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47 lines
2.1 KiB
Markdown
47 lines
2.1 KiB
Markdown
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# Component: Button
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* This component defines a button as a well encapsulated object.
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* A button device is defined by:
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* GPIO number on which the button is attached.
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* Active level which decided by peripheral hardware.
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* Trigger mode which decides whether to call serial trigger callback during pressing
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* Serial threshold seconds which decides that serial trigger callback will be called after how many seconds' pressing
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* A button device can provide:
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* One push event callback
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* One release event callback
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* One short-time tap event callback
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* One serial trigger event callback
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* Several long-time press event callback
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We can set different jitter filters for all the events.
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Once any of the long press callback is triggered, the short tap event will not be triggered.
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This components are based on GPIO provided by idf and soft timer provided by FreeRTOS.
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* To use the button device, you need to :
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* create a button object returned by iot_button_create().
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* Then hook different event callbacks to the button object.
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* To free the object, you can call iot_button_delete to delete the button object and free the memory that used.
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* Todo:
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* Add hardware timer mode(because sometimes soft-timer callback function is limited)
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### NOTE:
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> All the event callback function are realized by FreeRTOS soft timer APIs, the callback must follow the rule:
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```
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Button callback functions execute in the context of the timer service task.
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It is therefore essential that button callback functions never attempt to block.
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For example, a button callback function must not call vTaskDelay(), vTaskDelayUntil(), or specify a non zero block time when accessing a queue or a semaphore.
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```
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> In addition:
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> You can adjust the following macros within FreeRTOS to adjust the stack depth/queue length/task priority of the timer service.
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```
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#define configUSE_TIMERS //enable soft-timer
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#define configTIMER_TASK_PRIORITY // priority of the timers service task
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#define configQueue_LENGTH // length of timer command queue
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#define configTIMER_TASK_STACK_DEPTH // stack depth of the soft-timer
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```
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