I'm using SDK 15.0.0 with the nRF52840 and try to sleep without SoftDevice.
The function sys_sleep_request_ms(uint32_t sleep_time_ms) from sys_sleep.h sent me this interresting error Message in RTT-Viewer:
<error> app: ASSERTION FAILED at c:/Users/migr.NVLSI/Nordic_15_4/stack/components/SysAL/src/sys_queue.c:86
I'm not sure about my configuration, maybe I have to include sys_queue.c and initialize it. I wanted to show you that message, befor I continue my attempts.
Unfortunately I couldn't find any example implementation or documentation how to use this library.