Interface MCU on nRF52840 DK seems to be dead

[NewtoM]

Hi,

without any obvious reason one of our nRF52840 DKs stopped being visible over the USB  (J2) interface. The nRF52840 is still functional and can be programmed from another DK over the "Debug in" port. Switches on the faulty board are set correctly, we tried 3 different USB cables and two PCs - other DKs work in any combination, the faulty one works in none.

Is there any option to diagnose (and maybe revive) the interface MCU? We have tools (SEGGER J-Link, oscilloscope etc.) there. Or is there a separate fuse for the interface MCU that may be dead?

Thanks in advance!
Tamas

[Jared]

Hi,

Have you modified anything on the board itself, cut/shorted any solder bridges etc? Could you try re-programming the interface chip by following the step 4 here. Also, please try the other steps if that one doesn't help. What is the different switches configured to on the board? 

regards

Jared

[NewtoM]

Thank you Jared, step 4 from your link worked and we could revive the board.
Big thanx!