Can't find 128-bit UUID and service name

RE: Can't find 128-bit UUID and service name

Vidar Berg — Mon, 27 Apr 2020 09:34:36 GMT

Hi,

It is possible to discover services without knowing the UUIDs beforehand. To do that you need to pass a NULL pointer for the p_srvc_uuid input argument. The response will say BLE_UUID_TYPE_UNKNOWN whenever a new 128-bit service is discovered (ie one that hasn't been added with ble_vs_uuid_add()). You can then perform a GATT read on that handle to retrieve the UUID.

Here is how this is handled in the Python wrapper: https://github.com/NordicSemiconductor/pc-ble-driver-py/blob/8e5a9ffb7b6a655baeae7e4591f3ffc50cd62a5b/pc_ble_driver_py/ble_adapter.py#L266. Notice how the 128-bit base uuid gets added through ble_vs_uuid_add() after.

Relevant doc links:

- sd_ble_gattc_primary_services_discover

- GATTC Primary Service Discovery

[quote user="peter li"]BYT, How Can I search out all service , characteristic and characteristic description? Should I search all services first, then all characteristics, and finally all characteristic description? Or Should search services -> characteristics -> characteristic description then loop searches? Which search method is better?[/quote]

It seems like most implementations do it sequentially and start with the discovery of all services first, then proceed with all characteristics and descriptors (you can see this from the python wrapper implementation linked to above).

RE: Can't find 128-bit UUID and service name

peter li — Fri, 24 Apr 2020 10:06:10 GMT

HI ,

Thanks.

I found only use handle also can establish a connection. But I still want to search all UUIDs.. How can I do that if I don't want add the specified base ID in advance ? BYT, How Can I search out all service , characteristic and characteristic description? Should I search all services first, then all characteristics, and finally all characteristic description? Or Should search services -> characteristics -> characteristic description then loop searches? Which search method is better?

RE: Can't find 128-bit UUID and service name

Vidar Berg — Wed, 25 Mar 2020 12:37:03 GMT

Hi,

Are you more familiar with Python, or do you prefer working with C++? I made a GATT client with the pc-ble-driver-py (python wrapper) a while ago which is able to discover the 128-bit Nordic UART service (6E400001-B5A3-F393-E0A9-E50E24DCCA9E). The key difference compared to the regular heart rate collector example is that I added the 128-bit base UUID through ble_vs_uuid_add before initiating service discovery.

pc-ble-driver-py NUS client example:

devzone.nordicsemi.com/.../nus_5F00_central.zip