https://devzone.nordicsemi.com/f/nordic-q-a/27146/nrf51822-uart-speed-115200-is-inaccurateHello. I tried to use UART speed 115200. But my slave does not response. I connected slave to the arduino and it is working corectly. I got 2 oscillograms . From arduino and from NRF51. And I have seen that signal from NRF51 is inaccurate. bellow isen-USTelligent Community 13Fri, 08 Sep 2017 06:06:35 GMThttps://devzone.nordicsemi.com/thread/106908?ContentTypeID=1Fri, 08 Sep 2017 06:06:35 GMT137ad170-7792-4731-bb38-c0d22fbe4515:5f0f97d3-fc53-444b-b4e1-27efe77b91c4run_ar<p>The uart clock is derived from the High frequency clock. Did you also turn on the High frequency crystal?</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/106910?ContentTypeID=1Thu, 07 Sep 2017 21:30:14 GMT137ad170-7792-4731-bb38-c0d22fbe4515:35332b3d-8d99-488c-8ba5-436346e454a8VadimSavchuk<p>thank you for your answer. I use ble nano board from “red bear”. On this board I have 32.768 KHz crystal. And I use softdevise. When I config ble stack I use NRF_CLOCK_LFCLKSRC_XTAL_20_PPM define. If I undersood corectly already I have turned on external crystall</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/106909?ContentTypeID=1Thu, 07 Sep 2017 21:17:08 GMT137ad170-7792-4731-bb38-c0d22fbe4515:4be99890-6e5f-4eeb-8644-c7f739d9f25eTurbo J<p>Turn on the crystal oscillator.</p><div style="clear:both;"></div>