Timer library

Files
file	timer.c
file	timer.h

Classes
struct	timer

Functions
void	timer_set (struct timer *t, clock_time_t interval)
void	timer_reset (struct timer *t)
void	timer_restart (struct timer *t)
int	timer_expired (struct timer *t)
clock_time_t	timer_remaining (struct timer *t)

Detailed Description

The Contiki kernel does not provide support for timed events. Rather, an application that wants to use timers needs to explicitly use the timer library.

The timer library provides functions for setting, resetting and restarting timers, and for checking if a timer has expired. An application must "manually" check if its timers have expired; this is not done automatically.

A timer is declared as a struct timer and all access to the timer is made by a pointer to the declared timer.

Note

The timer library is not able to post events when a timer expires. The Event timers should be used for this purpose.

The timer library uses the Clock library to measure time. Intervals should be specified in the format used by the clock library.

See also

Event timers

Function Documentation

timer_expired()

int timer_expired

(

struct timer *

t

)

Check if a timer has expired.

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

Parameters

t	A pointer to the timer

Returns

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

timer_remaining()

clock_time_t timer_remaining

(

struct timer *

t

)

The time until the timer expires

This function returns the time until the timer expires.

Parameters

t	A pointer to the timer

Returns

The time until the timer expires

timer_reset()

void timer_reset

(

struct timer *

t

)

Reset the timer with the same interval.

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

Parameters

t	A pointer to the timer.

See also

timer_restart()

timer_restart()

void timer_restart

(

struct timer *

t

)

Restart the timer from the current point in time

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

Note

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

Parameters

t	A pointer to the timer.

See also

timer_reset()

timer_set()

void timer_set	(	struct timer *	t,
		clock_time_t	interval
	)

Set a timer.

This function is used to set a timer for a time sometime in the future. The function timer_expired() will evaluate to true after the timer has expired.

Parameters

t	A pointer to the timer
interval	The interval before the timer expires.