/**
  @page EXTI_ToggleLedOnIT EXTI example
  
  @verbatim
  ******************** (C) COPYRIGHT 2016 STMicroelectronics *******************
  * @file    Examples_LL/EXTI/EXTI_ToggleLedOnIT/readme.txt 
  * @author  MCD Application Team
  * @version V1.0.0
  * @date    14-April-2017
  * @brief   Description of the EXTI 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 EXTI and use GPIOs to toggle the user LEDs 
available on the board when a user button is pressed. It is based on the
STM32F1xx LL API. The peripheral initialization uses LL unitary service
functions for optimization purposes (performance and size).

In this example, one EXTI line (External lines 10 to 15) is configured to generate
an interrupt on each falling edge.

In the interrupt routine a led connected to a specific GPIO pin is toggled.

In this example:
    - External lines 10 to 15 is connected to PC.13 pin
      - when falling edge is detected on External lines 10 to 15 by pressing User push-button, LED2 toggles

On STM32F103RB-Nucleo:
    - External lines 10 to 15 is connected to User push-button


@par Directory contents 

  - EXTI/EXTI_ToggleLedOnIT/Inc/stm32f1xx_it.h          Interrupt handlers header file
  - EXTI/EXTI_ToggleLedOnIT/Inc/main.h                  Header for main.c module
  - EXTI/EXTI_ToggleLedOnIT/Inc/stm32_assert.h          Template file to include assert_failed function
  - EXTI/EXTI_ToggleLedOnIT/Src/stm32f1xx_it.c          Interrupt handlers
  - EXTI/EXTI_ToggleLedOnIT/Src/main.c                  Main program
  - EXTI/EXTI_ToggleLedOnIT/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>
 */
