https://devzone.nordicsemi.com/f/nordic-q-a/42484/nrf52dk-fail-to-connect-to-customer-boardHi 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 -----------&gt; Vdd --en-USTelligent Community 13Tue, 15 Jan 2019 09:06:28 GMThttps://devzone.nordicsemi.com/thread/165666?ContentTypeID=1Tue, 15 Jan 2019 09:06:28 GMT137ad170-7792-4731-bb38-c0d22fbe4515:d0221663-7460-46d2-ae5d-68c4d0f264daVidar Berg<p>It shouldn&#39;t be possible to program the 52 on the DK if you have voltage on &quot;VTG&quot;. Please try to connect &quot;VDD&quot; to &quot;VTG&quot; on port 20 and see if you&#39;re still able to program it.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/165655?ContentTypeID=1Tue, 15 Jan 2019 08:26:21 GMT137ad170-7792-4731-bb38-c0d22fbe4515:c4f9f28e-d701-42d6-a720-42f54bb52884CCY<p>yes, I group GND of DK board, Pin20 GND of DK and customer board GND together.&nbsp;&nbsp;</p> <p>If I use J-link command, it will directly connect to nrf52 on DK board and ignore customer board I connected.</p> <p>And even I change external power from 3.3V to 3.0V. VTref still shows 3.3V as below. Any idea how??</p> <p><img src="https://devzone.nordicsemi.com/resized-image/__size/320x240/__key/communityserver-discussions-components-files/4/J_2D00_link.jpg" alt=" " /></p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/165357?ContentTypeID=1Mon, 14 Jan 2019 08:38:49 GMT137ad170-7792-4731-bb38-c0d22fbe4515:35851ca8-cea2-4741-b8ab-2cdd45a7aab3Vidar Berg<p>Hi,&nbsp;</p> <p>Looks like you have connected the correct pins. Do you have common ground between the custom board and the DK as well?&nbsp;</p><div style="clear:both;"></div>