2017-11-22 07:16:29 +00:00
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Inter-Processor Call
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====================
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Overview
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--------
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Due to the dual core nature of the ESP32, there are instances where a certain
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function must be run in the context of a particular core (e.g. allocating
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ISR to an interrupt source of a particular core). The IPC (Inter-Processor
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Call) feature allows for the execution of functions on a particular CPU.
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A given function can be executed on a particular core by calling
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:cpp:func:`esp_ipc_call` or :cpp:func:`esp_ipc_call_blocking`. IPC is
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implemented via two high priority FreeRTOS tasks pinned to each CPU known as
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the IPC Tasks. The two IPC Tasks remain inactive (blocked) until
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:cpp:func:`esp_ipc_call` or :cpp:func:`esp_ipc_call_blocking` is called. When
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an IPC Task of a particular core is unblocked, it will preempt the current
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running task on that core and execute a given function.
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Usage
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-----
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:cpp:func:`esp_ipc_call` unblocks the IPC task on a particular core to execute
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a given function. The task that calls :cpp:func:`esp_ipc_call` will be blocked
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until the IPC Task begins execution of the given function.
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:cpp:func:`esp_ipc_call_blocking` is similar but will block the calling task
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until the IPC Task has completed execution of the given function.
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Functions executed by IPCs must be functions of type
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`void func(void *arg)`. To run more complex functions which require a larger
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stack, the IPC tasks' stack size can be configured by modifying
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2018-05-28 10:33:01 +00:00
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:envvar:`CONFIG_IPC_TASK_STACK_SIZE` in `menuconfig`. The IPC API is protected by a
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2017-11-22 07:16:29 +00:00
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mutex hence simultaneous IPC calls are not possible.
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Care should taken to avoid deadlock when writing functions to be executed by
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IPC, especially when attempting to take a mutex within the function.
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API Reference
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-------------
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.. include:: /_build/inc/esp_ipc.inc
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