Event timers
[Contiki system]

Event timers provides a way to generate timed events. More...

Data Structures
struct	etimer
	A timer. More...
Files
file	etimer.c
	Event timer library implementation.
file	etimer.h
	Event timer header file.
Functions called from timer interrupts, by the system
void	etimer_request_poll (void)
	Make the event timer aware that the clock has changed.
int	etimer_pending (void)
	Check if there are any non-expired event timers.
clock_time_t	etimer_next_expiration_time (void)
	Get next event timer expiration time.
Functions called from application programs
void	etimer_set (struct etimer *et, clock_time_t interval)
	Set an event timer.
void	etimer_reset (struct etimer *et)
	Reset an event timer with the same interval as was previously set.
void	etimer_restart (struct etimer *et)
	Restart an event timer from the current point in time.
void	etimer_adjust (struct etimer *et, int td)
	Adjust the expiration time for an event timer.
int	etimer_expired (struct etimer *et)
	Check if an event timer has expired.
clock_time_t	etimer_expiration_time (struct etimer *et)
	Get the expiration time for the event timer.
clock_time_t	etimer_start_time (struct etimer *et)
	Get the start time for the event timer.
void	etimer_stop (struct etimer *et)
	Stop a pending event timer.

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Detailed Description

Event timers provides a way to generate timed events.

An event timer will post an event to the process that set the timer when the event timer expires.

An event timer is declared as a struct etimer and all access to the event timer is made by a pointer to the declared event timer.

See also:

Simple timer library

Clock library (used by the timer library)

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Function Documentation

void etimer_adjust	(	struct etimer *	et,
		int	td
	)

Adjust the expiration time for an event timer.

Parameters:

	et	A pointer to the event timer.
	td	The time difference to adjust the expiration time with.

This function is used to adjust the time the event timer will expire. It can be used to synchronize periodic timers without the need to restart the timer or change the timer interval.

Note:

This function should only be used for small adjustments. For large adjustments use etimer_set() instead.

A periodic timer will drift unless the etimer_reset() function is used.

See also:

etimer_set()

etimer_reset()

clock_time_t etimer_expiration_time

(

struct etimer *

et

)

Get the expiration time for the event timer.

Parameters:

et

A pointer to the event timer

Returns:

The expiration time for the event timer.

This function returns the expiration time for an event timer.

CCIF int etimer_expired

(

struct etimer *

et

)

Check if an event timer has expired.

Parameters:

et

A pointer to the event timer

Returns:

Non-zero if the timer has expired, zero otherwise.

This function tests if an event timer has expired and returns true or false depending on its status.

Examples:

example-announcement.c, example-broadcast.c, example-collect.c, example-mesh.c, example-program.c, example-runicast.c, and example-unicast.c.

Referenced by PROCESS_THREAD().

clock_time_t etimer_next_expiration_time

(

void

)

Get next event timer expiration time.

Returns:

Next expiration time of all pending event timers. If there are no pending event timers this function returns 0.

This functions returns next expiration time of all pending event timers.

Referenced by Java_se_sics_cooja_corecomm_CLASSNAME_tick().

int etimer_pending

(

void

)

Check if there are any non-expired event timers.

Returns:

True if there are active event timers, false if there are no active timers.

This function checks if there are any active event timers that have not expired.

Referenced by Java_se_sics_cooja_corecomm_CLASSNAME_tick().

void etimer_request_poll

(

void

)

Make the event timer aware that the clock has changed.

This function is used to inform the event timer module that the system clock has been updated. Typically, this function would be called from the timer interrupt handler when the clock has ticked.

Referenced by Java_se_sics_cooja_corecomm_CLASSNAME_tick(), and main().

CCIF void etimer_reset

(

struct etimer *

et

)

Reset an event timer with the same interval as was previously set.

Parameters:

et

A pointer to the event timer.

This function resets the event timer with the same interval that was given to the event timer with the etimer_set() function. The start point of the interval is the exact time that the event timer last expired. Therefore, this function will cause the timer to be stable over time, unlike the etimer_restart() function.

See also:

etimer_restart()

void etimer_restart

(

struct etimer *

et

)

Restart an event timer from the current point in time.

Parameters:

et

A pointer to the event timer.

This function restarts the event timer with the same interval that was given to the etimer_set() function. The event timer will start at the current time.

Note:

A periodic timer will drift if this function is used to reset it. For periodic timers, use the etimer_reset() function instead.

See also:

etimer_reset()

CCIF void etimer_set	(	struct etimer *	et,
		clock_time_t	interval
	)

Set an event timer.

Parameters:

	et	A pointer to the event timer
	interval	The interval before the timer expires.

This function is used to set an event timer for a time sometime in the future. When the event timer expires, the event PROCESS_EVENT_TIMER will be posted to the process that called the etimer_set() function.

Examples:

example-announcement.c, example-broadcast.c, example-collect.c, example-program.c, example-runicast.c, example-unicast.c, and multi-threading.c.

Referenced by PROCESS_THREAD().

clock_time_t etimer_start_time

(

struct etimer *

et

)

Get the start time for the event timer.

Parameters:

et

A pointer to the event timer

Returns:

The start time for the event timer.

This function returns the start time (when the timer was last set) for an event timer.

void etimer_stop

(

struct etimer *

et

)

Stop a pending event timer.

Parameters:

et

A pointer to the pending event timer.

This function stops an event timer that has previously been set with etimer_set() or etimer_reset(). After this function has been called, the event timer will not emit any event when it expires.