創建任務就是將任務控制塊、任務堆棧、任務代碼等聯繫在一起，並且初始化任務控制塊的相應字段。在UCOSIII中我們通過函數OSTaskCreate ();來創建任務，OSTaskCreate();函數原型如下（在os_task.c中有定義）。創建一個任務之後，剛創建的任務就會進入就緒狀態，注意！不能夠在中斷服務程序中調用OSTaskCreate ();函數創建任務。
創建任務注意一下參數：任務控制塊、任務堆棧、任務優先級、任務函數。
void OSTaskCreate (OS_TCB *p_tcb,
CPU_CHAR *p_name,
OS_TASK_PTR p_task,
void *p_arg,
OS_PRIO prio,
CPU_STK *p_stk_base,
CPU_STK_SIZE stk_limit,
CPU_STK_SIZE stk_size,
OS_MSG_QTY q_size,
OS_TICK time_quanta,
void *p_ext,
OS_OPT opt,
OS_ERR *p_err)
{
CPU_STK_SIZE i;
#if OS_CFG_TASK_REG_TBL_SIZE > 0u
OS_REG_ID reg_nbr;
#endif
#if defined(OS_CFG_TLS_TBL_SIZE) && (OS_CFG_TLS_TBL_SIZE > 0u)
OS_TLS_ID id;
#endif
CPU_STK *p_sp;
CPU_STK *p_stk_limit;
CPU_SR_ALLOC();
#ifdef OS_SAFETY_CRITICAL
if (p_err == (OS_ERR *)0) {
OS_SAFETY_CRITICAL_EXCEPTION();
return;
}
#endif
#ifdef OS_SAFETY_CRITICAL_IEC61508
if (OSSafetyCriticalStartFlag == DEF_TRUE) {
*p_err = OS_ERR_ILLEGAL_CREATE_RUN_TIME;
return;
}
#endif
#if OS_CFG_CALLED_FROM_ISR_CHK_EN > 0u
if (OSIntNestingCtr > (OS_NESTING_CTR)0) { /* ---------- CANNOT CREATE A TASK FROM AN ISR ---------- */
*p_err = OS_ERR_TASK_CREATE_ISR;
return;
}
#endif
#if OS_CFG_ARG_CHK_EN > 0u /* ---------------- VALIDATE ARGUMENTS ------------------ */
if (p_tcb == (OS_TCB *)0) { /* User must supply a valid OS_TCB */
*p_err = OS_ERR_TCB_INVALID;
return;
}
if (p_task == (OS_TASK_PTR)0) { /* User must supply a valid task */
*p_err = OS_ERR_TASK_INVALID;
return;
}
if (p_stk_base == (CPU_STK *)0) { /* User must supply a valid stack base address */
*p_err = OS_ERR_STK_INVALID;
return;
}
if (stk_size < OSCfg_StkSizeMin) { /* User must supply a valid minimum stack size */
*p_err = OS_ERR_STK_SIZE_INVALID;
return;
}
if (stk_limit >= stk_size) { /* User must supply a valid stack limit */
*p_err = OS_ERR_STK_LIMIT_INVALID;
return;
}
if (prio >= OS_CFG_PRIO_MAX) { /* Priority must be within 0 and OS_CFG_PRIO_MAX-1 */
*p_err = OS_ERR_PRIO_INVALID;
return;
}
#endif
#if OS_CFG_ISR_POST_DEFERRED_EN > 0u
if (prio == (OS_PRIO)0) {
if (p_tcb != &OSIntQTaskTCB) {
*p_err = OS_ERR_PRIO_INVALID; /* Not allowed to use priority 0 */
return;
}
}
#endif
if (prio == (OS_CFG_PRIO_MAX - 1u)) {
if (p_tcb != &OSIdleTaskTCB) {
*p_err = OS_ERR_PRIO_INVALID; /* Not allowed to use same priority as idle task */
return;
}
}
OS_TaskInitTCB(p_tcb); /* Initialize the TCB to default values */
*p_err = OS_ERR_NONE;
/* --------------- CLEAR THE TASK'S STACK --------------- */
if ((opt & OS_OPT_TASK_STK_CHK) != (OS_OPT)0) { /* See if stack checking has been enabled */
if ((opt & OS_OPT_TASK_STK_CLR) != (OS_OPT)0) { /* See if stack needs to be cleared */
p_sp = p_stk_base;
for (i = 0u; i < stk_size; i++) { /* Stack grows from HIGH to LOW memory */
*p_sp = (CPU_STK)0; /* Clear from bottom of stack and up! */
p_sp++;
}
}
}
/* ------- INITIALIZE THE STACK FRAME OF THE TASK ------- */
#if (CPU_CFG_STK_GROWTH == CPU_STK_GROWTH_HI_TO_LO)
