nRF52 DK P20 debug out doesn't work

[kfcube]

nRF52DK

external board with 51822 and mems

I connect my external board with nRF52DK as this (left is board, right is nRF52DK):

SWCLK -> SWDCLK

SWDIO -> SWDIO

VCC -> VDD

GND -> GND

However, it doesn't work. There is NO power supply to my board, and I can't program to the external board through nRF52DK. I also can't see UART log out.

Please tell me what connection I did wrong or missing.

Thanks,

[kfcube]

VCC I connected to the #2 of p20, and GND connected to #8 (GND DETECT) of p20. I didn't provide power to my external board, as I thought the DK will do so? 

Thanks,