Question about input device


I would to know the logic flow that start from when I press a Button using an input device and finish when the Button on the screen is selected.

What MCU/Processor/Board and compiler are you using?


What do you want to achieve?

I want to use a custom input device to control my gui.

What have you tried so far?

I have tried to run the example that use the keyboard and the mouse (lv_demo_keypad_encoder). I have added my input drive to the example, but i’m not able to run all the functionalities that are in this example. In particular i have noticed that the events UP, DOWN, ENTER that I send using my input driver don’t are recognize proprerly from the rest of the example.
To run the enter button I have modified the msgbox_event_cb function as you can see in the code section. In this section I have copied my function that read the input data.
I don’t know if the use of the queue is a good idea, but i have created a task that read the input device (this is a 5 button shield that give me 5 events: UP, DOWN,LEFT,RIGHT and ENTER) and after the read, associate each of those events, with the lvgl input events, so I send to the GUI this events LV_KEY_ENTER, LV_KEY_UP e so on…
But unfortunately, seem to me that these events aren’t recognize properly.

Someone can help me to understand what are wrong in my code and how I control the objects in my GUI using an input device?

Code to reproduce

static void msgbox_event_cb(lv_obj_t * msgbox, lv_event_t e)
	//printf("msgbox_event_cb: %d\n",e);
        uint16_t b = lv_msgbox_get_active_btn(msgbox);
        if(b == 0 || b == 1) {
            lv_obj_reset_style_list(lv_layer_top(), LV_OBJ_PART_MAIN);
            lv_obj_set_click(lv_layer_top(), false);
            lv_event_send(tv, LV_EVENT_REFRESH, NULL);

static bool keyboard_read(lv_indev_drv_t * indev_drv, lv_indev_data_t * data)
    (void) indev_drv;      /*Unused*/
//    data->state = state;
//    data->key = keycode_to_ascii(last_key);
    uint32_t keyboard_event;
    if(xQueueReceive(gui_input_evt_queue, &keyboard_event, portMAX_DELAY)){
    	data->state = LV_INDEV_STATE_PR;
    	data->key = keyboard_event;
    	//printf("key board event: %d\n",keyboard_event);
    	data->state = LV_INDEV_STATE_REL;

    return false;

Screenshot and/or video

If possible, add screenshots and/or videos about the current state.


I assume that you have created the input device with LV_INDEV_TYPE_KEYPAD.

Generally, what you did should work, but I see these possible issues:

  1. portMAX_DELAY should 0 to return from keyboard_read is not key was pressed
  2. If keyboard_event is the pressed key. Be sure you use LV_KEY_UP/DOWN/ENTER values and not normal ASCII codes or keycodes from a keyboard.

A log from keyboard_read with state and key values would be useful to see what can be the issue.

Hi kisvegabor!
I’m sorry for the late reply, but I very busy with my work.
However now I’m able to read all keys that I need correctly.
The problem is that in my project I use a touchless input that I believe it’s different from other predefinited input device.
Now I have implemented this using keyboard input device, but there are some gesture that I have associated with dummy keys ( LV_KEY_BACKSPACE, LV_KEY_HOME etc…) and I don’t know if this is a problem.
However there is a way to associate some custom keys to my custom input device?

No problem.

You are free to define custom keys similarly to the built-in ones. E.g. #define MY_KEY_1 0x100

Hi kisvegabor,
your answer Is very usefull, many thanks!