/**
  @page SPI_OneBoard_HalfDuplex_DMA SPI example
  
  @verbatim
  ******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
  * @file    Examples_LL/SPI/SPI_OneBoard_HalfDuplex_DMA/readme.txt 
  * @author  MCD Application Team
  * @brief   Description of the SPI_OneBoard_HalfDuplex_DMA 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 SPI peripherals to transmit
bytes from an SPI Master device to an SPI Slave device in DMA mode. The example
is based on the STM32F2xx SPI LL API. Peripheral initialization is done using 
LL unitary services functions for optimization purpose (performance and size).

This example works with only one NUCLEO-F207ZG.

SPI1 Peripheral is configured in Master mode Half-Duplex Tx.
SPI3 Peripheral is configured in Slave mode Half-Duplex Rx.
GPIO associated to User push-button is linked with EXTI. 

Example execution:

LED1 is blinking Fast (200ms) and wait Key push-button action.
Press Key push-button on BOARD start a Half-Duplex communication through DMA.
On MASTER side (SPI1), Clock will be generated on SCK line, Transmission done on MOSI Line.
On SLAVE side (SPI3) reception is done through the MISO Line.

LED1 is On if data is well received.

In case of errors, LED1 is blinking Slowly (1s).

@par Directory contents 

  - SPI/SPI_OneBoard_HalfDuplex_DMA/Inc/stm32f2xx_it.h          Interrupt handlers header file
  - SPI/SPI_OneBoard_HalfDuplex_DMA/Inc/main.h                  Header for main.c module
  - SPI/SPI_OneBoard_HalfDuplex_DMA/Inc/stm32_assert.h          Template file to include assert_failed function
  - SPI/SPI_OneBoard_HalfDuplex_DMA/Src/stm32f2xx_it.c          Interrupt handlers
  - SPI/SPI_OneBoard_HalfDuplex_DMA/Src/main.c                  Main program
  - SPI/SPI_OneBoard_HalfDuplex_DMA/Src/system_stm32f2xx.c      STM32F2xx system source file

@par Hardware and Software environment

  - This example runs on STM32F207ZG devices.

  - This example has been tested with NUCLEO-F207ZG board and can be
    easily tailored to any other supported device and development board.

  - NUCLEO-F207ZG Set-up
    - Connect Master SCK  PA5 to Slave SCK  PB3
    - Connect Master MOSI PA7 to Slave MISO PB4

Relation with Board connector:
  PA5  is connected to pin 10 of CN7 connector
  PA7  is connected to pin 14 of CN7 connector
  PB3 is connected to pin 15 of CN7 connector
  PB4 is connected to pin 19 of CN7 connector

@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>
 */
