Task Scheduler

We’ve developed our scheduler based on our need for simplicity, and low-power efficiency. It plans which task needs to be run and when. This scheduler is not the full-blown RTOS (Real Time Operating System) and it doesn’t have real cooperative multitasking. One task is run and when this task exits, then another task is run.

It is important to not block the task but do the necessary operation quickly and let the scheduler run other tasks. In case you need to create some delay, then the one solution is to create for example a state machine and schedule to call the task later.

References

• Scheduler SDK Module
• GitHub Repository Example

Registering a Task

The first thing you will probably run into when working with Scheduler is registering a simple task to be run in x second(s) from now.

info

In the example below the code will initialize the LCD Module and then schedule a task to run after 5 seconds that will turn the LCD off.

You can also save the task ID when registering a task. Thanks to this you will be able to work on the task anytime you want (run it again, unregister the task).

Run Task Once Code Example

#include <application.h>

twr_scheduler_task_id_t turn_off_lcd_task_id;

static void disableLCD(void* param) {
    (void) param;
    twr_module_lcd_off();
}

void application_init(void)
{
    twr_log_init(TWR_LOG_LEVEL_DUMP, TWR_LOG_TIMESTAMP_ABS);

    twr_module_lcd_init();

    // Register to run disableLCD function in 5 seconds from the start of the code
    turn_off_lcd_task_id = twr_scheduler_register(disableLCD, NULL, twr_tick_get() + 5000);
}

Unregistering a Task

To unregister a task from the scheduler (for example when it is not needed to be run anymore) you have to use the void twr_scheduler_unregister(twr_scheduler_task_id_t task_id) function.

This takes ID of the to-be-unregistered task as a parameter.

Planning to Run Registered Task

If you register a task with third parameter as any value, the task will be run exactly once after the given time.

For example: twr_scheduler_register(disableLCD, NULL, twr_tick_get() + 5000); will run the task after 5 seconds

One time

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You can run twr_scheduler_register with a third parameter TWR_TICK_INFINITY (twr_scheduler_register(disableLCD, NULL, TWR_TICK_INFINITY);) to not run the task after registering but only when you want.

To run the registered task one more time in the future, you have to use one of the following functions.

void twr_scheduler_plan_current_now()
void twr_scheduler_plan_current_absolute(twr_tick_t tick)
void twr_scheduler_plan_current_relative(twr_tick_t tick)
void twr_scheduler_plan_current_from_now(twr_tick_t tick)

void twr_scheduler_plan_now(twr_scheduler_task_id_t task_id)
void twr_scheduler_plan_absolute(twr_scheduler_task_id_t task_id, twr_tick_t tick)
void twr_scheduler_plan_relative(twr_scheduler_task_id_t task_id, twr_tick_t tick)
void twr_scheduler_plan_from_now(twr_scheduler_task_id_t task_id, twr_tick_t tick)

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To run a current task again you can use functions from the first set (with the current in the name).

You have to call one of these functions in the task function itself for it to work.

For example, if you want to turn the LCD on and off after 5 seconds you can use these functions.

Run Current Task Code Example

#include <application.h>

twr_scheduler_task_id_t turn_off_lcd_task_id;

bool lcd_state = true;

static void disableLCD(void* param) {
    (void) param;

    if(lcd_state == true) {
      twr_module_lcd_off();
      ldc_state = false;
    }
    else {
      twr_module_lcd_on();
      ldc_state = true;
    }
  twr_scheduler_plan_current_from_now(twr_tick_get() + 5000);
}

void application_init(void) {
    twr_log_init(TWR_LOG_LEVEL_DUMP, TWR_LOG_TIMESTAMP_ABS);

    twr_module_lcd_init();

    // Register to run disableLCD function in 5 seconds from the start of the code
    turn_off_lcd_task_id = twr_scheduler_register(disableLCD, NULL, twr_tick_get() + 5000);
}

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To run a task anywhere you can use functions from the second set (without the current in the name).

For example, if you want to turn the LCD off 5 seconds after pushing a button you can use these functions.

Run Task From Anywhere Code Example

#include <application.h>

twr_scheduler_task_id_t turn_off_lcd_task_id;

twr_button_t button;

static void disableLCD(void* param) {
    (void) param;
    twr_module_lcd_off();
}

void button_event_handler(twr_button_t *self, twr_button_event_t event, void *event_param) {
  if (event == TWR_BUTTON_EVENT_CLICK) {
    twr_scheduler_plan_from_now(turn_off_lcd_task_id, twr_tick_get() + 5000)
  }
}

void application_init(void) {
    twr_log_init(TWR_LOG_LEVEL_DUMP, TWR_LOG_TIMESTAMP_ABS);

    twr_module_lcd_init();

    twr_button_init(&button, TWR_GPIO_BUTTON, TWR_GPIO_PULL_DOWN, false);
    twr_button_set_event_handler(&button, button_event_handler, NULL);

    // Register to run disableLCD function in 5 seconds from the start of the code
    turn_off_lcd_task_id = twr_scheduler_register(disableLCD, NULL, TWR_TICK_INFINITY);
}