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The Bluetooth GATT SDK for Python helps you implementing and communicating with any Bluetooth Low Energy device that has a GATT profile. As of now it supports:

• Discovering nearby Bluetooth Low Energy devices
• Connecting and disconnecting devices
• Implementing your custom GATT profile
• Accessing all GATT services
• Accessing all GATT characteristics
• Reading characteristic values
• Writing characteristic values
• Subscribing for characteristic value change notifications

Currently Linux is the only platform supported by this library. Unlike other libraries this GATT SDK is based directly on the mature and stable D-Bus API of BlueZ to interact with Bluetooth devices. In the future we would like to make this library platform-independent by integrating with more Bluetooth APIs of other operating systems such as MacOS and Windows.

The GATT SDK requiresPython 3.4+. Currently Linux is the only supported operating system and therefor it needs a recent installation ofBlueZ. It is tested to work fine with BlueZ 5.44, any release >= 5.38 should however work, too.

These instructions assume a Debian-based Linux.

On Linux theBlueZ library is necessary to access your built-in Bluetooth controller or Bluetooth USB dongle. Some Linux distributions provide a more up-to-date BlueZ package, some other distributions only install older versions that don't implement all Bluetooth features needed for this SDK. In those cases you want to either update BlueZ or build it from sources.

1. bluetoothd --version Obtains the version of the pre-installed BlueZ.bluetoothd daemon must run at startup to expose the Bluetooth API via D-Bus.
2. sudo apt-get install --no-install-recommends bluetooth Installs BlueZ
3. If the installed version is too old, proceed with next step:Installing BlueZ from sources

Thebluetoothd daemon provides BlueZ's D-Bus interfaces that is accessed by the GATT SDK to communicate with Bluetooth devices. The following commands download BlueZ 5.44 sources, built them and replace any pre-installedbluetoothd daemon. It's not suggested to remove any pre-installed BlueZ package as its deinstallation might remove necessary Bluetooth drivers as well.

1. sudo systemctl stop bluetooth
2. sudo apt-get update
3. sudo apt-get install libusb-dev libdbus-1-dev libglib2.0-dev libudev-dev libical-dev libreadline-dev libdbus-glib-1-dev unzip
4. cd
5. mkdir bluez
6. cd bluez
7. wget http://www.kernel.org/pub/linux/bluetooth/bluez-5.44.tar.xz
8. tar xf bluez-5.44.tar.xz
9. cd bluez-5.44
10. ./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var --enable-library
11. make
12. sudo make install
13. sudo ln -svf /usr/libexec/bluetooth/bluetoothd /usr/sbin/
14. sudo install -v -dm755 /etc/bluetooth
15. sudo install -v -m644 src/main.conf /etc/bluetooth/main.conf
16. sudo systemctl daemon-reload
17. sudo systemctl start bluetooth
18. bluetoothd --version # should now print 5.44

Please note that some distributions might use a different directory for system deamons, apply step 13 only as needed.

1. echo "power on" | sudo bluetoothctl Enables your built-in Bluetooth adapter or external Bluetooth USB dongle

BlueZ also provides an interactive commandline tool to interact with Bluetooth devices. You know that your BlueZ installation is working fine if it discovers any Bluetooth devices nearby.

sudo bluetoothctl Starts an interactive mode to talk to BlueZ

• power on Enables the Bluetooth adapter
• scan on Start Bluetooth device scanning and lists all found devices with MAC addresses
• connect AA:BB:CC:DD:EE:FF Connects to a Bluetooth device with specified MAC address
• exit Quits the interactive mode

To install this GATT module and the Python3 D-Bus dependency globally, run:

sudo pip3 install gattsudo apt-get install python3-dbus

To test if your setup is working, run thegattctl tool that is part of this SDK. Note that it must be run as root because on Linux, Bluetooth discovery by default is a restricted operation.

sudo gattctl --discoversudo gattctl --connect AA:BB:CC:DD:EE:FF # Replace the MAC address with your Bluetooth device's MAC addresssudo gattctl --help # To list all available commands

This SDK requires you to create subclasses ofgatt.DeviceManager andgatt.Device. The other two classesgatt.Service andgatt.Characteristic are not supposed to be subclassed.

gatt.DeviceManager manages all known Bluetooth devices and provides a device discovery to discover nearby Bluetooth Low Energy devices. You want to subclass this manager to access Bluetooth devices as they are discovered as well as to restrict the set of devices to those that you actually want to support by your manager implementation. By defaultgatt.DeviceManager discovers and returns all Bluetooth devices but you can restrict that by overridinggatt.DeviceManager.make_device().

gatt.Device is the base class for your Bluetooth device. You will need to subclass it to implement the Bluetooth GATT profile of your choice. Overridegatt.Device.services_resolved() to interact with the GATT profile, i.e. start reading from and writing to characteristics or subscribe to characteristic value change notifications.

