https://devzone.nordicsemi.com/f/nordic-q-a/28713/hfclkstart-without-16-32m-xoscI have a board with nrf51822 which is not equipped with HF crystal, but it has a LF one. As pointed out in some other threads, calling HFCLKSTART on a board without functional HF crystal results in never happening EVENTS_HFCLKSTARTED . This has theen-USTelligent Community 13Fri, 22 Dec 2017 11:02:43 GMThttps://devzone.nordicsemi.com/thread/113801?ContentTypeID=1Fri, 22 Dec 2017 11:02:43 GMT137ad170-7792-4731-bb38-c0d22fbe4515:18f041b4-0c7f-43ce-9429-973b53dc863fJ&#248;rn<p>I believe the HFCLK startup will time out, and you may be able to change the LFCLK source after that, but I have not tested this so I may be wrong. I will need to look further into this, however due to Christmas Holidays I will not be able to look at it until January.</p><div style="clear:both;"></div>