/**
  @page LPUART_WakeUpFromStop LPUART Wake up from Stop mode example

  @verbatim
  ******************** (C) COPYRIGHT 2014 STMicroelectronics *******************
  * @file    UART/LPUART_WakeUpFromStop/readme.txt 
   * @author  MCD Application Team
  * @version V1.0.0
  * @date    18-June-2014
  * @brief   Description of the LPUART-triggered MCU wake-up from STOP mode.
  ******************************************************************************
  *
  * 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 


Board: STM32L0538-DISCO RevB
Tx Pin: PB.10
Rx Pin: PB.11
   _________________________                       _________________________ 
  |           ______________|                     |______________           |
  |          |LPUART        |                     |        LPUART|          |
  |          |              |                     |              |          |
  |          |           TX |_____________________| RX           |          |
  |          |              |                     |              |          |
  |          |              |                     |              |          |
  |          |              |                     |              |          |
  |          |           RX |_____________________| TX           |          |
  |          |              |                     |              |          |
  |          |______________|                     |______________|          |
  |                         |                     |                         |
  |                         |                     |                         |
  | STM32 Board 1           |                     | STM32 Board 2           |
  | (follows a sequence of  |                     | (sends stimuli to wake  |
  | RUN/STOP modes)         |                     |  up STM32 Board 1)      |
  |_________________________|                     |_________________________|



This example shows how to configure the LPUART to wake up the MCU from STOP mode
when the proper stimulus is received.

Board 1 enters STOP mode and is awoken by Board 2 which sends
the proper data to wake up the board 1 MCU.
When the proper wake-up event is recognized, the WUF interrupt is triggered which wakes
up board 1.
To confirm its wake up, board 1 sends a confirmation message to board 2 which
checks it is the expected message.
This cycle is repeated 4 times to verify 4 different events
1°) wake-up by RXNE flag rising
2°) wake-up by Start Bit detection
3°) wake-up by 7-bit long address match
4°) wake-up by 4-bit long address match


WARNING: as both boards do not behave the same way, "BOARD_IN_STOP_MODE" 
compilation switch is defined in UART/LPUART_WakeUpFromStop/Src/main.c and must be
enabled at compilation time before loading the executable in board 1 (that which
is set in STOP mode).
The stimuli-transmitting board (board 2) needs to be loaded with an executable
software obtained with BOARD_IN_STOP_MODE disabled. 


At the very beginning, board 1 LED3 is ON then is turned off.
This means that board 1 has entered STOP mode.
Parallely, board 2 LED3 is quickly blinking (100 ms period). The user has 
just to wait for board 1 LED3 to be turned off then to press board 2 USER 
push-button to send the first wake-up stimulus to board 1. 
This starts the test sequence and no more action is required from the user
(a single USER push-button press is needed to start the full 4 wake-up events
test sequence). 

Board 1 LED3 behavior as described below allows to follow the 
test progress:

ON ____          _______          _______          _______          ____
       |        |       |        |       |        |       |        |    
OFF    |________|       |________|       |________|       |________|    
      Enter    Exit    Enter    Exit    Enter    Exit    Enter    Exit  
      Stop     Stop    Stop     Stop    Stop     Stop    Stop     Stop  
      Mode     Mode    Mode     Mode    Mode     Mode    Mode     Mode  
            (RXNE flag)      (Start Bit      (7-bit add.       (4-bit add.
                              Detection)        match)            match)
                               


Simultaneously, board 2 LED3 behavior shown below allows to follow the 
test progress on the other side:

  BLINKING   
ON ****________          _______          _______          _______          ____
               |        |       |        |       |        |       |        |    
OFF            |________|       |________|       |________|       |________|    
     USER     WkUp   2nd stim  WkUp   3rd stim  WkUp   4th stim  WkUp    LED ON  
     button   conf     sent    conf     sent    conf     sent    conf    to mark  
    pushed,   rcv'ed          rcv'ed           rcv'ed           rcv'ed   passed
  1st stimulus                                                            test 
     sent                                                                    
  (RXNE flag)      (Start Bit       (7-bit add.      (4-bit add.
                    Detection)         match)           match)
     

    
- If the test fails or if there is an initialization or transfer error, LED3
transmits a sequence of three dots, three dashes, three dots.

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.
Then the SystemClock_Config() function is used to configure the system
clock (SYSCLK) to run at 32 MHz.  


The LPUART is configured as follows:
    - BaudRate = 9600 baud  
    - Word Length = 8 bits (8 data bits, no parity bit)
    - One Stop Bit
    - Parity none
    - Hardware flow control disabled (RTS and CTS signals)


@note USARTx/UARTx instance used and associated resources can be updated in "main.h"
file depending hardware configuration used.

@note When the parity is enabled, the computed parity is inserted at the MSB
position of the transmitted data.

@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 Directory contents 

  - UART/LPUART_WakeUpFromStop/Inc/stm32l0xx_hal_conf.h    HAL configuration file
  - UART/LPUART_WakeUpFromStop/Inc/stm32l0xx_it.h          Interrupt handlers header file
  - UART/LPUART_WakeUpFromStop/Inc/main.h                  Header for main.c module  
  - UART/LPUART_WakeUpFromStop/Src/stm32l0xx_it.c          Interrupt handlers
  - UART/LPUART_WakeUpFromStop/Src/main.c                  Main program
  - UART/LPUART_WakeUpFromStop/Src/stm32f0xx_hal_msp.c     HAL MSP module
  - UART/LPUART_WakeUpFromStop/Src/system_stm32l0xx.c      STM32L0xx system source file


@par Hardware and Software environment 

  - This example runs on STM32L051xx, STM32L052xx, STM32L053xx STM32L062xx and 
    STM32L063xx device lines RevZ
    
  - This example has been tested with STM32L0538-DISCO RevB and can be
    easily tailored to any other supported device and development board.

  - STM32L0538-DISCO RevB Set-up
    - Connect a wire between 1st board PB10 pin (LPUART Tx) 
      to 2nd board PB11 pin (LPUART Rx)
    - Connect a wire between 1st board PB11 pin (LPUART Rx)
      to 2nd board PB10 pin (LPUART Tx)

@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>
 */
