前来支持

看Freertos头文件Semphr.h的注释。
2) Resource management.
*    In this usage scenario the count value indicates the number of resources
*    available.  To obtain control of a resource a task must first obtain a
*    semaphore - decrementing the semaphore count value.  When the count value
*    reaches zero there are no free resources.  When a task finishes with the
*    resource it 'gives' the semaphore back - incrementing the semaphore count
*    value.  In this case it is desirable for the initial count value to be
*    equal to the maximum count value, indicating that all resources are free.

这种用法应该是先take，再give回去。而不是像第一种用法（也就是楼主说的常用用法）那样，需要先give，然后才能take。

刚刚贴的代码怎么不见了？再贴一遍头文件中的注释，很明了：
* Counting semaphores are typically used for two things:
*
* 1) Counting events.
*
*    In this usage scenario an event handler will 'give' a semaphore each time
*    an event occurs (incrementing the semaphore count value), and a handler
*    task will 'take' a semaphore each time it processes an event
*    (decrementing the semaphore count value).  The count value is therefore
*    the difference between the number of events that have occurred and the
*    number that have been processed.  In this case it is desirable for the
*    initial count value to be zero.
*
* 2) Resource management.
*
*    In this usage scenario the count value indicates the number of resources
*    available.  To obtain control of a resource a task must first obtain a
*    semaphore - decrementing the semaphore count value.  When the count value
*    reaches zero there are no free resources.  When a task finishes with the
*    resource it 'gives' the semaphore back - incrementing the semaphore count
*    value.  In this case it is desirable for the initial count value to be
*    equal to the maximum count value, indicating that all resources are free.

我是东哥 发表于 2015-1-8 16:28
这种用法应该是先take，再give回去。而不是像第一种用法（也就是楼主说的常用用法）那样，需要先give，然后 ...

是的  因为我的 资源一开始是不可用的  

这是典型的 生产消费问题

串口接收数据（生产）

线程消费数据  

一开始是没有现成的数据的

而这个 函数接口  只能以另一种方式使用那就是一开始就存在资源，这在实际使用中是不合理的！！

支持楼主，留下记号，还能拿钱

serge 发表于 2015-1-8 21:50
支持楼主，留下记号，还能拿钱

哈哈 你来晚了钱都被他们拿完了~~

楼主强帖，当然要支持了。好好向楼主学习。

好贴，正好用的着啊。。

楼主写的太好了，刚拿到开发板，我要好好学习一下