The First Argument must be callable in start_notify

[Viswa1999]

• bleak version:
• Python version:
• Operating System:

Description

I am trying to get the live notification in start_notify, but I am getting this error, "The First Argument must be callable".

What I Did

I tried with numerous methods, but unable to solve. Can anybody suggest a solution?

[dlech]

A callable is a Python function/method, so this is what is expected to be passed as the argument. Can you share the code you tried?

[Viswa1999]

Traceback (most recent call last):
  File "C:\Users\VISSURES\Downloads\PythonBLE_UI_testing\PythonBLE_UI\main.py", line 304, in ble_get_notify
    await self.client.start_notify(BLE_read_Char, self.notification_handler(frame,BLE_read_Char))
  File "C:\Users\VISSURES\AppData\Local\Programs\Python\Python311-32\Lib\site-packages\bleak\__init__.py", line 832, in start_notify
    wrapped_callback = functools.partial(callback, characteristic)
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: the first argument must be callable
0107F1010048D7 : b6ab2ce3-a5aa-436a-817a-cc13a45aab76

[dlech]

The error message does not match the code you shared.

await self.client.start_notify(BLE_read_Char, self.notification_handler(frame,BLE_read_Char))

Is wrong.

 await self.client.start_notify(BLE_read_Char, self.notification_handler)

Looks OK.

[Viswa1999]

I tried this,

await self.client.start_notify(BLE_read_Char, self.notification_handler)

getting this stack trace error.

Traceback (most recent call last):
  File "C:\Users\VISSURES\AppData\Local\Programs\Python\Python311-32\Lib\threading.py", line 1038, in _bootstrap_inner    
    self.run()
  File "C:\Users\VISSURES\AppData\Local\Programs\Python\Python311-32\Lib\threading.py", line 975, in run
    self._target(*self._args, **self._kwargs)
  File "C:\Users\VISSURES\Downloads\PythonBLE_UI_testing\PythonBLE_UI\main.py", line 468, in get_notify
    await self.client.start_notify(BLE_read_Char, self.notification_handler)
  File "C:\Users\VISSURES\AppData\Local\Programs\Python\Python311-32\Lib\site-packages\bleak\__init__.py", line 834, in start_notify
    await self._backend.start_notify(characteristic, wrapped_callback, **kwargs)
  File "C:\Users\VISSURES\AppData\Local\Programs\Python\Python311-32\Lib\site-packages\bleak\backends\winrt\client.py", line 974, in start_notify
    await winrt_char.write_client_characteristic_configuration_descriptor_async(
OSError: [WinError -2140864509] The attribute cannot be written

The Read Characteristics provided is correct.

[dlech]

Sounds like the device isn't following the BLE spec. You can try logging Bluetooth packets and running the service explorer sample to try to see what is going on.

[Viswa1999]

Hi @dlech, We resolved the error, it was the BLEDescriptor issue. Thanks for your help.
Write the correct descriptors for notification and making the proper time delay in bleak, will send the data consistently through notification handler