70 lines
4.3 KiB
ReStructuredText
70 lines
4.3 KiB
ReStructuredText
Android's Context Hub Runtime Environment (CHRE)
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################################################
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Android's context hub enables the use of nanoapps. A single nanoapp has 3 entry points seen in
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`chre_api/chre/nanoapp.h`_:
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* A ``nanoappStart`` function used to notify the nanoapp that it is now active.
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* A ``nanoappHandleEvent`` function used to notify the nanoapp tha an event of interest took place.
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* A ``nanoappEnd`` function used to notify the nanoapp that it is now deactivated.
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The CHRE connects to several frameworks called Platform Abstraction Layers (PAL)s. Note that
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currently, none of these are implemented for Zephyr, but they are scheduled to be added. These
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frameworks include:
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#. *Audio* - a framework allowing nanoapps to get audio events. See `pal/audio.h`_ for API details.
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#. *GNSS* - a framework allowing nanoapps to manage location and measurement sessions. See
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`pal/gnss.h`_ for API details.
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#. *Sensor* - a framework allowing nanoapps to request changes to sensors configuration get
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data/bias events. See `pal/sensor.h`_ for API details.
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#. *System* - a framework allowing nanoapps to make common system requests such as logging, clock,
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and some basic memory allocation/deallocation. See `pal/system.h`_ for API details.
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#. *WiFi* - a framework allowing nanoapps to interact with the on board WiFi. See `pal/wifi.h`_ for
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API details.
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#. *WWAN* - a framework allowing nanoapps to interact with the WWAN module such as getting the
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current capabilities and info. See `pal/wwan.h`_ for API details.
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Building and expectations
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=========================
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To build the sample use the following west command:
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.. zephyr-app-commands::
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:zephyr-app: samples/modules/chre
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:board: native_sim
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:goals: build
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Once built and run, the sample application should:
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#. Print a hello message
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#. Notify that the event loop started via an ``inf`` level log
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#. Notify that a nanoapp was started and assigned an instance/app ID of 1 via a ``dbg`` level log
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#. Print a message saying that the nanoapp's start callback was called
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#. Send an event of type ``1`` and no data to the nanoapp
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#. Notify that the event was processed
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#. Call the ``nanoappEnd`` function of the nanoapp
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#. Print a message notifying that it's not possible to remove a system level nanoapp
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#. Exit the event loop
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Roadmap
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=======
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#. Add an implementation of the `pal/sensor.h`_ and `pal/system.h`_ to Zephyr. These will be
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standalone modules that can be used independently of CHRE, but when ``CONFIG_CHRE`` is enabled
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will also provide an implementation of ``chrePalSensorGetApi()`` and ``struct chrePalSystemApi``.
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#. Add a directory ``chre/nanoapps`` which will host various nanoapps to be used by the Zephyr
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community. These should each have their own Kconfig to enable them and set the appropriate
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dependencies. The first nanoapp will be a lid angle calculator which will use 2 accelerometers.
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#. Update the ``overlay.dts`` of this sample application to include 2 emulated accelerometers and
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configure them to return scripted data.
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#. Run this sample application and watch the nanoapp provide lid angle calculations based on 2
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accelerometers provided by the sensors PAL framework.
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.. _`chre_api/chre/nanoapp.h`: https://cs.android.com/android/platform/superproject/+/master:system/chre/chre_api/include/chre_api/chre/nanoapp.h;drc=7c60a553288d63e6e3370d679803da46dac723a4
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.. _`pal/audio.h`: https://cs.android.com/android/platform/superproject/+/master:system/chre/pal/include/chre/pal/audio.h;l=69;drc=6ca547ad175f80ce9f09f5b7b14fcc6f14565f5c
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.. _`pal/gnss.h`: https://cs.android.com/android/platform/superproject/+/master:system/chre/pal/include/chre/pal/gnss.h;l=152;drc=830255234157cc7afe5201dca19a7fb71ea850fe
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.. _`pal/sensor.h`: https://cs.android.com/android/platform/superproject/+/master:system/chre/pal/include/chre/pal/sensor.h;l=51;drc=23207906add05054a94dfab41b95bcfc39bedfe4
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.. _`pal/system.h`: https://cs.android.com/android/platform/superproject/+/master:system/chre/pal/include/chre/pal/system.h;l=49;drc=6ca547ad175f80ce9f09f5b7b14fcc6f14565f5c
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.. _`pal/wifi.h`: https://cs.android.com/android/platform/superproject/+/master:system/chre/pal/include/chre/pal/wifi.h;l=153;drc=b673b80ed98e1b6e6360bee4ba98e2cd8f4e0935
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.. _`pal/wwan.h`: https://cs.android.com/android/platform/superproject/+/master:system/chre/pal/include/chre/pal/wwan.h;l=69;drc=629361a803cb305c8575b41614e6e071e7141a03
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