以2400bps从计算机发送任一字节数据，当单片机收到该数据后，在此数据前加上一序号然后连同此数据一起发送至计算机，当序号超过255时归零-With 2400 BPS send any bytes of data a computer, when the microcontroller after receiving the data, the data with a serial number and then along with the data sent to the computer