STM32串口收发问题解决方案——HAL_UART_GetState使用技巧

一、背景

使用STM32串口同时接收和发送数据时。使用HAL_UART_GetState函数检查串口状态时，串口处于忙状态，就不会变回正常状态。这种情况让我想到有没有可能是stm32HAL库没有支持全双工，理论上来说串口应是全双工发送接收。

二、实验思路

![外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传](https://img-home.csdnimg.cn/images/20230724024159.png?origin_url=C%3A%5CUsers%5C11544%5CAppData%5CRoaming%5CTypora%5Ctypora-user-images%
5Cimage-20231129201001868.png&pos_id=img-uvCwFYzl-1701260500337)

HAL_UART_STATE_READY             = 0x20U,    //正常收法
HAL_UART_STATE_BUSY              = 0x24U, 	 //串口忙

深入查看UART_HandleTypeDef的定义

UART_HandleTypeDef huart1
    
typedef struct __UART_HandleTypeDef
{
  USART_TypeDef                 *Instance;        /*!< UART registers base address        */

  UART_InitTypeDef              Init;             /*!< UART communication parameters      */

  const uint8_t                 *pTxBuffPtr;      /*!< Pointer to UART Tx transfer Buffer */

  uint16_t                      TxXferSize;       /*!< UART Tx Transfer size              */

  __IO uint16_t                 TxXferCount;      /*!< UART Tx Transfer Counter           */

  uint8_t                       *pRxBuffPtr;      /*!< Pointer to UART Rx transfer Buffer */

  uint16_t                      RxXferSize;       /*!< UART Rx Transfer size              */

  __IO uint16_t                 RxXferCount;      /*!< UART Rx Transfer Counter           */

  __IO HAL_UART_RxTypeTypeDef ReceptionType;      /*!< Type of ongoing reception          */

  DMA_HandleTypeDef             *hdmatx;          /*!< UART Tx DMA Handle parameters      */

  DMA_HandleTypeDef             *hdmarx;          /*!< UART Rx DMA Handle parameters      */

  HAL_LockTypeDef               Lock;             /*!< Locking object                     */

  __IO HAL_UART_StateTypeDef    gState;           /*!< UART state information related to global Handle management
                                                       and also related to Tx operations.
                                                       This parameter can be a value of @ref HAL_UART_StateTypeDef */

  __IO HAL_UART_StateTypeDef    RxState;          /*!< UART state information related to Rx operations.
                                                       This parameter can be a value of @ref HAL_UART_StateTypeDef */

  __IO uint32_t                 ErrorCode;        /*!< UART Error code                    */
...

根据注释可知状态有发送状态gState和接收状态RxState。接着查看HAL_UART_GetState函数内容。

HAL_UART_StateTypeDef HAL_UART_GetState(UART_HandleTypeDef *huart)
{
  uint32_t temp1 = 0x00U, temp2 = 0x00U;
  temp1 = huart->gState;
  temp2 = huart->RxState;

  return (HAL_UART_StateTypeDef)(temp1 | temp2);
}

果然，官方是结合了两者的状态，只要其中一个处于忙状态就无法获取到真正的状态。

三、解决方法

以上图huart1为串口句柄为例，直接访问这两个状态即可。

	int ret_state = HAL_UART_STATE_READY;
	ret_state = huart3.RxState;
    while (ret_state != HAL_UART_STATE_READY)//等待就绪
    {
		//huart1.gState = HAL_UART_STATE_READY;
		printf("ret_state = %d\r\n",ret_state);
        timeout++;超时处理
		
        if (timeout > HAL_MAX_DELAY)
		{
			break;
		}
		ret_state = huart3.RxState;
    }


 	if(timeout > HAL_MAX_DELAY)
		{
			break;
		}
		ret_state = huart3.RxState;
    }