CODEWITHSUNDEEP
pythonbluetoothbluetooth-lowenergycharacteristics
Joseph Roberts
Joseph Roberts

Reputation: 569

Bluetooth Bluepy not finding all characteristics

I am using the bluepy library to communicate with a bluetooth device but it is not showing me all the characteristics.

When I run the following using gatttool I get:

[EE:50:F0:F8:3C:FF][LE]> char-desc 0x0019 0xffff
handle: 0x0019, uuid: 00002800-0000-1000-8000-00805f9b34fb
handle: 0x001a, uuid: 00002803-0000-1000-8000-00805f9b34fb
handle: 0x001b, uuid: 00001532-1212-efde-1523-785feabcd123
handle: 0x001c, uuid: 00002803-0000-1000-8000-00805f9b34fb
handle: 0x001d, uuid: 00001531-1212-efde-1523-785feabcd123
handle: 0x001e, uuid: 00002902-0000-1000-8000-00805f9b34fb
handle: 0x001f, uuid: 00002803-0000-1000-8000-00805f9b34fb
handle: 0x0020, uuid: 00001534-1212-efde-1523-785feabcd123

But when I run the following using Bluepy I get:

characteristics = self.peripheral.getCharacteristics(startHnd=0x0019, endHnd=0xFFFF, uuid=None)
for characteristic in characteristics:
    print("{}, hnd={}, supports {}".format(characteristic, hex(characteristic.handle), characteristic.propertiesToString()))

Characteristic <00001532-1212-efde-1523-785feabcd123>, hnd=0x1a, supports WRITE NO RESPONSE 
Characteristic <00001531-1212-efde-1523-785feabcd123>, hnd=0x1c, supports NOTIFY WRITE 
Characteristic <00001534-1212-efde-1523-785feabcd123>, hnd=0x1f, supports READ

I need to be able to write '\x01\x00' to characteristic:

handle: 0x001e, uuid: 00002902-0000-1000-8000-00805f9b34fb

followed by writing '\x01\x04' to characteristic:

handle: 0x001d, uuid: 00001531-1212-efde-1523-785feabcd123

but I am unable to because Bluepy is not finding the characteristic:

handle: 0x001e, uuid: 00002902-0000-1000-8000-00805f9b34fb

Why is this?

How can I write to the characteristic when Bluepy does not find it?

Why do the handles returned by Bluepy not match those returned by gatttool?

Thanks

Upvotes: 2

Views: 1844

Answers (1)

Jeremy H.
Jeremy H.

Reputation: 13

You are mistaken as to what those additional characteristics are. The uuids that begin with 000028xx are characteristic "declarations" as seen here: gatt declaration spec, and the uuids that begin with 000029xx are descriptors as seen here: gatt descriptor spec. They are not the characteristics itself, but describe details about one of the characteristics.

Upvotes: 0

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