串口通讯发送接收实验。在电脑上用串口调试工具发送一个数字给单片机，单片机接收这个数字后，将这个数字加上0x10，然后发送给串口调试工具，并在窗口中显示出来，接着再发送一串字符串给电脑，也在窗口中显示出来。-Serial Communication test for sending and receiving data. Using the serial communication tool to send a number to the 51 MCU, after 51MCU received it, add it with 0x10 and send it back to the serial communication tool and display it on the screen, then MCU send another string to the serial communication tool , and display it on the screen too.