换晶振导致stm32串口数据飞码的解决办法(补充)
今天（2014.4.21）把stm32f107的程序下载到stm32f103的板子上，发现串口收不到数据，突然想起晶振频率没有修改，#define HSE_VALUE ((uint32_t)13560000) /*!< Value of the External oscillator in Hz */ 这个要改回去，因为外接晶振是8M
之后试验，发现有数据，但是乱码。百思不得其解，无意中发现，PC的波特率设置为9600，板子的波特率设置为19200就不会乱码。刚好是2倍的关系。顺藤摸瓜问度娘！一个帖子也是这种情况，一个回答是“问题解决了，把target options里#define里的STM32F10X_HD_VL改成STM32F10X_MD就正常了（我用的是中密度器件）”，楼下有人说：
看库里面的stm32f10x.h文件，里面很多内容与系统时钟的配置有关。该文件会根据选择的芯片类型来进行时钟配置，要在此位置将选用的芯片类型去掉注释符。当然不想每次修改此文件，比较方便的方法就是你所说是在编译器的target options选项框中define。。。效果一样。
我翻开那个头文件
#if !defined (STM32F10X_LD) && !defined (STM32F10X_LD_VL) && !defined (STM32F10X_MD) && !defined (STM32F10X_MD_VL) && !defined (STM32F10X_HD) && !defined (STM32F10X_HD_VL) && !defined (STM32F10X_XL) && !defined (STM32F10X_CL)
/* #define STM32F10X_LD */ /*!< STM32F10X_LD: STM32 Low density devices */
/* #define STM32F10X_LD_VL */ /*!< STM32F10X_LD_VL: STM32 Low density Value Line devices */
/*#define STM32F10X_MD */ /*!< STM32F10X_MD: STM32 Medium density devices */
/* #define STM32F10X_MD_VL */ /*!< STM32F10X_MD_VL: STM32 Medium density Value Line devices */
/* #define STM32F10X_HD */ /*!< STM32F10X_HD: STM32 High density devices */
/* #define STM32F10X_HD_VL */ /*!< STM32F10X_HD_VL: STM32 High density value line devices */
/* #define STM32F10X_XL */ /*!< STM32F10X_XL: STM32 XL-density devices */
/* #define STM32F10X_CL */ /*!< STM32F10X_CL: STM32 Connectivity line devices */
#endif
/* Tip: To avoid modifying this file each time you need to switch between these
devices, you can define the device in your toolchain compiler preprocessor.
- Low-density devices are STM32F101xx, STM32F102xx and STM32F103xx microcontrollers
where the Flash memory density ranges between 16 and 32 Kbytes.
- Low-density value line devices are STM32F100xx microcontrollers where the Flash
memory density ranges between 16 and 32 Kbytes.
- Medium-density devices are STM32F101xx, STM32F102xx and STM32F103xx microcontrollers
where the Flash memory density ranges between 64 and 128 Kbytes.
- Medium-density value line devices are STM32F100xx microcontrollers where the
Flash memory density ranges between 64 and 128 Kbytes.
- High-density devices are STM32F101xx and STM32F103xx microcontrollers where
the Flash memory density ranges between 256 and 512 Kbytes.
- High-density value line devices are STM32F100xx microcontrollers where the
Flash memory density ranges between 256 and 512 Kbytes. - XL-density devices are STM32F101xx and STM32F103xx microcontrollers where
the Flash memory density ranges between 512 and 1024 Kbytes.
- Connectivity line devices are STM32F105xx and STM32F107xx microcontrollers.
*/
似乎有了思路。查找工程代码，定义了#define STM32F10X_MD_VL，（好像上一位工程师写错了），我修改为#define STM32F10X_MD，问题解决。
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