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76 lines
2.3 KiB
ReStructuredText
76 lines
2.3 KiB
ReStructuredText
.. _os_interrupt:
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===============================
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Operating system and interrupts
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===============================
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LVGL is **not thread-safe** by default.
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However, in the following conditions it's valid to call LVGL related
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functions:
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- In *events*. Learn more in :ref:`events`.
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- In *lv_timer*. Learn more in :ref:`timer`.
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Tasks and threads
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-----------------
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If you need to use real tasks or threads, you need a mutex which should
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be invoked before the call of :cpp:func:`lv_timer_handler` and released after
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it. Also, you have to use the same mutex in other tasks and threads
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around every LVGL (``lv_...``) related function call and code. This way
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you can use LVGL in a real multitasking environment. Just make use of a
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mutex to avoid the concurrent calling of LVGL functions.
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LVGL has a built-in mutex which can be used with:
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- :cpp:func:`lv_lock()` and :cpp:func:`lv_lock_isr()`
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- :cpp:func:`lv_unlock()`
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These functions are called internally in :cpp:func:`lv_timer_handler`
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and the users need to call them only from their own therads.
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To enable ``lv_lock/lv_unlock`` ``LV_USE_OS`` needs to be set to other
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than ``LV_OS_NONE``.
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Here is some pseudocode to illustrate the concept:
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.. code:: c
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void lvgl_thread(void)
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{
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while(1) {
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uint32_t time_till_next;
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time_till_next = lv_timer_handler(); /*lv_lock/lv_unlock is called internally*/
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thread_sleep(time_till_next); /* sleep for a while */
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}
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}
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void other_thread(void)
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{
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/* You must always hold the mutex while using LVGL APIs */
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lv_lock();
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lv_obj_t *img = lv_image_create(lv_screen_active());
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lv_unlock();
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while(1) {
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lv_lock();
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/* change to the next image */
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lv_image_set_src(img, next_image);
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lv_unlock();
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thread_sleep(2000);
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}
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}
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Interrupts
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----------
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Try to avoid calling LVGL functions from interrupt handlers (except
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:cpp:func:`lv_tick_inc` and :cpp:func:`lv_display_flush_ready`). But if you need to do
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this you have to disable the interrupt which uses LVGL functions while
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:cpp:func:`lv_timer_handler` is running.
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It's a better approach to simply set a flag or some value in the
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interrupt, and periodically check it in an LVGL timer (which is run by
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:cpp:func:`lv_timer_handler`).
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