![]() ![]() The kernel does not (cannot, really) attempt to serialize things by "assigning" timeouts to specific CPUs. The resulting calls(s) to sys_clock_announce() must be properly serialized by the driver such that a given tick is announced exactly once across the system. These can also be used for the current date and to measure time intervals. But the correspondence between the announced ticks and real-world time must be correct.Ī final note about SMP: note that the call to sys_clock_set_timeout() is made on any CPU, and reflects the next timeout desired globally. RTCs count seconds, minutes, hours, days, months, and years. Weve improved time precision within our infrastructure from 10 milliseconds to 100 microseconds, and released our own public NTP service. For the specific case of INT_MAX, the next call to sys_clock_announce() may occur at any point in the future, not just at INT_MAX ticks. The intent here is that the driver will schedule any needed timeout as far into the future as possible. Note also that it is conventional for the kernel to pass INT_MAX for ticks if it wants to preserve the uptime tick count but doesn't have a specific event to await. the system uptime counter is allowed to be wrong Itll help me focus on tasks as I often forget what day/time it is - and the little system clock is useless. An RTC (Real time clock) is a seperate chip with a. Conventional wisdom on instructables and other tutorial sites is that for accurate time keeping, you need an RTC unit (see pic, click here to read more on RTCs). I like that it has no title bar, is resizable and customizable. As an electronics, IOT and pyro enthousiast, I do a lot of projects that involve time keeping. See HIGH RESOLUTION TIMERS for a full description. I also wanted a clock with milliseconds but did not expect to find that. Returns the current time as an integer number of milliseconds. ![]() Note that ticks can also be passed the special value K_TICKS_FOREVER, indicating that no future timer interrupts are expected or required and that the system is permitted to enter an indefinite sleep even if this could cause rollover of the internal counter (i.e. I wanted a clock that displays the date at the same time. Similarly a ticks value of zero (or even negative) is legal and treated identically: it simply indicates the kernel would like the next tick announcement as soon as possible. The next tick", this convention was chosen to match legacy usage). it's legal to announce every tick and implement this function as a noop), the requirement is that one tick announcement should occur within one tick BEFORE the specified expiration (that is, passing ticks=1 means "announce Note that spurious calls to sys_clock_announce() are allowed (i.e. Informs the system clock driver that the next needed call to sys_clock_announce() will not be until the specified number of ticks from the the current time have elapsed. Ticks elapsed since last sys_clock_announce() call.Ĭlock APIs. Sys_clock_set_timeout ( int32_t ticks, bool idle) K_SECONDS( s) K_MSEC(( s) * MSEC_PER_SEC) Generate timeout delay from milliseconds. ![]() Generate timeout delay from system ticks. Generate timeout delay from microseconds. ![]()
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