/**
  @page RTC_Alarm RTC Alarm Example
  
  @verbatim
  ******************************************************************************
  * @file    RTC/RTC_Alarm/readme.txt 
  * @author  MCD Application Team
  * @brief   Description of the RTC Alarm example.
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2019 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  @endverbatim

@par Example Description 

How to configure and generate an RTC alarm using the RTC HAL API.

At the beginning of the main program the HAL_Init() function is called to reset 
all the peripherals, initialize the Flash interface and the systick.
The SystemClock_Config() function is used to configure the system clock for STM32H7A3xxQ Devices :
The CPU at 280 MHz.
The HCLK for CD Domain AXI and AHB3 peripherals, CD Domain AHB1/AHB2 peripherals and SRD Domain AHB4 peripherals at 280 MHz.
The APB clock dividers for CD Domain APB3 peripherals, CD Domain APB1 and APB2 peripherals and SRD Domain APB4 peripherals to run at 280 MHz/2.

The RTC peripheral configuration is ensured by the HAL_RTC_Init() function.
This later is calling the HAL_RTC_MspInit()function which core is implementing
the configuration of the needed RTC resources according to the used hardware (CLOCK, 
PWR, RTC clock source and BackUp). You may update this function to change RTC configuration.

@note LSI oscillator clock is used as RTC clock source by default.
      The user can use also LSE as RTC clock source. The user uncomment the adequate 
      line on the main.h file.
      @code
        #define RTC_CLOCK_SOURCE_LSI  
        /* #define RTC_CLOCK_SOURCE_LSE */
      @endcode
      LSI oscillator clock is delivered by a 32 kHz RC.
      LSE (when available on board) is delivered by a 32.768 kHz crystal.

HAL_RTC_SetDate() and HAL_RTC_SetTime() functions are called to initialize the 
time and the date.
HAL_RTC_SetAlarm_IT() function is then called to initialize the Alarm feature with 
interrupt mode.

In this example, the Time is set to 02:20:00 and the Alarm must be generated after 
30 seconds on 02:20:30.

While the 30 seconds are not elapsed yet LED1 is toggled with a period of 1 second.

LED1 is turned ON when the RTC Alarm is generated correctly.
The current time is updated and displayed on the debugger in aShowTime variable.

In case of error, LED3 is toggled with a period of 100 milliseconds.

@note Care must be taken when using HAL_Delay(), this function provides accurate delay (in milliseconds)
      based on variable incremented in SysTick ISR. This implies that if HAL_Delay() is called from
      a peripheral ISR process, then the SysTick interrupt must have higher priority (numerically lower)
      than the peripheral interrupt. Otherwise the caller ISR process will be blocked.
      To change the SysTick interrupt priority you have to use HAL_NVIC_SetPriority() function.
      
@note The application needs to ensure that the SysTick time base is always set to 1 millisecond
      to have correct HAL operation.

@Note If the  application is using the DTCM/ITCM memories (@0x20000000/0x0000000: not cacheable and only accessible
      by the Cortex M7 and the MDMA), no need for cache maintenance when the Cortex M7 and the MDMA access these RAMs.
      If the application needs to use DMA(or other masters) based access or requires more RAM, then the user has to:
              - Use a non TCM SRAM. (example : CD AXI-SRAM @ 0x24000000)
              - Add a cache maintenance mechanism to ensure the cache coherence between CPU and other masters (DMAs, DMA2D, LTDC, MDMA).
              - The addresses and the size of cacheable buffers (shared between CPU and other masters)
                must be properly defined to be aligned to L1-CACHE line size (32 bytes).

@Note It is recommended to enable the cache and maintain its coherence.
              Please refer to the AN4838 "Managing memory protection unit (MPU) in STM32 MCUs"
              Please refer to the AN4839 "Level 1 cache on STM32F7 Series and STM32H7 Series"

@par Keywords

System, RTC, Alarm, wakeup timer, Backup domain, Counter, LSE, LSI

@par Directory contents 

 - "RTC/RTC_Alarm/Inc": contains the example firmware header files
    - RTC/RTC_Alarm/Inc/main.h                   Main configuration file
    - RTC/RTC_Alarm/Inc/stm32h7xx_it.h           Interrupt handlers header file
    - RTC/RTC_Alarm/Inc/stm32h7xx_hal_conf.h     HAL Configuration file
    - RTC/RTC_Alarm/Inc/stm32h7xx_nucleo_conf.h  STM32H7xx board configuration file

 - "RTC/RTC_Alarm/Src": contains the example firmware source files
    - RTC/RTC_Alarm/Src/main.c                   Main program
    - RTC/RTC_Alarm/Src/stm32h7xx_hal_msp.c      Microcontroller specific packages initialization file.
    - RTC/RTC_Alarm/Src/stm32h7xx_it.c           Interrupt handlers
    - RTC/RTC_Alarm/Src/system_stm32h7xx.c       STM32H7xx system clock configuration file

@par Hardware and Software environment

  - This example runs on STM32H7A3xxQ devices.
  - This example has been tested with STMicroelectronics NUCLEO-H7A3ZI-Q 
    board and can be easily tailored to any other supported device 
    and development board.

@par How to use it ? 

In order to make the program work, you must do the following :
 - Open your preferred toolchain 
 - Rebuild all files and load your image into target memory
 - Run the example



 */