Difference between revisions of "RPi Bluetooth LE"

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= Bluetooth LE on the Raspberry Pi =
 
= Bluetooth LE on the Raspberry Pi =
  
At the time of writing Bluetooth Low Energy (BLE) is not well supported by the standard Raspberry Pi distributions. Some work is required to get it working, as described below.
+
The [https://www.raspberrypi.org/products/raspberry-pi-3-model-b/ Raspberry Pi 3] has built-in support for Bluetooth Low Energy (BLE). BLE is the technology behind many fitness trackers and smartwatches, and allows small, low-power devices to transmit and receive information from a central computer or smartphone.
 +
 
 +
This tutorial gets you started with Bluetooth Low Energy using a [http://www.ti.com/tool/cc2650stk Texas Instruments SensorTag] - these are small, robust, relatively cheap and do interesting things out of the box. You can buy one [http://www.ti.com/tool/cc2650stk#buy directly from TI], or in the UK they are available from [http://uk.rs-online.com/web/p/radio-frequency-development-kits/8735892/ RS] and [http://uk.farnell.com/texas-instruments/cc2650stk/evaluation-mod-simplelink-sensor/dp/2470181 Farnell].
  
 
== Pre-requisites ==
 
== Pre-requisites ==
  
=== Software ===
+
=== Compatible Hardware ===
 +
This page was written assuming the following hardware:
 +
* Raspberry Pi 3 Model B
 +
* Raspbian Jessie (April 2017), although later versions will probably work.
 +
* TI CC2650 SensorTag, firmware 1.30 (May 2016) or later
  
This page has been tested using the Raspbian ''Wheezy'' distribution, in particular the image at:
+
We'll also assume you are familiar with the basics of typing Bash commands using the [https://www.raspberrypi.org/documentation/usage/terminal/ command line].  
http://downloads.raspberrypi.org/raspbian/images/raspbian-2014-01-09/2014-01-07-wheezy-raspbian.zip
 
  
For reference, <tt>uname -a</tt> on the test system returned:
+
Older models of the Pi should work with an external USB adapter. The author has used these two successfully:
Linux raspberrypi 3.10.25+ #622 PREEMPT Fri Jan 3 18:41:00 GMT 2014 armv6l GNU/Linux 
+
* Plugable USB-BT4LE adapter: http://plugable.com/products/usb-bt4le (uses BCM20702 chipset)
 +
* CSR chipset adapter http://www.amazon.co.uk/Version-Bluetooth-Adapter-Compatible-Windows/dp/B00A0CBOTE
  
=== Hardware ===
 
  
You will need a Bluetooth 4.0 compatible USB adapter to use with the Pi. The following devices have been tested:
+
=== Basic installation checks ===
* Plugable USB-BT4LE adapter: http://plugable.com/products/usb-bt4le (uses BCM20702 chipset)
+
 
* CSR chipset adapter http://www.amazon.co.uk/Version-Bluetooth-Adapter-Compatible-Windows/dp/B00A0CBOTE
+
The Pi 3's built-in Bluetooth adapter is called ''hci0''. You can check it is operating correctly with the command:
 +
hciconfig
 +
 
 +
This should show something like this:
 +
hci0: Type: BR/EDR  Bus: UART
 +
BD Address: B8:27:EB:23:E2:A4  ACL MTU: 1021:8  SCO MTU: 64:1
 +
UP RUNNING
 +
RX bytes:1987 acl:0 sco:0 events:91 errors:0
 +
TX bytes:1647 acl:0 sco:0 commands:57 errors:0
 +
 
 +
If for some reason it is shown as <tt>DOWN</tt> you can re-enable it with:
 +
sudo hciconfig hci0 up
  
== BlueZ installation ==
+
=== Scanning using <tt>hcitool</tt> ===
  
By default, the Wheezy distribution comes without a Bluetooth stack. The <tt>bluez</tt> package is version 4.99, which has patchy support for Low Energy. You can build and install a more modern version as follows:
+
[[File:Sensortag-buttons.jpg|frameless|SensorTag with outer case removed]]
  
=== BlueZ 5.32 build instructions ===
+
If you've not already done so, take a look at TI's [http://www.ti.com/ww/en/wireless_connectivity/sensortag/gettingStarted.html Getting Started Guide] which explains how to set up the SensorTag.
  
