www.pudn.com > iccavrUCOS_m64.rar > os_task.c

 
#ifndef  OS_MASTER_FILE 
#include "includes.h" 
#endif 
 
/*$PAGE*/ 
/* 
********************************************************************************************************* 
*                                            CREATE A TASK 
* 
* Description: This function is used to have uC/OS-II manage the execution of a task.  Tasks can either 
*              be created prior to the start of multitasking or by a running task.  A task cannot be 
*              created by an ISR. 
* 
* Arguments  : task     is a pointer to the task's code 
* 
*              pdata    is a pointer to an optional data area which can be used to pass parameters to 
*                       the task when the task first executes.  Where the task is concerned it thinks 
*                       it was invoked and passed the argument 'pdata' as follows: 
* 
*                           void Task (void *pdata) 
*                           { 
*                               for (;;) { 
*                                   Task code; 
*                               } 
*                           } 
* 
*              ptos     is a pointer to the task's top of stack.  If the configuration constant  
*                       OS_STK_GROWTH is set to 1, the stack is assumed to grow downward (i.e. from high 
*                       memory to low memory).  'pstk' will thus point to the highest (valid) memory  
*                       location of the stack.  If OS_STK_GROWTH is set to 0, 'pstk' will point to the  
*                       lowest memory location of the stack and the stack will grow with increasing 
*                       memory locations. 
* 
*              prio     is the task's priority.  A unique priority MUST be assigned to each task and the 
*                       lower the number, the higher the priority. 
* 
* Returns    : OS_NO_ERR        if the function was successful. 
*              OS_PRIO_EXIT     if the task priority already exist  
*                               (each task MUST have a unique priority). 
*              OS_PRIO_INVALID  if the priority you specify is higher that the maximum allowed  
*                               (i.e. >= OS_LOWEST_PRIO) 
********************************************************************************************************* 
*/ 
 
#if OS_TASK_CREATE_EN 
OS_STK *OSTaskStkInit (void (*task)(void *pd), void *pdata, OS_STK *ptos, INT16U opt){ 
 
    INT8U  *stk; 
    INT8U  *stks;		// Temp. variable used for setting up AVR hardware stack 
    INT16U tmp; 
 
 
    opt     = opt;			// 'opt' is not used, prevent warning 
    stk     = (INT8U *)ptos;		// Wandlung von ptos in Bytezeiger 
	// AVR return stack ("hardware stack") 
    stks    = (INT8U *)(ptos)-(OS_TASK_DEF_STK_SIZE-32); 
 
	// the function address has an extra level of indirection. Fetch the 
    // actual address. 
    //     
    tmp = *(INT16U const *)task; 
    
	// 36 Bytes 
    *stks-- = (INT8U)tmp;	//Put task start address on top of hardware stack 
    *stks-- = (INT8U)(tmp >> 8); 
 
    *stk-- = (INT8U)0x00;		// R0  = 0x00 
    *stk-- = (INT8U)0x01;  
    *stk-- = (INT8U)0x02; 
    *stk-- = (INT8U)0x03; 
    *stk-- = (INT8U)0x04; 
    *stk-- = (INT8U)0x05; 
    *stk-- = (INT8U)0x06; 
    *stk-- = (INT8U)0x07; 
    *stk-- = (INT8U)0x08; 
    *stk-- = (INT8U)0x09; 
    *stk-- = (INT8U)0x10; 
    *stk-- = (INT8U)0x11; 
    *stk-- = (INT8U)0x12; 
    *stk-- = (INT8U)0x13; 
    *stk-- = (INT8U)0x14; 
    *stk-- = (INT8U)0x15; 
    tmp    = (INT16U)pdata; 
    *stk-- = (INT8U)tmp;	//Simulate call to function with argument 
    *stk-- = (INT8U)(tmp >> 8); 
    *stk-- = (INT8U)0x18; 
    *stk-- = (INT8U)0x19; 
    *stk-- = (INT8U)0x20; 
    *stk-- = (INT8U)0x21; 
    *stk-- = (INT8U)0x22; 
    *stk-- = (INT8U)0x23; 
    *stk-- = (INT8U)0x24; 
    *stk-- = (INT8U)0x25; 
    *stk-- = (INT8U)0x26; 
    *stk-- = (INT8U)0x27; 
	// the heap pointer Y=R29:R28 will not be stored 
    *stk-- = (INT8U)0x30; 
    *stk-- = (INT8U)0x31; 
//    *stk-- = (INT8U)0x3B; 
    *stk-- = (INT8U)0x80;	//SREG = Interrupts enabled 
 
    tmp    = (INT16U)(stks); 
    *stk-- = (INT8U)(tmp >> 8); 
    *stk   = (INT8U)(tmp); 
    return ((void *)stk); 
} 
 
INT8U OSTaskCreate (void (*task)(void *pd), void *pdata, OS_STK *ptos, INT8U prio) 
{ 
    void   *psp; 
    INT8U   err; 
 
 
    if (prio > OS_LOWEST_PRIO) {             /* Make sure priority is within allowable range           */ 
        return (OS_PRIO_INVALID); 
    } 
    OS_ENTER_CRITICAL(); 
    if (OSTCBPrioTbl[prio] == (OS_TCB *)0) { /* Make sure task doesn't already exist at this priority  */ 
        OSTCBPrioTbl[prio] = (OS_TCB *)1;    /* Reserve the priority to prevent others from doing ...  */ 
                                             /* ... the same thing until task is created.              */ 
        OS_EXIT_CRITICAL(); 
        psp = (void *)OSTaskStkInit(task, pdata, ptos, 0); /* Initialize the task's stack              */ 
        err = OSTCBInit(prio, psp, (void *)0, 0, 0, (void *)0, 0);          
        if (err == OS_NO_ERR) { 
            OS_ENTER_CRITICAL(); 
            OSTaskCtr++;                                   /* Increment the #tasks counter             */ 
            OS_EXIT_CRITICAL(); 
            if (OSRunning) {                 /* Find highest priority task if multitasking has started */ 
                OSSched(); 
            } 
        } else { 
            OS_ENTER_CRITICAL(); 
            OSTCBPrioTbl[prio] = (OS_TCB *)0;/* Make this priority available to others                 */ 
            OS_EXIT_CRITICAL(); 
        } 
        return (err); 
    } else { 
        OS_EXIT_CRITICAL(); 
        return (OS_PRIO_EXIST); 
    } 
} 
#endif