• 计时器是倒计时器，当计数器达到零时执行某个动作。用户通过回调函数提供这个动作。回调函数是用户声明的函数，在计时器到期时被调用。在回调函数中绝对不能进行阻塞调用（例如调用OSTimeDly()、OSTimeDlyHMSM()…或任何导致计时器任务阻塞或被删除的操作），这一点非常重要。

创建一个计时器

#if OS_TMR_EN > 0u
OS_TMR  *OSTmrCreate (INT32U           dly,INT32U           period,INT8U            opt,OS_TMR_CALLBACK  callback,void            *callback_arg,INT8U           *pname,INT8U           *perr)
{OS_TMR   *ptmr;
#ifdef OS_SAFETY_CRITICALif (perr == (INT8U *)0){OS_SAFETY_CRITICAL_EXCEPTION();return ((OS_TMR *)0);}#endif
#ifdef OS_SAFETY_CRITICAL_IEC61508if (OSSafetyCriticalStartFlag == OS_TRUE){OS_SAFETY_CRITICAL_EXCEPTION();return ((OS_TMR *)0);}#endif
#if OS_ARG_CHK_EN > 0uswitch (opt)                                            /* Validate arguments                                     */{case OS_TMR_OPT_PERIODIC:if (period == 0u){*perr = OS_ERR_TMR_INVALID_PERIOD;return ((OS_TMR *)0);}break;case OS_TMR_OPT_ONE_SHOT:if (dly == 0u){*perr = OS_ERR_TMR_INVALID_DLY;return ((OS_TMR *)0);}break;default:*perr = OS_ERR_TMR_INVALID_OPT;return ((OS_TMR *)0);}#endifif (OSIntNesting > 0u)                                  /* See if trying to call from an ISR                      */{*perr  = OS_ERR_TMR_ISR;return ((OS_TMR *)0);}OSSchedLock();ptmr = OSTmr_Alloc();                                   /* Obtain a timer from the free pool                      */if (ptmr == (OS_TMR *)0){OSSchedUnlock();*perr = OS_ERR_TMR_NON_AVAIL;return ((OS_TMR *)0);}ptmr->OSTmrState       = OS_TMR_STATE_STOPPED;          /* Indicate that timer is not running yet                 */ptmr->OSTmrDly         = dly;ptmr->OSTmrPeriod      = period;ptmr->OSTmrOpt         = opt;ptmr->OSTmrCallback    = callback;ptmr->OSTmrCallbackArg = callback_arg;
#if OS_TMR_CFG_NAME_EN > 0uif (pname == (INT8U *)0)                                /* Is 'pname' a NULL pointer?                             */{ptmr->OSTmrName    = (INT8U *) (void *)"?";}else{ptmr->OSTmrName    = pname;}#endifOSSchedUnlock();*perr = OS_ERR_NONE;return (ptmr);
}
#endif

重新启动一个计时器

#if OS_TMR_EN > 0u
BOOLEAN  OSTmrStart (OS_TMR   *ptmr,INT8U    *perr)
{
#ifdef OS_SAFETY_CRITICALif (perr == (INT8U *)0){OS_SAFETY_CRITICAL_EXCEPTION();return (OS_FALSE);}#endif
#if OS_ARG_CHK_EN > 0uif (ptmr == (OS_TMR *)0){*perr = OS_ERR_TMR_INVALID;return (OS_FALSE);}#endifif (ptmr->OSTmrType != OS_TMR_TYPE)                     /* Validate timer structure                               */{*perr = OS_ERR_TMR_INVALID_TYPE;return (OS_FALSE);}if (OSIntNesting > 0u)                                  /* See if trying to call from an ISR                      */{*perr  = OS_ERR_TMR_ISR;return (OS_FALSE);}OSSchedLock();switch (ptmr->OSTmrState){case OS_TMR_STATE_RUNNING:                          /* Restart the timer                                      */OSTmr_Unlink (ptmr);                           /* ... Stop the timer                                     */OSTmr_Link (ptmr, OS_TMR_LINK_DLY);            /* ... Link timer to timer wheel                          */OSSchedUnlock();*perr = OS_ERR_NONE;return (OS_TRUE);case OS_TMR_STATE_STOPPED:                          /* Start the timer                                        */case OS_TMR_STATE_COMPLETED:OSTmr_Link (ptmr, OS_TMR_LINK_DLY);            /* ... Link timer to timer wheel                          */OSSchedUnlock();*perr = OS_ERR_NONE;return (OS_TRUE);case OS_TMR_STATE_UNUSED:                           /* Timer not created                                      */OSSchedUnlock();*perr = OS_ERR_TMR_INACTIVE;return (OS_FALSE);default:OSSchedUnlock();*perr = OS_ERR_TMR_INVALID_STATE;return (OS_FALSE);}
}
#endif

