I try to turn off the system with sd_power_system_off()
// Go to system-off mode (this function will not return; wakeup will cause a reset).
err_code = sd_power_system_off();
SEGGER_RTT_printf(0, "sd_power_system_off(). err_code: %#04x\n" ,err_code);
APP_ERROR_CHECK(err_code);
But in the RTT Viewer (debugging with NRF_LOG), there is always an error, I printed the code number is 2006. I do not know the meaning of it and how to avoid it.
0> sd_power_system_off(). err_code: 2006
0> APP_ERROR:ERROR:Fatal