/**
  @page GPIO_EXTI GPIO EXTI example
  
  @verbatim
  ******************** (C) COPYRIGHT 2016 STMicroelectronics *******************
  * @file    GPIO/GPIO_EXTI/readme.txt 
  * @author  MCD Application Team
  * @brief   Description of the GPIO EXTI example.
  ******************************************************************************
  * @attention
  *
  * <h2><center>&copy; Copyright (c) 2016 STMicroelectronics.
  * All rights reserved.</center></h2>
  *
  * This software component is licensed by ST under BSD 3-Clause license,
  * the "License"; You may not use this file except in compliance with the
  * License. You may obtain a copy of the License at:
  *                        opensource.org/licenses/BSD-3-Clause
  *
  ******************************************************************************
  @endverbatim

@par Example Description

How to configure external interrupt lines.

In this example, 2 EXTI lines (EXTI_Line9-5 and EXTI_Line15_10) are configured to generate
an interrupt on each rising and falling edge, respectively. 
In the interrupt routine a led connected to a specific GPIO pin is toggled.

In this example:
    - EXTI_Line9-5 is connected to PE.06 pin
      - when falling edge is detected on EXTI_Line9-5 by pressing Key push-button, LED1 toggles

    - EXTI_Line15_10 is connected to PC.13 pin
      - when falling edge is detected on EXTI_Line15_10, LED2 toggles
      
On STM32303E-EVAL RevC:
    - EXTI_Line9-5 is connected to Key push-button
    - EXTI_Line15_10 is connected to Joystick Sel push-button

In this example, HCLK is configured at 72 MHz.

@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 

  - GPIO/GPIO_EXTI/Inc/stm32f3xx_hal_conf.h    HAL configuration file
  - GPIO/GPIO_EXTI/Inc/stm32f3xx_it.h          Interrupt handlers header file
  - GPIO/GPIO_EXTI/Inc/main.h                  Header for main.c module  
  - GPIO/GPIO_EXTI/Src/stm32f3xx_it.c          Interrupt handlers
  - GPIO/GPIO_EXTI/Src/main.c                  Main program
  - GPIO/GPIO_EXTI/Src/system_stm32f3xx.c      STM32F3xx system source file

@par Hardware and Software environment

  - This example runs on STM32F303xE devices.
    
  - This example has been tested with STM32303E-EVAL RevC 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>
 */
