Bluetooth LE: “Unsupported Remote Feature (0x1a)” error when connecting nRF52840 central to Raspberry Pi Zero 2W peripheral

RE: Bluetooth LE: “Unsupported Remote Feature (0x1a)” error when connecting nRF52840 central to Raspberry Pi Zero 2W peripheral

Faranak Karimi — Mon, 28 Apr 2025 19:10:12 GMT

Thanks a lot for your help Hung! you've been great help.

RE: Bluetooth LE: “Unsupported Remote Feature (0x1a)” error when connecting nRF52840 central to Raspberry Pi Zero 2W peripheral

Hung Bui — Mon, 28 Apr 2025 14:42:18 GMT

Hi Faranak,

[quote user="Faranak Karimi"]There is no newer SoftDevice for nRF5 SDK that already supports LL_PERIPHERAL_FEATURE_REQ, right?[/quote]

Correct, there is no drop in softdevice for nRF5 SDK that support LL_PERIPHERAL_FEATURE_REQ.

[quote user="Faranak Karimi"]If we stay on nRF5 SDK for the time being, the only practical fix is to disable the Peripheral-Feature procedure in BlueZ (or patch BlueZ to ignore the UNKNOWN_RSP). Do you see any other route?[/quote]

Correct. At this moment it's the only solution as far as I know.

RE: Bluetooth LE: “Unsupported Remote Feature (0x1a)” error when connecting nRF52840 central to Raspberry Pi Zero 2W peripheral

Faranak Karimi — Mon, 28 Apr 2025 14:22:30 GMT

Hi Hung,

thank you very much for digging into the trace and pointing out what’s happening.
If I understand your explanation correctly, Because nRF5 SDK (and the full SoftDevice that comes with it) has been frozen in maintenance mode since 2019, support for newer LL procedures such as LL_PERIPHERAL_FEATURE_REQ never made it in.

I checked the link you provided and my understanding is that the new SDK is based on ZypherOS and the APIs are different from what was used in older SoftDevice versions. Since my project is adding a feature to a semi-large legacy codebase, migrating to the new nRF Connect SDK is costly.

Could you please confirm that this reading is correct?
And, just to be sure:

There is no newer SoftDevice for nRF5 SDK that already supports LL_PERIPHERAL_FEATURE_REQ, right?
If we stay on nRF5 SDK for the time being, the only practical fix is to disable the Peripheral-Feature procedure in BlueZ (or patch BlueZ to ignore the UNKNOWN_RSP). Do you see any other route?

Thanks again for the quick and helpful answer!

RE: Bluetooth LE: “Unsupported Remote Feature (0x1a)” error when connecting nRF52840 central to Raspberry Pi Zero 2W peripheral

Hung Bui — Wed, 23 Apr 2025 13:48:25 GMT

Thanks Faranak,
I think it's clear now. The BlueZ sent the LL_PERIPHERAL_FEATURE_REQ, the nRF52 replied with UNKNOWN_RSP as it doesn't recognize this request. After that BlueZ terminate the connection.

You can follow what Emil suggested, update to newer BLE stack from Nordic.
Please be aware that nRF5 SDK (and the softdevice included with nRF5 SDK) has been put on maintenance mode since 2019. We haven't added new feature to it since then.

The new platform is nRF Connect SDK and the Softdevice controller stack included in the nRF Connect SDK.

You can get started with nRF Connect SDK using our Dev Academy course here: https://academy.nordicsemi.com/

RE: Bluetooth LE: “Unsupported Remote Feature (0x1a)” error when connecting nRF52840 central to Raspberry Pi Zero 2W peripheral

Faranak Karimi — Tue, 22 Apr 2025 14:47:26 GMT

[quote userid="109356" url="~/f/nordic-q-a/120846/bluetooth-le-unsupported-remote-feature-0x1a-error-when-connecting-nrf52840-central-to-raspberry-pi-zero-2w-peripheral/532353"]Maybe you can ask on the BlueZ mailing list why this behaviour exists?[/quote]

I will try to contact the for sure, as this seems odd to disconnect the connection due to a 0x1a.

