init lvgl code

LVGL.Simulator/lvgl/docs/porting/sleep.md

@@ -0,0 +1,31 @@
+```eval_rst
+.. include:: /header.rst
+:github_url: |github_link_base|/porting/sleep.md
+```
+# Sleep management
+
+The MCU can go to sleep when no user input happens. In this case, the main `while(1)` should look like this:
+
+```c
+while(1) {
+  /*Normal operation (no sleep) in < 1 sec inactivity*/
+  if(lv_disp_get_inactive_time(NULL) < 1000) {
+	  lv_task_handler();
+  }
+  /*Sleep after 1 sec inactivity*/
+  else {
+	  timer_stop();   /*Stop the timer where lv_tick_inc() is called*/
+	  sleep();		    /*Sleep the MCU*/
+  }
+  my_delay_ms(5);
+}
+```
+
+You should also add the following lines to your input device read function to signal a wake-up (press, touch or click etc.) has happened:
+```c
+lv_tick_inc(LV_DISP_DEF_REFR_PERIOD);  /*Force task execution on wake-up*/
+timer_start();                         /*Restart the timer where lv_tick_inc() is called*/
+lv_task_handler();                     /*Call `lv_task_handler()` manually to process the wake-up event*/
+```
+
+In addition to `lv_disp_get_inactive_time()` you can check `lv_anim_count_running()` to see if all animations have finished.