Unable to enter bootlader mode on NRF52840 DK Jlink.

[mnjLC]

Hello Team, 

I have been using a NRF52840DK to program external boards. Recently it started misbehaving and will not detect external boards connected to it. I would like to update the Jlink-OB firmaware on it. I tried to turn on the DK while the rest IF button is pressed but it does not show up with "BOOTLOADER" MSD. PCA Ver 3.0.0 2022.20. Let me know if I can try anything else.

Thanks!

[PaKa]

There is no support for the Bootloader mode on the 3.0.0 versions of the DKs. This mode was there to change between the JLINK version and the MBED version and these boards don't support the MBED part.

If you are having problems detecting the external board and this used to work:

Have you checked the voltage level of the external board and that this is the same level as the VDD on the DK?

Have you checked there are no missing connections in your cabling?

Have you hot plugged the external board? i.e plugging the cable in or out with power applied to any of the kits?

Have you ensured to power up/down the boards in a safe order? You should not apply power to the external board without having power to the DK.

[mnjLC]

I had a mismatch in terms of VDD. It now works after matching the VDD on DK and the external board.