基于（英蓓特）STM32V100的串口程序

This example provides a description of how  to use the USART with hardware flow
control and communicate with the Hyperterminal.
First, the USART2 sends the TxBuffer to the hyperterminal and still waiting for
a string from the hyperterminal that you must enter which must end by '\r'
character (keypad ENTER button). Each byte received is retransmitted to the
Hyperterminal.
The string that you have entered is stored in the RxBuffer array. The receive
buffer have a RxBufferSize bytes as maximum.

The USART2 is configured as follow:
    - BaudRate = 115200 baud 
    - Word Length = 8 Bits
    - One Stop Bit
    - No parity
    - Hardware flow control enabled (RTS and CTS signals)
    - Receive and transmit enabled
    - USART Clock disabled
    - USART CPOL: Clock is active low
    - USART CPHA: Data is captured on the second edge
    - USART LastBit: The clock pulse of the last data bit is not output to
                     the SCLK pin