https://devzone.nordicsemi.com/f/nordic-q-a/7446/can-t-connect-to-pca10028-over-ble-but-can-connect-to-pca10001Hello, I am having some strange results with some firmware I have been developing. I developed the firmware on the nRF51 Development Kit (PCA 10028) and the device advertises but I cannot connect to the device with the external crystal clock sourceen-USTelligent Community 13Tue, 09 Jun 2015 14:45:29 GMThttps://devzone.nordicsemi.com/thread/26532?ContentTypeID=1Tue, 09 Jun 2015 14:45:29 GMT137ad170-7792-4731-bb38-c0d22fbe4515:2bde9fb9-d771-4239-98c6-bff5155310f4Cory Mast<p>Thank you for your help. It appears I may have a physical problem with my low frequency oscillator. I read the NRF_CLOCK-&gt;LFCLKSTAT register and sure enough the oscillator was not running. I was able to track down another PCA10028 development kit and flash my code to it and it worked like a charm.</p> <p>Thanks for the quick response.</p> <p>Cory</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/26531?ContentTypeID=1Fri, 05 Jun 2015 12:23:28 GMT137ad170-7792-4731-bb38-c0d22fbe4515:f5f7d56e-4d84-48b0-b2df-729369904b77MartinBL<p>Hi. S110 V7.1 should work on rev 3 as per the compatibility matrix so that should not be a problem. It sounds like there might be a problem with the external low frequency oscillator. Are you able to check if the external crystal is actually running? You can do this by reading the NRF_CLOCK-&gt;LFCLKSTAT register in the clock manager, Chapter 13 Reference manual V3.0.</p> <p>Can you run other BLE examples from the SDK? Or a simple blinky LED example without BLE?</p><div style="clear:both;"></div>