Cannot set nrf52840-DK in boot mode

[dd_microlynx]

I cannot set the nrf52840-DK in boot mode so cannot use it to program other boards. 

It was working in the beginning but after programming the board with custom firmware I can no longer use it to program another board. 

I can reprogram the DK board fine but can't use it to program other boards.

I have tried everything described here: 

 RE: nrf52840-DK won't boot, isn't visible through File Explorer or J-Link 

and I do have version 3.0.0 board which I learnt from the post above that has nRF5340  as a debugger and cannot be set in boot mode by pressing the BOOT/RESET button but is not clear how can it be set then. 

Any thoughts on that would be appreciated.

[Amanda Hsieh]

Hi,

I cannot set the nrf52840-DK in boot mode so cannot use it to program other boards. 

To program and debug external boards with nRF52840DK, it doesn't need to put the DK in the boot mode. 

Which port do you use to connect the external board on the nRF52840DK?

Do you also provide power to the external board? You can use J-Link Commander to make sure the detected VTref is 3.3V. 

Regards,
Amanda H.

[dd_microlynx]

Hi, 

The external board has his own power supply. I use P19 (Debug Out) to connect to the external port. For programming I use nRF Connect for Desktop v4.2.1. 

[dd_microlynx]

After further evaluation I was able to program the external board. The confusion was that the programmer shows only the DK board on the device list even though is connected to the external board. I have decided to program it anyway and it flashed the external board. So it works but is little confusing. Thanks for the help. 

[Amanda Hsieh]

Thanks for the update. Happy to help.

-Amanda H.