[笔记].怎样给μC/OS-II的任务传递参数.[C][μC/OS-II]
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发表于 2010/6/21 15:19:41
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0 引子
近日，我在萧大哥的博客里闲逛，渐知μC/OS-II用途甚广，使用方便；于是 就照虎画猫，写几篇博文。
1 范例
（1） ucos_ii_test.c
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#include |
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#include |
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#include "includes.h" |
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// 定义任务的栈 |
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#define TASK_STACKSIZE 2048 |
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OS_STK task1_stk[TASK_STACKSIZE]; |
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OS_STK task2_stk[TASK_STACKSIZE]; |
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OS_STK task3_stk[TASK_STACKSIZE]; |
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OS_STK task4_stk[TASK_STACKSIZE]; |
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// 定义任务的优先级 |
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#define TASK1_PRIORITY 1 |
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#define TASK2_PRIORITY 2 |
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#define TASK3_PRIORITY 3 |
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#define TASK4_PRIORITY 4 |
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// 声明任务 |
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voidtask1(void* pData);// 任务1：传递整型参数 |
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voidtask2(void* pData);// 任务2：传递字符参数 |
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voidtask3(void* pData);// 任务3：传递字符串参数 |
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voidtask4(void* pData);// 任务4：传递结构体参数 |
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// 定义结构体 |
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typedefstruct |
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{ |
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intiA; |
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charcB; |
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charsC[10]; |
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}myStruct_t; |
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intmain() |
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{ |
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// |
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intiA=5; |
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// |
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charcB ='t'; |
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// |
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charsC[] ="test"; |
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// |
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myStruct_t pStr; |
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pStr.iA = 5; |
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pStr.cB ='t'; |
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strcpy(pStr.sC,"test"); |
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// 任务1：传递整型参数 |
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OSTaskCreateExt(task1, |
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&iA, |
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(void*)&task1_stk[TASK_STACKSIZE-1], |
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TASK1_PRIORITY, |
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TASK1_PRIORITY, |
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task1_stk, |
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TASK_STACKSIZE, |
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NULL, |
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0); |
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// 任务2：传递字符参数 |
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OSTaskCreateExt(task2, |
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&cB, |
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(void*)&task2_stk[TASK_STACKSIZE-1], |
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TASK2_PRIORITY, |
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TASK2_PRIORITY, |
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task2_stk, |
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TASK_STACKSIZE, |
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NULL, |
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0); |
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// 任务3：传递字符串参数 |
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OSTaskCreateExt(task3, |
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sC, |
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(void*)&task3_stk[TASK_STACKSIZE-1], |
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TASK3_PRIORITY, |
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TASK3_PRIORITY, |
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task3_stk, |
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TASK_STACKSIZE, |
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NULL, |
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0); |
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// 任务4：传到结构体参数 |
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OSTaskCreateExt(task4, |
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&pStr, |
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(void*)&task4_stk[TASK_STACKSIZE-1], |
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TASK4_PRIORITY, |
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TASK4_PRIORITY, |
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task4_stk, |
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TASK_STACKSIZE, |
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NULL, |
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0); |
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OSStart(); |
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return0; |
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} |
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// 任务1：传递整型参数 |
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voidtask1(void* pData) |
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{ |
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while(1) |
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{ |
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printf("task1, iA = %d\n", *((int*)pData)); |
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OSTimeDlyHMSM(0, 0, 1, 0); |
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} |
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} |
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// 任务2：传递字符参数 |
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voidtask2(void* pData) |
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{ |
