这个main()函数来自 board/CubeMx_Config/Src/main.c, 
替换掉 applications/main.c。
把被替换掉main（）函数中点灯的demo代码拿过来演示。
执行到  rt_thread_mdelay(500); 出现异常。
具体表现是进入 RT_ASSERT(thread != RT_NULL);

int main(void)
{
  /* USER CODE BEGIN 1 */

/* USER CODE END 1 */

/* MCU Configuration--------------------------------------------------------*/

/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

/* USER CODE BEGIN Init */

/* USER CODE END Init */

/* Configure the system clock */
  SystemClock_Config();

/* USER CODE BEGIN SysInit */

/* USER CODE END SysInit */

/* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_USART1_UART_Init();
  MX_ADC1_Init();
  MX_LPUART1_UART_Init();
  MX_RTC_Init();
  MX_SPI1_Init();
  MX_TIM16_Init();
  MX_TIM17_Init();
  MX_USB_PCD_Init();
  MX_I2C1_Init();
  MX_SPI2_Init();
  /* USER CODE BEGIN 2 */

/* USER CODE END 2 */

/* Infinite loop */
  /* USER CODE BEGIN WHILE */
 // while (1)
 // {
    /* USER CODE END WHILE */

/* USER CODE BEGIN 3 */
 // }
  /* USER CODE END 3 */

/* set LED0 pin mode to output */

int count = 1;
//  rt_pin_mode( LED1_Pin, PIN_MODE_OUTPUT);
     while (count++)
     {
         HAL_GPIO_WritePin(GPIOB, LED2_Pin|LED3_Pin|LED1_Pin, GPIO_PIN_SET);
  //       rt_pin_write((rt_base_t)LED1_Pin, PIN_HIGH);
         rt_thread_mdelay(500);
         HAL_GPIO_WritePin(GPIOB, LED2_Pin|LED3_Pin|LED1_Pin, GPIO_PIN_RESET);
//         rt_pin_write((rt_base_t)LED1_Pin, PIN_LOW);
         rt_thread_mdelay(500);
     }

return RT_EOK;

}