nRF52840 BLE connection frequently disconnects in OTA test use CMW500's connect mode

RE: nRF52840 BLE connection frequently disconnects in OTA test use CMW500's connect mode

Asbjørn — Tue, 11 Nov 2025 10:35:14 GMT

Hello Rong-Lin,

In nrf52840_sniffer_1 for example:

The central/cmw send a follow up feature request before the first one is completed and this is the violation. It seems the link is operating at the RSSI limit for one of them and central seems to be losing packages. The spec says you can request ll features multiple times, but you have to finish one exchange before next is initiated and this is what is not kept.

We cannot create a softdevice/BLE controller to accommodate this by bending the specification. From our point of view it will come back as we are violating the specification and create more questions and issues. Having a test HCI out there for this purpose is a matter of risk assessment from our point of view. If we were to release such a controller it is a higher risk that some will end up using it in production unintentionally or intentionally.

With regards to the another BLE vendor door lock. Don't know what sort of radio product that is inside that, but it is of course possible to bend the specification which could explain this, but I don't think it is a Nordic radio inside that door lock.

Best regards

Asbjørn

RE: nRF52840 BLE connection frequently disconnects in OTA test use CMW500's connect mode

RongLinQin — Thu, 06 Nov 2025 01:24:53 GMT

Hi Asbjørn:

We also captured logs from another BLE door lock from other manufacture which can run CMW5000 BLE OTA test normally. Could you help us to check these log?

Thanks!

devzone.nordicsemi.com/.../other_5F00_ble_5F00_device_5F00_test_5F00_ok.7z

BRs

Qin, Rong-Lin

RE: nRF52840 BLE connection frequently disconnects in OTA test use CMW500's connect mode

RongLinQin — Tue, 04 Nov 2025 09:00:32 GMT

Hi Asbjørn:

We would like to test the BLE OTA TIS of the nRF52840 over air. Currently, we use a wired serial port for testing, which requires breaking the enclosure to route out the serial lines, so we want to perform the test over air.

We captured the sniff log "sniff_nRF52840_CMW500.7z" using nRF Sniffer; each file corresponds to a complete connection cycle from establishment to disconnection. Could you help to check whether the LL_FEATURE_REQ/RSP cause disconnection? Is it possible to modify the Nordic SDK code to prevent this disconnect issue?

Thanks!

devzone.nordicsemi.com/.../sniff_5F00_nRF52840_5F00_CMW500.7z

BRs

Qin, Rong-Lin

RE: nRF52840 BLE connection frequently disconnects in OTA test use CMW500's connect mode

Asbjørn — Tue, 28 Oct 2025 14:10:50 GMT

Hello Rong-Lin,

thanks for the update and yes, this is correct and there are no plans from Nordic point of view to change the behaviour of our SoftDevice.

What is it you would like to test? PER of your system? Is there another approach that would allow you to find the information and verification you want?

Best regards

Asbjørn

RE: nRF52840 BLE connection frequently disconnects in OTA test use CMW500's connect mode

RongLinQin — Mon, 27 Oct 2025 08:39:00 GMT

Hi Asbjørn:

Following info is feedback from R&S：

The 'Connection mode' measurement on the CMW platform uses the LL_Feature_Req/Rsp as the mechanism to perform receiver (PER) measurements.
So, we are using this measurement mode as a way of allowing customers to test RF performance OTA.
However, in order to allow this mode of operation to work means ‘bending the rules’ of the Core Specification – I.e. it has been done by design and not by accident.

If we didn't do this then the measurement would not be possible.

Other devices don't have a issue with this approach.

We have already discussed it with the Nordic engineering team.

BRs

Qin, Rong-Lin

RE: nRF52840 BLE connection frequently disconnects in OTA test use CMW500's connect mode

Asbjørn — Thu, 23 Oct 2025 08:11:21 GMT

Hi,

I can't prove that it is the LL_FEATURE_ REQ sent twice that is causing the behavior you're seeing in this case based on the information I have received, but we have seen others have similar experiences with R&S and LL_FEATURE_ REQ. There's no workaround for it as it would be a specification violation to ignore the double request. Is there a log from the R&S that will print the commands sent and received? There it should be possible to see what sort of messages are going from the CMW just prior to the disconnect. That will also show if it actually is the double LL_FEATURE_ REQ that I suspect or if it is something else.

Best regards

Asbjørn

RE: nRF52840 BLE connection frequently disconnects in OTA test use CMW500's connect mode

RongLinQin — Tue, 21 Oct 2025 02:39:55 GMT

Hi Asbjørn:

Thanks for your information,

We are now checking it with R&S FAE, Looks like they have not any idea for that, but they said they will check it internally.

And for this message - LL_FEATURE_ REQ sent two time and violate BLE spec. not sure if there is any workaround which we can overcome this issue, e.g. in app layer, just return ok and not do anything for this message, would you please help check and give comment?

Thanks a lot.

Best Regards

RE: nRF52840 BLE connection frequently disconnects in OTA test use CMW500's connect mode

Asbjørn — Fri, 17 Oct 2025 09:50:15 GMT

Hello,

We've had other customers seeing issues with maintaining a link with the CMW and seen that in some situations the CMW will send two LL_FEATURE_REQ to the DUT and this breaks the connection as it is a violation of the BLE spec. I cannot for sure say that this is the same that you observe, but the description is very very similar. You'd have to get in touch with R&S to follow this with them in this case.

Best regards

Asbjørn