Attempts to revert nRF52840 dongle to production bootloader fail

[Chris Pearson]

I'm attempting to revert an nRF52840 dongle to the production bootloader. This dongle has a SWD connector soldered on for use with J-Link, and I have no difficulties flashing my own software onto it.

The problem is when trying to revert it to the production bootloader using the documentation at this link. I've downloaded the hex file, extracted graviton_bootloader_mbr_v1.0.1-[nRF5_SDK_15.0.1-1.alpha_f76d012].hex, and flashed it to the dongle. Once reset, the red LED pulses as expected.

However, when I connect the nRF Connect Programmer to it, I see the following error:

2021-09-22T23:30:07.590Z INFO Using USB SDFU protocol to communicate with target
2021-09-22T23:30:07.608Z ERROR Error when calling version command: Error: Error message for known response code from DFU target: The data object didn't match firmware/hardware, or missing crypto signature, or malformed protocol buffer, or command parse failed.
2021-09-22T23:30:07.608Z ERROR Error when fetching device versions: TypeError: Cannot read property 'part' of undefined

Does anyone have a suggestion as to what might be the issue here? I'm suspecting I might have to repackage that hex file, or that I'm missing some other steps besides simply flashing it.

Thanks!

[Einar Thorsrud]

Hi,

I was not able to test today, but I thought that .hex should include the correct public key. In any case the hex file that is currently used in production is attached here: 3250.graviton_bootloader_mbr_v1.0.1.hex. Can you test with that? If that also fails then we need to look a bit in other directions.

[Chris Pearson]

Thanks, but unfortunately I still get the same error in the Connect Programmer.

I've tried flashing that file in a couple of ways, such as using the J-Link Flash and erasing the chip then flashing the hex file, and with nrfjprog with the command:

nrfjprog -f nrf52 --program 3250.graviton_bootloader_mbr_v1.0.1.hex --chiperase

I have not yet tried this on another nRF52840 dongle that I have, mainly because it still has the factory bootloader and I don't want to risk losing the BLE scanner ability.  However, if there's a good reason to try that as a test, I could do it -- there's a SWD socket soldered onto it.