Firstly, you'll need a download and install a number of development libraries. From a [[RPi_Beginners#Intro_to_the_CLI_.28Command_Line_Interface.29|command prompt]] run:
+
To wake it up, press the button on the left-hand side (see illustration) and the green LED should flash, once per second.
 
sudo apt-get install libdbus-1-dev libdbus-glib-1-dev libglib2.0-dev libical-dev libreadline-dev libudev-dev libusb-dev make
 
  
Then, download the source:
+
On the Pi, enter the command:
mkdir -p work/bluepy
+
  sudo hcitool lescan
cd work/bluepy
 
wget https://www.kernel.org/pub/linux/bluetooth/bluez-5.32.tar.xz
 
tar xvf bluez-5.32.tar.xz
 
  
If successful, you'll now have a <tt>bluez-5.32</tt> source code directory on disk. To build it, do:
+
This will start a scan for any Bluetooth LE devices in range which are currently 'advertising'. You should shortly see something like this:
cd bluez-5.32
+
  pi@raspberrypi:~ $ sudo hcitool lescan
./configure --disable-systemd
+
  LE Scan ...
make
+
  B0:B4:48:ED:44:C3 (unknown)
 +
  B0:B4:48:ED:44:C3 CC2650 SensorTag
  
This will take half an hour or so. When this is done, do:
+
Type Control-C to stop <tt>lescan</tt>. The 12 hexadecimal digits (<tt>B0:B4:48:ED:44:C3</tt> in the example) are your tag's MAC address. You will need to know this when making Bluetooth LE connections to it.
sudo make install
 
  
== First tests ==
+
=== Connecting with <tt>gatttool</tt> ===
  
=== USB Checks ===
+
The <tt>gatttool</tt> utility can make connections to Bluetooth LE devices. To try this, make sure the SensorTag's LED is flashing then run:
 +
  gatttool -I -b <i>MAC-address</i>
  
To ensure the USB Bluetooth device is being seen, run
+
where ''MAC-address'' is the value reported by <tt>hcitool</tt> (see above). <tt>gatttool</tt> will give you a prompt, ending <tt>[LE]&gt;</tt>. Type <tt>connect</tt> to make a connection to the SensorTag. This is shown below:
lsusb
 
  
With the Plugable adapter shown above, the result will be similar to this:
+
  pi@raspberrypi:~ $ gatttool -I -b B0:B4:48:ED:44:C3
Bus 001 Device 002: ID 0424:9512 Standard Microsystems Corp.
+
  [B0:B4:48:ED:44:C3][LE]> connect
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
+
  Attempting to connect to B0:B4:48:ED:44:C3
Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp.
+
  Connection successful
Bus 001 Device 004: ID 0a5c:21e8 Broadcom Corp.
+
  [B0:B4:48:ED:44:C3][LE]>
  
The adapter is the one on <tt>Bus 001 Device 004</tt>. To show more information about the 'Broadcom' device, do:
+
You can then type a number of commands. The <tt>primary</tt> command lists the available 'Services', which are groups containing 'Characteristics' - these are data items which can be read or written to the device. So, to read the device name you could use the <tt>char-read-uuid</tt> command, giving it the ID of the Bluetooth [https://www.bluetooth.com/specifications/gatt/viewer?attributeXmlFile=org.bluetooth.characteristic.gap.device_name.xml Device Name characteristic]:
sudo lsusb -v -d 0a5c:
 
