说明：  使串口接受上位机发送的数据，当接受到8个连续数据后，将接收计数值加一后数出数码管显示，并将数据原封不动的发送会上位机。
(PC serial transmission of data, receives eight consecutive information, or to receive a numerical increase after a few out of the digital display, and will send the data was intact aircraft.)