pwm https://mp.weixin.qq.com/s?__biz=MzUxMjEyNDgyNw==&mid=2247490632&idx=1&sn=d023586303f1ebbb504ab24a4534c81a&chksm=f9686ebcce1fe7aaf03e20f6022844fb27627c2bb2d3dad3414b69cb0fca159fbefb6b7db058&scene=178&cur_album_id=1614665559315382276#rd
按键中断
https://www.cnblogs.com/yikoulinux/p/14259456.html 中断清除从源头开,防止反复请求又置1了
bootloadb https://blog.csdn.net/vianowu/article/details/9722755?utm_term=ARM%E6%8E%A7%E5%88%B6emmc&utm_medium=distribute.pc_aggpage_search_result.none-task-blog-2~all~sobaiduweb~default-0-9722755&spm=3001.4430
启动方式 https://blog.csdn.net/fengjunwang1980/article/details/51746542 异常
https://blog.csdn.net/qq_43743762/article/details/107392511
CPSR寄存器:
https://blog.csdn.net/david_luyang/article/details/6276533
串口通信 http://emb.hqyj.com/xuexi/20183703.html