FreeRTOS tasks, with LVGL

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1

I’m working on a project, where i use LVGL and freeRTOS. I’m having some issues related to my UI having some weird behaviour, but my main question is, should I use freeRTOS tasks for loading LVGL object? Also when using 1 object multiple times but changing the text by example, should i use semaphores? It’s a big project.

2

v9 and v8 recommendations

if you use separate threads to call lv_task_handler() and to change any object property you need to use mutex to prevent lvgl objects sharing

3

I pin all the creations of lvgl objects and the lv_task_handler() to core 1 and all the other functionality like webservers and wifi to core 0,if that is what u are saying.

4

I also never run any lvgl creation task at the same time. These are handled by wifi handlers and other stuff. The reason i’m asking is because i call the loading screen, so i change the text of a label inside, on sta getting the IP i call the loading screen again but with a different text for the label. This sometimes messes with the layout of my UI.

5

These are called in the main, so the task is called in the main and the function is the task that is running.

xTaskCreatePinnedToCore(lv_tick_task, "lv_tick_task", 1024*10, NULL, 8, NULL, 1);

static void lv_tick_task(void * pvParameters)
{
    while (1)
    {
        lv_task_handler();
        vTaskDelay((20) / portTICK_PERIOD_MS);
    }
}

Then by example these are 2 different calls for the loading screen, at 2 different places in the code.

xTaskCreatePinnedToCore(loading_screen_task, "loading_screen_task", 4096, (void*)"Connecting To Wifi...", 5, NULL, 1);

xTaskCreatePinnedToCore(loading_screen_task, "loading_screen_task", 4096, (void*)"http://192.168.4.1/index.html", 3, NULL, 1);

this is the loading screen task

void loading_screen_task(void * pvParameters) {
    const char * text = (const char *) pvParameters;

    ui_show_loading_screen(text);
    vTaskDelete(NULL);
}
6

so you should use mutex when you call lv_task_handler()

xSemaphoreTake(xLvMutex, portMAX_DELAY);
lv_task_handler();
xSemaphoreGive(xLvMutex);

and when you need to lock mutex around every LVGL (lv_... ) related function call and code in the other threads. as far as I understand ui_show_loading_screen() updates your ui elements so:

xSemaphoreTake(xLvMutex, portMAX_DELAY);
ui_show_loading_screen(text);
xSemaphoreGive(xLvMutex);

LVGL is not thread-safe .

7

it is recommended to handle lvgl in one thread to keep safe

8

Thanks! i’ll try it.