UART interrupt mode is working but HAL_UART_Transmit_DMA not work why?

[parth kothiya]

I want to send and receive data using DMA but HAL_UART_Transmit_DMA this function not sending any data returns HAL_BUSY error.

while uart in interrupt mode both send & receive data works fine.

how can i send data using DMA ?

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2021 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 "i2c.h"
#include "tim.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 tx_buffer[20] = {0};
extern DMA_HandleTypeDef hdma_usart1_tx;
/* 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_TIM3_Init();
  MX_USART1_UART_Init();
  MX_USART2_UART_Init();
  MX_DMA_Init();
  MX_I2C2_Init();
  /* USER CODE BEGIN 2 */
  for (uint8_t n = 0; n < 20; ++n) {
	tx_buffer[n] = n;
}
  /* USER CODE END 2 */
 
  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */
 
    /* USER CODE BEGIN 3 */
	  HAL_GPIO_WritePin(DR_ENABLE_GPIO_Port,DR_ENABLE_Pin,GPIO_PIN_SET);
	  		if (HAL_UART_Transmit_DMA(&huart1, tx_buffer, 20) == HAL_OK) {
	  			HAL_GPIO_WritePin(DR_ENABLE_GPIO_Port,DR_ENABLE_Pin,GPIO_PIN_RESET);
	  			HAL_GPIO_TogglePin(ERROR_LED_GPIO_Port, ERROR_LED_Pin);
	  		}
	  		if(HAL_GPIO_ReadPin(X0_GPIO_Port, X0_Pin) == GPIO_PIN_SET){
	  			HAL_GPIO_WritePin(Y0_GPIO_Port, Y0_Pin, GPIO_PIN_SET);
	  		}else {
	  			HAL_GPIO_WritePin(Y0_GPIO_Port, Y0_Pin, GPIO_PIN_RESET);
	  		}
 
	  		if (HAL_GPIO_ReadPin(X1_GPIO_Port, X1_Pin) == GPIO_PIN_SET) {
	  			HAL_GPIO_WritePin(Y1_GPIO_Port, Y1_Pin,GPIO_PIN_SET);
	  		} else {
	  			HAL_GPIO_WritePin(Y1_GPIO_Port, Y1_Pin,GPIO_PIN_RESET);
	  		}
 