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while(1) |
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{ |
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printf("task2, cB = %c\n", *((char*)pData)); |
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OSTimeDlyHMSM(0, 0, 1, 0); |
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} |
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} |
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// 任务3：传递字符串参数 |
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voidtask3(void* pData) |
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{ |
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while(1) |
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{ |
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printf("task3, sC = %s\n", (char*)pData); |
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OSTimeDlyHMSM(0, 0, 1, 0); |
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} |
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} |
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// 任务4：传递结构体参数 |
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voidtask4(void* pData) |
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{ |
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while(1) |
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{ |
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printf("task4, iA = %i\n", ((myStruct_t *)pData)->iA); |
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printf("task4, cB = %c\n", ((myStruct_t *)pData)->cB); |
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printf("task4, sC = %s\n", ((myStruct_t *)pData)->sC); |
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OSTimeDlyHMSM(0, 0, 1, 0); |
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} |
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} |
（2）运行结果
2 解析
从OSTaskCreateExt()的源代码中，可知pData就是所能传递的参数。
第48行，传递整型变量iA的地址；但是pdata却是空型指针。为了匹配存储内容，在第99行，将从&iA开始的存储区域强制转化为整型 指针，故有(int*)pData；使用（*）访问内容即可，如*((int*)pData)。如表1所示。
表1 task1中所传参数的存储映射
| 表达式 | 存储地址 | 存储长度 | 存储内容 |
intiA=5; |
&iA | sizeof(int) | 5 |
void* pData |
不变 | 未知 | 未知 |
*((int*)pData) |
不变 | sizeof(int) | 5 |
任务2的字符参数与任务1的整型参数类似，如表2所示。
| 表达式 | 存储地址 | 存储长度 | 存储内容 |
charcB ='t'; |
&cB | sizeof(char) | t |
void* pData |
不变 | 未知 | 未知 |
*((char*)pData) |
不变 | sizeof(char) | t |
任务3中%s本身只需传入参数的地址即可，故使用(char*)pData将 从*pData开始的存储区域强制转化为char型指针即可。
任务4中，传入的参数是结构体，另写博文浅析。
总之，以上所谓传递的四种参数类型，皆是在在传递地址，以准确映射所在地址的存储内容。
3 附录
（1）INT8U OSTaskCreateExt() 源代码
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/* |
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********************************************************************************************************* |
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* CREATE A TASK (Extended Version) |
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* |
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* Description: This function is used to have uC/OS-II manage the execution of a task. Tasks can either |
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* be created prior to the start of multitasking or by a running task. A task cannot be |
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* created by an ISR. This function is similar to OSTaskCreate() except that it allows |
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* additional information about a task to be specified. |
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* |
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* Arguments : task is a pointer to the task's code |
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* |
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* pdata is a pointer to an optional data area which can be used to pass parameters to |
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* the task when the task first executes. Where the task is concerned it thinks |
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* it was invoked and passed the argument 'pdata' as follows: |
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* |
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* void Task (void *pdata) |
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* { |
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* for (;;) { |
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* Task code; |
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* } |
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* } |
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* |
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* ptos is a pointer to the task's top of stack. If the configuration constant |
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* OS_STK_GROWTH is set to 1, the stack is assumed to grow downward (i.e. from high |
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* memory to low memory). 'pstk' will thus point to the highest (valid) memory |
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* location of the stack. If OS_STK_GROWTH is set to 0, 'pstk' will point to the |
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* lowest memory location of the stack and the stack will grow with increasing |
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* memory locations. 'pstk' MUST point to a valid 'free' data item. |
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* |
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* prio is the task's priority. A unique priority MUST be assigned to each task and the |
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* lower the number, the higher the priority. |
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* |
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* id is the task's ID (0..65535) |
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* |
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* pbos is a pointer to the task's bottom of stack. If the configuration constant |
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* OS_STK_GROWTH is set to 1, the stack is assumed to grow downward (i.e. from high |
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* memory to low memory). 'pbos' will thus point to the LOWEST (valid) memory |
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* location of the stack. If OS_STK_GROWTH is set to 0, 'pbos' will point to the |
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* HIGHEST memory location of the stack and the stack will grow with increasing |
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* memory locations. 'pbos' MUST point to a valid 'free' data item. |
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* |
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* stk_size is the size of the stack in number of elements. If OS_STK is set to INT8U, |
