Symbol SysTick_Handler multiply defined (by port.o and bsp_timer.o).

    #ifndef FREERTOS_CONFIG_H
    #define FREERTOS_CONFIG_H
    /*-----------------------------------------------------------
    * Application specific definitions.
    * * These definitions should be adjusted for your particular hardware and
    * application requirements.
    * * THESE PARAMETERS ARE DESCRIBED WITHIN THE 'CONFIGURATION' SECTION OF THE
    * FreeRTOS API DOCUMENTATION AVAILABLE ON THE FreeRTOS.org WEB SITE.
    * * See http://www.freertos.org/a00110.html.
    *----------------------------------------------------------*/
    
    
    
    #define configUSE_PREEMPTION 1	//使能抢占式调度器
    #define configUSE_IDLE_HOOK 0	//系统主频 168MHz。
    #define configUSE_TICK_HOOK 0	//系统时钟节拍 1KHz，即 1ms。
    #define configCPU_CLOCK_HZ ( ( unsigned long ) 168000000 )
    #define configTICK_RATE_HZ ( ( TickType_t ) 1000 )
    #define configMAX_PRIORITIES ( 5 )	//定义可供用户使用的最大优先级数，如果这个定义的是 5，那么用户可以使用的优先级号是 0,1,2,3,4，不包含 5
    #define configMINIMAL_STACK_SIZE ( ( unsigned short ) 128 )
    #define configTOTAL_HEAP_SIZE ( ( size_t ) ( 30 * 1024 ) )	//定义堆大小，FreeRTOS 内核，用户动态内存申请，任务栈等都需要用这个空间。
    #define configMAX_TASK_NAME_LEN ( 16 )
    #define configUSE_TRACE_FACILITY 0
    #define configUSE_16_BIT_TICKS 0
    #define configIDLE_SHOULD_YIELD 1
    /* Co-routine definitions. */
    #define configUSE_CO_ROUTINES 0
    #define configMAX_CO_ROUTINE_PRIORITIES ( 2 )
    /* Set the following definitions to 1 to include the API function, or zero
    to exclude the API function. */
    #define INCLUDE_vTaskPrioritySet 1
    #define INCLUDE_uxTaskPriorityGet 1
    #define INCLUDE_vTaskDelete 1
    #define INCLUDE_vTaskCleanUpResources 0
    #define INCLUDE_vTaskSuspend 1
    #define INCLUDE_vTaskDelayUntil 1
    #define INCLUDE_vTaskDelay 1
    /* Cortex-M specific definitions. */
    #ifdef __NVIC_PRIO_BITS
    /* __BVIC_PRIO_BITS will be specified when CMSIS is being used. */
    #define configPRIO_BITS __NVIC_PRIO_BITS
    #else
    #define configPRIO_BITS 4 /* 15 priority levels */
    #endif
    /* The lowest interrupt priority that can be used in a call to a "set priority"
    function. */
    #define configLIBRARY_LOWEST_INTERRUPT_PRIORITY 0x0f
    /* The highest interrupt priority that can be used by any interrupt service
    routine that makes calls to interrupt safe FreeRTOS API functions. DO NOT CALL
    INTERRUPT SAFE FREERTOS API FUNCTIONS FROM ANY INTERRUPT THAT HAS A HIGHER
    PRIORITY THAN THIS! (higher priorities are lower numeric values. */
    #define configLIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY 0x01
    /* Interrupt priorities used by the kernel port layer itself. These are generic
    to all Cortex-M ports, and do not rely on any particular library functions. */
    #define configKERNEL_INTERRUPT_PRIORITY ( configLIBRARY_LOWEST_INTERRUPT_PRIORITY << (8 - configPRIO_BITS) )
    /* !!!! configMAX_SYSCALL_INTERRUPT_PRIORITY must not be set to zero !!!!
    See http://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html. */
    #define configMAX_SYSCALL_INTERRUPT_PRIORITY ( configLIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY << (8 - configPRIO_BITS) )
    /* Normal assert() semantics without relying on the provision of an assert.h
    header file. */
    #define configASSERT( x ) if( ( x ) == 0 ) { taskDISABLE_INTERRUPTS(); for( ;; ); }
    /* Definitions that map the FreeRTOS port interrupt handlers to their CMSIS
    standard names. */
    
    #define vPortSVCHandler SVC
    #define xPortPendSVHandler PendSV
    #define xPortSysTickHandler SysTick
    
    #endif /* FREERTOS_CONFIG_H */