参考文献1:http://blog.youkuaiyun.com/u010854102/article/details/47259471
参考文献2:http://wiki.t-firefly.com/index.php/Firefly-RK3288/GPIO
参考文献3:http://developer.t-firefly.com/thread-2436-1-1.html
参考文献4:http://blog.youkuaiyun.com/kris_fei/article/details/69553422
参考文献5:http://blog.youkuaiyun.com/cjsycyl/article/details/46310939