Timer service
[Generic system services]

---

Detailed Description

This module provides timeout callbacks.

Files
file	timer.c
	Timer implementation (license: GPLv2).
file	timer.h
	Timer header (license: GPLv2).
Modules
	Timer service configuration
Typedefs
typedef void(*	timer_callback )(int timer)
	The type of callback function executed when a timer expires.
Functions
void	timer_interval ()
	Global timeout handling function.
int	timer_alloc (timer_callback callback, uintptr_t user)
	Allocates a timer.
void	timer_free (int timer)
	Deallocates a timer.
bool	timer_set (int timer, uint32_t millis)
	Starts or restarts a timer.
bool	timer_stop (int timer)
	Stops the timer.
bool	timer_expired (int timer)
	Checks wether a timer has expired or was stopped manually.
uintptr_t	timer_get_user (int timer)
	Retrieves the user-defined data attached to a timer.
bool	timer_set_user (int timer, uintptr_t user)
	Assigns user-defined data to a timer.

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Function Documentation

void timer_interval

(

)

Global timeout handling function.

This function must be continuously called once for every time slice. This is usually done from the application main loop. However, it should not be done from an interrupt service routine to avoid race conditions.

The accuracy of the timer service is principally dependent on the accuracy of the timer interval between calls of this function. So do your best to guarantee constant intervals.

The length of the time slice is configured with TIMER_MS_PER_TICK.

int timer_alloc	(	timer_callback	callback,
		uintptr_t	user
	)

Allocates a timer.

The given callback function is executed whenever the timer expires. The user value is attached to the timer and given as an extra argument to the callback function. It is not used by the timer module in any way.

Parameters:

[in]	callback	The function to execute whenever the timer expires.
[in]	user	The user-defined value.

Returns:

A non-negative timer identifier on success, -1 on failure.

void timer_free

(

int

timer

)

Deallocates a timer.

The timer being deallocated is stopped and marked as free.

Parameters:

[in]

timer

The identifier of the timer which to deallocate.

bool timer_set	(	int	timer,
		uint32_t	millis
	)

Starts or restarts a timer.

The timer expires after millis milliseconds.

Note:

Timers do not automatically restart. Call this function from the timeout callback function to restart the timer.

Parameters:

[in]	timer	The identifier of the timer which to start.
[in]	millis	The number of milliseconds after which the timer will expire.

Returns:

true if the timer has successfully been started, false on failure.

bool timer_stop

(

int

timer

)

Stops the timer.

Parameters:

[in]

timer

The identifier of the timer which to stop.

Returns:

true if the timer has been stopped, false on failure.

bool timer_expired

(

int

timer

)

Checks wether a timer has expired or was stopped manually.

Parameters:

[in]

timer

The identifier of the timer which to check.

Returns:

true if the timer is not running, false otherwise.

uintptr_t timer_get_user

(

int

timer

)

Retrieves the user-defined data attached to a timer.

Parameters:

[in]

timer

The identifier of the timer of which to retrieve the data.

Returns:

The user-defined data of the timer on success, 0 on failure.

bool timer_set_user	(	int	timer,
		uintptr_t	user
	)

Assigns user-defined data to a timer.

Parameters:

[in]	timer	The identifier of the timer which to assign the data to.
[in]	user	The data which to assign to the timer.

Returns:

true on success, false on failure.