Clock Boottime Helpers

Overview

Boottime helpers convert the clock_time monotonic counter into standard time formats. The resulting values represent time since boot and do not depend on RTC or wall-clock settings.

API

rt_err_t rt_clock_boottime_get_us(struct timeval *tv);
rt_err_t rt_clock_boottime_get_s(time_t *t);
rt_err_t rt_clock_boottime_get_ns(struct timespec *ts);

All functions return RT_EOK on success or -RT_ERROR if the clock source is unavailable. The returned values are monotonic and suitable for measuring elapsed time.

rt_clock_boottime_get_us

rt_err_t rt_clock_boottime_get_us(struct timeval *tv);

• Purpose: get time since boot as seconds + microseconds.
• Parameters: tv must be a valid pointer to struct timeval.
• Return values:
  • RT_EOK: data written to tv.
  • -RT_ERROR: no valid clock_time source or conversion failed.
• Notes:
  • tv_usec is derived from the clock_time resolution and may not be exact microseconds if the underlying counter does not align to 1 us.

rt_clock_boottime_get_s

rt_err_t rt_clock_boottime_get_s(time_t *t);

• Purpose: get time since boot in whole seconds.
• Parameters: t must be a valid pointer to time_t.
• Return values:
  • RT_EOK: *t updated.
  • -RT_ERROR: no valid clock_time source or conversion failed.
• Notes:
  • Sub-second precision is discarded; use rt_clock_boottime_get_us() or rt_clock_boottime_get_ns() if needed.

rt_clock_boottime_get_ns

rt_err_t rt_clock_boottime_get_ns(struct timespec *ts);

• Purpose: get time since boot as seconds + nanoseconds.
• Parameters: ts must be a valid pointer to struct timespec.
• Return values:
  • RT_EOK: data written to ts.
  • -RT_ERROR: no valid clock_time source or conversion failed.
• Notes:
  • tv_nsec reflects the clock_time resolution; it may not be 1 ns granularity if the counter frequency is lower.

Example

#include <drivers/clock_time.h>
 
static void demo_boottime(void)
{
    struct timespec ts;
 
    if (rt_clock_boottime_get_ns(&ts) == RT_EOK)
    {
        rt_kprintf("boottime: %ld.%09ld\n", (long)ts.tv_sec, ts.tv_nsec);
    }
}

Notes

• The boottime helpers are used by the soft RTC implementation to build a stable base time.
• If no clock_time source is registered, the subsystem falls back to the tick counter and the resolution matches RT_TICK_PER_SECOND.