FreeRTOS移植以及任务

FreeRTOS移植
1.在sys.h中需要把SYSTEM_SUPPORT_OS 改为 1，支持我们使用 FreeRTOS

//0,不支持 os
//1,支持 os
#define SYSTEM_SUPPORT_OS 1 //定义系统文件夹是否支持 OS

2.出现报错
…\SYSTEM\usart\usart.c(6): error: #5: cannot open source input file “includes.h”: No such file or directory
即需要修改usart.c 文件：

```c
默认是添加的 UCOS 中的 includes.h 头文件，修改以后如下：
//如果使用 os,则包括下面的头文件即可.
#if SYSTEM_SUPPORT_OS
#include "FreeRTOS.h" //os 使用
#endif
``

3.delay.c函数需要大改

FreeRTOS 的系统时钟是由滴答定时器提供的，需要根据FreeRTOS的系统节拍来初始化滴答定时器，delay_init()就是来完成这个功能的。
FreeRTOS 的系统时钟节拍由宏 configTICK_RATE_HZ 来设置，这个值我们可以自由设置，但是一旦设置好以后我们就要根据这个值来初始化滴答定时器，其实就是设置滴答定时器的中断周期。在基础例程中滴答定时器的时钟频率设置的是 AHB 的 1/8，这里为了兼容 FreeRTOS 将滴答定时器的时钟频率改为了 AHB，也就是 72MHz！这一点一定要注意！
完整delay.c文件

#include "delay.h"
// 	 
//如果需要使用OS,则包括下面的头文件即可.
#if SYSTEM_SUPPORT_OS
#include "FreeRTOS.h"					//ucos 使用	  
#include "task.h"  //文件在FreeRTOS\include
#endif


static u8  fac_us=0;							//us延时倍乘数			   
static u16 fac_ms=0;							//ms延时倍乘数,在ucos下,代表每个节拍的ms数

extern void xPortSysTickHandler(void);
 //systick中断服务函数,使用ucos时用到
void SysTick_Handler(void)
    {
        if(xTaskGetSchedulerState()!=taskSCHEDULER_NOT_STARTED)
        {
            xPortSysTickHandler();
        }
    }

//初始化延迟函数
//SYSTICK的时钟固定为AHB时钟，基础例程里面SYSTICK时钟频率为AHB/8
//这里为了兼容FreeRTOS，所以将SYSTICK的时钟频率改为AHB的频率！
//SYSCLK:系统时钟频率
void delay_init()
{
	u32 reload;
	SysTick_CLKSourceConfig(SysTick_CLKSource_HCLK);//选择外部时钟  HCLK
	fac_us=SystemCoreClock/1000000;				//不论是否使用OS,fac_us都需要使用
	reload=SystemCoreClock/1000000;				//每秒钟的计数次数 单位为M  
	reload*=1000000/configTICK_RATE_HZ;			//根据configTICK_RATE_HZ设定溢出时间
												//reload为24位寄存器,最大值:16777216,在72M下,约合0.233s左右	
	fac_ms=1000/configTICK_RATE_HZ;				//代表OS可以延时的最少单位	   

	SysTick->CTRL|=SysTick_CTRL_TICKINT_Msk;   	//开启SYSTICK中断
	SysTick->LOAD=reload; 						//每1/configTICK_RATE_HZ秒中断一次	
	SysTick->CTRL|=SysTick_CTRL_ENABLE_Msk;   	//开启SYSTICK    
}

//延时nus
//nus:要延时的us数.	
//nus:0~204522252(最大值即2^32/fac_us@fac_us=168)	    								   
void delay_us(u32 nus)
{		
	u32 ticks;
	u32 told,tnow,tcnt=0;
	u32 reload=SysTick->LOAD;				//LOAD的值	    	 
	ticks=nus*fac_us; 						//需要的节拍数 
	told=SysTick->VAL;        				//刚进入时的计数器值
	while(1)
	{
		tnow=SysTick->VAL;	
		if(tnow!=told)
		{	    
			if(tnow<told)tcnt+=told-tnow;	//这里注意一下SYSTICK是一个递减的计数器就可以了.
			else tcnt+=reload-tnow+told;	    
			told=tnow;
			if(tcnt>=ticks)break;			//时间超过/等于要延迟的时间,则退出.
		}  
	};										    
}  
//延时nms
//nms:要延时的ms数
//nms:0~65535
void delay_ms(u32 nms)
{	
	if(xTaskGetSchedulerState()!=taskSCHEDULER_NOT_STARTED)//系统已经运行
	{		
		if(nms>=fac_ms)						//延时的时间大于OS的最少时间周期 
		{ 
   			vTaskDelay(nms/fac_ms);	 		//FreeRTOS延时
		}
		nms%=fac_ms;						//OS已经无法提供这么小的延时了,采用普通方式延时    
	}
	delay_us((u32)(nms*1000));				//普通方式延时
}

## FreeRTOS任务

//延时nms,不会引起任务调度
//nms:要延时的ms数
void delay_xms(u32 nms)
{
	u32 i;
	for(i=0;i<nms;i++) delay_us(1000);
}

任务句柄： * TaskHandle_t

struct tskTaskControlBlock; /* The old naming convention is used to prevent breaking kernel aware debuggers. */
typedef struct tskTaskControlBlock * TaskHandle_t;

最终要溯源到 tskTaskControlBlock， tskTaskControlBlock是一个任务句柄结构体，在tasks.c文件中

ypedef struct tskTaskControlBlock       /* The old naming convention is used to prevent breaking kernel aware debuggers. */
{
    volatile StackType_t * pxTopOfStack; /*< Points to the location of the last item placed on the tasks stack.  THIS MUST BE THE FIRST MEMBER OF THE TCB STRUCT. */

    #if ( portUSING_MPU_WRAPPERS == 1 )
        xMPU_SETTINGS xMPUSettings; /*< The MPU settings are defined as part of the port layer.  THIS MUST BE THE SECOND MEMBER OF THE TCB STRUCT. */
    #endif

    ListItem_t xStateListItem;                  /*< The list that the state list item of a task is reference from denotes the state of that task (Ready, Blocked, Suspended ). */
    ListItem_t xEventListItem;                  /*< Used to reference a task from an event list. */
