/**
  @page USART_Communication_Tx_IT USART Transmitter example (IT mode)
  
  @verbatim
  ******************** (C) COPYRIGHT 2016 STMicroelectronics *******************
  * @file    Examples_LL/USART/USART_Communication_Tx_IT/readme.txt 
  * @author  MCD Application Team
  * @brief   Description of the USART_Communication_Tx_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 to send characters
asynchronously to HyperTerminal (PC) in Interrupt mode; 
This example is based on STM32F0xx USART LL API; 
Peripheral initialization 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. 
Virtual Com port feature of STLINK could be used for UART communication between board and PC.

Example execution:
On press on push button , USART TX Empty interrupt is enabled.
First character of buffer to be transmitted is written into USART Transmit Data Register (TDR) in order to initialise transfer procedure.
When character is sent from TDR, a TXE interrupt occurs. 
USART IRQ Handler routine is sending next character on USART Tx line. 
IT will be raised until last byte is to be transmitted : Then, Transmit Complete (TC) interrupt is enabled 
instead of TX Empty (TXE). 
On last byte transmission complete, LED is turned on.
In case of errors, LED is blinking (1sec period).

Program is written so that, any new press on User push-button will lead to new transmission of complete buffer.

@par Directory contents 

  - USART/USART_Communication_Tx_IT/Inc/stm32f0xx_it.h          Interrupt handlers header file
  - USART/USART_Communication_Tx_IT/Inc/main.h                  Header for main.c module
  - USART/USART_Communication_Tx_IT/Inc/stm32_assert.h          Template file to include assert_failed function
  - USART/USART_Communication_Tx_IT/Src/stm32f0xx_it.c          Interrupt handlers
  - USART/USART_Communication_Tx_IT/Src/main.c                  Main program
  - USART/USART_Communication_Tx_IT/Src/system_stm32f0xx.c      STM32F0xx system source file


@par Hardware and Software environment

  - This example runs on STM32F072xB devices.
    
  - This example has been tested with STM32F072RB-Nucleo RevC board and can be
    easily tailored to any other supported device and development board.

  - STM32F072RB-Nucleo RevC Set-up
    In order to select use of Virtual Com port feature of STLINK for connection between STM32F072RB-Nucleo RevC 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), GPIOs connected
    to USART1 TX/RX (PA.09 and PA.10) should be wired
    to respectively RX and TX pins of PC UART (could be done through a USB to UART adapter).
    Connect GND between STM32 board and PC UART.

  - 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. Press on User push button on board to initiate data transfer.

@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>
 */
