/**
  @page COMP_CompareGpioVsVrefInt_IT COMP example
  
  @verbatim
  ******************************************************************************
  * @file    Examples/COMP/COMP_CompareGpioVsVrefInt_IT/readme.txt
  * @author  MCD Application Team
  * @brief   Description of the COMP_CompareGpioVsVrefInt_IT Example.
  ******************************************************************************
  *
  * Copyright (c) 2020 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 the COMP peripheral to compare the external
voltage applied on a specific pin with the Internal Voltage Reference. 

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.

The SystemClock_Config() function is used to configure the system clock for STM32WL55JCIx  Devices

When the comparator input crosses (either rising or falling edges) the internal 
reference voltage VREFINT (1.22V), the comparator generates an interrupt
and exit from STOP mode.

The System enters STOP mode 5 seconds after the comparator is started and 
after any system wake-up triggered by the comparator interrupt.

In this example, the comparator input is connected on pin PB4 (Arduino connector CN8 pin A3, Morpho connector CN7 pin 34).
The user shall apply a voltage on and each time the comparator input crosses VrefInt (1.21V), MCU is awake,
system clock is reconfigured and LED2 is ON.

If LED3 is toggling continuously without any voltage update, it indicates that the system 
generated an error.

@note This example can not be used in debug mode because GPIO used by debugger are set in analog mode
      to optimize power consumption, and because system enters in Stop mode (debugging features disabled).
      To enable debug capability when program is out of Stop mode (to not change mode of GPIO used by debugger),
      a solution is to comment call of function MX_GPIO_Init.

@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

Comparator, COMP, analog, voltage, analog input, threshold, VrefInt

@par Directory contents 

  - COMP/COMP_CompareGpioVsVrefInt_IT/Inc/stm32wlxx_nucleo_conf.h     BSP configuration file
  - COMP/COMP_CompareGpioVsVrefInt_IT/Inc/stm32wlxx_hal_conf.h    HAL configuration file
  - COMP/COMP_CompareGpioVsVrefInt_IT/Inc/stm32wlxx_it.h          COMP interrupt handlers header file
  - COMP/COMP_CompareGpioVsVrefInt_IT/Inc/main.h                  Header for main.c module
  - COMP/COMP_CompareGpioVsVrefInt_IT/Src/stm32wlxx_it.c          COMP interrupt handlers
  - COMP/COMP_CompareGpioVsVrefInt_IT/Src/main.c                  Main program
  - COMP/COMP_CompareGpioVsVrefInt_IT/Src/stm32wlxx_hal_msp.c     HAL MSP file 
  - COMP/COMP_CompareGpioVsVrefInt_IT/Src/system_stm32wlxx.c      STM32WLxx system source file


@par Hardware and Software environment 

  - This example runs on STM32WL55JCIx devices.

  - This example has been tested with NUCLEO-WL55JC RevC board and can be
    easily tailored to any other supported device and development board.

  - Apply an external variable voltage on PB4 (Arduino connector CN8 pin A3, Morpho connector CN7 pin 34) with average voltage 1.22V.
    
    
@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>
 */