STM32频率计

此程序使用STM32实现了频率计的功能，当频率比较低时，测量结果十分准确。高频时，略有误差，但是不能侧得的频率过高。

/**************************************************************************//**
 * @file     core_cm3.c
 * @brief    CMSIS Cortex-M3 Core Peripheral Access layer Source File
 * @version  V1.30
 * @date     30. October 2009
 *
 * @note
 * Copyright （C） 2009 ARM Limited. All rights reserved.
 *
 * @par
 * ARM Limited （ARM） is supplying this software for use with Cortex-M 
 * processor based microcontrollers.  This file can be freely distributed 
 * within development tools that are supporting such ARM based processors. 
 *
 * @par
 * THIS SOFTWARE IS PROVIDED “AS IS“.  NO WARRANTIES WHETHER EXPRESS IMPLIED
 * OR STATUTORY INCLUDING BUT NOT LIMITED TO IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE.
 * ARM SHALL NOT IN ANY CIRCUMSTANCES BE LIABLE FOR SPECIAL INCIDENTAL OR
 * CONSEQUENTIAL DAMAGES FOR ANY REASON WHATSOEVER.
 *
 ******************************************************************************/

#include 

/* define compiler specific symbols */
#if defined （ __CC_ARM   ）
  #define __ASM            __asm                                      /*!< asm keyword for ARM Compiler          */
  #define __INLINE         __inline                                   /*!< inline keyword for ARM Compiler       */

#elif defined （ __ICCARM__ ）
  #define __ASM           __asm                                       /*!< asm keyword for IAR Compiler          */
  #define __INLINE        inline                                      /*!< inline keyword for IAR Compiler. Only avaiable in High optimization mode! */

#elif defined   （  __GNUC__  ）
  #define __ASM            __asm                                      /*!< asm keyword for GNU Compiler          */
  #define __INLINE         inline                                     /*!< inline keyword for GNU Compiler       */

#elif defined   （  __TASKING__  ）
  #define __ASM            __asm                                      /*!< asm keyword for TASKING Compiler      */
  #define __INLINE         inline                                     /*!< inline keyword for TASKING Compiler   */

#endif


/* ###################  Compiler specific Intrinsics  ########################### */

#if defined （ __CC_ARM   ） /*------------------RealView Compiler -----------------*/
/* ARM armcc specific functions */

/**
 * @brief  Return the Process Stack Pointer
 *
 * @return ProcessStackPointer
 *
 * Return the actual process stack pointer
 */
__ASM uint32_t __get_PSP（void）
{
  mrs r0 psp
  bx lr
}

/**
 * @brief  Set the Process Stack Pointer
 *
 * @param  topOfProcStack  Process Stack Pointer
 *
 * Assign the value ProcessStackPointer to the MSP 
 * （process stack pointer） Cortex processor register
 */
__ASM void __set_PSP（uint32_t topOfProcStack）
{
  msr psp r0
  bx lr
}

/**
 * @brief  Return the Main Stack Pointer
 *
 * @return Main Stack Pointer
 *
 * Return the curren

 属性            大小     日期    时间   名称
----------- ---------  ---------- -----  ----
     目录           0  2013-08-07 16:14  频率计\
     目录           0  2013-08-07 16:14  频率计\Libraries\
     目录           0  2013-08-07 16:14  频率计\Libraries\CMSIS\
     目录           0  2013-08-07 16:14  频率计\Libraries\CMSIS\CM3\
     目录           0  2013-08-07 16:14  频率计\Libraries\CMSIS\CM3\CoreSupport\
     文件       17273  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\CoreSupport\core_cm3.c
     文件       85714  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\CoreSupport\core_cm3.h
     目录           0  2013-08-07 16:14  频率计\Libraries\CMSIS\CM3\DeviceSupport\
     目录           0  2013-08-07 16:14  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\
     目录           0  2013-08-07 16:14  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\
     目录           0  2013-08-07 16:14  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\
     目录           0  2013-08-07 16:14  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\arm\
     文件       15763  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\arm\startup_stm32f10x_cl.s
     文件       15500  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\arm\startup_stm32f10x_hd.s
     文件       15767  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\arm\startup_stm32f10x_hd_vl.s
     文件       12373  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\arm\startup_stm32f10x_ld.s
     文件       13653  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\arm\startup_stm32f10x_ld_vl.s
     文件       12762  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\arm\startup_stm32f10x_md.s
     文件       14070  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\arm\startup_stm32f10x_md_vl.s
     文件       15952  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\arm\startup_stm32f10x_xl.s
     目录           0  2013-08-07 16:14  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\gcc_ride7\
     文件       12955  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\gcc_ride7\startup_stm32f10x_cl.s
     文件       13042  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\gcc_ride7\startup_stm32f10x_hd.s
     文件       12451  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\gcc_ride7\startup_stm32f10x_hd_vl.s
     文件        9698  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\gcc_ride7\startup_stm32f10x_ld.s
     文件       10445  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\gcc_ride7\startup_stm32f10x_ld_vl.s
     文件       10154  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\gcc_ride7\startup_stm32f10x_md.s
     文件       10941  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\gcc_ride7\startup_stm32f10x_md_vl.s
     文件       13143  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\gcc_ride7\startup_stm32f10x_xl.s
     目录           0  2013-08-07 16:14  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\iar\
     文件       16629  2010-10-18 20:09  频率计\Libraries\CMSIS\CM3\DeviceSupport\ST\STM32F10x\startup\iar\startup_stm32f10x_cl.s
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