How to use debug output on nrf5340 DK to program external board?

I am trying to program an external board using the development kid following the instructions HERE

I am using the debug out P20.

I have tried supplying the board frm either USB and Li-ON by switching the position of the SW9. For both cases I have verified that vdd_nrf is 1.8V.

I am connecting the usb pins at:

  • Pin 1 (white mark in header, micro USB B): 5V USB
  • Pin 2(micro USB B): SWDIO
  • Pin 3 (micro USB B): RESET
  • Pin 4 (micro USB B): SWDCLK
  • Pin 5 (micro USB B): GND

I set the vdd_nrf to 1,8v and i use an external supply for the external board of 1.8v.

However when flashing, it keeps going to the DK nrf5340 rather than to the external board.

Am I missing something?