55 lines
1.9 KiB
ReStructuredText
55 lines
1.9 KiB
ReStructuredText
.. _task_wdt_api:
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Task Watchdog
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#############
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Overview
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********
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Many microcontrollers feature a hardware watchdog timer peripheral. Its purpose
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is to trigger an action (usually a system reset) in case of severe software
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malfunctions. Once initialized, the watchdog timer has to be restarted ("fed")
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in regular intervals to prevent it from timing out. If the software got stuck
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and does not manage to feed the watchdog anymore, the corrective action is
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triggered to bring the system back to normal operation.
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In real-time operating systems with multiple tasks running in parallel, a
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single watchdog instance may not be sufficient anymore, as it can be used for
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only one task. This software watchdog based on kernel timers provides a method
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to supervise multiple threads or tasks (called watchdog channels).
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An existing hardware watchdog can be used as an optional fallback if the task
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watchdog itself or the scheduler has a malfunction.
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The task watchdog uses a kernel timer as its backend. If configured properly,
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the timer ISR is never actually called during normal operation, as the timer is
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continuously updated in the feed calls.
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It's currently not possible to have multiple instances of task watchdogs.
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Instead, the task watchdog API can be accessed globally to add or delete new
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channels without passing around a context or device pointer in the firmware.
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The maximum number of channels is predefined via Kconfig and should be adjusted
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to match exactly the number of channels required by the application.
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Configuration Options
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*********************
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Related configuration options can be found under
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:zephyr_file:`subsys/task_wdt/Kconfig`.
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* :kconfig:`CONFIG_TASK_WDT`
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* :kconfig:`CONFIG_TASK_WDT_CHANNELS`
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* :kconfig:`CONFIG_TASK_WDT_HW_FALLBACK`
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* :kconfig:`CONFIG_TASK_WDT_MIN_TIMEOUT`
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* :kconfig:`CONFIG_TASK_WDT_HW_FALLBACK_DELAY`
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API Reference
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*************
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.. doxygengroup:: task_wdt_api
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