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* 'stk_size' corresponds to the number of bytes available. If OS_STK is set to |
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* INT16U, 'stk_size' contains the number of 16-bit entries available. Finally, if |
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* OS_STK is set to INT32U, 'stk_size' contains the number of 32-bit entries |
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* available on the stack. |
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* |
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* pext is a pointer to a user supplied memory location which is used as a TCB extension. |
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* For example, this user memory can hold the contents of floating-point registers |
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* during a context switch, the time each task takes to execute, the number of times |
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* the task has been switched-in, etc. |
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* |
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* opt contains additional information (or options) about the behavior of the task. The |
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* LOWER 8-bits are reserved by uC/OS-II while the upper 8 bits can be application |
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* specific. See OS_TASK_OPT_??? in uCOS-II.H. |
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* |
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* Returns : OS_NO_ERR if the function was successful. |
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* OS_PRIO_EXIT if the task priority already exist |
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* (each task MUST have a unique priority). |
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* OS_PRIO_INVALID if the priority you specify is higher that the maximum allowed |
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* (i.e. > OS_LOWEST_PRIO) |
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********************************************************************************************************* |
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*/ |
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INT8U OSTaskCreateExt (void(*task)(void*pd), |
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void*pdata, |
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OS_STK *ptos, |
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INT8U prio, |
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INT16U id, |
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OS_STK *pbos, |
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INT32U stk_size, |
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void*pext, |
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INT16U opt) |
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{ |
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#if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */ |
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OS_CPU_SR cpu_sr; |
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#endif |
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OS_STK *psp; |
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INT8U err; |
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#if OS_ARG_CHK_EN > 0 |
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if(prio > OS_LOWEST_PRIO) {/* Make sure priority is within allowable range */ |
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return(OS_PRIO_INVALID); |
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} |
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#endif |
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OS_ENTER_CRITICAL(); |
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if(OSTCBPrioTbl[prio] == (OS_TCB *)0) {/* Make sure task doesn't already exist at this priority */ |
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OSTCBPrioTbl[prio] = (OS_TCB *)1;/* Reserve the priority to prevent others from doing ... */ |
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/* ... the same thing until task is created. */ |
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OS_EXIT_CRITICAL(); |
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if(((opt & OS_TASK_OPT_STK_CHK) != 0x0000) ||/* See if stack checking has been enabled */ |
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((opt & OS_TASK_OPT_STK_CLR) != 0x0000)) {/* See if stack needs to be cleared */ |
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#if OS_STK_GROWTH == 1 |
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(void)memset(pbos, 0, stk_size *sizeof(OS_STK)); |
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#else |
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(void)memset(ptos, 0, stk_size *sizeof(OS_STK)); |
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#endif |
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} |
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psp = (OS_STK *)OSTaskStkInit(task, pdata, ptos, opt);/* Initialize the task's stack */ |
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err = OS_TCBInit(prio, psp, pbos, id, stk_size, pext, opt); |
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if(err == OS_NO_ERR) { |
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OS_ENTER_CRITICAL(); |
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OSTaskCtr++;/* Increment the #tasks counter */ |
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OS_EXIT_CRITICAL(); |
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if(OSRunning == TRUE) {/* Find HPT if multitasking has started */ |
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OS_Sched(); |
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} |
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}else{ |
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OS_ENTER_CRITICAL(); |
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OSTCBPrioTbl[prio] = (OS_TCB *)0;/* Make this priority avail. to others */ |
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OS_EXIT_CRITICAL(); |
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} |
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return(err); |
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} |
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OS_EXIT_CRITICAL(); |
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return(OS_PRIO_EXIST); |
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} |
4 参考
1.真 OO無雙.(原 創) 如何傳參數到每個task? (SOC) (Nios II) (μC/OS-II) (DE2-70)
2. Micrium.Micrium-uCOS-II-V286.ZIP\Micrium\SOFTWARE\uCOS-II\Source\os_task.c
