/**
  @page WWDG_Example Window Watchdog example
  
  @verbatim
  ******************** (C) COPYRIGHT 2016 STMicroelectronics *******************
  * @file    WWDG/WWDG_Example/readme.txt 
  * @author  MCD Application Team
  * @version V1.5.0
  * @date    14-April-2017
  * @brief   Description of the Window Watchdog example.
  ******************************************************************************
  *
  * Redistribution and use in source and binary forms, with or without modification,
  * are permitted provided that the following conditions are met:
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  *      this list of conditions and the following disclaimer.
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  *      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
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  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  ******************************************************************************
  @endverbatim

@par Example Description 

This example guides you through the different configuration steps by means of the 
HAL API to perform periodic WWDG counter update and simulate a software fault that 
generates an MCU WWDG reset when a predefined time period has elapsed.

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 64 MHz.

The WWDG peripheral configuration is ensured by the HAL_WWDG_Init() function.
This later is calling the HAL_WWDG_MspInit()function which core is implementing
the configuration of the needed WWDG resources according to the used hardware (CLOCK, 
GPIO, DMA and NVIC). You may update this function to change WWDG configuration.

The WWDG timeout is set to 58 ms and the refresh window is set to 80. 
The WWDG counter is refreshed around 50ms in the main program infinite loop to 
prevent a WWDG reset.
LED2 is also toggled around 50ms indicating that the program is running.

An EXTI Line is connected to a GPIO pin, and configured to generate an interrupt
on the rising edge of the signal.

The EXTI Line is used to simulate a software failure: once the EXTI Line event 
occurs by pressing the User push-button (PC.13), the corresponding interrupt is served.
  
In the ISR, a write to invalid address generates a Hardfault exception containing
an infinite loop and preventing to return to main program (the WWDG counter is 
not refreshed).

As a result, when the WWDG counter falls to 63, the WWDG reset occurs.

If the WWDG reset is generated, after the system resumes from reset, LED2 is turned ON for 4 seconds.

If the EXTI Line event does not occur, the WWDG counter is indefinitely refreshed
in the main program infinite loop, and there is no WWDG reset.

LED2 is turned OFF if any error occurs.

@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 

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


@par Hardware and Software environment

  - This example runs on STM32F103xB devices.
    
  - This example has been tested with STM32F103RB-Nucleo 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>
 */
 