停止一个计时器

#if OS_TMR_EN > 0u
BOOLEAN  OSTmrStop (OS_TMR  *ptmr,INT8U    opt,void    *callback_arg,INT8U   *perr)
{OS_TMR_CALLBACK  pfnct;
#ifdef OS_SAFETY_CRITICALif (perr == (INT8U *)0){OS_SAFETY_CRITICAL_EXCEPTION();return (OS_FALSE);}#endif
#if OS_ARG_CHK_EN > 0uif (ptmr == (OS_TMR *)0){*perr = OS_ERR_TMR_INVALID;return (OS_FALSE);}#endifif (ptmr->OSTmrType != OS_TMR_TYPE)                           /* Validate timer structure                         */{*perr = OS_ERR_TMR_INVALID_TYPE;return (OS_FALSE);}if (OSIntNesting > 0u)                                        /* See if trying to call from an ISR                */{*perr  = OS_ERR_TMR_ISR;return (OS_FALSE);}OSSchedLock();switch (ptmr->OSTmrState){case OS_TMR_STATE_RUNNING:OSTmr_Unlink (ptmr);                                 /* Remove from current wheel spoke                  */*perr = OS_ERR_NONE;switch (opt){case OS_TMR_OPT_CALLBACK:pfnct = ptmr->OSTmrCallback;                /* Execute callback function if available ...       */if (pfnct != (OS_TMR_CALLBACK)0){(*pfnct) ((void *)ptmr, ptmr->OSTmrCallbackArg); /* Use callback arg when timer was created */}else{*perr = OS_ERR_TMR_NO_CALLBACK;}break;case OS_TMR_OPT_CALLBACK_ARG:pfnct = ptmr->OSTmrCallback;                /* Execute callback function if available ...       */if (pfnct != (OS_TMR_CALLBACK)0){(*pfnct) ((void *)ptmr, callback_arg);  /* ... using the 'callback_arg' provided in call    */}else{*perr = OS_ERR_TMR_NO_CALLBACK;}break;case OS_TMR_OPT_NONE:break;default:*perr = OS_ERR_TMR_INVALID_OPT;break;}OSSchedUnlock();return (OS_TRUE);case OS_TMR_STATE_COMPLETED:                              /* Timer has already completed the ONE-SHOT or ...  */case OS_TMR_STATE_STOPPED:                                /* ... timer has not started yet.                   */OSSchedUnlock();*perr = OS_ERR_TMR_STOPPED;return (OS_TRUE);case OS_TMR_STATE_UNUSED:                                 /* Timer was not created                            */OSSchedUnlock();*perr = OS_ERR_TMR_INACTIVE;return (OS_FALSE);default:OSSchedUnlock();*perr = OS_ERR_TMR_INVALID_STATE;return (OS_FALSE);}
}
#endif

删除一个计时器

#if OS_TMR_EN > 0u
BOOLEAN  OSTmrDel (OS_TMR  *ptmr,INT8U   *perr)
{
#ifdef OS_SAFETY_CRITICALif (perr == (INT8U *)0){OS_SAFETY_CRITICAL_EXCEPTION();return (OS_FALSE);}#endif
#if OS_ARG_CHK_EN > 0uif (ptmr == (OS_TMR *)0){*perr = OS_ERR_TMR_INVALID;return (OS_FALSE);}#endifif (ptmr->OSTmrType != OS_TMR_TYPE)                     /* Validate timer structure                               */{*perr = OS_ERR_TMR_INVALID_TYPE;return (OS_FALSE);}if (OSIntNesting > 0u)                                  /* See if trying to call from an ISR                      */{*perr  = OS_ERR_TMR_ISR;return (OS_FALSE);}OSSchedLock();switch (ptmr->OSTmrState){case OS_TMR_STATE_RUNNING:OSTmr_Unlink (ptmr);                           /* Remove from current wheel spoke                        */OSTmr_Free (ptmr);                             /* Return timer to free list of timers                    */OSSchedUnlock();*perr = OS_ERR_NONE;return (OS_TRUE);case OS_TMR_STATE_STOPPED:                          /* Timer has not started or ...                           */case OS_TMR_STATE_COMPLETED:                        /* ... timer has completed the ONE-SHOT time              */OSTmr_Free (ptmr);                             /* Return timer to free list of timers                    */OSSchedUnlock();*perr = OS_ERR_NONE;return (OS_TRUE);case OS_TMR_STATE_UNUSED:                           /* Already deleted                                        */OSSchedUnlock();*perr = OS_ERR_TMR_INACTIVE;return (OS_FALSE);default:OSSchedUnlock();*perr = OS_ERR_TMR_INVALID_STATE;return (OS_FALSE);}
}
#endif