The SDK entry point is theDeviceManager class. Check the following example to dicover any Bluetooth Low Energy device nearby.

importgattclassAnyDeviceManager(gatt.DeviceManager):defdevice_discovered(self,device):print("Discovered [%s] %s"% (device.mac_address,device.alias()))manager=AnyDeviceManager(adapter_name='hci0')manager.start_discovery()manager.run()

Please note that communication with your Bluetooth adapter happens over BlueZ's D-Bus API, hence an event loop needs to be run in order to receive all Bluetooth related events. You can start and stop the event loop viarun() andstop() calls to yourDeviceManager instance.

Oncegatt.DeviceManager has discovered a Bluetooth device you can use thegatt.Device instance that you retrieved fromgatt.DeviceManager.device_discovered() to connect to it. Alternatively you can create a new instance ofgatt.Device using the name of your Bluetooth adapter (typicallyhci0) and the device's MAC address.

The following implementation ofgatt.Device connects to any Bluetooth device and prints all relevant events:

importgattmanager=gatt.DeviceManager(adapter_name='hci0')classAnyDevice(gatt.Device):defconnect_succeeded(self):super().connect_succeeded()print("[%s] Connected"% (self.mac_address))defconnect_failed(self,error):super().connect_failed(error)print("[%s] Connection failed: %s"% (self.mac_address,str(error)))defdisconnect_succeeded(self):super().disconnect_succeeded()print("[%s] Disconnected"% (self.mac_address))defservices_resolved(self):super().services_resolved()print("[%s] Resolved services"% (self.mac_address))forserviceinself.services:print("[%s]  Service [%s]"% (self.mac_address,service.uuid))forcharacteristicinservice.characteristics:print("[%s]    Characteristic [%s]"% (self.mac_address,characteristic.uuid))device=AnyDevice(mac_address='AA:BB:CC:DD:EE:FF',manager=manager)device.connect()manager.run()

As with device discovery, remember to start the Bluetooth event loop withgatt.DeviceManager.run().

As soon asgatt.Device.services_resolved() has been called by the SDK, you can access all GATT services and characteristics. Services are stored in theservices attribute ofgatt.Device and eachgatt.Service instance has acharacteristics attribute.

To read a characteristic value first get the characteristic and then callread_value().gatt.Device.characteristic_value_updated() will be called when the value has been retrieved.

The following example reads the device's firmware version after all services and characteristics have been resolved:

importgattmanager=gatt.DeviceManager(adapter_name='hci0')classAnyDevice(gatt.Device):defservices_resolved(self):super().services_resolved()device_information_service=next(sforsinself.servicesifs.uuid=='0000180a-0000-1000-8000-00805f9b34fb')firmware_version_characteristic=next(cforcindevice_information_service.characteristicsifc.uuid=='00002a26-0000-1000-8000-00805f9b34fb')firmware_version_characteristic.read_value()defcharacteristic_value_updated(self,characteristic,value):print("Firmware version:",value.decode("utf-8"))device=AnyDevice(mac_address='AA:BB:CC:DD:EE:FF',manager=manager)device.connect()manager.run()

To write a characteristic value simply callwrite_value(value) on the characteristic withvalue being an array of bytes. Thencharacteristic_write_value_succeeded() orcharacteristic_write_value_failed(error) will be called on yourgatt.Device instance.

To subscribe for characteristic value change notifications callenable_notifications() on the characteristic. Then, on yourgatt.Device instance,characteristic_enable_notification_succeeded() orcharacteristic_enable_notification_failed() will be called. Every time the Bluetooth device sends a new value,characteristic_value_updated() will be called.

Pleaseopen an issue for this repository.

Contributions are welcome via pull requests. Please open an issue first in case you want to discus your possible improvements to this SDK.

The GATT SDK for Python is available under the MIT License.