nRF52DK fail to connect to customer board

[CCY]

Hi

I got the problem to connect customer board(nRF52) via SWD. 

My connection should be fine and customer board is also supplied 3,3V by external power.

How I wire 52Dk with customer board.

52DK(pin20)                  Customer Board

Vtag    ----------->                 Vdd ----------> 3.3V external power

GND    ----------->                 GND---------> ground with external power

CLK  -------------->                 CLK

DIO----------------->                DIO

I try to use nrodic command tool to recover customer board. It didn't work.

And I also try to use nRFgo but it show "unknown error"

And here is the error when I try nRF connect.

I read some read some articles with similar issue in DevZone but still can not find an answer now.

[Vidar Berg]

Hi, 

Looks like you have connected the correct pins. Do you have common ground between the custom board and the DK as well? 

[CCY]

yes, I group GND of DK board, Pin20 GND of DK and customer board GND together.  

If I use J-link command, it will directly connect to nrf52 on DK board and ignore customer board I connected.

And even I change external power from 3.3V to 3.0V. VTref still shows 3.3V as below. Any idea how??

[Vidar Berg]

It shouldn't be possible to program the 52 on the DK if you have voltage on "VTG". Please try to connect "VDD" to "VTG" on port 20 and see if you're still able to program it.