/**
  @page USART_Communication_Rx_IT USART Receiver example (IT Mode)
  
  @verbatim
  ******************** (C) COPYRIGHT 2016 STMicroelectronics *******************
  * @file    Examples_LL/USART/USART_Communication_Rx_IT/readme.txt 
  * @author  MCD Application Team
  * @version V1.0.0
  * @date    14-April-2017
  * @brief   Description of the USART_Communication_Rx_IT 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 shows how to configure GPIO and USART peripheral for receiving characters
from HyperTerminal (PC) in Asynchronous mode using Interrupt mode. Peripheral initialization is
done using LL unitary services functions for optimization purpose (performance and size).

USART Peripheral is configured in asynchronous mode (115200 bauds, 8 data bit, 1 start bit, 1 stop bit, no parity).
No HW flow control is used.
GPIO associated to User push-button is linked with EXTI. 
USART RX Not Empty interrupt is enabled.
Virtual Com port feature of STLINK could be used for UART communication between board and PC.

Example execution:
When character is received on USART Rx line, a RXNE interrupt occurs. 
USART IRQ Handler routine is then checking received character value. 
On a specific value ('S' or 's'), LED2 is turned On. 
Received character is echoed on Tx line.
On press on push button, LED2 is turned Off.
In case of errors, LED2 is blinking.

@par Directory contents 

  - USART/USART_Communication_Rx_IT/Inc/stm32f1xx_it.h          Interrupt handlers header file
  - USART/USART_Communication_Rx_IT/Inc/main.h                  Header for main.c module
  - USART/USART_Communication_Rx_IT/Inc/stm32_assert.h          Template file to include assert_failed function
  - USART/USART_Communication_Rx_IT/Src/stm32f1xx_it.c          Interrupt handlers
  - USART/USART_Communication_Rx_IT/Src/main.c                  Main program
  - USART/USART_Communication_Rx_IT/Src/system_stm32f1xx.c      STM32F1xx system source file


@par Hardware and Software environment

  - This example runs on STM32F103xB devices.
    
  - This example has been tested with STM32F103RB-Nucleo board and can be
    easily tailored to any other supported device and development board.
    
  - STM32F103RB-Nucleo Set-up
    In order to select use of Virtual Com port feature of STLINK for connection between STM32F103RB-Nucleo and PC,
    User has to set USE_VCP_CONNECTION define to 1 in main.h file.
    If so, please ensure that USART communication between the target MCU and ST-LINK MCU is properly enabled 
    on HW board in order to support Virtual Com Port (Default HW SB configuration allows use of VCP)

    If VCP is not used (USE_VCP_CONNECTION define set to 0 in main.h file), Connect USART1 TX/RX 
    to respectively RX and TX pins of PC UART (could be done through a USB to UART adapter) :
    - Connect STM32 MCU board USART1 TX pin (GPIO PA.09 connected to pin 21 of CN10 connector)
      to PC COM port RX signal
    - Connect STM32 MCU board USART1 RX pin (GPIO PA.10 connected to pin 33 of CN10 connector)
      to PC COM port TX signal
    - Connect STM32 MCU board GND to PC COM port GND signal
    
  - Launch serial communication SW on PC (as HyperTerminal or TeraTerm) with proper configuration 
    (115200 bauds, 8 bits data, 1 stop bit, no parity, no HW flow control). 
    Port should be selected according to USE_VCP_CONNECTION value.

  - Launch the program. Enter characters on PC communication SW side.

@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>
 */
