Esp32 panic error by calling lv_ function

How-to
1

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

esp32, esp-wrover-kit

What LVGL version are you using?

8.2

What have you tried so far?

In aTask “Serial.printf(" %d", (int)lv_slider_get_value(ui_SlideValue));” When I run this code, the following error message is displayed and the esp32 reboots. What did I do wrong?

I created a slide in guiTask and displayed it on the screen. In aTask, I tried to get the slide value and display it.

static void aTask(void *pvParameters)
{
 ...
  while (1)
  {
      Serial.printf(" %d", (int)lv_slider_get_value(ui_SlideValue));
      vTaskDelay(pdMS_TO_TICKS(500));  
  }
}

static void guiTask(void *pvParameter)
{
  ...
    ui_SlideValue= lv_slider_create(ui_Screen1);
    lv_slider_set_range(ui_SlideValue, 0, 255);
    lv_slider_set_value(ui_SlideValue, 128, LV_ANIM_OFF);
    if (lv_slider_get_mode(ui_SlideValue) == LV_SLIDER_MODE_RANGE)
        lv_slider_set_left_value(ui_SlideValue, 0,
                                 LV_ANIM_OFF);
    lv_obj_set_width(ui_SlideValue, 150);
    lv_obj_set_height(ui_SlideValue, 10);
    lv_obj_set_x(ui_SlideValue, -3);
    lv_obj_set_y(ui_SlideValue, -33);
    lv_obj_set_align(ui_SlideValue, LV_ALIGN_CENTER);
  ...
  while (1)
  {
    vTaskDelay(pdMS_TO_TICKS(10));

   if (pdTRUE == xSemaphoreTake(xGuiSemaphore, portMAX_DELAY))
    {
      lv_timer_handler();
      // Serial.print("+");
     xSemaphoreGive(xGuiSemaphore);
    }
  }
}

error

Guru Meditation Error: Core  1 panic'ed (LoadProhibited). Exception was unhandled.

Core  1 register dump:
PC      : 0x4018a3c7  PS      : 0x00060c30  A0      : 0x800d1496  A1      : 0x3ffbcb20
A2      : 0x00000000  A3      : 0x3ffb99d4  A4      : 0x3ffb9988  A5      : 0x00000000
A6      : 0x00000001  A7      : 0x80000001  A8      : 0x8008da2b  A9      : 0x3ffbcae0
A10     : 0x3ffd0598  A11     : 0x3ffbf198  A12     : 0x3ffd059c  A13     : 0x00060c23
A14     : 0x00060c20  A15     : 0x00000001  SAR     : 0x00000013  EXCCAUSE: 0x0000001c  
EXCVADDR: 0x00000048  LBEG    : 0x4008ab49  LEND    : 0x4008ab59  LCOUNT  : 0xffffffff
2

When aTask is executed and (int)lv_slider_get_value(ui_SlideValue)) was called, the parameter ui_SlideValue was null because it was not assigned an address. A panic occurred because the function called a parameter with a null address.
After checking if (ui_SlideValue != nullptr) as shown below, it worked normally.

static void aTask(void *pvParameters)
{
…
while (1)
{
if (ui_SlideMotorPwm != nullptr)
{
Serial.printf(“ui_SlideMotorPwm: %d”, ui_SlideMotorPwm);
}
}