完美解决HAL库HAL_UART_Transmit_DMA（）不延时就发不了下一条的问题-Toy模板网

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问题原因

在连续用HAL_UART_Transmit_DMA（）函数的时候，会遇到只能发出第一条的问题，原因是DMA传输数据到串口这个外设太快了，传输完后程序并不会在该处停留，但是串口发送需要时间，运行到下一条HAL_UART_Transmit_DMA（）函数的时候，上一条数据还没来得及发完，导致串处于BUZY（即 HAL_UART_STATE_BUSY ）状态

如果串口处于BUZY状态，则HAL_UART_Transmit_DMA（）不会进入发送程序，直接return HAL_BUSY;这就导致了HAL_UART_Transmit_DMA（）不能连续运行，

目前网上主流的解决办法是延时一定时间或while(HAL_DMA_GetState(&hdma_usart1_tx) == HAL_DMA_STATE_BUZY)，等串口发完数据在执行下一条指令。但是这样让CPU卡在这里，让DMA和串口外设的速度优势荡然无存，并且，HAL_DMA_GetState（）好像只要初始化之后它的状态就不会生变化，要采用if((&huart1)->gState == HAL_UART_STATE_READY)进行判断比较有用。

于是我采用了如下办法

解决方法

    while (1)
  {
        if((&huart1)->gState == HAL_UART_STATE_READY)
        {    
            if(dma_uartThread == 4)
               dma_uartThread=0;
         
        dma_state=1;
            dma_uartThread++;
        }
                
    if(dma_state)
{
    switch(dma_uartThread)
    {
        case 1:
            HAL_UART_Transmit_DMA(&huart1,dma_sentTest1,sizeof(dma_sentTest1));
           dma_state=0;
        break;
        
        case 2:
            HAL_UART_Transmit_DMA(&huart1,dma_sentTest2,sizeof(dma_sentTest2));
          dma_state=0;
        break;
                
                 case 3:
                        HAL_UART_Transmit_DMA(&huart1,dma_sentTest3,sizeof(dma_sentTest3));
                    dma_state=0;
                break;
                 
                    case 4:
                        HAL_UART_Transmit_DMA(&huart1,dma_sentTest4,sizeof(dma_sentTest4));
                    dma_state=0;
                break;
        

    }

    
}
     
    
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
  }

解释说明：

uint8_t dma_sentTest1[]="\r\n111AAABBBCCC\r\n"; //测试用字符串1
uint8_t dma_sentTest2[]="\r\n222dddaaaeee\r\n";//测试用字符串2
uint8_t dma_sentTest3[]="\r\n333qddcvdfvf\r\n";//测试用字符串3
uint8_t dma_sentTest4[]="\r\n444csdcvfdvb\r\n";//测试用字符串4

uint8_t dma_receive[50];//接收用数组
uint8_t dma_uartThread=0;//发送线程标志
uint8_t dma_state=0;//DMA发送串口状态标志

在每次需要调用 HAL_UART_Transmit_DMA（）前通过if((&huart1)->gState == HAL_UART_STATE_READY) 判断一下是否准备好了发送

如果准备好了则 dma_state置1，这样cpu就有权进入switch函数进行发送数据了，为了防止重复发送，我们引入线程“指针” dma_uartThread，这样就可以依次执行了。

本文是我作为一个初学者浅薄的理解，当时遇到了这个问题但却找不到答案，如果有误欢迎指出讨论。

以下是完整代码，初始化配置用cubeMX生成

我觉得用定时器应该也可以解决这个问题，有空试试文章来源地址https://www.toymoban.com/news/detail-510454.html

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2023 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 "dma.h"
#include "usart.h"
#include "gpio.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
 
/* 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 dma_sentTest1[]="\r\n111AAABBBCCC\r\n";
uint8_t dma_sentTest2[]="\r\n222dddaaaeee\r\n";
uint8_t dma_sentTest3[]="\r\n333qddcvdfvf\r\n";
uint8_t dma_sentTest4[]="\r\n444csdcvfdvb\r\n";
uint8_t dma_receive[50];
uint8_t dma_uartThread=0;
uint8_t dma_state=0;
/* 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 */
extern DMA_HandleTypeDef hdma_usart1_tx;
/* 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 */
 
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
    /*HAL_DMA_GetState(&hdma_usart1_tx) == HAL_DMA_STATE_READY*/
  while (1)
  {
        if((&huart1)->gState == HAL_UART_STATE_READY)
        {    
            if(dma_uartThread == 4)
               dma_uartThread=0;
         
        dma_state=1;
            dma_uartThread++;
        }
                
    if(dma_state)
{
    switch(dma_uartThread)
    {
        case 1:
            HAL_UART_Transmit_DMA(&huart1,dma_sentTest1,sizeof(dma_sentTest1));
           dma_state=0;
        break;
        
        case 2:
            HAL_UART_Transmit_DMA(&huart1,dma_sentTest2,sizeof(dma_sentTest2));
          dma_state=0;
        break;
                
                 case 3:
                        HAL_UART_Transmit_DMA(&huart1,dma_sentTest3,sizeof(dma_sentTest3));
                    dma_state=0;
                break;
                 
                    case 4:
                        HAL_UART_Transmit_DMA(&huart1,dma_sentTest4,sizeof(dma_sentTest4));
                    dma_state=0;
                break;
        

    }

    
}
     
    
    /* 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 */

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