[quote userid="109356" url="~/f/nordic-q-a/120846/bluetooth-le-unsupported-remote-feature-0x1a-error-when-connecting-nrf52840-central-to-raspberry-pi-zero-2w-peripheral/532353"]Otherwise, maybe you can upgrade the nRF Bluetooth stack to a newer version supporting this request?[/quote]

This is my first time around nRF Devices and Bluetooth stack in general, I am not sure how can I do this? I already use the most recent SoftDevice provided by Nordic. If you could go into more details on how can I achieve this, that would be massive help.

RE: Bluetooth LE: “Unsupported Remote Feature (0x1a)” error when connecting nRF52840 central to Raspberry Pi Zero 2W peripheral

Faranak Karimi — Tue, 22 Apr 2025 14:38:42 GMT

Thanks for the response. You guys were absolutely right, there were some frames missing, I tried sniffing the frames again and this time event counter seems to increase smoothly

and now we can see the "LE Read Remote Used Features" and also the terminate request coming from Raspberrypi.
devzone.nordicsemi.com/.../Ras_5F00_dongle_5F00_Unsuccessful_5F00_connection_5F00_recapture.pcapng
I attached the recorded file again.

RE: Bluetooth LE: “Unsupported Remote Feature (0x1a)” error when connecting nRF52840 central to Raspberry Pi Zero 2W peripheral

Emil Lenngren — Tue, 22 Apr 2025 12:52:13 GMT

I can see that the LL_UNKNOWN_RSP contains the "unknown type" field LL_PERIPHERAL_FEATURE_REQ, which means that the RPi sent this request and the central (nrf52) does not support this type of request. It seems very harsh that the RPi disconnects the connection due to this. The connection can of course be kept alive despite this problem. Maybe you can ask on the BlueZ mailing list why this behaviour exists? The Peripheral Feature Request is an optional feature to support, so it should not be uncommon for this to happen.

Otherwise, maybe you can upgrade the nRF Bluetooth stack to a newer version supporting this request?

RE: Bluetooth LE: “Unsupported Remote Feature (0x1a)” error when connecting nRF52840 central to Raspberry Pi Zero 2W peripheral

Hung Bui — Tue, 22 Apr 2025 12:13:49 GMT

Hi Faranak,
As Emil already mentioned, please try to capture the sniffer trace again. Please try to put the sniffer close to both of the devices.
From what you described it's most likely the issue with the Peripheral that it doesn't accept the 0x1a response from the nRF52 and terminate the connection.
If you can provide us better traces we would be able to compare the issue between the connection to a phone and to the nRF52.

I don't see the "LE Read Remote Used Features" request in the traces you provided.

RE: Bluetooth LE: “Unsupported Remote Feature (0x1a)” error when connecting nRF52840 central to Raspberry Pi Zero 2W peripheral

Emil Lenngren — Tue, 22 Apr 2025 08:59:52 GMT

Unfortunately, it seems the sniffer missed capturing some packets. If you expand "nRF Sniffer for Bluetooth LE", you can see that the Event counter goes from 0 to 2 to 4 to 6. Maybe you can try to capture again and make sure all packets are captured?

RE: Bluetooth LE: “Unsupported Remote Feature (0x1a)” error when connecting nRF52840 central to Raspberry Pi Zero 2W peripheral

Faranak Karimi — Tue, 22 Apr 2025 08:29:05 GMT

Yes. Since my original problem was the connection disruption between Raspberrypi zero 2w and a customized nrf52840 dongle, after your recommendation used NRF52840-DK as an sniffer to capture the traffic between these 2 devices.

the selected frames are the ones that are transferred after connection, the connection seems to end after these exchanges. I attached the complete recorded details in "Ras_dongle_Unsuccessful_connection.pcapng".
I also attached the recording of connection between my Raspberrypi and phone(In central mode), which is successful. I thought this might be helpful since both nrf52 and my phone use bluetooth version 5 and raspberry's bluetooth version is 4.

devzone.nordicsemi.com/.../Ras_5F00_dongle_5F00_Unsuccessful_5F00_connection.pcapng

devzone.nordicsemi.com/.../Ras_5F00_Phone_5F00_Successful_5F00_connection_5F00_and_5F00_pairing_5F00_filtered.pcapng

Thanks in advance for your help.

RE: Bluetooth LE: “Unsupported Remote Feature (0x1a)” error when connecting nRF52840 central to Raspberry Pi Zero 2W peripheral

Emil Lenngren — Sun, 20 Apr 2025 15:23:29 GMT

Have you tried running nRF Sniffer on a separate devkit to see what's going on in the air traffic?