https://devzone.nordicsemi.com/f/nordic-q-a/128174/54l15-uart-communication-issue-with-low-temperatureHello, We developped a new rf board with 54l15 &#181;c. We discovered our UART communication have some errors with -16 &#176;. At -20 &#176; the device doesn&#39;t respond. I changed our devicetree to use external crystal, but i still have UART errors at -16&#176; en-USTelligent Community 13Tue, 19 May 2026 13:01:58 GMThttps://devzone.nordicsemi.com/thread/566527?ContentTypeID=1Tue, 19 May 2026 13:01:58 GMT137ad170-7792-4731-bb38-c0d22fbe4515:dde9c3ef-e48d-42d8-a1ba-e9b5e8403491Vidar Berg<p>Hello,</p> <p><span>Please request the HFXO&nbsp;through the &quot;onoff&quot; API as shown in the&nbsp;</span><span>hf_clock_request() function here:&nbsp;</span><a href="https://github.com/nrfconnect/sdk-nrf/blob/f35cddd506a9a779305feb0f52fcbf99b03bee23/tests/drivers/grtc/grtc_clk_output/src/main.c#L49">https://github.com/nrfconnect/sdk-nrf/blob/f35cddd506a9a779305feb0f52fcbf99b03bee23/tests/drivers/grtc/grtc_clk_output/src/main.c#L49</a>&nbsp;at the beginning of main() if you are not already doing that<span>. </span><span>This API is globally reference counted, which means the HFXO will be kept&nbsp;running even if the bluetooth&nbsp;stack or another SDK module releases its request for this clock source.&nbsp;</span></p> <p><span>Best regards,</span></p> <p><span>Vidar</span></p><div style="clear:both;"></div>