2:C3:D4:E5:F6 -I
[78:A5:04:5B:7D:9A][LE]>

Now we connect to the deivce (note in older version of gattool the prefix would change from “[ ]” to “[CON]” now it changes the colour of the BT MAC):

[A1:B2:C3:D4:E5:F6][LE]> connect
Attempting to connect to A1:B2:C3:D4:E5:F6
Connection successful
[A1:B2:C3:D4:E5:F6][LE]>

We can request the device characteristics:

[A1:B2:C3:D4:E5:F6][LE]> characteristics
handle: 0x0002, char properties: 0x02, char value handle: 0x0003, uuid: 00002a00-0000-1000-8000-00805f9b34fb
handle: 0x0004, char properties: 0x02, char value handle: 0x0005, uuid: 00002a01-0000-1000-8000-00805f9b34fb
handle: 0x0006, char properties: 0x02, char value handle: 0x0007, uuid: 00002a04-0000-1000-8000-00805f9b34fb
handle: 0x0009, char properties: 0x20, char value handle: 0x000a, uuid: 00002a05-0000-1000-8000-00805f9b34fb
handle: 0x000d, char properties: 0x02, char value handle: 0x000e, uuid: 00002a23-0000-1000-8000-00805f9b34fb
handle: 0x000f, char properties: 0x02, char value handle: 0x0010, uuid: 00002a24-0000-1000-8000-00805f9b34fb
handle: 0x0011, char properties: 0x02, char value handle: 0x0012, uuid: 00002a25-0000-1000-8000-00805f9b34fb
handle: 0x0013, char properties: 0x02, char value handle: 0x0014, uuid: 00002a26-0000-1000-8000-00805f9b34fb
handle: 0x0015, char properties: 0x02, char value handle: 0x0016, uuid: 00002a27-0000-1000-8000-00805f9b34fb
handle: 0x0017, char properties: 0x02, char value handle: 0x0018, uuid: 00002a28-0000-1000-8000-00805f9b34fb
handle: 0x0019, char properties: 0x02, char value handle: 0x001a, uuid: 00002a29-0000-1000-8000-00805f9b34fb
handle: 0x001b, char properties: 0x02, char value handle: 0x001c, uuid: 00002a2a-0000-1000-8000-00805f9b34fb
handle: 0x001d, char properties: 0x02, char value handle: 0x001e, uuid: 00002a50-0000-1000-8000-00805f9b34fb
handle: 0x0020, char properties: 0x12, char value handle: 0x0021, uuid: f000aa01-0451-4000-b000-000000000000
handle: 0x0023, char properties: 0x0a, char value handle: 0x0024, uuid: f000aa02-0451-4000-b000-000000000000
handle: 0x0025, char properties: 0x0a, char value handle: 0x0026, uuid: f000aa03-0451-4000-b000-000000000000
handle: 0x0028, char properties: 0x12, char value handle: 0x0029, uuid: f000aa21-0451-4000-b000-000000000000
handle: 0x002b, char properties: 0x0a, char value handle: 0x002c, uuid: f000aa22-0451-4000-b000-000000000000
handle: 0x002d, char properties: 0x0a, char value handle: 0x002e, uuid: f000aa23-0451-4000-b000-000000000000
handle: 0x0030, char properties: 0x12, char value handle: 0x0031, uuid: f000aa41-0451-4000-b000-000000000000
handle: 0x0033, char properties: 0x0a, char value handle: 0x0034, uuid: f000aa42-0451-4000-b000-000000000000
handle: 0x0035, char properties: 0x0a, char value handle: 0x0036, uuid: f000aa44-0451-4000-b000-000000000000
handle: 0x0038, char properties: 0x12, char value handle: 0x0039, uuid: f000aa81-0451-4000-b000-000000000000
handle: 0x003b, char properties: 0x0a, char value handle: 0x003c, uuid: f000aa82-0451-4000-b000-000000000000
handle: 0x003d, char properties: 0x0a, char value handle: 0x003e, uuid: f000aa83-0451-4000-b000-000000000000
handle: 0x0040, char properties: 0x12, char value handle: 0x0041, uuid: f000aa71-0451-4000-b000-000000000000
handle: 0x0043, char properties: 0x0a, char value handle: 0x0044, uuid: f000aa72-0451-4000-b000-000000000000
handle: 0x0045, char properties: 0x0a, char value handle: 0x0046, uuid: f000aa73-0451-4000-b000-000000000000
handle: 0x0048, char properties: 0x10, char value handle: 0x0049, uuid: 0000ffe1-0000-1000-8000-00805f9b34fb
handle: 0x004d, char properties: 0x0a, char value handle: 0x004e, uuid: f000aa65-0451-4000-b000-000000000000
handle: 0x004f, char properties: 0x0a, char value handle: 0x0050, uuid: f000aa66-0451-4000-b000-000000000000
handle: 0x0052, char properties: 0x1a, char value handle: 0x0053, uuid: f000ac01-0451-4000-b000-000000000000
handle: 0x0055, char properties: 0x0a, char value handle: 0x0056, uuid: f000ac02-0451-4000-b000-000000000000
handle: 0x0057, char properties: 0x0a, char value handle: 0x0058, uuid: f000ac03-0451-4000-b000-000000000000
handle: 0x005a, char properties: 0x12, char value handle: 0x005b, uuid: f000ccc1-0451-4000-b000-000000000000
handle: 0x005d, char properties: 0x08, char value handle: 0x005e, uuid: f000ccc2-0451-4000-b000-000000000000
handle: 0x005f, char properties: 0x08, char value handle: 0x0060, uuid: f000ccc3-0451-4000-b000-000000000000
handle: 0x0062, char properties: 0x1c, char value handle: 0x0063, uuid: f000ffc1-0451-4000-b000-000000000000
handle: 0x0066, char properties: 0x1c, char value handle: 0x0067, uuid: f000ffc2-0451-4000-b000-000000000000
[A1:B2:C3:D4:E5:F6][LE]> 

Request the name of the device by querying the appropriate characteristic by hhandle:

[A1:B2:C3:D4:E5:F6][LE]> char-read-hnd 0x3
Characteristic value/descriptor: 53 65 6e 73 6f 72 54 61 67 20 32 2e 30 
[A1:B2:C3:D4:E5:F6][LE]> 

The response is returned as a hexadecimal string. To make it readable we need to convert it to ASCII with some simple python:

 python
Python 2.7.10 (default, Sep  8 2015, 17:20:17) 
[GCC 5.1.1 20150618 (Red Hat 5.1.1-4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> "53656e736f7254616720322e30".decode("hex")
'SensorTag 2.0'
>>> 

So that’s the basics of playing with Bluetooth Smart on the command line. I want to work out all of the characteristics and write a simple python daemon to poll the device and then write the output to different locations depending on the config like to a text file or to a MQTT message bus.

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