https://devzone.nordicsemi.com/f/nordic-q-a/78172/how-to-use-high-frequency-to-run-some-codehi. I use nrf52840 sdk nRF5_SDK_17.0.2_d674dde. I need to control the H and L changes of IO within 300ns, I want to turn on the high-frequency part when necessary, and turn it off after this part runs. External crystal oscillator 32Mhz.so how toen-USTelligent Community 13Wed, 04 Aug 2021 09:32:15 GMThttps://devzone.nordicsemi.com/thread/323259?ContentTypeID=1Wed, 04 Aug 2021 09:32:15 GMT137ad170-7792-4731-bb38-c0d22fbe4515:79082198-a07f-4533-955b-ccf34add53dfjohn.liu<p>thanks your for help</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/323059?ContentTypeID=1Tue, 03 Aug 2021 10:58:09 GMT137ad170-7792-4731-bb38-c0d22fbe4515:980d7d4a-b61b-4fe7-a204-8a3491a27b34Vidar Berg<p>Hi,</p> <p>You can call <span><a title="sd_clock_hfclk_request" href="https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s132.api.v7.3.0/group___n_r_f___s_o_c___f_u_n_c_t_i_o_n_s.html?cp=4_7_3_1_2_7_2_3#ga3e5afb495a1b0307c749cc268df94a74">sd_clock_hfclk_request</a></span>() to make the Softdevice turn on the 32 MHz crystal oscillator when you need a high accuracy clock source, and <span><a title="sd_clock_hfclk_release" href="https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s132.api.v7.3.0/group___n_r_f___s_o_c___f_u_n_c_t_i_o_n_s.html?cp=4_7_3_1_2_7_2_2#ga7dcec5b896ce32fe70e9b54d7b523f55">sd_clock_hfclk_release</a></span>() when you don&#39;t need it any longer (reduces the system IDLE current).</p> <p></p><div style="clear:both;"></div>