Cyclic functions

The cyclic function execution infrastruture provides a way to periodically execute code, e.g. every 100ms. Examples for such functions might be LED blinking etc. The functions that are hooked into this cyclic list should be small timewise as otherwise the execution of the other code that relies on a high frequent polling (e.g. UART rx char ready check) might be delayed too much. To detect cyclic functions with a too long execution time, the Kconfig option CONFIG_CYCLIC_MAX_CPU_TIME_US is introduced, which configures the max allowed time for such a cyclic function. If it’s execution time exceeds this time, this cyclic function will get removed from the cyclic list.

Registering a cyclic function

To register a cyclic function, use something like this:

static void cyclic_demo(void *ctx)
    /* Just a small dummy delay here */

int board_init(void)
    struct cyclic_info *cyclic;

    /* Register demo cyclic function */
    cyclic = cyclic_register(cyclic_demo, 10 * 1000, "cyclic_demo", NULL);
    if (!cyclic)
    printf("Registering of cyclic_demo failed\n");

    return 0;

This will register the function cyclic_demo() to be periodically executed all 10ms.

How is this cyclic functionality integrated / executed?

The cyclic infrastructure integrates the main function responsible for calling all registered cyclic functions cyclic_run() into the common WATCHDOG_RESET macro. This guarantees that cyclic_run() is executed very often, which is necessary for the cyclic functions to get scheduled and executed at their configured periods.