STM32CubeF7/Projects/STM32F769I-Discovery/Examples/GPIO/GPIO_EXTI

/**
  @page GPIO_EXTI GPIO EXTI example
  
  @verbatim
  ******************************************************************************
  * @file    GPIO/GPIO_EXTI/readme.txt 
  * @author  MCD Application Team
  * @brief   Description of the GPIO EXTI example.
  ******************************************************************************
  *
  * Copyright (c) 2016 STMicroelectronics. All rights reserved.
  *
  * 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, one EXTI line (EXTI0) is configured to generate
an interrupt on each rising edge.
In the interrupt routine a led connected to a specific GPIO pin is toggled.

In this example:
    - EXTI0 is connected to PA.0 pin
      - when rising edge is detected on EXTI0 by pressing User button, LED2 toggles once

On STM32F769I-DISCO:
    - EXTI0 is connected to Use button

In this example, HCLK is configured at 216 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 Keywords

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

@Note If the user code size exceeds the DTCM-RAM size or starts from internal cacheable memories (SRAM1 and SRAM2),that is shared between several processors,
      then it is highly recommended to enable the CPU cache and maintain its coherence at application level.
      The address and the size of cacheable buffers (shared between CPU and other masters)  must be properly updated to be aligned to cache line size (32 bytes).

@Note It is recommended to enable the cache and maintain its coherence, but depending on the use case
      It is also possible to configure the MPU as "Write through", to guarantee the write access coherence.
      In that case, the MPU must be configured as Cacheable/Bufferable/Not Shareable.
      Even though the user must manage the cache coherence for read accesses.
      Please refer to the AN4838 “Managing memory protection unit (MPU) in STM32 MCUs”
      Please refer to the AN4839 “Level 1 cache on STM32F7 Series”

@par Directory contents 

  - GPIO/GPIO_EXTI/Inc/stm32f7xx_hal_conf.h    HAL configuration file
  - GPIO/GPIO_EXTI/Inc/stm32f7xx_it.h          Interrupt handlers header file
  - GPIO/GPIO_EXTI/Inc/main.h                  Header for main.c module  
  - GPIO/GPIO_EXTI/Src/stm32f7xx_it.c          Interrupt handlers
  - GPIO/GPIO_EXTI/Src/main.c                  Main program
  - GPIO/GPIO_EXTI/Src/system_stm32f7xx.c      STM32F7xx system source file

@par Hardware and Software environment

  - This example runs on STM32F767xx/STM32F769xx/STM32F777xx/STM32F779xx devices.
    
  - This example has been tested with STM32F769I-DISCO 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>
 */