说明：  单片机与PC通信实例 功能：从PC机串口端接收13个字节的数据，然后将接收到的数据加上 "Serial Port OK!"的后缀后，发送给PC作为应答
(Examples of MCU and PC communication function: serial client machine from the PC to receive 13 bytes of data, and then will receive the data together with the Serial Port OK! Suffix after sent to the PC as a response)