update lvgl simulator on ubuntu

lv_sim_linux/lvgl/docs/porting/tick.rst

@@ -0,0 +1,33 @@
+.. _tick:
+
+==============
+Tick interface
+==============
+
+LVGL needs a system tick to know the elapsed time for animations and other
+tasks.
+
+There are two ways to provide the tick to LVGL:
+
+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
+
+   - SDL: ``lv_tick_set_cb(SDL_GetTicks);``
+   - Arduino: ``lv_tick_set_cb(my_tick_get_cb);``, where ``my_tick_get_cb`` is: ``static uint32_t my_tick_get_cb(void) { return millis(); }``
+   - FreeRTOS: ``lv_tick_set_cb(xTaskGetTickCount);``
+   - STM32: ``lv_tick_set_cb(HAL_GetTick);``
+   - ESP32: ``lv_tick_set_cb(my_tick_get_cb);``, where ``my_tick_get_cb`` is a wrapper for ``esp_timer_get_time() / 1000;``
+
+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.
+
+The ticks (milliseconds)  should be independent from any other activities of the MCU.
+
+For example this works, but LVGL's timing will be incorrect as the execution time of ``lv_timer_handler`` is not considered:
+
+.. code:: c
+   // Bad idea
+   lv_timer_handler();
+   lv_tick_inc(5);
+   my_delay_ms(5);
+
+API
+---