为什么HAL_UART_RxCpltCallback每次通信运行两次？

我使用的是 STM32L073RZT6 MCU 和 Cube IDE V1.11。使用 .IOC，我在 PB7-6 上实例化了 UART1，启用了全局中断并为 RX 提供了 DMA 服务。在 PC 端，我将 PuTTy 用作嗅探器，将 UART 转 USB 电缆用于 COMS。我在下面提供了配置、PuTTy 输出和代码片段的屏幕截图。每次我向 MCU 传输一个字符时，rx 回调都会运行两次，但是在第二次运行时，rx 缓冲区似乎被重置并传输“无”。虽然我对这种添加的行为感到困惑，但我主要关心的是为什么它会运行两次回调。任何指导将不胜感激。谢谢你。

/* USER CODE BEGIN PV */
volatile uint8_t uart_tx_buffer[4];
volatile uint8_t uart_rx_buffer[4];
const uint8_t uart_default_msg[8] = {'W', 'A', 'I', 'T', 'I', 'N', 'G', 0x0D};
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_DMA_Init(void);
static void MX_USART1_UART_Init(void);
/* USER CODE BEGIN PFP */
/* USER CODE END PFP */
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
/* USER CODE END 0 */
/**
* @brief The application entry point.
* @retval int
*/
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_DMA_Init();
MX_USART1_UART_Init();
/* USER CODE BEGIN 2 */
HAL_UART_Receive_DMA(&huart1, uart_rx_buffer, 1);
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
HAL_UART_Transmit(&huart1, uart_default_msg, 8, 100);
HAL_Delay(10000);
}
/* USER CODE END 3 */
}
/* USER CODE BEGIN 4 */
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart){
int i = 0;
switch(uart_rx_buffer[0]){
case('p'):
uart_tx_buffer[0] = 'p';
uart_tx_buffer[1] = 'u';
uart_tx_buffer[2] = 'l';
uart_tx_buffer[3] = 's';
i++;
HAL_UART_Transmit(&huart1, uart_tx_buffer, 4, 100);
break;
case('h'):
uart_tx_buffer[0] = 'h';
uart_tx_buffer[1] = 'e';
uart_tx_buffer[2] = 'a';
uart_tx_buffer[3] = 't';
i++;
HAL_UART_Transmit(&huart1, uart_tx_buffer, 4, 100);
break;
default:
uart_tx_buffer[0] = 'N';
uart_tx_buffer[1] = 'o';
uart_tx_buffer[2] = 'n';
uart_tx_buffer[3] = 'e';
HAL_UART_Transmit(&huart1, uart_tx_buffer, 4, 100);
i++;
break;
}
// HAL_UART_Receive_DMA(&huart1, uart_rx_buffer, 1);
}
/* USER CODE END 4 */