/**
  @page PWR_PVD PWR Programmable Voltage Detector (PVD) example
  
  @verbatim
  ******************** (C) COPYRIGHT 2016 STMicroelectronics *******************
  * @file    PWR/PWR_PVD/readme.txt 
  * @author  MCD Application Team
  * @version V1.5.0
  * @date    14-April-2017
  * @brief   Description of the PWR Programmable Voltage Detector (PVD) 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 

How to configure the programmable voltage detector by using an external interrupt 
line. External DC supply must be used to supply Vdd.

In this example, EXTI line 16 is configured to generate an interrupt on each rising
or falling edge of the PVD output signal (which indicates that the Vdd voltage is
moving below or above the PVD threshold). As long as the voltage is above the 
target threshold (2.5V), LED1 is blinking with a 200 ms-period; when the voltage drops
below the threshold, LED1 stops blinking and remains constantly on (or appears
to be turned off if the voltage is getting really low); when the voltage moves back
above the target threshold, LED1 starts blinking again.
If LED3 is on, it means that the system has generated an error.

@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 

  - PWR/PWR_PVD/Inc/stm32f1xx_hal_conf.h     HAL Configuration file
  - PWR/PWR_PVD/Inc/stm32f1xx_it.h           Header for stm32f1xx_it.c
  - PWR/PWR_PVD/Inc/main.h                   Header file for main.c
  - PWR/PWR_PVD/Src/system_stm32f1xx.c       STM32F1xx system clock configuration file
  - PWR/PWR_PVD/Src/stm32f1xx_it.c           Interrupt handlers
  - PWR/PWR_PVD/Src/main.c                   Main program

@par Hardware and Software environment

  - This example runs on STM32F103xG devices
    
  - This example has been tested with STMicroelectronics STM3210E-EVAL RevD
    board and can be easily tailored to any other supported device
    and development board.

  - STM3210E-EVAL RevD Set-up
    To apply an external power supply input, the user can resort to
    pin 69 (3V3) of the daughter board extension connector CN10 and any GND pin
    of the same connector (pin 1, 19 or 39)
    Next,         
    - LED1 (GREEN) connected to PF.06 pin indicates the behavior of
    the test software as explained above.

@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>
 */