	  		if (HAL_GPIO_ReadPin(X2_GPIO_Port, X2_Pin) == GPIO_PIN_SET) {
	  			HAL_GPIO_WritePin(Y2_GPIO_Port, Y2_Pin,GPIO_PIN_SET);
	  		} else {
	  			HAL_GPIO_WritePin(Y2_GPIO_Port, Y2_Pin,GPIO_PIN_RESET);
	  		}
	  		if (HAL_GPIO_ReadPin(X3_GPIO_Port, X3_Pin) == GPIO_PIN_SET) {
	  			HAL_GPIO_WritePin(Y3_GPIO_Port, Y3_Pin,GPIO_PIN_SET);
	  		} else {
	  			HAL_GPIO_WritePin(Y3_GPIO_Port, Y3_Pin,GPIO_PIN_RESET);
	  		}
	  		if (HAL_GPIO_ReadPin(X4_GPIO_Port, X4_Pin) == GPIO_PIN_SET) {
	  			HAL_GPIO_WritePin(Y4_GPIO_Port, Y4_Pin,GPIO_PIN_SET);
	  		} else {
	  			HAL_GPIO_WritePin(Y4_GPIO_Port, Y4_Pin,GPIO_PIN_RESET);
	  		}
	  		if (HAL_GPIO_ReadPin(X5_GPIO_Port, X5_Pin) == GPIO_PIN_SET) {
	  			HAL_GPIO_WritePin(Y5_GPIO_Port, Y5_Pin,GPIO_PIN_SET);
	  		} else {
	  			HAL_GPIO_WritePin(Y5_GPIO_Port, Y5_Pin,GPIO_PIN_RESET);
	  		}
	  		if (HAL_GPIO_ReadPin(X6_GPIO_Port, X6_Pin) == GPIO_PIN_SET) {
	  			HAL_GPIO_WritePin(Y6_GPIO_Port, Y6_Pin,GPIO_PIN_SET);
	  		} else {
	  			HAL_GPIO_WritePin(Y6_GPIO_Port, Y6_Pin,GPIO_PIN_RESET);
	  		}
	  		if (HAL_GPIO_ReadPin(X7_GPIO_Port, X7_Pin) == GPIO_PIN_SET) {
	  			HAL_GPIO_WritePin(Y7_GPIO_Port, Y7_Pin,GPIO_PIN_SET);
	  		} else {
	  			HAL_GPIO_WritePin(Y7_GPIO_Port, Y7_Pin,GPIO_PIN_RESET);
	  		}
	  		if (HAL_GPIO_ReadPin(X8_GPIO_Port, X8_Pin) == GPIO_PIN_SET) {
	  			HAL_GPIO_WritePin(Y1_GPIO_Port, Y1_Pin,GPIO_PIN_SET);
	  		} else {
	  			HAL_GPIO_WritePin(Y1_GPIO_Port, Y1_Pin,GPIO_PIN_RESET);
	  		}
	  		if (HAL_GPIO_ReadPin(X9_GPIO_Port, X9_Pin) == GPIO_PIN_SET) {
	  			HAL_GPIO_WritePin(Y1_GPIO_Port, Y1_Pin,GPIO_PIN_SET);
	  		} else {
	  			HAL_GPIO_WritePin(Y1_GPIO_Port, Y1_Pin,GPIO_PIN_RESET);
	  		}
	  		if (HAL_GPIO_ReadPin(X10_GPIO_Port, X10_Pin) == GPIO_PIN_SET) {
	  			HAL_GPIO_WritePin(Y1_GPIO_Port, Y1_Pin,GPIO_PIN_SET);
	  		} else {
	  			HAL_GPIO_WritePin(Y1_GPIO_Port, Y1_Pin,GPIO_PIN_RESET);
	  		}
	  		if (HAL_GPIO_ReadPin(X11_GPIO_Port, X11_Pin) == GPIO_PIN_SET) {
	  			HAL_GPIO_WritePin(Y1_GPIO_Port, Y1_Pin,GPIO_PIN_SET);
	  		} else {
	  			HAL_GPIO_WritePin(Y1_GPIO_Port, Y1_Pin,GPIO_PIN_RESET);
	  		}
	  		if (HAL_GPIO_ReadPin(X12_GPIO_Port, X12_Pin) == GPIO_PIN_SET) {
	  			HAL_GPIO_WritePin(Y1_GPIO_Port, Y1_Pin,GPIO_PIN_SET);
	  		} else {
	  			HAL_GPIO_WritePin(Y1_GPIO_Port, Y1_Pin,GPIO_PIN_RESET);
	  		}
	  		if (HAL_GPIO_ReadPin(X13_GPIO_Port, X13_Pin) == GPIO_PIN_SET) {
	  			HAL_GPIO_WritePin(Y1_GPIO_Port, Y1_Pin,GPIO_PIN_SET);
	  		} else {
	  			HAL_GPIO_WritePin(Y1_GPIO_Port, Y1_Pin,GPIO_PIN_RESET);
	  		}
 
  }
  /* USER CODE END 3 */
}
 
/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
  RCC_PeriphCLKInitTypeDef PeriphClkInit = {0};
 
  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL12;
  RCC_OscInitStruct.PLL.PREDIV = RCC_PREDIV_DIV1;
  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_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
 
  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK)
  {
    Error_Handler();
  }
  PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_USART1;
  PeriphClkInit.Usart1ClockSelection = RCC_USART1CLKSOURCE_PCLK1;
  if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != 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 */
 

[TDK]

There are examples you can follow that show the proper method of using it.

You didn't post what chip you're working with, so here is one example at random:

https://github.com/STMicroelectronics/STM32CubeF4/blob/2f3b26f16559f7af495727a98253067a31182cfc/Projects/STM324xG_EVAL/Examples/UART/UART_Hyperterminal_DMA/Src/main.c