1. Oscar Acena
  2. pygattlib

Overview

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Index

Description

This is a Python library to use the GATT Protocol for Bluetooth LE devices. It is a wrapper around the implementation used by gatttool in bluez package. It does not call other binaries to do its job :)

Installation

There are many ways of installing this library: using Python Pip, using the Debian package, or manually compiling it.

Python pip

Install as ever (you may need to install the packages listed on DEPENDS files):

$ sudo pip install gattlib

You can install for Python3 too, just use pip3

Debian way

Add the following line to your sources list:

deb http://babel.esi.uclm.es/arco sid main

And install using apt-get (or similar):

$ sudo apt-get update
$ sudo apt-get install python-gattlib

You can install for Python3 too (Debian package is called python3-gattlib).

Compiling from source

You should install the needed packages, which are described on DEPENDS file. Take special care about versions: libbluetooth-dev should be 4.101 or greater. Then, just type:

$ make
[...]

If you want to compile for Python 3, you need to:

$ make PYTHON_VER=3

Then, to install, just:

$ make install

Usage

This library provides two ways of work: sync and async. The Bluetooth LE GATT protocol is asynchronous, so, when you need to read some value, you make a petition, and wait for response. From the perspective of the programmer, when you call a read method, you need to pass it a callback object, and it will return inmediatly. The response will be "injected" on that callback object.

This Python library allows you to call using a callback object (async), or without it (sync). If you does not provide a callback (working sync.), the library internally will create one, and will wait until a response arrives, or a timeout expires. Then, the call will return with the received data.

Discovering devices

To discover BLE devices, use the DiscoveryService provided. You need to create an instance of it, indicating the Bluetooth device you want to use. Then call the method discover, with a timeout. It will return a dictionary with the address and name of all devices that responded the discovery.

Note: it is very likely that you will need admin permissions to do a discovery, so run this script using sudo (or something similar).

As example:

from gattlib import DiscoveryService

service = DiscoveryService("hci0")
devices = service.discover(2)

for address, name in devices.items():
    print("name: {}, address: {}".format(name, address))

Reading data

First of all, you need to create a GATTRequester, passing the address of the device to connect to. Then, you can read a value defined by either by its handle or by its UUID. For example:

from gattlib import GATTRequester

req = GATTRequester("00:11:22:33:44:55")
name = req.read_by_uuid("00002a00-0000-1000-8000-00805f9b34fb")[0]
steps = req.read_by_handle(0x15)[0]

Reading data asynchronously

The process is almost the same: you need to create a GATTRequester passing the address of the device to connect to. Then, create a GATTResponse object, on which receive the response from your device. This object will be passed to the async method used.

NOTE: It is important to maintain the Python process alive, or the response will never arrive. You can wait on that response object, or you can do other things meanwhile.

The following is an example of response waiting:

from gattlib import GATTRequester, GATTResponse

req = GATTRequester("00:11:22:33:44:55")
response = GATTResponse()

req.read_by_handle_async(0x15, response)
while not response.received():
    time.sleep(0.1)

steps = response.received()[0]

And then, an example that inherits from GATTResponse to be notified when the response arrives:

from gattlib import GATTRequester, GATTResponse

class NotifyYourName(GATTResponse):
    def on_response(self, name):
        print("your name is: {}".format(name))

response = NotifyYourName()
req = GATTRequester("00:11:22:33:44:55")
req.read_by_handle_async(0x15, response)

while True:
    # here, do other interesting things
    sleep(1)

Writing data

The process to write data is the same as for read. Create a GATTRequest object, and use the method write_by_handle to send the data. As a note, data must be a string, but you can convert it from bytearray or something similar. See the following example:

from gattlib import GATTRequester

req = GATTRequester("00:11:22:33:44:55")
req.write_by_handle(0x10, str(bytearray([14, 4, 56])))

Receiving notifications

To receive notifications from remote device, you need to overwrite the on_notification method of GATTRequester. This method is called each time a notification arrives, and has two params: the handle where the notification was produced, and a string with the data that came in the notification event. The following is a brief example:

from gattlib import GATTRequester

class Requester(GATTRequester):
    def on_notification(self, handle, data):
        print("- notification on handle: {}\n".format(handle))

You can receive indications as well. Just overwrite the method on_indication of GATTRequester.

Disclaimer

This software may harm your device. Use it at your own risk.

THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM “AS IS” WITHOUT
WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND
PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE
DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR
CORRECTION.