https://devzone.nordicsemi.com/f/nordic-q-a/63307/unable-to-connect-through-j-link-getting-error-could-not-find-core-in-coresight-setupHi, I&#39;m having issue connecting to the nRF52840_DK through J-Link and nrfjprog. I was able to connect to it the first time and upload simple BLE sample, but afterwards I have had no luck connecting to the device again. We have tested this on bothen-USTelligent Community 13Thu, 02 Jul 2020 11:03:05 GMThttps://devzone.nordicsemi.com/thread/258066?ContentTypeID=1Thu, 02 Jul 2020 11:03:05 GMT137ad170-7792-4731-bb38-c0d22fbe4515:e6b1a0ec-0d38-4078-b52a-4bb57a5ea7adKenneth<p>It looks like you are programming an external board, have you measured VDD on the external board? It needs to be 3V to debug and program from the nRF52840-DK. You need to connect GND, SWDIO, SWDCLK and VDD between nRF52840-DK and external board.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/258048?ContentTypeID=1Thu, 02 Jul 2020 10:19:20 GMT137ad170-7792-4731-bb38-c0d22fbe4515:920cd823-5d7b-40b4-b41e-2077b009f419awneil[quote userid="91638" url="~/f/nordic-q-a/63307/unable-to-connect-through-j-link-getting-error-could-not-find-core-in-coresight-setup"]looks like an power issue, but we have tried with a fully charged battery[/quote] <p>have you checked the rest of the power supply components? Is the&nbsp;<span>nRF52840 actually receiving power?</span></p><div style="clear:both;"></div>