上一节讲了利用累计定时中断次数实现LED灯闪烁，这个例子同时也第一次展示了我最完整的实战程序框架：

用switch语句实现状态机，外加定时中断。这个框架看似简单，实际上就是那么简单。我做的所有开发项目都是基于这个简单框架，

但是非常好用。上一节只有一个单任务的LED灯在闪烁，这节开始，我们多增加一个蜂鸣器报警的任务，要教会大家四个知识点：



第一点：蜂鸣器的驱动程序框架编写。



第二点：多任务处理的程序框架。



第三点：如何控制蜂鸣器声音的长叫和短叫。



第四点：如何知道1秒钟需要多少个定时中断，也就是如何按比例修正时间精度。



具体内容，请看源代码讲解。



实现功能：同时跑两个任务，第一个任务让一个LED灯1秒钟闪烁一次。第二个任务让蜂鸣器在前面3秒发生一次短叫报警，在后面6秒发生一次长叫报警，反复循环。

-Speaking on a cumulative timer interrupt frequency using LED lights flashing, this example also shows my first real full procedural fr a mework:

With a switch statement to achieve a state machine, plus a timer interrupt. This fr a mework may seem simple, actually so simple. I do all the development projects are based on this simple fr a mework,

But it is very easy to use. Previous section only a single task LED lights flashing, this festival started, we multi-task a buzzer alarm increases, the knowledge to teach you four points:



First point: Driver fr a mework buzzer preparation.



The second point: the procedural fr a mework of multi-tasking.



The third point: how to control the buzzer sounds and the short length is called is called.



The fourth point: How do you know how much a 1 second timer interrupt, which is how a pro rata correction time accuracy.



Details, see the source code to explain.



Function: run two tasks simultaneously, the first task to make a LED light fla