  
=== Using hcitool ===
+
  [B0:B4:48:ED:44:C3][LE]> char-read-uuid 00002a00-0000-1000-8000-00805f9b34fb
 +
  handle: 0x0003 value: 53 65 6e 73 6f 72 54 61 67 20 32 2e 30
  
If this is working, run the <tt>hciconfig</tt> tool:
+
(These are the ASCII values for ''SensorTag 2.0''.
pi@raspberrypi ~ $ hciconfig
 
hci0: Type: BR/EDR  Bus: USB
 
BD Address: 00:02:72:14:27:0E  ACL MTU: 1021:8  SCO MTU: 64:1
 
DOWN
 
RX bytes:2715 acl:1 sco:0 events:146 errors:0
 
TX bytes:2500 acl:0 sco:0 commands:133 errors:0
 
  
If the bluetooth adapter (<tt>hci0</tt> in the above example) is down as <tt>DOWN</tt>, you will need to enable it with:
+
The Sensortag User Guide at http://processors.wiki.ti.com/index.php/CC2650_SensorTag_User's_Guide lists all the available services and characteristics. For example, to turn on the optical sensor, we need to discover the 'handle' for the configuration characteristic (with ID ''f000aa72-0451-4000-b000-000000000000''), then write an 0x01 byte to it:
sudo hciconfig hci0 up
 
  
=== Scanning for LE devices ===
+
  [B0:B4:48:ED:44:C3][LE]> characteristics 1 ffff f000aa72-0451-4000-b000-000000000000
 +
  handle: 0x0046, char properties: 0x0a, char value handle: 0x0047, uuid: f000aa72-0451-4000-b000-000000000000
 +
  [B0:B4:48:ED:44:C3][LE]> char-write-req 47 01
 +
  Characteristic value was written successfully
  
If you have any Bluetooth LE devices, you can start scanning for them with:
+
In the example above the handle value was 0x47 (it may change with firmware versions). One the sensor is enabled, the light level can then be read from characteristic ''f000aa71-0451-4000-b000-000000000000'':
sudo hcitool lescan
 
  
For the [http://www.ti.com/sensortag TI SensorTag], pressing the button on the side will ensure the device is awake and broadcasting advertising packets. Other LE devices may need a similar action - please consult the relevant user manual.
+
  [B0:B4:48:BF:C9:83][LE]> char-read-uuid f000aa71-0451-4000-b000-000000000000
 +
  handle: 0x0044 value: bc 0a
  
=== Testing connections ===
+
In this example the light level bytes are ''bc 0a'', and will change with the amount of light falling on the CC2650 device.
  
The <tt>lescan</tt> command above should have displayed the MAC address (six hex digits, like ''00:1e:3f:22:4b:a7'') of any Bluetooth LE devices in range and available for connection. You can check a particular device by attempting to make (and then drop) a connection to it, using a command like:
 
sudo hcitool lecc 00:1e:3f:22:4b:a7
 
  
(Obviously, replace 00:1e ... with a MAC address from your <tt>lescan</tt> output).
+
== Using Bluetooth LE with Python ==
  
== Using Bluetooth LE from Python ==
+
=== Installing <tt>bluepy</tt> ===
 +
Using <tt>gatttool</tt> is very laborious for doing any useful work, so it's a good idea to use a programming language. The ''bluepy'' package is one way to use Bluetooth LE commands from Python - it can be installed from https://pypi.python.org/pypi using the <tt>pip</tt> command. If you don't already have <tt>pip</tt>, on the Pi or other Debian systems it is easily installed with:
  
You can communicate with Bluetooth LE devices from Python using the '''bluepy''' package. This is currently source code you need to build yourself; there isn't an official installer for it yet.
+
  sudo apt-get install python-pip
  
Fetch the source by changing directory to a suitable work area and running:
+
Before installing ''bluepy'' you will also need some support libraries:
git clone https://github.com/IanHarvey/bluepy.git
 
