UCOSIII信号量

谁借莪１个温暖的怀抱￠ 2022-06-01 23:51 275阅读 0赞

**信号量通常分为两种**

> 二进制信号量  
> 计数型信号量

**二进制信号量**  
二进制信号量只能取0和1两个值

**计数型信号量**  
计数型信号量的范围由OS\_SEM\_CTR决定。OS\_SEM\_CTR可以为8位，16位和32位

**API函数**

//创建
    void OSSemCreate (OS_SEM *p_sem,
                      CPU_CHAR *p_name,
                      OS_SEM_CTR cnt,
                      OS_ERR *p_err);
    
    //删除
    OS_OBJ_QTY OSSemDel (OS_SEM *p_sem,
                         OS_OPT opt,
                         OS_ERR *p_err);
    
    //等待-1
    OS_SEM_CTR OSSemPend (OS_SEM *p_sem,
                          OS_TICK timeout,
                          OS_OPT opt,
                          CPU_TS *p_ts,
                          OS_ERR *p_err);
    
    //取消等待
    OS_OBJ_QTY OSSemPendAbort (OS_SEM *p_sem,
                               OS_OPT opt,
                               OS_ERR *p_err);
    
    //释放+1
    OS_SEM_CTR OSSemPost (OS_SEM *p_sem,
                          OS_OPT opt,
                          OS_ERR *p_err);
    
    
    //设置值
    void OSSemSet (OS_SEM *p_sem,
                   OS_SEM_CTR cnt,
                   OS_ERR *p_err);

**应用举例**

void start_task(void *p_arg)
    {
        OS_CRITICAL_ENTER();    //进入临界区
    
        //创建一个信号量
        OSSemCreate ((OS_SEM*   )&MY_SEM,
                     (CPU_CHAR* )"MY_SEM",
                     (OS_SEM_CTR)1,     
                     (OS_ERR*   )&err);
    
        //创建TASK1任务
        OSTaskCreate((OS_TCB    * )&Task1_TaskTCB,      
                     (CPU_CHAR  * )"Task1 task",        
                     (OS_TASK_PTR )task1_task,          
                     (void      * )0,                   
                     (OS_PRIO     )TASK1_TASK_PRIO,     
                     (CPU_STK   * )&TASK1_TASK_STK[0],  
                     (CPU_STK_SIZE)TASK1_STK_SIZE/10,   
                     (CPU_STK_SIZE)TASK1_STK_SIZE,      
                     (OS_MSG_QTY  )0,                   
                     (OS_TICK     )0,                   
                     (void      * )0,                   
                     (OS_OPT      )OS_OPT_TASK_STK_CHK|OS_OPT_TASK_STK_CLR,
                     (OS_ERR    * )&err);           
    
        //创建TASK2任务
        OSTaskCreate((OS_TCB    * )&Task2_TaskTCB,      
                     (CPU_CHAR  * )"Task2 task",        
                     (OS_TASK_PTR )task2_task,          
                     (void      * )0,                   
                     (OS_PRIO     )TASK2_TASK_PRIO,     
                     (CPU_STK   * )&TASK2_TASK_STK[0],  
                     (CPU_STK_SIZE)TASK2_STK_SIZE/10,   
                     (CPU_STK_SIZE)TASK2_STK_SIZE,      
                     (OS_MSG_QTY  )0,                   
                     (OS_TICK     )0,                   
                     (void      * )0,                   
                     (OS_OPT      )OS_OPT_TASK_STK_CHK|OS_OPT_TASK_STK_CLR,
                     (OS_ERR    * )&err);                
    
        OS_CRITICAL_EXIT(); //退出临界区
    }
    
    //任务1的任务函数
    void task1_task(void *p_arg)
    {
        OS_ERR err;
        u8 task1_str[]="First task Running!";
        while(1)
        {
            printf("\r\n任务1:\r\n");
            OSSemPend(&MY_SEM,0,OS_OPT_PEND_BLOCKING,0,&err);   //请求信号量
            memcpy(share_resource,task1_str,sizeof(task1_str)); //向共享资源区拷贝数据
            printf("%s\r\n",share_resource);    //串口输出共享资源区数据 
            OSSemPost (&MY_SEM,OS_OPT_POST_1,&err);             //发送信号量
            OSTimeDlyHMSM(0,0,1,0,OS_OPT_TIME_PERIODIC,&err);   //延时1s
        }
    }
    
    //任务2的任务函数
    void task2_task(void *p_arg)
    {   
        OS_ERR err;
        u8 task2_str[]="Second task Running!";
        while(1)
        {
            printf("\r\n任务2:\r\n");
            OSSemPend(&MY_SEM,0,OS_OPT_PEND_BLOCKING,0,&err);   //请求信号量
            memcpy(share_resource,task2_str,sizeof(task2_str)); //向共享资源区拷贝数据
            printf("%s\r\n",share_resource);    //串口输出共享资源区数据 
            OSSemPost (&MY_SEM,OS_OPT_POST_1,&err);             //发送信号量
            OSTimeDlyHMSM(0,0,1,0,OS_OPT_TIME_PERIODIC,&err);   //延时1s
        }
    }

**实验现象**  
![1][]

`UCOSIII优先级反转：`[http://blog.csdn.net/zhangxuechao\_/article/details/78912393][http_blog.csdn.net_zhangxuechao_article_details_78912393]

[1]: /images/20220602/5df0af17ec954074b38ffdee0b8920a1.png
[http_blog.csdn.net_zhangxuechao_article_details_78912393]: http://blog.csdn.net/zhangxuechao_/article/details/78912393