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How to reset DMA buffer for UART

Question asked by Raider E on Jan 19, 2017
Latest reply on Aug 20, 2017 by khastar.mehdi

Hi Everyone, 

 

Just a little issue, I would like to reset the receiving buffer of the DMA in circular mode every time it completes reception. If i know the exact size of received data problem solved the DMA buffer will reset when its full. However, I receive various size of data (strings), say every 100 ms from a connected device and it makes parsing much easier if the DMA buffer reset

uint8_t rxbytes[32]="";
  
HAL_UART_Receive_DMA(&huart1, (uint8_t *)rxbytes, 32); // use DMA

MSP file (DMA config for UART1):

void HAL_UART_MspInit(UART_HandleTypeDef* huart)
{

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

  /* USER CODE END USART1_MspInit 0 */
    /* Peripheral clock enable */
    __HAL_RCC_USART1_CLK_ENABLE();
 
    /**USART1 GPIO Configuration   
    PB14     ------> USART1_TX
    PB15     ------> USART1_RX
    */
    GPIO_InitStruct.Pin = GPIO_PIN_14|GPIO_PIN_15;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_PULLUP;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
    GPIO_InitStruct.Alternate = GPIO_AF4_USART1;
    HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

    /* Peripheral DMA init*/
 
    hdma_usart1_rx.Instance = DMA2_Stream2;
    hdma_usart1_rx.Init.Channel = DMA_CHANNEL_4;
    hdma_usart1_rx.Init.Direction = DMA_PERIPH_TO_MEMORY;
    hdma_usart1_rx.Init.PeriphInc = DMA_PINC_DISABLE;
    hdma_usart1_rx.Init.MemInc = DMA_MINC_ENABLE;
    hdma_usart1_rx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
    hdma_usart1_rx.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
    hdma_usart1_rx.Init.Mode = DMA_CIRCULAR;
    hdma_usart1_rx.Init.Priority = DMA_PRIORITY_LOW;
    hdma_usart1_rx.Init.FIFOMode = DMA_FIFOMODE_DISABLE;
    if (HAL_DMA_Init(&hdma_usart1_rx) != HAL_OK)
    {
      Error_Handler();
    }

    __HAL_LINKDMA(huart,hdmarx,hdma_usart1_rx);

    /* Peripheral interrupt init */
    HAL_NVIC_SetPriority(USART1_IRQn, 0, 0);
    HAL_NVIC_EnableIRQ(USART1_IRQn);
  /* USER CODE BEGIN USART1_MspInit 1 */
//    /* Peripheral interrupt init */
//       HAL_NVIC_SetPriority(USART1_IRQn, 0, 0);
//       HAL_NVIC_EnableIRQ(USART1_IRQn);
//     /* USER CODE BEGIN USART1_MspInit 1 */
  /* USER CODE END USART1_MspInit 1 */
  }

}

void HAL_UART_MspDeInit(UART_HandleTypeDef* huart)
{

  if(huart->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   
    PB14     ------> USART1_TX
    PB15     ------> USART1_RX
    */
    HAL_GPIO_DeInit(GPIOB, GPIO_PIN_14|GPIO_PIN_15);

    /* Peripheral DMA DeInit*/
    HAL_DMA_DeInit(huart->hdmarx);

    /* Peripheral interrupt DeInit*/
    HAL_NVIC_DisableIRQ(USART1_IRQn);

  }
  /* USER CODE BEGIN USART1_MspDeInit 1 */

  /* USER CODE END USART1_MspDeInit 1 */

}


peripherals and clock configurations:


void SystemClock_Config(void)
{

  RCC_OscInitTypeDef RCC_OscInitStruct;
  RCC_ClkInitTypeDef RCC_ClkInitStruct;
  RCC_PeriphCLKInitTypeDef PeriphClkInitStruct;

    /**Configure the main internal regulator output voltage
    */
  __HAL_RCC_PWR_CLK_ENABLE();

  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

    /**Initializes the CPU, AHB and APB busses clocks
    */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLM = 8;
  RCC_OscInitStruct.PLL.PLLN = 192;
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
  RCC_OscInitStruct.PLL.PLLQ = 2;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }

    /**Activate the Over-Drive mode
    */
  if (HAL_PWREx_EnableOverDrive() != HAL_OK)
  {
    Error_Handler();
  }

    /**Initializes the CPU, AHB and APB busses 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_DIV4;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV4;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_6) != HAL_OK)
  {
    Error_Handler();
  }

  PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_USART1;
  PeriphClkInitStruct.Usart1ClockSelection = RCC_USART1CLKSOURCE_PCLK2;
  if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) != HAL_OK)
  {
    Error_Handler();
  }

    /**Configure the Systick interrupt time
    */
  HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);

    /**Configure the Systick
    */
  HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);

  /* SysTick_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(SysTick_IRQn, 15, 0);
}

void MX_USART1_UART_Init(void)
{

  huart1.Instance = USART1;
  huart1.Init.BaudRate = 38400;
  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;
  huart1.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
  huart1.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_RXOVERRUNDISABLE_INIT;
  huart1.AdvancedInit.OverrunDisable = UART_ADVFEATURE_OVERRUN_DISABLE;
  if (HAL_UART_Init(&huart1) != HAL_OK)
  {
    Error_Handler();
  }

}

/**
  * Enable DMA controller clock
  */
void MX_DMA_Init(void)
{
  /* DMA controller clock enable */
  __HAL_RCC_DMA2_CLK_ENABLE();

  /* DMA interrupt init */
  /* DMA2_Stream0_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(DMA2_Stream0_IRQn, 5, 0);
  HAL_NVIC_EnableIRQ(DMA2_Stream0_IRQn);
  /* DMA2_Stream2_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(DMA2_Stream2_IRQn, 5, 0);
  HAL_NVIC_EnableIRQ(DMA2_Stream2_IRQn);


}


One more question is for some reason I had to set the baud rate on my UART to 38400 in order to get 19200!! I checked it on oscilloscope and indeed this is the case, any thing alarming in my settings. Thank you all in advance.

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