File syn_timer.h¶

FileList > sched > syn_timer.h

Software timer service — one-shot and periodic timers. More...

#include "../common/syn_defs.h"
#include <stdbool.h>

Classes¶

Type	Name
struct	SYN_Timer Software timer descriptor.

Public Types¶

Type	Name
typedef void(*	SYN_TimerCallback Timer expiry callback.

Public Functions¶

Type	Name
bool	syn_timer_expired (SYN_Timer * timer) Poll whether the timer has expired.
void	syn_timer_init (SYN_Timer * timer, uint32_t period_ms, bool periodic, SYN_TimerCallback callback, void * user_data) Initialize a software timer.
uint32_t	syn_timer_next_expiry (const SYN_Timer * timers, size_t count) Get the earliest expiry tick among a set of active timers.
uint32_t	syn_timer_remaining (const SYN_Timer * timer) Get the remaining time until the next expiry.
void	syn_timer_service (SYN_Timer * timers, size_t count) Service an array of timers.
void	syn_timer_set_period (SYN_Timer * timer, uint32_t period_ms) Change the timer's period. Takes effect on next start or next periodic reload.
void	syn_timer_start (SYN_Timer * timer) Start (or restart) the timer.
void	syn_timer_stop (SYN_Timer * timer) Stop the timer. It will not fire until started again.

Public Static Functions¶

Type	Name
bool	syn_timer_is_active (const SYN_Timer * timer) Check if a timer is currently active (running).

Detailed Description¶

Timers are caller-owned structs with a callback. They can be used with or without the scheduler. In a bare main loop, call syn_timer_service() each iteration. With the scheduler, run it from a high-priority task.

Timers are driven by syn_port_get_tick_ms() — resolution depends on how often you call syn_timer_service().

** **

static SYN_Timer heartbeat;

void on_heartbeat(SYN_Timer *t, void *ctx) {
    syn_gpio_toggle(LED_PIN);
}

syn_timer_init(&heartbeat, 1000, true, on_heartbeat, NULL);
syn_timer_start(&heartbeat);

while (1) {
    syn_timer_service(&heartbeat, 1);
}

Public Types Documentation¶

typedef SYN_TimerCallback¶

Timer expiry callback.

typedef void(* SYN_TimerCallback) (struct SYN_Timer *timer, void *user_data);

Parameters:

timer The timer that expired.
user_data User-provided context pointer.

Public Functions Documentation¶

function syn_timer_expired¶

Poll whether the timer has expired.

bool syn_timer_expired (
    SYN_Timer * timer
)

If expired and periodic, the timer is automatically re-armed. If expired and one-shot, the timer is stopped.

This can be used instead of (or in addition to) the callback.

Parameters:

timer Timer to check.

Returns:

true if the timer has expired since the last check.

function syn_timer_init¶

Initialize a software timer.

void syn_timer_init (
    SYN_Timer * timer,
    uint32_t period_ms,
    bool periodic,
    SYN_TimerCallback callback,
    void * user_data
)

The timer is created in the stopped state. Call syn_timer_start() to begin counting.

Parameters:

timer Timer to initialize.
period_ms Period in milliseconds.
periodic true for repeating timer, false for one-shot.
callback Function called on expiry (may be NULL if using polling).
user_data User context pointer passed to callback.

function syn_timer_next_expiry¶

Get the earliest expiry tick among a set of active timers.

uint32_t syn_timer_next_expiry (
    const SYN_Timer * timers,
    size_t count
)

Scans the timer array and returns the minimum target_tick of any active timer whose deadline is in the future. Used by the tickless scheduler to account for software timer wakeups.

Parameters:

timers Array of timers to scan.
count Number of timers in the array.

Returns:

Earliest expiry tick, or UINT32_MAX if no timers are active or all have already expired.

function syn_timer_remaining¶

Get the remaining time until the next expiry.

uint32_t syn_timer_remaining (
    const SYN_Timer * timer
)

Parameters:

timer Timer to query.

Returns:

Remaining milliseconds, or 0 if expired/stopped.

function syn_timer_service¶

Service an array of timers.

void syn_timer_service (
    SYN_Timer * timers,
    size_t count
)

Checks each timer for expiry and calls its callback if set. Call this from your main loop, a scheduler task, or a periodic ISR.

Parameters:

timers Array of timers.
count Number of timers in the array.

function syn_timer_set_period¶

Change the timer's period. Takes effect on next start or next periodic reload.

void syn_timer_set_period (
    SYN_Timer * timer,
    uint32_t period_ms
)

Parameters:

timer Timer.
period_ms New period in milliseconds.

function syn_timer_start¶

Start (or restart) the timer.

void syn_timer_start (
    SYN_Timer * timer
)

Sets the target tick to now + period_ms and marks the timer active.

Parameters:

timer Timer to start.

function syn_timer_stop¶

Stop the timer. It will not fire until started again.

void syn_timer_stop (
    SYN_Timer * timer
)

Parameters:

timer Timer to stop.

Public Static Functions Documentation¶

function syn_timer_is_active¶

Check if a timer is currently active (running).

static inline bool syn_timer_is_active (
    const SYN_Timer * timer
)

Parameters:

timer Timer to query.

Returns:

true if active.

The documentation for this class was generated from the following file src/syntropic/sched/syn_timer.h