recovering NRF52DK with bootloader

[danmcb]

I have a DK board with nRF52832 that I've been using several months with no problems.

Today I wanted to try an experiment and did some modifications to the startup ASM file, and since then I am unable to reprogram. Initially, the jLink wa sno longer visible from my host system.

I tried the following sequence:

- put the DK in bootloader mode

- drag-drop the latest jLink file into the bootloader

- cycle the power (now the jLink is visible)

- try this command (see screenshot below)

I can also try programming with a jLink programmer I guess. Other than that, is there anything I can do? logfile attached

8358.log.log

[danmcb]

I also tried with a Segger JLink unit, still no success.

Trashing a single dev board is not that big of a deal for us, but what is annoying is not knowing why. I understand that modifying asm startup code is a delicate matter, but it should not brick the board so that FLASH cannot be erased any more (unless maybe the code was playing with SWO interface somehow, which mine does not).

I've seen a number of these tickets where people could not recover and most have not had a reply from Nordic. It would be great to get, at least, some explanation of why this has happened and perhaps how to avoid it.

[Vidar Berg]

Hello,

You should not be able to brick the device even if you are playing around with the startup files. The only known configuration/condition that can cause the chip to become in an unrecoverable state is the one described in the errata here: [176] System: Flash erase through CTRL-AP fails due to watchdog time-out.

Initially, the jLink wa sno longer visible from my host system.

Sounds like it could have been a temporary bad USB connection? The FW running on the nRF should definitely not affect how the Jlink FW runs on the interface MCU.

danmcb said:

the code was playing with SWO interface somehow, which mine does not).

The SWD interface is always available regardless of SWO/trace settings.

danmcb said:

I've seen a number of these tickets where people could not recover and most have not had a reply from Nordic. It would be great to get, at least, some explanation of why this has happened and perhaps how to avoid it.

It's usually a bad connection somewhere or wrong logic levels (i.e. mismatch between programmer and target). But there seems to seems to be some communication between the Jlink and nrf in your case at least.

danmcb said:

I also tried with a Segger JLink unit, still no success.

Could you try with the latest version of nrfjprog as well?