轮询方式串口弊端

Tutorial: 电子电路 Category: 嵌入式 Published: 2026-08-29 08:09:36 Views: 0 Likes: 0 Comments: 0

116.4.6轮询方式串口弊端

/* ==================== Core\Inc\main.h ==================== */
/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.h
  * @brief          : Header for main.c file.
  *                   This file contains the common defines of the application.
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2024 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  */
/* USER CODE END Header */

/* Define to prevent recursive inclusion -------------------------------------*/
#ifndef __MAIN_H
#define __MAIN_H

#ifdef __cplusplus
extern "C" {
#endif

/* Includes ------------------------------------------------------------------*/
#include "stm32f1xx_hal.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */

/* USER CODE END Includes */

/* Exported types ------------------------------------------------------------*/
/* USER CODE BEGIN ET */

/* USER CODE END ET */

/* Exported constants --------------------------------------------------------*/
/* USER CODE BEGIN EC */

/* USER CODE END EC */

/* Exported macro ------------------------------------------------------------*/
/* USER CODE BEGIN EM */

/* USER CODE END EM */

/* Exported functions prototypes ---------------------------------------------*/
void Error_Handler(void);

/* USER CODE BEGIN EFP */

/* USER CODE END EFP */

/* Private defines -----------------------------------------------------------*/
#define LED2_Pin GPIO_PIN_5
#define LED2_GPIO_Port GPIOE
#define LED1_Pin GPIO_PIN_5
#define LED1_GPIO_Port GPIOB

/* USER CODE BEGIN Private defines */

/* USER CODE END Private defines */

#ifdef __cplusplus
}
#endif

#endif /* __MAIN_H */

/* ==================== Core\Inc\gpio.h ==================== */
/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file    gpio.h
  * @brief   This file contains all the function prototypes for
  *          the gpio.c file
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2024 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  */
/* USER CODE END Header */
/* Define to prevent recursive inclusion -------------------------------------*/
#ifndef __GPIO_H__
#define __GPIO_H__

#ifdef __cplusplus
extern "C" {
#endif

/* Includes ------------------------------------------------------------------*/
#include "main.h"

/* USER CODE BEGIN Includes */

/* USER CODE END Includes */

/* USER CODE BEGIN Private defines */

/* USER CODE END Private defines */

void MX_GPIO_Init(void);

/* USER CODE BEGIN Prototypes */

/* USER CODE END Prototypes */

#ifdef __cplusplus
}
#endif
#endif /*__ GPIO_H__ */


/* ==================== Core\Inc\usart.h ==================== */
/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file    usart.h
  * @brief   This file contains all the function prototypes for
  *          the usart.c file
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2024 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  */
/* USER CODE END Header */
/* Define to prevent recursive inclusion -------------------------------------*/
#ifndef __USART_H__
#define __USART_H__

#ifdef __cplusplus
extern "C" {
#endif

/* Includes ------------------------------------------------------------------*/
#include "main.h"

/* USER CODE BEGIN Includes */
#include <stdio.h>
/* USER CODE END Includes */

extern UART_HandleTypeDef huart1;

/* USER CODE BEGIN Private defines */
extern uint8_t u_buf[256];
#define printf(...)  HAL_UART_Transmit(&huart1, (uint8_t *)u_buf, sprintf((char*)u_buf, __VA_ARGS__), 0xffff)
/* USER CODE END Private defines */

void MX_USART1_UART_Init(void);

/* USER CODE BEGIN Prototypes */

/* USER CODE END Prototypes */

#ifdef __cplusplus
}
#endif

#endif /* __USART_H__ */


/* ==================== Core\Src\main.c ==================== */
/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2024 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  */
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "usart.h"
#include "gpio.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include <string.h>
/* USER CODE END Includes */

/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */

/* USER CODE END PTD */

/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */

/* USER CODE END PD */

/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */

/* USER CODE END PM */

/* Private variables ---------------------------------------------------------*/

/* USER CODE BEGIN PV */
uint8_t UART_Recv[5];
uint8_t DHT11_Buf[30];
/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(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_USART1_UART_Init();
  /* USER CODE BEGIN 2 */

