NRF52 locked, can't recover

[brett_anderson]

I have custom hardware that is working fine. No issues. I can program, erase, debug with no issues. I have been working on making some changes in the bootloader, and I've run into some issues with two chips completely locking up and I can't recover them.

Seems to occur after exiting debug in Keil, specifically debugging the bootloader.

The chip locks up, and I can not recover using nRFgo Studio or nrfjprog.

nrfjprog --recover --log
nrfjprog verion 9.6.0
--------------------------------------------------------------------------------
FUNCTION: open_dll.
FUNCTION: open_dll.
FUNCTION: enum_emu_snr.
FUNCTION: enum_emu_snr.
FUNCTION: enum_emu_snr.
FUNCTION: enum_emu_snr.
FUNCTION: connect_to_emu_with_snr.
FUNCTION: connect_to_emu_with_snr.
FUNCTION: connect_to_emu_without_snr.
FUNCTION: enum_emu_snr.
Device "NRF52832_XXAA" selected.
FUNCTION: read_connected_emu_snr.
FUNCTION: read_connected_emu_snr.
FUNCTION: read_device_family.
FUNCTION: read_device_family.
Not supported by current CPU + target interface combination.
JLinkARM.dll CORESIGHT_WriteAPDPReg returned error -2.
JLinkARM.dll CORESIGHT_WriteAPDPReg returned error -102.
FUNCTION: close_dll.
FUNCTION: close_dll.

The two boards in question are now sitting in a state where they are dumping power and warming up. I can't stop them, as they are sealed units with internal batteries. I have no idea what state the chip is in, because I can no longer connect to it.

Any thoughts on what I might have done, or how I could recover them? (Other than a power cycle, which would require I break them open).

[Hung Bui]

Which programmer did you use ? Do you have 3.3V VDD with the battery ? Have you tried to use Jlink Commander ? Maybe the answer from RK here can help ?

[brett_anderson]

I'm using a J-Link Ultra+. Voltage is good. I have a bunch of these devices. It seems to be a problem with Keil. I was using the bootloader example from sdk 12.2. I started the project over and it works again.

The big question is what happened in the compiled hex file that was somehow blocking the mcu from recovery?

I am back working with the new project, but if anyone else runs into this it would be nice to know what happened.