In the past, you need modify rtc_api.c in mbed-dev source code. From this revision, you can just use RTC function all of conditions (Normal, Reset, Stand-by, Power OFF).

Auto generated API documentation and code listings for Nucleo_RTC_battery_bkup_pwr_off_okay

Code

check_revision.cpp [code]
main.cpp [code]
uart_as_stdio.cpp [code]
uart_as_stdio.h [code]