  /* USER CODE END 2 */

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

	  HAL_UART_Receive(&huart1, UART_Recv, 4, 1000);
	  if(strcmp("LED1", (char *)UART_Recv)==0)
	  {
		  HAL_GPIO_TogglePin(LED1_GPIO_Port, LED1_Pin);
		  memset(UART_Recv, '\0', 4);
	  }
	  if(!strcmp("LED2", (char *)UART_Recv))
	  {
		  HAL_GPIO_TogglePin(LED2_GPIO_Port, LED2_Pin);
		  memset(UART_Recv, '\0', 4);
	  }
	  sprintf((char *)DHT11_Buf,"H2:%f T2:%f\n",30.1,36.5);
	  HAL_UART_Transmit(&huart1, (char *)DHT11_Buf, strlen(DHT11_Buf), 1000);
	  printf("Hellow world wfeng %d!\n",123);


    /* USER CODE END WHILE */

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

/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }

  /** Initializes the CPU, AHB and APB buses clocks
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
  {
    Error_Handler();
  }
}

/* USER CODE BEGIN 4 */

/* USER CODE END 4 */

/**
  * @brief  This function is executed in case of error occurrence.
  * @retval None
  */
void Error_Handler(void)
{
  /* USER CODE BEGIN Error_Handler_Debug */
  /* User can add his own implementation to report the HAL error return state */
  __disable_irq();
  while (1)
  {
  }
  /* USER CODE END Error_Handler_Debug */
}

#ifdef  USE_FULL_ASSERT
/**
  * @brief  Reports the name of the source file and the source line number
  *         where the assert_param error has occurred.
  * @param  file: pointer to the source file name
  * @param  line: assert_param error line source number
  * @retval None
  */
void assert_failed(uint8_t *file, uint32_t line)
{
  /* USER CODE BEGIN 6 */
  /* User can add his own implementation to report the file name and line number,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */

/* ==================== Core\Src\gpio.c ==================== */
/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file    gpio.c
  * @brief   This file provides code for the configuration
  *          of all used GPIO pins.
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2024 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  */
/* USER CODE END Header */

/* Includes ------------------------------------------------------------------*/
#include "gpio.h"

/* USER CODE BEGIN 0 */

/* USER CODE END 0 */

/*----------------------------------------------------------------------------*/
/* Configure GPIO                                                             */
/*----------------------------------------------------------------------------*/
/* USER CODE BEGIN 1 */

/* USER CODE END 1 */

/** Configure pins as
        * Analog
        * Input
        * Output
        * EVENT_OUT
        * EXTI
*/
void MX_GPIO_Init(void)
{

  GPIO_InitTypeDef GPIO_InitStruct = {0};

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOE_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(LED2_GPIO_Port, LED2_Pin, GPIO_PIN_SET);

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(LED1_GPIO_Port, LED1_Pin, GPIO_PIN_SET);

  /*Configure GPIO pin : PtPin */
  GPIO_InitStruct.Pin = LED2_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_PULLUP;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(LED2_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pin : PtPin */
  GPIO_InitStruct.Pin = LED1_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_PULLUP;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(LED1_GPIO_Port, &GPIO_InitStruct);

}

/* USER CODE BEGIN 2 */

/* USER CODE END 2 */

/* ==================== Core\Src\usart.c ==================== */
/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file    usart.c
  * @brief   This file provides code for the configuration
  *          of the USART instances.
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2024 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  */
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "usart.h"

/* USER CODE BEGIN 0 */
uint8_t u_buf[256];
/* USER CODE END 0 */

UART_HandleTypeDef huart1;

/* USART1 init function */

void MX_USART1_UART_Init(void)
{

  /* USER CODE BEGIN USART1_Init 0 */

  /* USER CODE END USART1_Init 0 */

  /* USER CODE BEGIN USART1_Init 1 */

  /* USER CODE END USART1_Init 1 */
  huart1.Instance = USART1;
  huart1.Init.BaudRate = 115200;
  huart1.Init.WordLength = UART_WORDLENGTH_8B;
  huart1.Init.StopBits = UART_STOPBITS_1;
  huart1.Init.Parity = UART_PARITY_NONE;
  huart1.Init.Mode = UART_MODE_TX_RX;
  huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart1.Init.OverSampling = UART_OVERSAMPLING_16;
  if (HAL_UART_Init(&huart1) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN USART1_Init 2 */

  /* USER CODE END USART1_Init 2 */

}

void HAL_UART_MspInit(UART_HandleTypeDef* uartHandle)
{

  GPIO_InitTypeDef GPIO_InitStruct = {0};
  if(uartHandle->Instance==USART1)
  {
  /* USER CODE BEGIN USART1_MspInit 0 */

  /* USER CODE END USART1_MspInit 0 */
    /* USART1 clock enable */
    __HAL_RCC_USART1_CLK_ENABLE();

