IO operation functions
[UART Exported Functions]

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                      ##### IO operation functions #####
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    This subsection provides a set of functions allowing to manage the UART asynchronous
    and Half duplex data transfers.

    (#) There are two mode of transfer:
       (+) Blocking mode: The communication is performed in polling mode.
            The HAL status of all data processing is returned by the same function
            after finishing transfer.
       (+) No-Blocking mode: The communication is performed using Interrupts
           or DMA, These API's return the HAL status.
           The end of the data processing will be indicated through the
           dedicated UART IRQ when using Interrupt mode or the DMA IRQ when
           using DMA mode.
           The HAL_UART_TxCpltCallback(), HAL_UART_RxCpltCallback() user callbacks
           will be executed respectively at the end of the transmit or Receive process
           The HAL_UART_ErrorCallback()user callback will be executed when a communication error is detected

    (#) Blocking mode API's are :
        (+) HAL_UART_Transmit()
        (+) HAL_UART_Receive()

    (#) Non-Blocking mode API's with Interrupt are :
        (+) HAL_UART_Transmit_IT()
        (+) HAL_UART_Receive_IT()
        (+) HAL_UART_IRQHandler()

    (#) No-Blocking mode API's with DMA are :
        (+) HAL_UART_Transmit_DMA()
        (+) HAL_UART_Receive_DMA()
        (+) HAL_UART_DMAPause()
        (+) HAL_UART_DMAResume()
        (+) HAL_UART_DMAStop()

    (#) A set of Transfer Complete Callbacks are provided in No_Blocking mode:
        (+) HAL_UART_TxHalfCpltCallback()
        (+) HAL_UART_TxCpltCallback()
        (+) HAL_UART_RxHalfCpltCallback()
        (+) HAL_UART_RxCpltCallback()
        (+) HAL_UART_ErrorCallback()

    (#) In Non-Blocking mode transfers, possible errors are split into 2 categories.
        Errors are handled as follows :
       (+) Error is considered as Recoverable and non blocking : Transfer could go till end, but error severity is 
           to be evaluated by user : this concerns Frame Error, Parity Error or Noise Error in Interrupt mode reception .
           Received character is then retrieved and stored in Rx buffer, Error code is set to allow user to identify error type,
           and HAL_UART_ErrorCallback() user callback is executed. Transfer is kept ongoing on UART side.
       (+) Error is considered as Blocking : Transfer could not be completed properly and is aborted.
           This concerns Overrun Error In Interrupt mode reception and all errors in DMA mode.
           Error code is set to allow user to identify error type, and HAL_UART_ErrorCallback() user callback is executed.

    -@- In the Half duplex communication, it is forbidden to run the transmit
        and receive process in parallel, the UART state HAL_UART_STATE_BUSY_TX_RX can't be useful.