pc_ble_driver_py takes a lot of time to discover services, characteristics, and descriptors

[Roman H]

Hi everyone.

I'm using pc_ble_driver_py with nRF52840 USB dongle with burned connectivity_4.1.1_usb_with_s140_6.1.1.hex.

pc_ble_driver_py is modified by me to support BLE5.0 features.

It looks like everything works well, but timings spent on the discovering services, characteristics, and descriptors are too long (up to 25-30 seconds) and depend on PC used.

I have localized the place where most of the time spent, it is between sending the command via UART (ASIO library) to BLE dongle and waiting for the response.

I was trying to decrease connection interval, but discovery timings stay the same.

Also, I have tried to use pc_ble_driver DLL in bare C, but here timings are well.

Does this issue is known? Or do you have any suggestions on how to decrease discovery timings?

Thanks.

[Einar Thorsrud]

Hi,

It is difficult to say what could cause the delay(s) without knowing more. Do you have a log or similar showing the flow that you can upload here together with your code? A sniffer trace could also be useful so that we can see what happens on air.

[Roman H]

Unfortunately, I can't share the code. But I'm using the Python library provided by Nordic with some changes to support BLE 5.0. I haven't changed the procedures of the services, characteristics and descriptors discovery. 

[Roman H]

Hi, I'll try to get a sniffer log as soon as possible.

Also, I was playing with the connection interval, but the timing was almost the same as for 100 ms and as for 10 ms.

[Roman H]

ATT(py).csv

Hi. Log from sniffer attached.

[Einar Thorsrud]

Hi,

This is just ATT traffic. Can you upload a full sniffer trace (with all layers)? Prefrably in the sniffers native format.

[Roman H]

Yes of course.

Here is also RAW sniffer log files.

We are using Frontline BPA low energy Bluetooth protocol analyzer.

SnifferLog.zip

[Einar Thorsrud]

Hi,

Looking at the sniffer trace  I see that the connection interval is 80 ms, but you are probably right that it doe snot have a large effect. There is a significant overhead using serialization. Also, I see a  there is a lot of Find Information Requests and responses back and forth, so you are trying to discover all services. That takes a long time. You could speed it ut by looking for specific services, as suggested here.

[Roman H]

Einar Thorsrud said:

Also, I see a  there is a lot of Find Information Requests and responses back and forth, so you are trying to discover all services. That takes a long time.

Yes, we are discovering all services, characteristics, and descriptors, but the main issue here is that when we using DLL in C code the timing is OK. We have a timing issue only when we use wrapped DLL with Python.

[Einar Thorsrud]

Hi,

I see. I do not see any reason why there is a significant difference between pc-ble-driver and pc-ble-driver-py. Let me loo into it and get back to you.

[Roman H]

Hi Einar, 

Do you have any progress with my case?

[Einar Thorsrud]

Hi,

I bumped the issue now and talked to the developer. He is looking into it and hopefully, we will have some updates soon.

[Roman H]

Hi Einar,

Do you have any updates?