﻿/**
  @page PWR_EnterStandbyMode PWR standby example
  
  @verbatim
  ******************************************************************************
  * @file    Examples_LL/PWR/PWR_EnterStandbyMode/readme.txt 
  * @author  MCD Application Team
  * @brief   Description of the PWR STANDBY mode example.
  ******************************************************************************
  *
  * Copyright (c) 2019 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 enter the Standby mode and wake up from this mode by using an external 
reset or a wakeup interrupt.

In the associated software, the system clock is set to 16 MHz, an EXTI line
is connected to the User push-button (SW1) thru PC.04 and configured to generate an 
interrupt on falling edge upon key press.
LED2 is toggled each 200 ms in order to indicate that MCU is in RUN mode.

When a falling edge is detected on the EXTI line, an interrupt is generated. 
In the EXTI handler routine, the wake-up pin LL_PWR_WAKEUP_PIN2 is enabled and the 
corresponding wake-up flag cleared. Then, the system enters Standby mode causing 
LED2 to stop toggling. 

Next, the user can wake-up the system in pressing the User push-button (SW1) which is 
connected to the wake-up pin LL_PWR_WAKEUP_PIN2.
A falling edge on WKUP pin will wake-up the system from Standby.
@note Wake-up pin connection: On board STM32WB Nucleo64, pin PC13 is not connected to user button by default, solder bridge SB48 must be closed.
      Alternate solution: connect a wire between PC4 (pin connected to user button) and PC13.
Alternatively, an external RESET of the board will lead to a system wake-up as well.

After wake-up from Standby mode, program execution restarts in the same way as 
after a RESET and LED2 restarts toggling.

LED2 is used to monitor the system state as follows:
 - LED2 fast toggling: system in RUN mode
 - LED2 slow toggling: system in RUN mode after exiting from Standby mode
 - LED2 off : system in Standby mode

These steps are repeated in an infinite loop.

@note To measure MCU current consumption on board STM32WB Nucleo,
      board configuration must be applied:
      - remove all jumpers on connector JP5 to avoid leakages between ST-Link circuitry and STM32WB device.
      - remove jumper JP2 and connect an amperemeter to measure current between the 2 connectors of JP2.

@note On STM32WB, both CPU1 and CPU2 must be in Standby mode to set the entire system in Standby mode.
      In this example, RF stack is not started-up, therefore CPU2 is not started-up and CPU1 configures the CPU2 low-power mode.
      If this example would be ported to another application, user should start RF stack or manage CPU2 low-power mode.

@note This example can not be used in DEBUG mode due to the fact 
      that the Cortex-M4 core is no longer clocked during low power mode 
      so debugging features are disabled.

@par Keywords

Power, PWR, Standby mode, Interrupt, EXTI, Wakeup, Low Power, External reset,

@par Directory contents 

  - PWR/PWR_EnterStandbyMode/Inc/stm32wbxx_it.h          Interrupt handlers header file
  - PWR/PWR_EnterStandbyMode/Inc/main.h                  Header for main.c module
  - PWR/PWR_EnterStandbyMode/Inc/stm32_assert.h          Template file to include assert_failed function
  - PWR/PWR_EnterStandbyMode/Src/stm32wbxx_it.c          Interrupt handlers
  - PWR/PWR_EnterStandbyMode/Src/main.c                  Main program
  - PWR/PWR_EnterStandbyMode/Src/system_stm32wbxx.c      STM32WBxx system source file


@par Hardware and Software environment

  - This example runs on STM32WB55xx devices.
    
  - This example has been tested with STMicroelectronics P-NUCLEO-WB55
    board and can be easily tailored to any other supported device
    and development board.

  - P-NUCLEO-WB55 Set-up
    - LED2 connected to PB.00 pin
    - User push-button connected to pin PC.13 (External line 15 to 10)
    - WakeUp Pin LL_PWR_WAKEUP_PIN2 connected to PC.13

@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>
 */
