Help with Queues in FreeRTOS (CMSIS-RTOS v2)--running into a weird memory issue

[ShawnHymel]

I'm using STM32CubeIDE and created a project for the Nucleo-L476RG with FreeRTOS selected. I switched the Timebase Source to TIM6 to allow FreeRTOS to have SysTick. I created 2 tasks and 1 queue (for the default 16x queue size of uint16_t). Here are my tasks (the idea is to have LD2 toggle more and more slowly as time passes):

/* USER CODE BEGIN Header_startBlinkTask */
/**
  * @brief  Function implementing the blinkTask thread.
  * @param  argument: Not used 
  * @retval None
  */
/* USER CODE END Header_startBlinkTask */
void startBlinkTask(void *argument)
{
  /* USER CODE BEGIN 5 */
  uint16_t msg;
  uint16_t delay = 500; // Default delay
  osStatus_t status;
 
  /* Infinite loop */
  for(;;)
  {
 
    // Assign delay based on message in queue
    status = osMessageQueueGet(msgQueueHandle, &msg, NULL, 0);
 
    // If message was received, update delay
    if ( status == osOK )
    {
      delay = msg;
    }
 
    // Blink with given delay
    HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_5);
    osDelay(delay);
  }
 
  // In case we accidentally exit from task loop
  osThreadTerminate(NULL);
 
  /* USER CODE END 5 */ 
}
 
/* USER CODE BEGIN Header_startUITask */
/**
* @brief Function implementing the uiTask thread.
* @param argument: Not used
* @retval None
*/
/* USER CODE END Header_startUITask */
void startUITask(void *argument)
{
  /* USER CODE BEGIN startUITask */
  uint16_t desiredDelay = 0;
 
  /* Infinite loop */
  for(;;)
  {
    desiredDelay += 100;
    osMessageQueuePut(msgQueueHandle, &desiredDelay, 0, osWaitForever);
    osDelay(1000);
  }
 
  // In case we accidentally exit from task loop
  osThreadTerminate(NULL);
 
  /* USER CODE END startUITask */
}

However, when I run this, the LED blinks once and then hangs. I stepped through the osMessageQueueGet() function and found that when there was a message waiting at the head of the queue, the memory location for the message is oddly cleared within the function.

I was able to track it down to the xTaskGetSchedulerState() function (please see attached screenshots). Before entering xTaskGetSchedulerState() (queue-01.png), you can see that the memory location 0x20000D78 contains my data (decimal 100), which is the head of the queue. As soon as I step into xTaskGetSchedulerState() (queue-02.png), that memory location is mysteriously cleared (set to 0). Queue-03.png shows that this memory location stays cleared after returning from that function.

I am very new to FreeRTOS and just now learning about queues. I figure that I must have something wrong in my code to be causing this. I am working through "Mastering STM32" by Carmine Noviello, but since he uses CMSIS-RTOS v1, I'm trying to update my code to CMSIS-RTOS v2 (with this example: https://www.keil.com/pack/doc/CMSIS/RTOS2/html/group__CMSIS__RTOS__Message.html#gaa515fc8b956f721a8f72b2c505813bfc).

Any help would be appreciated!