Relationship between lv_tick_inc and lv_task_handler

How-to
1

Hi @kisvegabor , @embeddedt

I have some questions about relationship between the 2 function described in the subtitle.
Could you support me?

What LVGL version are you using?

LVGL 7.10.1

Description

I am using FreeRTOS, and set 1 tick = 5ms
I place lv_tick_inc in vApplicationTickHook, and lv_task_handler in main()
Then I create a lv_task with period = 1s as below code:
lv_task_create(func, 200, LV_TASK_PRIO_MID, NULL);
※In fun(), print a count variable

■ If use lv_tick_inc(1)
func() will be called each about 1s
■ If use lv_tick_inc(5)
func() will be called each about 200ms

  1. Could you explain the meaning of tick_period of lv_tick_inc() ?
  2. How does it affect lv_task_handler?
  3. If I change tick_period of lv_tick_inc(), how can I calculate the period of lv_task?
  4. Is there a risk if I increase tick_period significantly ( such as 5, 10, 100 )?
2

Good questions!

LVGL has no concept of your system’s time by default. You use lv_tick_inc to inform LVGL that a certain amount of time has elapsed since the previous call to lv_tick_inc.

In your case, FreeRTOS’ tick is set to 5ms, meaning that vApplicationTickHook is called every 5ms. When you call lv_tick_inc(1), you are informing LVGL that 1ms of time has passed since the last call, when really 5ms of time has passed. That’s why func is only called at 1/5 of the desired rate.

lv_tick_inc(5) correctly informs LVGL that 5ms of time has passed.

The period you specified there was 200ms. I think the reason you are seeing the function called every 1s is because you’re calling lv_tick_inc with the wrong value.

If you change the tick period of lv_tick_inc, you should update FreeRTOS’ tick speed to match, and vice versa. I don’t recommend keeping them out of sync.

It is recommended to keep it between about 5-10ms so that LVGL can perform animations accurately. Otherwise, it will still work, but you will notice choppiness due to the very infrequent ticks.

3

Hi @embeddedt

Thanks for your reply soon!

It is recommended to keep it between about 5-10ms so that LVGL can perform animations accurately. Otherwise, it will still work, but you will notice choppiness due to the very infrequent ticks.

As you said,
Only one tick by OS, Lvgl performs 5 animations in one call lv_task_hander(), and it takes time to cause a timeout case in my app design. :frowning: