官方历程：
STM32Cube\Repository\STM32Cube_FW_L4_V1.13.0\Projects\NUCLEO-L496ZG\Examples_MIX\PWR\PWR_STANDBY_RTC\MDK-ARM
参考：https://blog.csdn.net/sudaroot/article/details/85626218
我参考的历程说明：@par Example Description
How to enter Standby mode and wake up from this mode using
an external reset or the RTC wakeup timer through the STM32L4xx RTC and RCC HAL
and LL API. The LL API is used for performance improvement.
本例程描绘如何进入待机模式并出来，通过复位或者RTC.使用了LL库的API.
It allows to measure the current consumption in STANDBY mode with RTC enabled.
In the associated software, the system clock is set to 80 MHz and the SysTick is
programmed to generate an interrupt each 1 ms.
历程的系统时钟是80M 驱动1MS一次。
The Low Speed Internal (LSI) clock is used as RTC clock source by default.
EXTI_Line20 is internally connected to the RTC Wakeup event.
历程RTC用的是LSI 中断线20是唤醒事件
The system automatically enters STANDBY mode 5 sec. after start-up. The RTC wake-up
is configured to generate an interrupt on rising edge about 33 sec. afterwards.
Current consumption in STANDBY mode with RTC feature enabled can be measured during that time.
More than half a minute is chosen to ensure current convergence to its lowest operating point.
Note: Due to LSI frequency variations, wake-up time is not guarantee. Adjustements need to be
done after getting the real measurement of LSI oscillator (or if available, LSE oscillator can
be used as well)
After wake-up from STANDBY mode, program execution restarts in the same way as after
a RESET.
实例用了HAL-LL两个包！
换一个\STM32Cube\Repository\STM32Cube_FW_L4_V1.11.0\Projects\NUCLEO-L476RG\Examples_LL\PWR\PWR_EnterStandbyMode
这个路径下面有若干个历程
原来LL已经这流行了，下次继续这个历程吧，独立的LL