STM32开发板实验的系统文件代码，主要为了配置系统时钟与外设配置以及各外设的用法-STM32 development board serial experiments code system files, mainly in order to configure the system clock and peripheral configuration

成功移植了contiki操作系统的代码，编译在keil5下编译生成HEX文件下载到STM32即可实现LED闪烁与串口打印功能。(The code of Contiki operation system is successfully transplanted, compiled and compiled under keil5, and HEX files are downloaded to STM32 to achieve LED scintillation and serial port p