docs(os) add example and clarify some poinits

lvgl · Oct 28, 2021 · d996453 · d996453
1 parent 1cce91f
commit d996453
Showing 1 changed file with 34 additions and 1 deletion.
diff --git a/docs/porting/os.md b/docs/porting/os.md
@@ -16,6 +16,39 @@ If you need to use real tasks or threads, you need a mutex which should be invok
 Also, you have to use the same mutex in other tasks and threads around every LVGL (`lv_...`) related function call and code.
 This way you can use LVGL in a real multitasking environment. Just make use of a mutex to avoid the concurrent calling of LVGL functions.
 
+Here is some pseudocode to illustrate the concept:
+
+```c
+static mutex_t lvgl_mutex;
+
+void lvgl_thread(void)
+{
+    while(1) {
+        mutex_lock(&lvgl_mutex);
+        lv_task_handler();
+        mutex_unlock(&lvgl_mutex);
+        thread_sleep(10); /* sleep for 10 ms */
+    }
+}
+
+void other_thread(void)
+{
+    /* You must always hold the mutex while using LVGL APIs */
+    mutex_lock(&lvgl_mutex);
+    lv_obj_t *img = lv_img_create(lv_scr_act());
+    mutex_unlock(&lvgl_mutex);
+
+    while(1) {
+        mutex_lock(&lvgl_mutex);
+        /* change to the next image */
+        lv_img_set_src(img, next_image);
+        mutex_unlock(&lvgl_mutex);
+        thread_sleep(2000);
+    }
+}
+```
+
 ## Interrupts
 Try to avoid calling LVGL functions from interrupt handlers (except `lv_tick_inc()` and `lv_disp_flush_ready()`). But if you need to do this you have to disable the interrupt which uses LVGL functions while `lv_timer_handler` is running.
-It's a better approach to set a flag or some value and periodically check it in an `lv_timer`.
+
+It's a better approach to simply set a flag or some value in the interrupt, and periodically check it in an LVGL timer (which is run by `lv_timer_handler`).