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666935dd6d
Adds a backend for pw::chrono::SystemTimer based on embOS's software timer API. Change-Id: I0d03c2b2b6474bcefb968a20897748f552ca1a7e Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/50860 Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com> Pigweed-Auto-Submit: Ewout van Bekkum <ewout@google.com> Reviewed-by: Wyatt Hepler <hepler@google.com>
38 lines
1.4 KiB
ReStructuredText
38 lines
1.4 KiB
ReStructuredText
.. _module-pw_chrono_embos:
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---------------
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pw_chrono_embos
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---------------
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``pw_chrono_embos`` is a collection of ``pw_chrono`` backends that are
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implemented using embOS v4 for 32bit targets.
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.. warning::
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This module is still under construction, the API is not yet stable.
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SystemClock backend
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-------------------
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The embOS based ``system_clock`` backend implements the
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``pw_chrono:system_clock`` facade by using ``OS_GetTime32()``. An
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InterruptSpinLock is used to manage overflows in a thread and interrupt safe
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manner to produce a signed 64 bit timestamp. Note that this does NOT use
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``OS_GetTime_us64()`` which is not always available, this could be considered
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for a future alternative backend for the SystemClock.
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The ``SystemClock::now()`` must be used more than once per overflow of the
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native embOS ``OS_GetTime32()`` overflow. Note that this duration may
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vary if ``OS_SUPPORT_TICKLESS`` is used.
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SystemTimer backend
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-------------------
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The embOS based ``system_timer`` backend implements the
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``pw_chrono:system_timer`` facade by using embOS's software timer API.
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``pw::chrono::SystemTimer`` instances use ``OS_TIMER_EX`` &
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``OS_CreateTimerEx``, dynamic memory allocation is never used.
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Build targets
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-------------
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The GN build for ``pw_chrono_embos`` has one target: ``system_clock``.
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The ``system_clock`` target provides the
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``pw_chrono_backend/system_clock_config.h`` and ``pw_chrono_embos/config.h``
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headers and the backend for the ``pw_chrono:system_clock``.
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