[转载]MATLAB 定时器_淡然之枫

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[转载]MATLAB 定时器

(2013-08-26 15:48:56)

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转载

原文地址：MATLAB 定时器作者：王双木

MATLAB中的定时器timer可以定时触发，周期性地执行指定的函数，而不会影响整个系统对用户其它操作的响应。

建立一个定时器timer对象

T = timer; % constructs a timer object with default attributes T = timer('PropertyName1', PropertyValue1, 'PropertyName2', PropertyValue2,...); % constructs a timer object in which the given property name/value pairs are set on the object.

Timer对象支持的全部属性和合法值如下表所示，可以通过get(timer)函数查看timer的相关属性，也可以使用set(timer)设置timer的各类属性：

Property Name	Property Description	Data Types, Values, Defaults, Access
`AveragePeriod`	Average time between `TimerFcn` executions since the timer started. Note: Value is `NaN` until timer executes two timer callbacks.	Data type	`double`
		Default	`NaN`
		Read only	Always
`BusyMode`	Action taken when a timer has to execute `TimerFcn` before the completion of previous execution of `TimerFcn`. `'drop'` — Do not execute the function. `'error'` — Generate an error. Requires `ErrorFcn` to be set. `'queue'` — Execute function at next opportunity.	Data type	Enumerated string
		Values	`'drop'` `'error'` `'queue'`
		Default	`'drop'`
		Read only	While `Running` = `'on'`
`ErrorFcn`	Function that the timer executes when an error occurs. This function executes before the `StopFcn`. See Creating Callback Functions for more information.	Data type	Text string, function handle, or cell array
		Default	None
		Read only	Never
`ExecutionMode`	Determines how the timer object schedules timer events. See Timer Object Execution Modes for more information.	Data type	Enumerated string
		Values	`'singleShot'` `'fixedDelay'` `'fixedRate'` `'fixedSpacing'`
		Default	`'singleShot'`
		Read only	While `Running = 'on'`
`InstantPeriod`	The time between the last two executions of `TimerFcn`.	Data type	`double`
		Default	`NaN`
		Read only	Always
`Name`	User-supplied name.	Data type	Text string
		Default	`'timer-``i``'`, where `i` is a number indicating the `i`th timer object created this session. To reset `i` to 1, execute the `clear classes` command.
		Read only	Never
`ObjectVisibility`	Provides a way for application developers to prevent end-user access to the timer objects created by their application. The `timerfind` function does not return an object whose `ObjectVisibility` property is set to `'off'`. Objects that are not visible are still valid. If you have access to the object (for example, from within the M-file that created it), you can set its properties.	Data type	Enumerated string
		Values	`'off'` `'on'`
		Default	`'on'`
		Read only	Never
`Period`	Specifies the delay, in seconds, between executions of `TimerFcn`.	Data type	`double`
		Value	Any number >= 0.001
		Default	1.0
		Read only	While `Running` = `'on'`
`Running`	Indicates whether the timer is currently executing.	Data type	Enumerated string
		Values	`'off'` `'on'`
		Default	`'off'`
		Read only	Always
`StartDelay`	Specifies the delay, in seconds, between the start of the timer and the first execution of the function specified in `TimerFcn`.	Data type	`double`
		Values	Any number >= 0
		Default	0
		Read only	While `Running` =`'on'`
`StartFcn`	Function the timer calls when it starts. See Creating Callback Functions for more information.	Data type	Text string, function handle, or cell array
		Default	None
		Read only	Never
`StopFcn`	Function the timer calls when it stops. The timer stops when You call the timer `stop` function The timer finishes executing `TimerFcn`, i.e., the value of `TasksExecuted` reaches the limit set by `TasksToExecute`. An error occurs (The `ErrorFcn` is called first, followed by the `StopFcn`.) See Creating Callback Functions for more information.	Date type	Text string, function handle, or cell array
		Default	None
		Read only	Never
`Tag`	User supplied label.	Data type	Text string
		Default	Empty string (`''`)
		Read only	Never
`TasksToExecute`	Specifies the number of times the timer should execute the function specified in the `TimerFcn` property.	Data type	`double`
		Values	Any number > 0
		Default	1
		Read only	Never
`TasksExecuted`	The number of times the timer has called `TimerFcn` since the timer was started.	Data type	`double`
		Values	Any number >= 0
		Default	0
		Read only	Always
`TimerFcn`	Timer callback function. See Creating Callback Functions for more information.	Data type	Text string, function handle, or cell array
		Default	None
		Read only	Never
`Type`	Identifies the object type.	Data type	Text string
		Values	`'timer'`
		Read only	Always
`UserData`	User-supplied data.	Data type	User-defined
		Default	`[]`
		Read only	Never

例1，设置一个10秒间隔的定时器，时间到则回调函数onTimer：

T = timer('Period',10.0,'ExecutionMode','FixedRate', 'TimerFcn',{@onTimer,arg});

Period 触发周期设置为10s，ExecutionMode是执行的方式，可以有三种选择，详见MATLAB Help， TimerFcn指定触发时所执行函数的句柄，在这里我们建立一个函数onTimer，arg 作为参数传递到 onTimer 中去。

注意onTimer的定义：
function onTimer (obj,events,arg)
前两个参数是必不可少的，最后的arg才是用户传递的数据。在这个函数中你基本上可以无视前两个参数。

在MATLAB Help的index中输入timer，可以察看详细的说明。

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