This is a Python library to use the GATT Protocol for Bluetooth LE devices. It uses D-Bus to control the underlying hardware. It does not call other binaries to do its job :)
You can install this library using Python pip. If you use Debian/Ubuntu, you may also
install using the provided Debian package.
As easy as always:
pip install gattlibThere is a single Debian package available from https://github.com/oscaracena/pygattlib/releases. Just download it and install using the following command:
sudo apt install ./python3-gattlib*.debThis 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.
To discover BLE devices, use the DiscoveryService provided. You need
to create an instance of it, indicating the Bluetooth adapter you want
to use. Then call the method discover. Here you have some options. If
you provide a timeout, then it will wait that amount of time and
return a dictionary with the address and name of all the devices that
responded the discovery. For example:
from gattlib import DiscoveryService
service = DiscoveryService("hci0")
devices = service.discover(timeout=5)
for address, name in devices.items():
print("name: {}, address: {}".format(name, address))If you don't provide a timeout, then you must give a
callback function. The discover will return inmediatly, but the
process will still be running on a separated thread. When a new device
is discovered, the callback will be called (with the name and address as
it's arguments). For example:
import time
from gattlib import DiscoveryService
def on_new_device(name, address):
print("name: {}, address: {}".format(name, address))
service = DiscoveryService("hci0")
service.discover(callback=on_new_device)
try:
# You can do here other things, while discovering is still running
time.sleep(9999)
except KeyboardInterrupt:
service.stop()As a third option, you may provide both the timeout and the callback.
In that case, the call to discover is blocking, and it will return the
discovered devices when the timeout expired. Also, while it is running and
a new device is found, it will call the provided callback.
In order to manage a discovered device, you need to create an instance of
GATTRequester, using its address. Then, you can call connect() to create
a new connection to that device. If the device is not paired, it will try to
pair as well. For example:
import sys
from gattlib import GATTRequester
if len(sys.argv) < 2:
print("Usage: {} <addr>".format(sys.argv[0]))
sys.exit(1)
print("Connecting...")
requester = GATTRequester(sys.argv[1], auto_connect=False)
requester.connect()
print("Done.")The connect() method has the following arguments:
wait: boolean, to indicate if you want to wait for this method to complete
or not.on_connect: Callable, used to provide a callback that will be called when the
connection is stablished, and will be called again if the connection is reset.on_fail: Callable, used to provide a callback to be called when an error on
connection process occur.on_disconnect: Callable, a callback that will be called if the device is
disconnected, for whatever reason it be.You may also subclass the GATTRequester, and override the on_connect(),
on_connect_failed(msg: str) and on_disconnect() methods. Something like this:
class MyRequester(GATTRequester):
def on_connect(self):
print("Connected OK.")
def on_connect_failed(self, msg):
print("Could not connect! :(")
print(f"ERROR was: {msg}")
def on_disconnect(self):
print("Disconnected!")Once connected to a device, you can retrieve a list of its GATT services,
calling discover_primary(). This method will return a list of Service UUIDs.
For example:
import sys
from gattlib import GATTRequester
if len(sys.argv) < 2:
print("Usage: {} <addr>".format(sys.argv[0]))
sys.exit(1)
requester = GATTRequester(sys.argv[1], auto_connect=True)
print("Find GATT Primary services...")
primary = requester.discover_primary()
for prim in primary:
print(f"- {prim}")You can, also, discover the list of characteristics of a service, given its
UUID. To do so, use the method discover_characteristics(). Like this:
import sys
from gattlib import GATTRequester
if len(sys.argv) != 3:
print("Usage: {} <addr> <service-UUID>".format(sys.argv[0]))
sys.exit(1)
requester = GATTRequester(sys.argv[1], auto_connect=True)
print("Find GATT Characteristics of given service...")
chars = requester.discover_characteristics(service_uuid=sys.argv[2])
for c in chars:
print(f"- {c}")First of all, you need to create a GATTRequester, passing the address
of the device to connect to. Then, you can read some characteristic's value
given its UUID. For example:
from gattlib import GATTRequester
req = GATTRequester("00:11:22:33:44:55")
value = req.read_by_uuid("00002a00-0000-1000-8000-00805f9b34fb")The process is almost the same: you need to create a GATTRequester
passing the address of the device to connect to. Then, define a function
callback on which receive the response from your device. This callback
will be passed to the *_async method used.
NOTE: It is important to keep the Python process alive, or the
response will never arrive. You can wait on an Event object, or you
can do other things meanwhile.
The following is an example of async reading:
import sys
from threading import Event
from gattlib import GATTRequester
ready = Event()
def on_response(value):
print(f"Value: {value}")
ready.set()
requester = GATTRequester("00:11:22:33:44:55")
requester.read_by_uuid_async(
char_uuid = sys.argv[2],
on_response = on_response)
print("Async reading, waiting response...")
ready.wait()The process to write data is the same as for read. Create a GATTRequest object,
and use the method write_by_uuid to send the data. This method will issue a
write request. As a note, data must be a bytes object. See the following
example:
from gattlib import GATTRequester
req = GATTRequester("00:11:22:33:44:55")
req.write_by_uuid(0x10, bytes([14, 4, 56]))You can also use the write_cmd() to send a write command instead. It has the
same parameters as write_by_uuid: the uuid id and a bytes object. As an
example:
from gattlib import GATTRequester
req = GATTRequester("00:11:22:33:44:55")
req.write_cmd(0x001e, bytes([16, 1, 4]))FIXME: update!
To receive notifications from a remote device, you will need to enable them on each characteristic (that supports notifications or indications).
For that, you have two options: 1) provide a callback function:
from gattlib import GATTRequester
def on_notification(value):
print(f"- notification arrived, value: {value}")
char_uuid = "00002a00-0000-1000-8000-00805f9b34fb"
req = GATTRequester("00:11:22:33:44:55")
req.enable_notifications(char_uuid, on_notification)or 2) override the on_notification() method of GATTRequester:
from gattlib import GATTRequester
class Requester(GATTRequester):
def on_notification(self, value):
print(f"- notification arrived, value: {value}")
char_uuid = "00002a00-0000-1000-8000-00805f9b34fb"
req = GATTRequester("00:11:22:33:44:55")
req.enable_notifications(char_uuid)This second option is not recommended when you enable notifications on different characteristics, as they will share the same callback, and you will have trouble filtering the notification source. In that case, set a different callback, or use a partial to add a parameter with the source id.
If you encounter any problem, ensure first that your hardware is compatible and working fine. To check if your adapter supports BLE, you can use:
sudo hciconfig hci0 lestatesTo check if the device that you want to talk to is discoverable, run:
bluetoothctl scan leAnd check if it appears on the results. Moreover, you need the bluetooth service registered on DBus. To see if that's the case, run:
gdbus introspect --system --dest org.bluez --object-path /org/bluez/hci0This software may harm your device. Use it at your own risk.
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