六首唱歌的音乐程序循环,是在单片机学习板子上开发的，按一个键（p3.4）可以换歌曲。-six singing the music program cycle, is studying the way in SCM developed, the press of a button (p3.4) could change songs.

步进电机控制程序p3.2正转,p3.3反转,p3.4停止-stepper motor control procedures is to p3.2, p3.3 inversion, p3.4 stop

同济大学的 陈以一教授的《钢结构基本原理》第3章