/**
  @page I2C_TwoBoards_RestartComIT I2C Two Boards Communication IT  with Restart condition example
  
  @verbatim
  ******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
  * @file    I2C/I2C_TwoBoards_RestartComIT/readme.txt 
  * @author  MCD Application Team
  * @brief   Description of the I2C Two Boards IT Communication with Restart condition example.
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2017 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  @endverbatim

@par Example Description 

How to handle single I2C data buffer transmission/reception between two boards, 
in interrupt mode and with restart condition.

   _________________________                        _________________________
  |           ______________|     ___VDD____       |______________           |
  |          | I2C1         |     |        |       |          I2C1|          |
  |          |              |     R (4.7K) R       |              |          |
  |          |      SCL(PB6)|_____|________|_______|(PB6)SCL      |          |
  |          |              |              |       |              |          |
  |          |              |              |       |              |          |
  |          |              |              |       |              |          |
  |          |      SDA(PB7)|______________|_______|(PB7)SDA      |          |
  |          |              |                      |              |          |
  |          |______________|                      |______________|          |
  |      __                 |                      |             __          |
  |     |__|                |                      |            |__|         |
  |     USER             GND|______________________|GND         USER         |
  |                         |                      |                         |
  |_STM32F103RB_NUCLEO______|                      |_STM32F103RB_NUCLEO______|


This example guides you through the different configuration steps by mean of HAL API 
to ensure I2C Data buffer transmission and reception using Interrupt.
The communication is done with 2 Boards through I2C.

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 64 MHz.

The I2C peripheral configuration is ensured by the HAL_I2C_Init() function.
This later is calling the HAL_I2C_MspInit()function which core is implementing
the configuration of the needed I2C resources according to the used hardware (CLOCK, 
GPIO and NVIC). You may update this function to change I2C configuration.

The I2C communication is then initiated.
The project is split in two parts the Master Board and the Slave Board
- Master Board
  The HAL_I2C_Master_Sequential_Transmit_IT() and the HAL_I2C_Master_Sequential_Receive_IT() functions 
  allow respectively the transmission and the reception of a predefined data buffer
  in Master mode.
- Slave Board
  The HAL_I2C_EnableListen_IT(), HAL_I2C_Slave_Sequential_Receive_IT() and the HAL_I2C_Slave_Sequential_Transmit_IT() functions 
  allow respectively the "Listen" the I2C bus for address match code event, reception and the transmission of a predefined data buffer
  in Slave mode.
The user can choose between Master and Slave through "#define MASTER_BOARD"
in the "main.c" file.
If the Master board is used, the "#define MASTER_BOARD" must be uncommented.
If the Slave board is used the "#define MASTER_BOARD" must be commented.

For this example the aTxBuffer is predefined and the aRxBuffer size is same as aTxBuffer.
                       
On Master board side:
 - Wait User push-button to be pressed.
 - Request write communication after a Start condition by sending aTxBuffer through HAL_I2C_Master_Sequential_Transmit_IT() to I2C Slave 
   - LED2 is turned ON when the transmission process is completed.
 - Then wait User push-button to be pressed.
 - Request read communication after a Repeated Start condition through HAL_I2C_Master_Sequential_Receive_IT() to I2C Slave.
 - Receive data from Slave in aRxBuffer.
   - LED2 is turned OFF when the reception process is completed.
Finally, aRxBuffer and aTxBuffer are compared through Buffercmp() in order to 
check buffers correctness.
 - LED2 is slowly blinking (1 sec. period) when there is an error in communication process.(communication is stopped if any, using infinite loop)

On Slave board side:
 - Go Listen mode by calling HAL_I2C_EnableListen_IT().
 - Acknowledge Address match code.
 - Slave receives data into aRxBuffer through HAL_I2C_Slave_Sequential_Receive_IT().
   - LED2 is turned ON when the reception process is completed.
 - Then slave transmits data by sending aTxBuffer through HAL_I2C_Slave_Sequential_Transmit_IT().
   - LED2 is turned OFF when the transmission process is completed.
Finally, aRxBuffer and aTxBuffer are compared through Buffercmp() in order to 
check buffers correctness.
LED2 is slowly blinking (1 sec. period) when there is an error in transmission/reception process,
or buffers compared error. (communication is stopped if any, using infinite loop)

@note I2Cx instance used and associated resources can be updated in "main.h"
       file depending hardware configuration used.

@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 needs to ensure that the SysTick time base is always set to 1 millisecond
      to have correct HAL operation.

@par Directory contents 

  - I2C/I2C_TwoBoards_RestartComIT/Inc/stm32f1xx_hal_conf.h    HAL configuration file
  - I2C/I2C_TwoBoards_RestartComIT/Inc/stm32f1xx_it.h          I2C interrupt handlers header file
  - I2C/I2C_TwoBoards_RestartComIT/Inc/main.h                  Header for main.c module  
  - I2C/I2C_TwoBoards_RestartComIT/Src/stm32f1xx_it.c          I2C interrupt handlers
  - I2C/I2C_TwoBoards_RestartComIT/Src/main.c                  Main program
  - I2C/I2C_TwoBoards_RestartComIT/Src/system_stm32f1xx.c      STM32F1xx system source file
  - I2C/I2C_TwoBoards_RestartComIT/Src/stm32f1xx_hal_msp.c     HAL MSP 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
    - Connect Master board PB6 to Slave Board PB6
    - Connect Master board PB7 to Slave Board PB7
    - Connect Master board GND to Slave Board GND
    - Check that a pull-up resistor is connected on one I2C SDA pin
    - Check that a pull-up resistor is connected on one I2C SCL pin
    - PB6 is connected to pin 3 on CN5 connector ( pin 17 on CN10 connector)
    - PB7 is connected to pin 21 CN7 coonector
    - VDD is connected to pin 8 on CN5 connector ( pin7 on CN10 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
    o Uncomment "#define MASTER_BOARD" and load the project in Master Board
    o Comment "#define MASTER_BOARD" and load the project in Slave Board
 - Run the example


 */
