Overview

Bluetooth

Bluetooth is a standard set of binary protocols for short-range wireless communication between devices.

• Bluetooth “Classic” (BR/EDR) supports speeds up to about 24Mbps.
• Bluetooth 4.0 introduces a low energy mode, “Bluetooth Low Energy” (BLE or LE, also known as “Bluetooth Smart”), that operates at 1Mbps. This mode allows devices to leave their transmitters off most of the time. As a result it is “Low Energy”.

BLE functionality is dominated by key/value pairs that create a Generic Attribute Profile (GATT).

BLE defines multiple roles that devices can play:

• The Broadcaster (beacon) is a transmitter only application.
• The Observer (scanner) is for receiver only applications.
• Devices acting in the Peripheral role can receive connections.
• Devices acting in the Central role can connect to Peripheral devices.

BlueZ

BlueZ is a Bluetooth stack for the Linux family of operating systems. Support for BlueZ can be found in many Linux distributions available.

The highest level of API on BlueZ is the DBus API which can be daunting to users unfamiliar with such APIs. python-bluezero offers users a more gentle learning curve to using Bluetooth functionality on Linux.

Bluezero API Complexity

This section gives guidelines about the complexity of different python-bluezero APIs. We will use the terms Level 1, 10 and 100. A new user would start at Level 1 as this should offer the least friction. If at a later stage a greater level of control is needed then the user can progress on to the other levels. As the user becomes more experienced they may not need Bluezero and will use BlueZ on its own. The numbers for the API levels represent the steps in code and knowledge required with each step.

Level 1

• At this level the interface will be pythonic.
• The API will not assume knowledge of Bluetooth, DBus or event loops.
• For something to exist at this level there will need to be a public Bluetooth Profile in existence so that users does not need to enter UUIDs etc.
• This might be specific hardware such as the BBC micro:bit or it could be more generalised hardware such as Heart Rate Monitors.

Level 10

• At this level the API will be pythonic.
• The API will require some knowledge of Bluetooth such as UUIDs of services and characteristics for selecting required services.
• The API will not expose DBus terminology and will simplify event loops.

Level 100

• At this level the interface is expecting the user to know Bluetooth, DBus and event loops.
• DBus function names are not Pythonic and may be exposed at the level.
• This level will be very specific to the Linux kernel and so it will be difficult to port this to other operating systems that do not have the BlueZ Daemon running.
• The previous more abstracted API levels should be easier to port to any hardware.

Summary of Bluezero Files

Level 1	Level 10	Level 100	shared
microbit.py	broadcaster.py	adapter.py	tools.py
eddystone_beacon.py	central.py	advertisement.py	constants.py
	observer.py	device.py	dbus_tools.py
	peripheral.py	GATT.py	async_tools.py
		localGATT.py
		media_player.py