关于rt_timer_control的疑问

发布于 2012-09-13 12:55:11 浏览：5837 订阅该版

rt_timer_init初始化一个rt_timer flag为 RT_TIMER_FLAG_ONE_SHOT

然后通过调用在线程内先rt_timer_stop，然后通过rt_timer_control 设置RT_TIMER_CTRL_SET_TIME值和RT_TIMER_CTRL_SET_PERIODIC

结果发现定时器还是只运行一次，观察源码发现在timer.c文件中rt_timer_control 函数如下：

```c
rt_err_t rt_timer_control(rt_timer_t timer, rt_uint8_t cmd, void *arg)
{
	/* timer check */
	RT_ASSERT(timer != RT_NULL);

switch (cmd)
	{
	case RT_TIMER_CTRL_GET_TIME:
		*(rt_tick_t *)arg = timer->init_tick;
		break;

case RT_TIMER_CTRL_SET_TIME:
		timer->init_tick = *(rt_tick_t *)arg;
		break;

case RT_TIMER_CTRL_SET_ONESHOT:
		timer->parent.flag &= ~(1 << RT_TIMER_FLAG_PERIODIC);
		break;

case RT_TIMER_CTRL_SET_PERIODIC:
		timer->parent.flag |= (1 << RT_TIMER_FLAG_PERIODIC);
		break;
	}

return RT_EOK;
}
```

宏定义中
```c
 #define RT_TIMER_FLAG_PERIODIC          0x2             /**< periodic timer 
```
也就是通过rt_timer_control函数设置RT_TIMER_CTRL_SET_PERIODIC，
```c
timer->parent.flag |= (1 << 2)  ==> timer->parent.flag |= 4
```
实际上是timer->parent.flag的第2位置1, 4=B100

在rt_timer_check函数中检测是否周期定时器部分代码如下

```c
if ((t->parent.flag & RT_TIMER_FLAG_PERIODIC) && (t->parent.flag & RT_TIMER_FLAG_ACTIVATED))
			{
				/* start it */
				t->parent.flag &= ~RT_TIMER_FLAG_ACTIVATED;
				rt_timer_start(t);
			}
			else
			{
				/* stop timer */
				t->parent.flag &= ~RT_TIMER_FLAG_ACTIVATED;
			}
```

flag的第0位用来标示定时器启动和停止

这里检测时候周期定时器是判断的flag的第1位

也就是说设置的周期定时器的标志位和检测的标志位不同，不知道我理解的对不对？

请多多指教。