Programming: Unable to flash chip after flashing a bad hex

[meehien]

I was trying to test the ZBOSS NCP Host and flashed the image ncp.nrf52840dk_nrf52840.hex from the package provided.

Now my device stopped working an I am unable to interact with it via pyocd. There seems to be a timeout issue of some kind:

% pyocd list
#   Probe/Board             Unique ID                                          Target  
-----------------------------------------------------------------------------------------
  0   ARM DAPLink CMSIS-DAP   10283602005f75a200000000000000000000000097969902   n/a    

% pyocd erase -t nrf52840 --chip
0000443 W Board ID 1028 is not recognized [mbed_board]
0005557 C Error: 1 [__main__]

% pyocd flash -t nrf52840 nrf52840_m2_devkit_circuitpython_5.3.0.hex
0000449 W Board ID 1028 is not recognized [mbed_board]
0005565 C Error: 1 [__main__]

Do you have any recovery procedure that I can follow to restore my device?

[caizelin]

@meehien Does this bad hex set P0.17 low when it boots?
According to the nRF52840 M.2 Module Schematic, the P0.17 is connected to the RESET pin for self-reset functionality. This pin can not be set to LOW without any additional action, or the device will run into a self-reset loop.

[meehien]

I had a quick look at the schematic you provided and that of the nRF52840 M.2 Developer Kit. Is it P0.17 you are refering to or P0.18? In your link, I belive P0.18 is the reset. I was not able to find where P0.17 is on the DevKi8t board, but I can confirm that the P0.18 Reset is pulled LOW on boot. Any suggestions on how to approach this?

EDIT: I was able to manually pull the P0.18 pin HIGH and erase the device. Now it seems to be working. Thanks for pointing me in the right direction.