    UBaseType_t uxPriority;                     /*< The priority of the task.  0 is the lowest priority. */
    StackType_t * pxStack;                      /*< Points to the start of the stack. */
    char pcTaskName[ configMAX_TASK_NAME_LEN ]; /*< Descriptive name given to the task when created.  Facilitates debugging only. */ /*lint !e971 Unqualified char types are allowed for strings and single characters only. */

    #if ( ( portSTACK_GROWTH > 0 ) || ( configRECORD_STACK_HIGH_ADDRESS == 1 ) )
        StackType_t * pxEndOfStack; /*< Points to the highest valid address for the stack. */
    #endif

    #if ( portCRITICAL_NESTING_IN_TCB == 1 )
        UBaseType_t uxCriticalNesting; /*< Holds the critical section nesting depth for ports that do not maintain their own count in the port layer. */
    #endif

    #if ( configUSE_TRACE_FACILITY == 1 )
        UBaseType_t uxTCBNumber;  /*< Stores a number that increments each time a TCB is created.  It allows debuggers to determine when a task has been deleted and then recreated. */
        UBaseType_t uxTaskNumber; /*< Stores a number specifically for use by third party trace code. */
    #endif

    #if ( configUSE_MUTEXES == 1 )
        UBaseType_t uxBasePriority; /*< The priority last assigned to the task - used by the priority inheritance mechanism. */
        UBaseType_t uxMutexesHeld;
    #endif

    #if ( configUSE_APPLICATION_TASK_TAG == 1 )
        TaskHookFunction_t pxTaskTag;
    #endif

    #if ( configNUM_THREAD_LOCAL_STORAGE_POINTERS > 0 )
        void * pvThreadLocalStoragePointers[ configNUM_THREAD_LOCAL_STORAGE_POINTERS ];
    #endif

    #if ( configGENERATE_RUN_TIME_STATS == 1 )
        configRUN_TIME_COUNTER_TYPE ulRunTimeCounter; /*< Stores the amount of time the task has spent in the Running state. */
    #endif

    #if ( configUSE_NEWLIB_REENTRANT == 1 )

        /* Allocate a Newlib reent structure that is specific to this task.
         * Note Newlib support has been included by popular demand, but is not
         * used by the FreeRTOS maintainers themselves.  FreeRTOS is not
         * responsible for resulting newlib operation.  User must be familiar with
         * newlib and must provide system-wide implementations of the necessary
         * stubs. Be warned that (at the time of writing) the current newlib design
         * implements a system-wide malloc() that must be provided with locks.
         *
         * See the third party link http://www.nadler.com/embedded/newlibAndFreeRTOS.html
         * for additional information. */
        struct  _reent xNewLib_reent;
    #endif

    #if ( configUSE_TASK_NOTIFICATIONS == 1 )
        volatile uint32_t ulNotifiedValue[ configTASK_NOTIFICATION_ARRAY_ENTRIES ];
        volatile uint8_t ucNotifyState[ configTASK_NOTIFICATION_ARRAY_ENTRIES ];
    #endif

    /* See the comments in FreeRTOS.h with the definition of
     * tskSTATIC_AND_DYNAMIC_ALLOCATION_POSSIBLE. */
    #if ( tskSTATIC_AND_DYNAMIC_ALLOCATION_POSSIBLE != 0 ) /*lint !e731 !e9029 Macro has been consolidated for readability reasons. */
        uint8_t ucStaticallyAllocated;                     /*< Set to pdTRUE if the task is a statically allocated to ensure no attempt is made to free the memory. */
    #endif

    #if ( INCLUDE_xTaskAbortDelay == 1 )
        uint8_t ucDelayAborted;
    #endif

    #if ( configUSE_POSIX_ERRNO == 1 )
        int iTaskErrno;
    #endif
} tskTCB;

xTaskCreate()函数的参数：

BaseType_t xTaskCreate( TaskFunction_t pxTaskCode,
                            const char * const pcName, /*lint !e971 Unqualified char types are allowed for strings and single characters only. */
                            const configSTACK_DEPTH_TYPE usStackDepth,
                            void * const pvParameters,
                            UBaseType_t uxPriority,
                            TaskHandle_t * const pxCreatedTask )