Flashed the nRF Sniffer for Bluetooth LE into my nRF52840 DK (version 3) and now cannot do anything else with the DK

[Omer ZAK]

I took the DevAcademy Bluetooth Low Energy Fundamentals course (https://academy.nordicsemi.com/topic/nrf-sniffer-for-bluetooth-le/).

To do the sixth lesson, I burned the nRF Sniffer for Bluetooth LE into my nRF52840 DK (version 3) and used it to sniff BLE communications between a 3rd party module (Seeed XIAO BLE) and a Samsung tablet, using Wireshark. All worked well.

After finishing the course, I wanted to re-flash the nRF52840 DK with applications using VS Code, to continue my development work.

However, it proved to be impossible. It seems that the regular bootloader was obliterated. Attempts to power-cycle it with pressing RESET button were unsuccessful, powering the DK through either of the two USB connectors.

I found in the downloads section a bootloader file: j-link-ob-sam3u128-v2-nordicsemi-170724.bin

However, the Programmer (which I used to flash the sniffer) accepts only *.hex files (potentially inside *.zip files). So I am currently stuck as far as the nRF52840 DK is concerned. It continues to work well as a packet sniffer, however.

I'd like to get advice how to program a working bootloader into the nRF52840 DK, or confirm that it is impossible and I am stuck with the role of sniffer for this card - in which case I'll buy another nRF52840 DK.

[Hung Bui]

Hi Omer, 

It's very strange that the board is not programable after you flash the sniffer firmware. 

Could you let me know how you flashed the sniffer firmware ? 

The sniffer firmware is no different from a ordinary application for the nRF52840 so it shouldn't cause the problem with the programming interface. 

Could you try using nrfjprog.exe commandline tool to recover the chip. 
Please show us the log when you run "nrfjprog.exe --recover" 

After the update to switch to nRF53 as the programmer/interface chip, it's not possible (or not needed) to update the Interface chip with the binary j-link-ob-sam3u128-v2-nordicsemi-170724.bin. 

[Omer ZAK]

Hi Bui,

Thanks for your reply.

The suggestion to "recover the chip" solved my problem and the board is now working as usual.

I used the "Recover Board" operation in "nRF Connect for VS Code" which I assume runs "nrfjprog --recover" behind the curtains.

By the way, answering your question, I flashed the nRF52840 DK with the sniffer firmware using:

Programmer v3.0.8, invoked from nRF Connect for Desktop v4.0.1, which was run from the file nrfconnect-4.0.1-x86_64.AppImage running under Linux Debian 11.6 (Bullseye).

So the real problem was the beginner problem of not finding, in documentation, instructions what to do if the board becomes un-flash-able.