esp-idf/docs/api-reference/system/hooks.rst
Ivan Grokhotkov cda22d9aaf docs: add FreeRTOS API docs
- Use `code` tags instead of a mix of `<pre></pre>` and
  `@verbatim .. @endverbatim`
- Remove manually added function prototypes from comment blocks
- Remove of grouping (`\defgroup`) — some extra work is needed
  to make groups compatible with the way we auto-generate API
  reference from Doxygen XML files. It's pretty easy to add the
  grouping directives back if/when we implement support for
  Doxygen groups in the later stages of documentation build
  process.
- Hide private APIs under `@cond .. @endcond`
- Convert some comments into Doxygen-compatible ones
- Fix various documentation issues: missing documentation for
  some parameters, mismatch between parameter names in comment
  block and in function prototype.
- Add doxygen comments for functions which didn't have them
  (thread local storage).
- Add [out] param tags where necessary
- Redefine `xTaskCreate` and `xTaskCreateStatic` as inline
  functions instead of macros.
2017-12-07 12:01:14 +08:00

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.. _hooks_api_reference:
FreeRTOS Hooks
==============
Overview
--------
FreeRTOS consists of Idle Hooks and Tick Hooks which allow for application
specific funtiionality to be added to the Idle Task and Tick Interrupt. The
ESP32 is dual core in nature, hence the ESP-IDF provides its own Idle and Tick
Hooks that are dual core compatible in addition to the hooks provided by Vanilla
FreeRTOS.
Vanilla FreeRTOS Hooks
----------------------
Idle and Tick Hooks in vanilla FreeRTOS are implemented by defining
implementations for the functions ``vApplicationIdleHook`` and
``vApplicationTickHook`` respectively somewhere in the application. Vanilla
FreeRTOS will run the user defined Idle Hook every iteration of the Idle Task,
whereas the user defined Tick Hook will run once per tick interrupt (given that
there are no pended ticks).
Due to vanilla FreeRTOS being designed for single core, ``vApplicationIdleHook``
and ``vApplicationTickHook`` will be run in both cores on the ESP32. In
other words, the same Idle Hook and Tick Hook are used for both cores.
To enable the vanilla FreeRTOS hooks in ESP-IDF, :ref:`CONFIG_FREERTOS_LEGACY_HOOKS`
must be enabled in ``make menuconfig``. :ref:`CONFIG_FREERTOS_LEGACY_IDLE_HOOK`
and :ref:`CONFIG_FREERTOS_LEGACY_TICK_HOOK` should also be enabled.
ESP-IDF Idle and Tick Hooks
---------------------------
Due to the dual core nature of the ESP32, it may be necessary for some
applications to have seperate Idle Hooks for each core. Furthermore, it may
be necessary for Idle and Tick Hooks to have execute multiple functionalities
that are configurable at run time. Therefore the ESP-IDF provides it's own Idle
and Tick Hooks in addition to the hooks provided by Vanilla FreeRTOS.
The ESP-IDF Hooks do not operate in the same way as Vanilla FreeRTOS Hooks
where users provide a definition for each of the hooks. Instead, the ESP-IDF
Hooks are predefined to call a list of user registered callbacks specific to
each core. Users can register and deregister callbacks which are run on the
Idle or Tick Hook of a specific core.
API Reference
-------------
.. include:: /_build/inc/esp_freertos_hooks.inc