BTZen is a library to asynchronously access Bluetooth devices using Python
language. It provides simple API over complex D-Bus Bluez interface.
Features
The main features of BTZen are
- Connect and access multiple Bluetooth devices in parallel with Python
asynchronous coroutines.
- GATT notification interface integrated into main API of the library.
- Automatic reconnections to devices.
- Access to serial devices implementing Stollmann (Telit) protocol.
- Support for devices, which do not follow the Bluetooth specification
fully like SensorTag (CC2650STK) or Thingy:52.
- Support for Bluez managed interfaces of devices, i.e. battery level.
- Allow to implement support for new devices easily.
The library can be used with any Bluetooth Smart device. It was tested with
- SensorTag (CC2650STK) to read temperature, pressure, humidity, light,
accelerometer data and state of the buttons.
- Thingy:52 to read temperature, pressure, humidity, light data and state
of the button.
- Mi Smart Scale to read weight data.
- OSTC dive computer to read serial device data using Stollmann (Telit)
protocol.
The library is tested with default asyncio
event loop and its drop-in
replacement uvloop <https://github.com/MagicStack/uvloop>
_. Use of
uvloop
increases performance of the library.
The scripts in scripts
directory demonstrate reading data from various
devices.
NOTE: The first version of SensorTag (CC2541DK) is not supported at the
moment. If you still own the device and would like it to be supported,
please raise an issue <https://github.com/wrobell/btzen/issues>
_.
API Changes
Please note that since version 0.6.0 the API changed. The benefits are
- support different makes of devices with single API
- it is much easier to implement functionality for new devices
- shutting down of BTZen connection sessions is more reliable
If pre-0.6.0 version of BTZen is required, then use appropriate versioning
in installation requirements of your project.
Documentation
This project's documentation is lacking at the moment. Some useful tips
might be found in this README file and files at
https://github.com/wrobell/btzen/tree/master/doc
Installation
Use pip
to install BTZen library (Cython needs to be installed first),
for example::
pip install --user cython
pip install --user btzen
BTZen uses experimental API of Bluez adapter interface to connect to
Bluetooth devices. The bluetoothd
daemon has to be started with
experimental option on. This can be permanently achieved by setting
Experimental
to true
in /etc/bluez/main.conf
file.
Change AutoEnable
option to true in /etc/bluetooth/main.conf
to
automate powering up of Bluetooth controllers. Otherwise a controller might
need to be switched on manually with bluetoothctl
tool. BTZen library
does not perform this operation.
Connection Management
BTZen uses ConnectDevice
method of Bluez adapter interface to discover
and connect to Bluetooth devices. MAC address of a device needs to be known
in order to connect.
BTZen connection manager allows to connect and disconnect Bluetooth devices
without restarting of an application. If an application is reading data
from multiple Bluetooth devices, the application can continue working if,
for example, a sensor requires battery change.
Please note
- when trying to connect to a device using BTZen library, do not start scan
with other programs, i.e.
bluetoothctl
- if a device is disconnected with an external program, the external program
has to be used to reconnect
Obtaining MAC Address
If Bluetooth device MAC address is not known
- Start
bluetoothctl
. - Start scan.
- Save discovered MAC address.
- Optionally, remove device with
remove
command of bluetoothctl
utility. - Start BTZen based application using the discovered MAC address.
Performance
The library enables programmers to communicate with mutliple devices in
parallel without using threads. This avoids context switching of threads
and minimizes memory requirements, which makes BTZen more efficient than
other, similar libraries. To keep the library as fast as possible, Cython
is used to access Bluez D-Bus API. BTZen can be used with uvloop
for even
more increased performance of an application.
Support for GATT notification interface allows efficient use of Bluetooth
devices. For example, data from sensors like accelerometers can be read
only when sensor wakes up and transmits data after sensor has been moved.
This limits amount of transferred data and avoids draining battery of the
sensor, which will happen if data is polled at regular, short intervals.
Requirements
BTZen library requires the following software components
- Python 3.11
- bluez 5.68
sd-bus
(kart of systemd
)- Cython 3.0.0
License
BTZen library is licensed under terms of GPL license, version 3, see
COPYING <https://www.gnu.org/licenses/gpl-3.0.en.html>
_ file for details.