http://blog.csdn.net/pengrui18/article/details/24740973
https://www.maximintegrated.com/cn/app-notes/index.mvp/id/4600
http://www.360doc.com/content/15/1230/17/27708084_524223594.shtml
DS18B20 crc 算法
原文：http://www.cnblogs.com/prayer521/p/6138862.html
