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33 lines
1.2 KiB
33 lines
1.2 KiB
.. _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 the elapsed time for animations and other
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tasks.
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There are two ways to provide the tick to LVGL:
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1. Call ``lv_tick_set_cb(my_get_milliseconds_function);``: `my_get_milliseconds_function` needs to tell how many milliseconds have elapsed since start up. Most of the platforms have built-in functions that can be used as they are. For example
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- SDL: ``lv_tick_set_cb(SDL_GetTicks);``
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- Arduino: ``lv_tick_set_cb(millis);``
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- FreeRTOS: ``lv_tick_set_cb(xTaskGetTickCount);``
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- STM32: ``lv_tick_set_cb(HAL_GetTick);``
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- ESP32: ``lv_tick_set_cb(my_tick_get_cb);``, where ``my_tick_get_cb`` is a wrapper for ``esp_timer_get_time() / 1000;``
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2. Call ``lv_tick_inc(x)`` periodically, where ``x`` is the elapsed milliseconds since the last call. ``lv_tick_inc`` should be called from a high priority interrupt.
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The ticks (milliseconds) should be independent from any other activities of the MCU.
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For example this works, but LVGL's timing will be incorrect as the execution time of ``lv_timer_handler`` is not considered:
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.. code:: c
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// Bad idea
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lv_timer_handler();
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lv_tick_inc(5);
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my_delay_ms(5);
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API
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---
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