I2C HAL

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                        ##### How to use this driver #####
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  [..]
    The I2C HAL driver can be used as follows:

    (#) Declare a I2C_HandleTypeDef handle structure, for example:
        I2C_HandleTypeDef  hi2c;

    (#)Initialize the I2C low level resources by implement the HAL_I2C_MspInit() API:
        (##) Enable the I2Cx interface clock
        (##) I2C pins configuration
            (+++) Enable the clock for the I2C GPIOs
            (+++) Configure I2C pins as alternate function open-drain
        (##) NVIC configuration if you need to use interrupt process
            (+++) Configure the I2Cx interrupt priority
            (+++) Enable the NVIC I2C IRQ Channel
        (##) DMA Configuration if you need to use DMA process
            (+++) Declare a DMA_HandleTypeDef handle structure for the transmit or receive stream
            (+++) Enable the DMAx interface clock using
            (+++) Configure the DMA handle parameters
            (+++) Configure the DMA Tx or Rx Stream
            (+++) Associate the initialized DMA handle to the hi2c DMA Tx or Rx handle
            (+++) Configure the priority and enable the NVIC for the transfer complete interrupt on
                  the DMA Tx or Rx Stream

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