    __HAL_RCC_GPIOA_CLK_ENABLE();
    /**USART1 GPIO Configuration
    PA9     ------> USART1_TX
    PA10     ------> USART1_RX
    */
    GPIO_InitStruct.Pin = GPIO_PIN_9;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

    GPIO_InitStruct.Pin = GPIO_PIN_10;
    GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

  /* USER CODE BEGIN USART1_MspInit 1 */

  /* USER CODE END USART1_MspInit 1 */
  }
}

void HAL_UART_MspDeInit(UART_HandleTypeDef* uartHandle)
{

  if(uartHandle->Instance==USART1)
  {
  /* USER CODE BEGIN USART1_MspDeInit 0 */

  /* USER CODE END USART1_MspDeInit 0 */
    /* Peripheral clock disable */
    __HAL_RCC_USART1_CLK_DISABLE();

    /**USART1 GPIO Configuration
    PA9     ------> USART1_TX
    PA10     ------> USART1_RX
    */
    HAL_GPIO_DeInit(GPIOA, GPIO_PIN_9|GPIO_PIN_10);

  /* USER CODE BEGIN USART1_MspDeInit 1 */

  /* USER CODE END USART1_MspDeInit 1 */
  }
}

/* USER CODE BEGIN 1 */

/* USER CODE END 1 */

一、轮询方式串口弊端

1.1 通用同步异步收发器介绍

USART 外设位于 CPU 与引脚之间，负责把并行字节转换为串行位流，也负责把串行位流还原为并行字节。简化结构如下：

发送方向：
CPU/总线 ─写DR/TDR→ 发送数据寄存器 ─→ 发送移位寄存器 ─→ TX引脚
                        │                    │
                       TXE                  TC

接收方向：
RX引脚 ─→ 接收移位寄存器 ─→ 接收数据寄存器DR/RDR ─读→ CPU/总线
             │                      │
          位采样/校验              RXNE

关键状态的意义：

标志	含义	常见动作
RXNE	接收数据寄存器非空	读取 DR 后清除
TXE	发送数据寄存器空	可以写入下一个字节
TC	整帧发送完毕，移位寄存器也空	需要确认总线真正发送结束时使用
ORE	上一字节未及时读取，新字节又到达	处理数据并清错误状态
FE	停止位采样不正确	检查波特率、线路和帧格式
NE	接收时检测到噪声	检查接地、线缆和干扰
PE	奇偶校验失败	检查两端校验配置
IDLE	收到数据后又检测到一个帧时间的空闲	可作为不定长数据结束事件

轮询、中断和 DMA 使用的是同一个 USART 硬件，区别主要在于“谁搬运数据、CPU 如何得知事件”：

flowchart LR
    U[USART数据寄存器] --> P[轮询：CPU反复查标志并搬运]
    U --> I[中断：事件发生后CPU进入中断搬运]
    U --> D[DMA：DMA控制器自动在外设和内存间搬运]

1.2 轮询方式分析

HAL_UART_Receive(&huart1, buf, 4, 1000) 会在函数内部等待 4 个字节。等待期间，CPU 反复检查状态寄存器中的 RXNE 和错误标志；每收到一个字节，就读取数据寄存器并写入内存。4 字节全部收到时返回 HAL_OK，超时则返回 HAL_TIMEOUT。

flowchart TD
    A[调用轮询接收] --> B{RXNE置位?}
    B -- 否 --> C{超时?}
    C -- 否 --> B
    C -- 是 --> E[返回HAL_TIMEOUT]
    B -- 是 --> D[读DR并保存1字节]
    D --> F{达到Size?}
    F -- 否 --> B
    F -- 是 --> G[返回HAL_OK]

弊端不是“每秒只查询一次”，而是等待期间 CPU 一直困在调用中：

没有数据时仍消耗 CPU 时间检查状态；
Timeout 过长会拖慢按键、显示、传感器等其他任务；
Timeout 过短又可能在一帧尚未收完时提前退出；
固定 Size 难以处理长度不定、带回车换行的数据；
高波特率下如果其他代码长时间关中断或阻塞，可能来不及读取而产生 ORE。

本工程主循环中的 HAL_Delay() 会额外延迟下一轮处理，但它不是 USART 轮询机制的固有周期。

轮询方式也并非完全不能使用。启动阶段打印少量日志、等待一条短命令、通信时序简单且阻塞时间可接受时，它的代码最直观。需要并行处理其他任务时，可改用中断；连续高速或较大数据量时，可使用 DMA；不定长数据通常结合空闲事件与 DMA。

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