/**
  @page RTC_Tamper RTC Tamper Example
  
  @verbatim
  ******************** (C) COPYRIGHT 2016 STMicroelectronics *******************
  * @file    RTC/RTC_Tamper/readme.txt 
  * @author  MCD Application Team
  * @version V1.5.0
  * @date    14-April-2017
  * @brief   Description of the RTC Tamper example.
  ******************************************************************************
  *
  * Redistribution and use in source and binary forms, with or without modification,
  * are permitted provided that the following conditions are met:
  *   1. Redistributions of source code must retain the above copyright notice,
  *      this list of conditions and the following disclaimer.
  *   2. Redistributions in binary form must reproduce the above copyright notice,
  *      this list of conditions and the following disclaimer in the documentation
  *      and/or other materials provided with the distribution.
  *   3. Neither the name of STMicroelectronics nor the names of its contributors
  *      may be used to endorse or promote products derived from this software
  *      without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  ******************************************************************************
  @endverbatim

@par Example Description 

Configuration of the RTC HAL API to write/read data to/from RTC Backup registers. 
It also demonstrates the tamper detection feature.

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.
Then the SystemClock_Config() function is used to configure the system
clock (SYSCLK) to run at 72 MHz.

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 40 kHz RC.
      LSE (when available on board) is delivered by a 32.768 kHz crystal.

HAL_RTCEx_SetTamper_IT() function is then called to initialize the Tamper with 
interrupt mode.

The associated firmware performs the following:
1. It configures the Tamper pin to be falling edge, and enables the Tamper 
   interrupt.
2. It writes the data to all RTC Backup data registers, then check whether the 
   data were correctly written. If yes, LED2 turns ON, otherwise LED3 turns ON.
3. Applying a low level on the TAMPER_BUTTON_PIN(PC.13) by pressing Tamper push-button,
   the RTC backup data registers are reset and the Tamper interrupt is generated 
   and LED1 turns ON. 
   The corresponding ISR then checks whether the RTC Backup data registers are cleared. 
   If yes LED4 toggles, otherwise LED3 turns ON.

@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 need to ensure that the SysTick time base is always set to 1 millisecond
      to have correct HAL operation.

@par Directory contents 

  - RTC/RTC_Tamper/Inc/stm32f1xx_hal_conf.h    HAL configuration file
  - RTC/RTC_Tamper/Inc/stm32f1xx_it.h          Interrupt handlers header file
  - RTC/RTC_Tamper/Inc/main.h                  Header for main.c module  
  - RTC/RTC_Tamper/Src/stm32f1xx_it.c          Interrupt handlers
  - RTC/RTC_Tamper/Src/main.c                  Main program
  - RTC/RTC_Tamper/Src/stm32f1xx_hal_msp.c     HAL MSP module
  - RTC/RTC_Tamper/Src/system_stm32f1xx.c      STM32F1xx system source file


@par Hardware and Software environment

  - This example runs on STM32F103xG devices.
  - This example has been tested with STMicroelectronics STM3210E-EVAL RevD 
    evaluation 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


 * <h3><center>&copy; COPYRIGHT STMicroelectronics</center></h3>
 */
 