16位整形数值转换为16进制字符串，可用于串口通讯时的数据类型转换。-int16 to hex string

实现串口读写功能。其中读取需要增加读取显示出16进制格式，如1A 2C 3D 5F-Serial read and write function. Which read the need to increase the read display out of 16 hex format, such as 2C 3D 5F 1A...