IrDA mode functions
[USART_Private_Functions]

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                        ##### IrDA mode functions #####
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    [..] This subsection provides a set of functions allowing to manage the USART
         IrDA communication.
    [..] IrDA is a half duplex communication protocol. If the Transmitter is busy, 
         any data on the IrDA receive line will be ignored by the IrDA decoder 
         and if the Receiver is busy, data on the TX from the USART to IrDA will 
         not be encoded by IrDA. While receiving data, transmission should be 
         avoided as the data to be transmitted could be corrupted.
    [..] IrDA communication is possible through the following procedure:
         (#) Program the Baud rate, Word length = 8 bits, Stop bits, Parity, 
             Transmitter/Receiver modes and hardware flow control values using 
             the USART_Init() function.
         (#) Configures the IrDA pulse width by configuring the prescaler using  
             the USART_SetPrescaler() function.
         (#) Configures the IrDA  USART_IrDAMode_LowPower or USART_IrDAMode_Normal 
             mode using the USART_IrDAConfig() function.
         (#) Enable the IrDA using the USART_IrDACmd() function.
         (#) Enable the USART using the USART_Cmd() function.         
    [..]
    (@) A pulse of width less than two and greater than one PSC period(s) may or 
        may not be rejected.
    (@) The receiver set up time should be managed by software. The IrDA physical 
        layer specification specifies a minimum of 10 ms delay between 
        transmission and reception (IrDA is a half duplex protocol).
    (@) In IrDA mode, the following bits must be kept cleared:
        (+@) LINEN, STOP and CLKEN bits in the USART_CR2 register.
        (+@) SCEN and HDSEL bits in the USART_CR3 register.