lejos.nxt
Class NXTEvent

java.lang.Object
  lejos.nxt.NXTEvent

public class NXTEvent
extends Object

This class allows communication of event data between the leJOS firmware and the leJOS low level classes. It can be used to detect I/O completion, Port values changing, button presses etc. To use create a class having the required device type and filter (this may identify a particular port, or I/O operation). Then call the waitEvent function to wait for events from the firmware. This call will block until either the firmware signals an event or the timeout occurs. Upon completion the eventData field will contain information about the event(s) that have been reported. Events themselves are normally reset by calling the associated function to read/write the associated device. If an event is not cleared, it will be reported again in subsequent calls to eventWait.

NOTE: This is a low level system interface and should probably not be used directly by user code.

Author:

andy

Field Summary

static int	ANALOG_PORTS Event type for the Analogue ports
static int	BLUETOOTH Event type for the Bluetooth device
static int	BUTTONS Event type for the NXT Buttons
static int	I2C_PORTS Event type for the i2c ports
static int	NONE Event type for no hardware events
static int	RS485 Event type for the RS485 device
static int	SYSTEM Event type for system events
static int	TIMEOUT
static int	USB Event type for the USB device
static int	USER1 These bits are reserved in the eventData field to indicate that a user event has occurred.
static int	USER2
static int	USER3
static int	USER4
static long	WAIT_FOREVER Value used to make a timeout be forever.

Constructor Summary

NXTEvent()

Method Summary

static NXTEvent	allocate(int type, int filter, int update) Create a new event ready for use.
void	clearEvent(int event) Clear an event.
void	free() Release an event.
int	getEventData()
int	getFilter() Return the current filter settings.
void	notifyEvent(int event) This call can be used to raise a user event.
int	registerEvent() Register this event with the system.
void	setFilter(int filter) Set the filter to be applied to this event.
int	unregisterEvent() Unregister this event.
int	waitEvent(int newFilter, long timeout) Wait for an event to occur using the specified filter or for the specified timeout.
int	waitEvent(long timeout) Wait for an event to occur or for the specified timeout.
static boolean	waitEvent(NXTEvent[] events, long timeout) Wait for multiple events.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

NONE

public static final int NONE

Event type for no hardware events

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Constant Field Values

BLUETOOTH

public static final int BLUETOOTH

Event type for the Bluetooth device

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USB

public static final int USB

Event type for the USB device

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RS485

public static final int RS485

Event type for the RS485 device

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Constant Field Values

ANALOG_PORTS

public static final int ANALOG_PORTS

Event type for the Analogue ports

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Constant Field Values

I2C_PORTS

public static final int I2C_PORTS

Event type for the i2c ports

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BUTTONS

public static final int BUTTONS

Event type for the NXT Buttons

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Constant Field Values

SYSTEM

public static final int SYSTEM

Event type for system events

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Constant Field Values

TIMEOUT

public static final int TIMEOUT

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Constant Field Values

USER1

public static final int USER1

These bits are reserved in the eventData field to indicate that a user event has occurred. User events are created by the notifyEvent method.

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Constant Field Values

USER2

public static final int USER2

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USER3

public static final int USER3

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USER4

public static final int USER4

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Constant Field Values

WAIT_FOREVER

public static final long WAIT_FOREVER

Value used to make a timeout be forever.

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Constant Field Values

Constructor Detail

NXTEvent

public NXTEvent()

Method Detail

registerEvent

public int registerEvent()

Register this event with the system. Events must be registered before they are waited on.

Returns:

>= 0 if the event has been registered < 0 if not.

unregisterEvent

public int unregisterEvent()

Unregister this event. After calling this function the event should not be waited on.

Returns:

>= 0 if the event was unregistered < 0 if not

waitEvent

public int waitEvent(long timeout)
              throws InterruptedException

Wait for an event to occur or for the specified timeout. If a timeout occurs then the TIMEOUT event bit will be set in the result. This bit is the sign bit so timeouts can be detected by testing for a -ve result.

Parameters:

timeout - the timeout in ms. Note a value of <= 0 will return immeadiately.

Returns:

the event flags

Throws:

InterruptedException

waitEvent

public int waitEvent(int newFilter,
                     long timeout)
              throws InterruptedException

Wait for an event to occur using the specified filter or for the specified timeout.

Parameters:

newFilter - The type specific filter for this wait.

timeout - the timeout in ms. Note a value of <= 0 will return immediately.

Returns:

the event flags or 0 if the event timed out

Throws:

InterruptedException

waitEvent

public static boolean waitEvent(NXTEvent[] events,
                                long timeout)
                         throws InterruptedException

Wait for multiple events.

Parameters:

events - an array of events to wait on.

timeout - the wait timeout. Note a value of <= 0 will return immediately.

Returns:

true if an event occurred, false otherwise.

Throws:

InterruptedException

notifyEvent

public void notifyEvent(int event)

This call can be used to raise a user event. User events will wake a thread from an eventWait call.

Parameters:

event -

clearEvent

public void clearEvent(int event)

Clear an event.

Parameters:

event - The events to be cleared.

getEventData

public int getEventData()

setFilter

public void setFilter(int filter)

Set the filter to be applied to this event.

Parameters:

filter - The new filter value.

getFilter

public int getFilter()

Return the current filter settings.

Returns:

the filter

allocate

public static NXTEvent allocate(int type,
                                int filter,
                                int update)

Create a new event ready for use.

Parameters:

type - The event type.

filter - The event specific filter.

update - The update period used when checking the event.

Returns:

The new event object.

free

public void free()

Release an event.