  
This should create a directory <tt>bluepy/</tt>. If you have already fetched all the packages needed in ''BlueZ 5.30 Build Instructions' above, you can build the source with just:
+
  sudo apt-get install libglib2.0-dev
  
  cd bluepy/bluepy
+
Then you can run:
  make
 
  
If successful you will have built an executable <tt>bluepy-helper</tt>.
+
  sudo pip install bluepy
  
To test this, first ensure that <tt>hcitool lecc</tt> works (see above) so you can manually create a connection, then run <tt>btle.py</tt> giving it your peripheral's MAC address, e.g.
+
If successful, it will show a message such as this:
  
  python btle.py 00:1e:3f:22:4b:a7
+
      Installing blescan script to /usr/local/bin
 +
      Installing sensortag script to /usr/local/bin
 +
  Successfully installed bluepy
 +
  Cleaning up...  
  
This will attempt to enumerate the services and characteristics presented by the device.
 
  
There is currently no official documentation for the '''bluepy''' module; you will need to use the Python source as example code.
+
= Using Bluetooth LE with Go (Golang) =
 
== Using Bluetooth LE with Go (Golang) ==
 
  
 
[https://github.com/paypal/gatt Gatt] is a [https://golang.org/ Go] package, which provides developers to create BLE applications for Linux and OS X.
 
[https://github.com/paypal/gatt Gatt] is a [https://golang.org/ Go] package, which provides developers to create BLE applications for Linux and OS X.

Revision as of 07:28, 26 June 2017

Bluetooth LE on the Raspberry Pi

The Raspberry Pi 3 has built-in support for Bluetooth Low Energy (BLE). BLE is the technology behind many fitness trackers and smartwatches, and allows small, low-power devices to transmit and receive information from a central computer or smartphone.

This tutorial gets you started with Bluetooth Low Energy using a Texas Instruments SensorTag - these are small, robust, relatively cheap and do interesting things out of the box. You can buy one directly from TI, or in the UK they are available from RS and Farnell.

Pre-requisites

Compatible Hardware

This page was written assuming the following hardware:

  • Raspberry Pi 3 Model B
  • Raspbian Jessie (April 2017), although later versions will probably work.
  • TI CC2650 SensorTag, firmware 1.30 (May 2016) or later

We'll also assume you are familiar with the basics of typing Bash commands using the command line.

Older models of the Pi should work with an external USB adapter. The author has used these two successfully:


Basic installation checks

The Pi 3's built-in Bluetooth adapter is called hci0. You can check it is operating correctly with the command:

hciconfig

This should show something like this:

hci0:	Type: BR/EDR  Bus: UART
	BD Address: B8:27:EB:23:E2:A4  ACL MTU: 1021:8  SCO MTU: 64:1
	UP RUNNING 
	RX bytes:1987 acl:0 sco:0 events:91 errors:0
	TX bytes:1647 acl:0 sco:0 commands:57 errors:0
 

If for some reason it is shown as DOWN you can re-enable it with:

sudo hciconfig hci0 up

Scanning using hcitool

SensorTag with outer case removed

If you've not already done so, take a look at TI's Getting Started Guide which explains how to set up the SensorTag.

To wake it up, press the button on the left-hand side (see illustration) and the green LED should flash, once per second.

On the Pi, enter the command:

 sudo hcitool lescan

This will start a scan for any Bluetooth LE devices in range which are currently 'advertising'. You should shortly see something like this:

 pi@raspberrypi:~ $ sudo hcitool lescan 
 LE Scan ...
 B0:B4:48:ED:44:C3 (unknown)
 B0:B4:48:ED:44:C3 CC2650 SensorTag

Type Control-C to stop lescan. The 12 hexadecimal digits (B0:B4:48:ED:44:C3 in the example) are your tag's MAC address. You will need to know this when making Bluetooth LE connections to it.

