Module kernel::hil::time

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Hardware agnostic interfaces for time and timers within the Tock kernel.

These traits are designed to be able encompass the wide variety of hardware counters in a general yet efficient way. They abstract the frequency of a counter through the Frequency trait and the width of a time value through the Ticks trait. Higher-level software abstractions should generally rely on standard and common implementations of these traits (e.g.. u32 ticks and 16MHz frequency). Hardware counter implementations and peripherals can represent the actual hardware units an translate into these more general ones.




  • Interface for receiving notification when a particular time (Counter value) is reached. Clients use the AlarmClient trait to signal when the counter has reached a pre-specified value set in set_alarm. Alarms are intended for low-level time needs that require precision (i.e., firing on a precise clock tick). Software that needs more functionality but can tolerate some jitter should use the Timer trait instead.
  • Callback handler for when an Alarm fires (a Counter reaches a specific value).
  • Represents a free-running hardware counter that can be started and stopped.
  • Represents a clock’s frequency in Hz, allowing code to transform between computer time units and wall clock time. It is typically an associated type for an implementation of the Time trait.
  • Callback handler for when a counter has overflowed past its maximum value and returned to 0.
  • An integer type defining the width of a time value, which allows clients to know when wraparound will occur.
  • Represents a moment in time, obtained by calling now.
  • Interface for controlling callbacks when an interval has passed. This interface is intended for software that requires repeated and/or one-shot timers and is willing to experience some jitter or imprecision in return for a simpler API that doesn’t require actual calculation of counter values. Software that requires more precisely timed callbacks should use the Alarm trait instead.
  • Callback handler for when a timer fires.
  • Represents a static moment in time, that does not change over repeated calls to Time::now.