说明：  使用单片机的GPIO模拟SWD协议时序，实现对另一个单片机进行编程，修改内存变量，可以在此基础上实现离线下载器，调试器等功能。
(GPIO of single-chip microcomputer is used to simulate the sequence of SWD protocol, to realize the programming of another single-chip microcomputer, to modify the memory variables, and to realize the offline Downloader, debugger and other functions on this basis.)