https://devzone.nordicsemi.com/f/nordic-q-a/15694/esb-no-external-crystalHi I have a custom board with no external crystal. Using S130 works fine, but I want to enhance communication with some data being sent over ESB using timeslot API. Therefore I&#39;m running with this clock config: #define NRF_CLOCK_LFCLKSRC {.sourceen-USTelligent Community 13Fri, 12 Aug 2016 10:14:41 GMThttps://devzone.nordicsemi.com/thread/59935?ContentTypeID=1Fri, 12 Aug 2016 10:14:41 GMT137ad170-7792-4731-bb38-c0d22fbe4515:a8d6d241-0664-44f7-a899-3e945dffcdec&#216;yvind Karlsen<p>Without a HF crystal you cannot use the radio for BLE, and you will also have limited success with proprietary protocols. It will fail conformance without an external HF crystal.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/59938?ContentTypeID=1Fri, 12 Aug 2016 09:35:49 GMT137ad170-7792-4731-bb38-c0d22fbe4515:4be5fbd6-9c3c-4c88-811b-aca1cab79887Martin<p>No, currently not.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/59937?ContentTypeID=1Fri, 12 Aug 2016 09:27:07 GMT137ad170-7792-4731-bb38-c0d22fbe4515:54cb1ff2-3337-4814-b037-ce74035c4580&#216;yvind Karlsen<p>Do you not have an external HF crystal?</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/59936?ContentTypeID=1Fri, 12 Aug 2016 09:02:52 GMT137ad170-7792-4731-bb38-c0d22fbe4515:6331a8bd-69d2-4fa2-9804-66018783d7aaMartin<p>Does this work even without an external crystal?</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/59934?ContentTypeID=1Fri, 12 Aug 2016 06:03:47 GMT137ad170-7792-4731-bb38-c0d22fbe4515:4923694b-8133-4817-a86f-35a3d2030fcdJ&#248;rgen Kvalvaag<p>ESB requires the HFCLK to be running, i believe it is not using the LFCLK at all.</p> <p>Try adding</p> <pre><code>NRF_CLOCK-&gt;EVENTS_HFCLKSTARTED = 0; NRF_CLOCK-&gt;TASKS_HFCLKSTART = 1; while (NRF_CLOCK-&gt;EVENTS_HFCLKSTARTED == 0); </code></pre> <p>near the start of main().</p><div style="clear:both;"></div>