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Timer API

The Timer API provides millisecond-precision timing and a scheduled task queue for periodic operations.

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System configuration

Clock settings:
  • System clock: 16 MHz
  • Timer resolution: 1 millisecond
  • Maximum scheduled tasks: 32

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Data structures

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TimerScheduledTask_t

Defines a scheduled task that executes periodically.
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task
void (*task)(void *)
Function pointer to execute
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context
void *
Context pointer passed to the task function
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interval
uint16_t
Execution interval in milliseconds
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ticks
uint16_t
Ticks elapsed since last execution (internal)

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Initialization

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TimerInit

Initializes the timer system with 1ms resolution. 
void TimerInit();
Usage: 
TimerInit();
This must be called during system initialization before using any timer functions.

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Time functions

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TimerGetMillis

Returns milliseconds elapsed since system start. 
uint32_t TimerGetMillis();
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returns
uint32_t
Milliseconds since initialization (wraps after ~49 days)
Example: 
uint32_t start = TimerGetMillis();
// ... perform operation ...
uint32_t elapsed = TimerGetMillis() - start;

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TimerDelayMicroseconds

Blocking delay for microsecond-precision timing. 
void TimerDelayMicroseconds(uint16_t microseconds);
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microseconds
uint16_t
Delay duration in microseconds
This is a blocking delay. Use scheduled tasks for non-blocking operations.

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Scheduled tasks

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TimerRegisterScheduledTask

Registers a task to execute periodically. 
uint8_t TimerRegisterScheduledTask(
    void *task,
    void *context,
    uint16_t interval
);
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task
void (*)(void *)
Function to execute periodically
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context
void *
Context pointer passed to task function
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interval
uint16_t
Execution interval in milliseconds
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returns
uint8_t
Task ID (0-31), or TIMER_TASK_DISABLED if queue is full
Example: 
void MyPeriodicTask(void *context) {
    IBus_t *ibus = (IBus_t *)context;
    IBusCommandCDCAnnounce(ibus);
}

// Register task to run every 1000ms
uint8_t taskId = TimerRegisterScheduledTask(
    &MyPeriodicTask,
    &ibus,
    1000
);

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TimerUnregisterScheduledTask

Unregisters a scheduled task by function pointer. 
uint8_t TimerUnregisterScheduledTask(void *task);
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task
void *
Function pointer of task to remove
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returns
uint8_t
1 if task was found and removed, 0 otherwise

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TimerUnregisterScheduledTaskById

Unregisters a scheduled task by ID. 
void TimerUnregisterScheduledTaskById(uint8_t taskId);
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taskId
uint8_t
Task ID returned from TimerRegisterScheduledTask

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TimerProcessScheduledTasks

Processes all scheduled tasks (called from main loop). 
void TimerProcessScheduledTasks();
This function is called automatically in the main application loop. You typically don’t need to call it directly.

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Task management

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TimerResetScheduledTask

Resets the tick counter for a task, restarting its interval. 
void TimerResetScheduledTask(uint8_t taskId);
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taskId
uint8_t
Task ID to reset

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TimerSetTaskInterval

Changes the execution interval of a scheduled task. 
void TimerSetTaskInterval(uint8_t taskId, uint16_t interval);
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taskId
uint8_t
Task ID to modify
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interval
uint16_t
New interval in milliseconds

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TimerTriggerScheduledTask

Immediately executes a scheduled task without waiting for its interval. 
void TimerTriggerScheduledTask(uint8_t taskId);
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taskId
uint8_t
Task ID to trigger
The task’s interval timer is not reset by this function.

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Constants

#define TIMER_TASKS_MAX 32          // Maximum number of scheduled tasks
#define TIMER_TASK_DISABLED 0       // Returned when task registration fails

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See also

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