https://devzone.nordicsemi.com/f/nordic-q-a/25930/j-link-does-not-connect-to-nrf51822I want to reprogram a nRF51822 xxAC device on a existing product. I have a J-Link (SEGGER) device with latest firmware. I&#39;m running the SEGGER J-Flash V6.20e utility. I have connected the DIO and CLK lines to the SWD lines on the J-Link I also connecteden-USTelligent Community 13Tue, 17 Oct 2017 09:53:35 GMThttps://devzone.nordicsemi.com/thread/102136?ContentTypeID=1Tue, 17 Oct 2017 09:53:35 GMT137ad170-7792-4731-bb38-c0d22fbe4515:35a79afa-6052-4cbd-9c01-c20f09737d09Jasper<p>Eventually got the J-Link to connect to the device and program. The problem it seems was that the nRF SCLK pin was blown. It could have been when I soldered on to the pin or maybe when I measured.</p> <p>I simply used another PCB and it all worked fine.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/102135?ContentTypeID=1Mon, 16 Oct 2017 12:54:52 GMT137ad170-7792-4731-bb38-c0d22fbe4515:e9adf2ef-8657-4a8a-9b34-03718904e536Bj&#248;rn Kvaale<p>Which Segger J-Link device are you using? I think 3.0 V should be fine for programming, but this could depend on which J-Link device you are using. What is interesting is that the DIO &amp; CLK are only 1.2 V. This does not seem correct. Have you taken a look at these two cases yet (<a href="https://devzone.nordicsemi.com/question/118806/programming-nrf51822-using-jlink/">case 1</a> &amp; <a href="https://devzone.nordicsemi.com/question/47612/program-nrf51822-using-j-link-cortex-m/">case 2</a>)? It seems your cable connections are setup correctly, as you have connected SWDIO, SWDCLK, GND and VCC. Just double check this to make sure the J-Link is correctly connected to the nrf51. Also, check the two cases I linked to and see if any of those tips might be helpful. Kind Regards, Bjørn</p><div style="clear:both;"></div>