中文说明：
AD转换的Matlab程序，将输入电压转换成时间(脉冲宽度信号)或频率(脉冲频率)，然后由定时器/计数器获得数字值
English Description：
AD conversion of the Matlab program, the input voltage is converted into a time (pulse width signal) or a frequency (pulse frequency), and then to obtain a digital value by the timer/counter