https://devzone.nordicsemi.com/f/nordic-q-a/46640/hfclk-start-and-usageDear Nordic Support, Processor: nRF52840 / S140 soft device / SDK 15.3.0 I have a question about the use of the HFCLK in relation to the soft device. Our board has both a 32.768kHz and a 32MHz crystal. Currently, we configure the LFCLK to use theen-USTelligent Community 13Fri, 26 Apr 2019 08:32:24 GMThttps://devzone.nordicsemi.com/thread/183985?ContentTypeID=1Fri, 26 Apr 2019 08:32:24 GMT137ad170-7792-4731-bb38-c0d22fbe4515:3bb895f8-68d0-4b0b-aeef-48e1c7b69d53Vidar Berg<p>Hi,</p> <p>The Softdevice will always start the HFXO before a RADIO event, and release it afterward to reduce the base current (e.g., <a href="https://infocenter.nordicsemi.com/topic/sds_s132/SDS/s1xx/ble_power_profiles/advertising_event.html?cp=3_4_1_0_17_0">advertisement event</a>). The reason for this is that the RADIO requires an accurate clock source to transmit at the correct frequency. If you want the HFXO always on you can call&nbsp;&nbsp;<a href="https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s140.api.v6.1.1/group___n_r_f___s_o_c___f_u_n_c_t_i_o_n_s.html?cp=3_4_2_1_2_7_2_3#ga3e5afb495a1b0307c749cc268df94a74">sd_clock_hfclk_request()</a>&nbsp;after enabling the Softdevice, but this will most likely increase the average power consumption.&nbsp;</p> <p>Regards,</p> <p>Vidar</p><div style="clear:both;"></div>