p_stk_limit = p_stk_base + stk_limit;
#else
p_stk_limit = p_stk_base + (stk_size - 1u) - stk_limit;
#endif
p_sp = OSTaskStkInit(p_task,
p_arg,
p_stk_base,
p_stk_limit,
stk_size,
opt);
/* -------------- INITIALIZE THE TCB FIELDS ------------- */
p_tcb->TaskEntryAddr = p_task; /* Save task entry point address */
p_tcb->TaskEntryArg = p_arg; /* Save task entry argument */
p_tcb->NamePtr = p_name; /* Save task name */
p_tcb->Prio = prio; /* Save the task's priority */
p_tcb->StkPtr = p_sp; /* Save the new top-of-stack pointer */
p_tcb->StkLimitPtr = p_stk_limit; /* Save the stack limit pointer */
p_tcb->TimeQuanta = time_quanta; /* Save the #ticks for time slice (0 means not sliced) */
#if OS_CFG_SCHED_ROUND_ROBIN_EN > 0u
if (time_quanta == (OS_TICK)0) {
p_tcb->TimeQuantaCtr = OSSchedRoundRobinDfltTimeQuanta;
} else {
p_tcb->TimeQuantaCtr = time_quanta;
}
#endif
p_tcb->ExtPtr = p_ext; /* Save pointer to TCB extension */
p_tcb->StkBasePtr = p_stk_base; /* Save pointer to the base address of the stack */
p_tcb->StkSize = stk_size; /* Save the stack size (in number of CPU_STK elements) */
p_tcb->Opt = opt; /* Save task options */
#if OS_CFG_TASK_REG_TBL_SIZE > 0u
for (reg_nbr = 0u; reg_nbr < OS_CFG_TASK_REG_TBL_SIZE; reg_nbr++) {
p_tcb->RegTbl[reg_nbr] = (OS_REG)0;
}
#endif
#if OS_CFG_TASK_Q_EN > 0u
OS_MsgQInit(&p_tcb->MsgQ, /* Initialize the task's message queue */
q_size);
#else
(void)&q_size;
#endif
OSTaskCreateHook(p_tcb); /* Call user defined hook */
#if defined(OS_CFG_TLS_TBL_SIZE) && (OS_CFG_TLS_TBL_SIZE > 0u)
for (id = 0u; id < OS_CFG_TLS_TBL_SIZE; id++) {
p_tcb->TLS_Tbl[id] = (OS_TLS)0;
}
OS_TLS_TaskCreate(p_tcb); /* Call TLS hook */
#endif
/* --------------- ADD TASK TO READY LIST --------------- */
OS_CRITICAL_ENTER();
OS_PrioInsert(p_tcb->Prio);
OS_RdyListInsertTail(p_tcb);
#if OS_CFG_DBG_EN > 0u
OS_TaskDbgListAdd(p_tcb);
#endif
OSTaskQty++; /* Increment the #tasks counter */
if (OSRunning != OS_STATE_OS_RUNNING) { /* Return if multitasking has not started */
OS_CRITICAL_EXIT();
return;
}
OS_CRITICAL_EXIT_NO_SCHED();
OSSched();
}*p_tcb ------ 任務的控制塊OS_TCB
*p_name ------ 指向任務的名字
p_task ------ 執行任務代碼，也就是任務函數的名字
*p_arg ------ 傳遞給任務的參數
prio ------ 任務優先級，數值越低優先級越高，用戶不能夠使用系統任務使用的那些優先級，
優先級0：中斷服務服務管理任務 OS_IntQTask()
優先級1：時鐘節拍任務 OS_TickTask()優先級2：定時任務 OS_TmrTask()
優先級OS_CFG_PRIO_MAX-2：統計任務 OS_StatTask()
優先級OS_CFG_PRIO_MAX-1：空閒任務 OS_IdleTask()
*p_stk_base ------ 指向任務堆棧的基地址
stk_limit ------ 任務堆棧深度，用來檢測和確保堆棧不溢出
stk_size ------ 任務堆棧大小
q_size COSIII------ 使用任務消息隊列時 任務內部消息隊列能夠接收的最大消息數目,爲0時禁止接收消息
time_quanta ------ 同一優先級下的多個任務是採用時間片輪轉調度。當使能時間片輪轉時的時間片長度，爲0時爲默認長度。在使能時間片輪轉調用時用來設置時間片長度，默認節拍爲時鐘節拍除以10.
*p_ext ------ 指向用戶補充的存儲區。
opt ------ 包含任務的特定選項，有如下選項可以設置。
OS_OPT_TASK_NONE 表示沒有任何選項
OS_OPT_TASK_STK_CHK 指定是否允許檢測該任務的堆棧
OS_OPT_TASK_STK_CLR 指定是否清除該任務的堆棧
OS_OPT_TASK_SAVE_FP 指定是否存浮點寄存器，CPU需要浮點運算硬件並且有專用代碼保護浮點 寄存器
*p_err ------ 用來保存調用該函數後返回的錯誤代碼。