https://devzone.nordicsemi.com/f/nordic-q-a/89044/flash-and-debug-custom-nrf5340-failsHello, I&#39;using nRF Connect SDK 1.9.1 on linux mint PC. nrfjprog version : 10.15.3 external Jlink version :JLink_V758b nRF chip : nRF5340 I&#39;m able to flash, debug the nRF5340 DK without any problem with west, nrfjprog, JLinkExe, SEGGER Embedded Studioen-USTelligent Community 13Fri, 24 Jun 2022 09:18:40 GMThttps://devzone.nordicsemi.com/thread/374087?ContentTypeID=1Fri, 24 Jun 2022 09:18:40 GMT137ad170-7792-4731-bb38-c0d22fbe4515:9ce693c4-0bc8-4cbf-8c80-454ddb87a818yousseflxn<p>Hello&nbsp;<span>Einar,</span><br />Thank you for your response.<br />I found the reason that cause&nbsp;the problem with flashing external board.<br />The new board powered bu 1.8V and I did not connect Vref from the DK to 1.8V from the external board.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/372805?ContentTypeID=1Thu, 16 Jun 2022 12:20:25 GMT137ad170-7792-4731-bb38-c0d22fbe4515:55bb79e6-28b1-4bec-b6b0-085ee19b6393Einarh<p>Hello!</p> <p>Have you looked at this page in the documentation?</p> <p><a href="http://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/ug_nrf5340.html#readback-protection">http://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/ug_nrf5340.html#readback-protection</a></p> <blockquote> <p><span>Make sure to recover the network core before you recover the application core.</span></p> </blockquote> <p><span>Best regards,</span></p> <p><span>Einar</span></p><div style="clear:both;"></div>