uart_4lineLCD1602_keycode_buzz

代码说明：

  使用到蜂鸣器、Lcd1602、ZLG7289和串口，键盘实现加法器，控制LCD1602和蜂鸣器音乐播放。借助串口调试助手，可以用电脑发送字符，替代键盘，完成上述三种功能。(To use the buzzer, Lcd1602, ZLG7289 and serial port, a keyboard adder, and a buzzer control LCD1602 music player. With serial debugging assistant, a computer can send characters, instead of the keyboard, the above three functions.)