/**
  @page PWR_PVD PWR Programmable Voltage Detector (PVD) example
  
  @verbatim
  ******************** (C) COPYRIGHT 2014 STMicroelectronics *******************
  * @file    PWR/PWR_PVD/readme.txt 
  * @author  MCD Application Team
  * @version V1.1.0
  * @date    18-June-2014
  * @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 
This example shows how to configure the programmable voltage detector using
an external interrupt line. 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 below the PVD threshold).
In the interrupt routine the LED2 is toggled every time the voltage drops below 
or above the target threshold.

In this example, the PVD detection level set to 2.5V.

If LED2 is toggling successively: This indicates that the system generates 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/stm32l0xx_conf.h     Library Configuration file
  - PWR/PWR_PVD/Inc/stm32l0xx_it.h       Header for stm32l0xx_it.c
  - PWR/PWR_PVD/Inc/main.h               header file for main.c
  - PWR/PWR_PVD/Src/system_stm32l0xx.c   STM32L0xx system clock configuration file
  - PWR/PWR_PVD/Src/stm32l0xx_it.c       Interrupt handlers
  - PWR/PWR_PVD/Src/main.c               Main program
  - PWR/PWR_PVD/Src/stm32l0xx_hal_msp.c  HAL MSP module


@par Hardware and Software environment

  - This example runs on STM32L051xx, STM32L052xx, STM32L053xx STM32L062xx and 
    STM32L063xx device lines RevZ

  - This example has been tested with STMicroelectronics STM32L053R8-Nucleo board
    and can be easily tailored to any other supported device and development board.

  - STM32L053R8-Nucleo Set-up
    - Remove the jumper JP5
    - Apply an external voltage to the pin4 of CN6 
    - Use LED2 connected to PA.05 pin


@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>
 */