Connecting with gatttool

The gatttool utility can make connections to Bluetooth LE devices. To try this, make sure the SensorTag's LED is flashing then run:

 gatttool -I -b MAC-address

where MAC-address is the value reported by hcitool (see above). gatttool will give you a prompt, ending [LE]>. Type connect to make a connection to the SensorTag. This is shown below:

 pi@raspberrypi:~ $ gatttool -I -b B0:B4:48:ED:44:C3
 [B0:B4:48:ED:44:C3][LE]> connect
 Attempting to connect to B0:B4:48:ED:44:C3
 Connection successful
 [B0:B4:48:ED:44:C3][LE]>

You can then type a number of commands. The primary command lists the available 'Services', which are groups containing 'Characteristics' - these are data items which can be read or written to the device. So, to read the device name you could use the char-read-uuid command, giving it the ID of the Bluetooth Device Name characteristic:

 [B0:B4:48:ED:44:C3][LE]> char-read-uuid 00002a00-0000-1000-8000-00805f9b34fb
 handle: 0x0003 	 value: 53 65 6e 73 6f 72 54 61 67 20 32 2e 30 

(These are the ASCII values for SensorTag 2.0.

The Sensortag User Guide at http://processors.wiki.ti.com/index.php/CC2650_SensorTag_User's_Guide lists all the available services and characteristics. For example, to turn on the optical sensor, we need to discover the 'handle' for the configuration characteristic (with ID f000aa72-0451-4000-b000-000000000000), then write an 0x01 byte to it:

 [B0:B4:48:ED:44:C3][LE]> characteristics 1 ffff f000aa72-0451-4000-b000-000000000000
 handle: 0x0046, char properties: 0x0a, char value handle: 0x0047, uuid: f000aa72-0451-4000-b000-000000000000
 [B0:B4:48:ED:44:C3][LE]> char-write-req 47 01
 Characteristic value was written successfully

In the example above the handle value was 0x47 (it may change with firmware versions). One the sensor is enabled, the light level can then be read from characteristic f000aa71-0451-4000-b000-000000000000:

 [B0:B4:48:BF:C9:83][LE]> char-read-uuid f000aa71-0451-4000-b000-000000000000
 handle: 0x0044 	 value: bc 0a 

In this example the light level bytes are bc 0a, and will change with the amount of light falling on the CC2650 device.


Using Bluetooth LE with Python

Installing bluepy

Using gatttool is very laborious for doing any useful work, so it's a good idea to use a programming language. The bluepy package is one way to use Bluetooth LE commands from Python - it can be installed from https://pypi.python.org/pypi using the pip command. If you don't already have pip, on the Pi or other Debian systems it is easily installed with:

 sudo apt-get install python-pip

Before installing bluepy you will also need some support libraries:

 sudo apt-get install libglib2.0-dev

Then you can run:

 sudo pip install bluepy

If successful, it will show a message such as this:

     Installing blescan script to /usr/local/bin
     Installing sensortag script to /usr/local/bin
 Successfully installed bluepy
 Cleaning up...  


Using Bluetooth LE with Go (Golang)

Gatt is a Go package, which provides developers to create BLE applications for Linux and OS X.

Developers install Go language on the host machine, and cross-compile the applications for RPi.

The package accesses HCI devices directly via HCI sockets provided by BlueZ core (kernel space), so it doesn't require the BlueZ userland package.

To test the example programs (sample GATT server and clients):

Cross-compile the server example for an ARMv6 target device.

 GOARCH=arm GOARM=6 GOOS=linux go build examples/server.go
 cp server <target device>

Start the server on the target device

 sudo ./server

Cross-compile the client example (discoverer) for an ARMv6 target device.

 GOARCH=arm GOARM=6 GOOS=linux go build examples/discoverer.go
 cp discoverer <target device>

Run the discoverer to scan surrounding peripheral devices.

 sudo ./discoverer

Links: other Bluetooth Low Energy resources