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. 

[Einar Thorsrud]

Hi,

I am sorry for the late reply. I do not have any update yet, unfortunately. I do not have a timeline for when we will have an improvement for the pc-ble-driver-py performance.

[Roman H]

Hi. I see :( .

[Ingfu]

Hi,

I intent to use the pc-ble-driver-py for a commercial product. After spending quite a lot time to get everything running, I also ran into throughput issues. While we do not require exceptionally high data rates, it would be really great, if there was an increase of the data rates achievable d with the python bindings.

[Bjørn Inge]

Hi Roman,

thanks for sharing logs and traces. It does all show that there is something causing delay, though it's not clear to say what's causing it. 

Have you tried to run with an unmodified version of ble-driver-py? That would make it easier to reproduce on our end.

[Roman H]

Hi Bjorn.

Unfortunately not.

But from logs, you can see than the main time-consuming part is communication between python and DLL.

[Ingfu]

Hi Roman,

did you make any progress on this issue? I am still struggling with the pc-ble-driver-py performance myself.

[Einar Thorsrud]

Hi,

We have not been able to reproduce performance issues on pc-ble-driver-py based on SoftDevice v5. SoftDevice version 6 is not fully supported on the pc-ble-driver(-py) for now (and will not be in the near future). So my recommendation is to stick with v5.

[Roman H]

Hi Ingfu.

Unfortunately not.

[Roman H]

If I'm not mistaken, v5 do not support BLE 5.0 features.

That's why we have started adding support of the v6 to the pc-ble-driver-py on our own.

And faced with that performance issue.