/**
  @page RTC_Calendar RTC Hardware Calendar example
  
  @verbatim
  ******************** (C) COPYRIGHT 2013 STMicroelectronics *******************
  * @file    RTC/RTC_Calendar/readme.txt 
  * @author  MCD Application Team
  * @version V1.3.0
  * @date    13-November-2013
  * @brief   Description of the RTC Hardware Calendar example.
  ******************************************************************************
  *
  * Licensed under MCD-ST Liberty SW License Agreement V2, (the "License");
  * You may not use this file except in compliance with the License.
  * You may obtain a copy of the License at:
  *
  *        http://www.st.com/software_license_agreement_liberty_v2
  *
  * Unless required by applicable law or agreed to in writing, software 
  * distributed under the License is distributed on an "AS IS" BASIS, 
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  *
  ******************************************************************************
  @endverbatim

@par Example Description 

This example shows how to use the RTC peripheral.
As an application example, it demonstrates how to setup the RTC peripheral, in 
terms of prescaler and interrupts, to be used to keep time and to generate 
alarm interrupt. 

One from the following clock can be used as RTC clock source (uncomment the
corresponding define in main.c): 
  - LSE oscillator clock usually delivered by a 32.768 kHz quartz.
  - LSI oscillator clock
  
The RTC is in the backup (BKP) domain, still powered by VBAT when VDD is switched off,
so the RTC configuration is not lost if a battery is connected to the VBAT pin. 
A key value is written in backup data register 0 to indicate if the RTC is already
configured.

The program behaves as follows:

1)After startup the program checks the backup data register 0 value:
  - BKP_DR0 value not correct: (RTC_BKP_DR0 value is not correct or has not yet
    been programmed when the program is executed for the first time) the RTC is
    configured.
    
  - BKP_DR0 value correct: this means that the RTC is configured and the time
    and Alarm A are displayed on Debugger.

2)When an External Reset occurs the BKP domain is not reset and the RTC configuration
  is not lost. LED4 is ON.

3)When power on reset occurs:
  - If a battery is connected to the VBAT pin: the BKP domain is not reset and
    the RTC configuration is not lost. LED3 is ON.
      
  - If no battery is connected to the VBAT pin: the BKP domain is reset and the
    RTC configuration is lost.

4)When an RTC Alarm A event occurs the RTC Alarm interrupt is generated and the
  LED1 is toggled.
   
  - When TAMPER button is pressed, the current time is displayed on Debugger.
  - When WAKEUP button is pressed, the current alarm A is displayed on Debugger. 

LED2 is turned ON when the RTC configuration is done correctly.


@par Directory contents 

  - RTC/RTC_Calendar/system_stm32f4xx.c   STM32F4xx system clock configuration file
  - RTC/RTC_Calendar/stm32f4xx_conf.h     Library Configuration file
  - RTC/RTC_Calendar/stm32f4xx_it.c       Interrupt handlers
  - RTC/RTC_Calendar/stm32f4xx_it.h       Interrupt handlers header file
  - RTC/RTC_Calendar/main.c               Main program
  - RTC/RTC_Calendar/main.h               Main program header file
     
     
@par Hardware and Software environment 

  - This example runs on STM32F405xx/407xx, STM32F415xx/417xx and STM32F427xx/437xx devices.
    
  - This example has been tested with STMicroelectronics STM324xG-EVAL (STM32F40xx/
    STM32F41xx Devices) and STM32437I-EVAL (STM32F427xx/STM32F437xx Devices) 
    evaluation boards and can be easily tailored to any other supported device 
    and development board. 
    
  - STM324xG-EVAL/STM32437I-EVAL Set-up
    - Use the TAMPER push-button connected to PC.13 pin (EXTI Line13).
    - Use the WAKEUP push-button connected to PA.00 pin (EXTI Line0).
    - Make sure that jumper JP19 is in position 2-3 to connect the 3V battery to VBAT pin
    
    
@par How to use it ? 

In order to make the program work, you must do the following:
 - Copy all source files from this example folder to the template folder under
   Project\STM32F4xx_StdPeriph_Templates
 - Open your preferred toolchain
 - Select the project workspace related to the used device 
   - If "STM32F40_41xxx" is selected as default project Add the following files in the project source list:
     - Utilities\STM32_EVAL\STM3240_41_G_EVAL\stm324xg_eval.c
      
   - If "STM32F427_437xx" is selected as default project Add the following files in the project source list:
     - Utilities\STM32_EVAL\STM324x7I_EVAL\stm324x7i_eval.c
       
 - Rebuild all files and load your image into target memory
 - Run the example
    
 * <h3><center>&copy; COPYRIGHT STMicroelectronics</center></h3>
 */
