https://devzone.nordicsemi.com/f/nordic-q-a/83931/error-nrf_calendar-and-app_ble_uart-about-rtcHI I am using nrf52840 and I want to merge nrf_calendar and app_ble_uart example, added ssd1306 oled 128x32 spi and mpu6050 as well, but the error is from nrf_calendar, in this line... i gess.xd CAL_RTC-&gt;TASKS_START = 1. because when is executingen-USTelligent Community 13Mon, 24 Jan 2022 23:10:42 GMThttps://devzone.nordicsemi.com/thread/349384?ContentTypeID=1Mon, 24 Jan 2022 23:10:42 GMT137ad170-7792-4731-bb38-c0d22fbe4515:979dcf62-bbd1-4e4d-a572-91b17c270b5eMarcos Tadeo<p>hi&nbsp;</p> <p>yes, you right,&nbsp; I removed LFCLK and now it works</p> <p>thank you&nbsp;<span>J&oslash;rgen</span></p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/349201?ContentTypeID=1Mon, 24 Jan 2022 10:59:12 GMT137ad170-7792-4731-bb38-c0d22fbe4515:abd9acb9-6c3b-45b6-a72f-b1cc06ffeb99J&#248;rgen Holmefjord<p>Hi,</p> <p>If you have enabled the softdevice, you need to&nbsp;remove the part that starts the LFCLK. The LFCLK is always running when the softdevice is enabled, so there is no need to start it explicitly in the application. <a href="https://infocenter.nordicsemi.com/topic/sds_s140/SDS/s1xx/sd_resource_reqs/hw_block_interrupt_vector.html">Writing to the NRF_CLOCK registers after softdevice is enabled is restricted</a>, and will possibly cause memory access violation and/or assertions.</p> <p>Best regards,<br />Jørgen</p><div style="clear:both;"></div>