https://devzone.nordicsemi.com/f/nordic-q-a/13301/cannot-connect-to-nrf51-dongle-using-jlinkexeHi, I am working on a school project, and I need to use a nRF51 dongle as a BLE master. However, when I try to use JLinkExe to connect to the dongle, it fails all the time. The console output as shown in the attached image. Thanks in advance.en-USTelligent Community 13Tue, 19 Apr 2016 05:16:00 GMThttps://devzone.nordicsemi.com/thread/50706?ContentTypeID=1Tue, 19 Apr 2016 05:16:00 GMT137ad170-7792-4731-bb38-c0d22fbe4515:5aa642c8-b016-44da-8e4e-75cb7dbd08d7jiadong<p>Hi Dan,</p> <p>Thank you for your answer and it works. But when I use the &quot;TestCSpeed&quot; command, it returns that &quot;No RAM available @ address 0x0. Could not determine CPU clock&quot;. What is the issue with that?</p> <p>Thank you again. :-)</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/50705?ContentTypeID=1Tue, 19 Apr 2016 04:07:39 GMT137ad170-7792-4731-bb38-c0d22fbe4515:fa36fce8-2959-46d2-989b-48b43adbf778Dan Danknick<p>Switch over to the SWD interface from JTAG. That will very likely solve your problem and let you see the nRF51 dongle.</p><div style="clear:both;"></div>