Experiment 9 The host computer controls the buzzer through serial communication Referenced example program: 4Serial Interface The experiment involves modules: serial port module, buzzer module. Purpose: 1. Familiar with the communication process of the upper and lower computers. 2. Independently design the program, and master the method of processing the data received by the serial port. Experiment Difficulty: 5 Experimental requirements and phenomena: The upper computer (computer) sends numbers to the lower computer (board) through the serial port, and the lower computer controls the buzzer to ring n times. according to the received number n. Reference Guide: You need to add the part of the main function that processes the data received from the serial port and sounds the corresponding buzzer number based on the number received.