STM32CubeF4

/**
  @page EXTI_ToggleLedOnIT_Init EXTI example
  
  @verbatim
  ******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
  * @file    Examples_LL/EXTI/EXTI_ToggleLedOnIT_Init/readme.txt 
  * @author  MCD Application Team
  * @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

This example describes how to configure the EXTI and use
GPIOs to toggle the user LEDs available on the board when
a user button is pressed. This example is based on the
STM32F4xx LL API. Peripheral initialization is done using LL
initialization function to demonstrate LL init usage.

In this example, one EXTI line (EXTI13) 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:
    - EXTI13 is connected to PC.13 pin
      - when falling edge is detected on EXTI13 by pressing User push-button, LED2 toggles

On NUCLEO-F411RE:
    - EXTI13 is connected to User push-button

@par Keywords

System, GPIO, Output, Alternate function, EXTI, Toggle

@par Directory contents 

  - EXTI/EXTI_ToggleLedOnIT_Init/Inc/stm32f4xx_it.h          Interrupt handlers header file
  - EXTI/EXTI_ToggleLedOnIT_Init/Inc/main.h                  Header for main.c module
  - EXTI/EXTI_ToggleLedOnIT_Init/Inc/stm32_assert.h          Template file to include assert_failed function
  - EXTI/EXTI_ToggleLedOnIT_Init/Src/stm32f4xx_it.c          Interrupt handlers
  - EXTI/EXTI_ToggleLedOnIT_Init/Src/main.c                  Main program
  - EXTI/EXTI_ToggleLedOnIT_Init/Src/system_stm32f4xx.c      STM32F4xx system source file

@par Hardware and Software environment

  - This example runs on STM32F411xx devices.
    
  - This example has been tested with NUCLEO-F411RE 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>
 */