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46 lines
1.2 KiB
ReStructuredText
46 lines
1.2 KiB
ReStructuredText
.. _tick:
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==============
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Tick interface
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==============
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LVGL needs a system tick to know elapsed time for animations and other
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tasks.
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If you want to use a custom function to :cpp:func:`lv_tick_get`, you can
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register a "tick_get_cb" with :cpp:func:`lv_tick_set_cb`.
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For example:
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.. code:: c
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lv_tick_set_cb(SDL_GetTicks);
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You need to call the :cpp:expr:`lv_tick_inc(tick_period)` function periodically
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and provide the call period in milliseconds. For example,
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:cpp:expr:`lv_tick_inc(1)` when calling every millisecond.
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:cpp:func:`lv_tick_inc` should be called in a higher priority routine than
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:cpp:func:`lv_task_handler` (e.g. in an interrupt) to precisely know the
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elapsed milliseconds even if the execution of :cpp:func:`lv_task_handler` takes
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more time.
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With FreeRTOS :cpp:func:`lv_tick_inc` can be called in ``vApplicationTickHook``.
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On Linux based operating systems (e.g. on Raspberry Pi) :cpp:func:`lv_tick_inc`
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can be called in a thread like below:
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.. code:: c
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void * tick_thread (void *args)
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{
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while(1) {
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usleep(5*1000); /*Sleep for 5 millisecond*/
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lv_tick_inc(5); /*Tell LVGL that 5 milliseconds were elapsed*/
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}
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}
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API
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---
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