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How to Reset the DMA receiving buffer

Question asked by Raider E on Jan 23, 2017

I am not dealing with continuous streaming of data, I just send a command to the connected device and wait a reply on the UART using DMA. Now using DMA I can only start seeing data after a while, say 1sec!!. I I liteerally added a hal_delay(1000) before I start processing data. If I use normal reception without DMA it works instantly and dont have to wait!!, but the problem is I am afraid to lose some data if the process was interrupted or something. One more thing, I would like also to reset the DMA buffer after every reception but not sure how to do so and is there a way to check if reception is complete with DMA, (i.e., no more bytes are coming). I am using the HAL library and put DMA in a circular mode.

 

 HAL_UART_Receive_DMA(&huart1, (uint8_t *)&rxbytes, 100);
//   HAL_UART_Receive(huart, (uint8_t *)rxbytes, 32,100);

Uart settings:

/**
  ******************************************************************************
  * File Name          : USART.c
  * Description        : This file provides code for the configuration
  *                      of the USART instances.
  ******************************************************************************
  *
  * Copyright (c) 2017 STMicroelectronics International N.V.
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  * modification, are permitted, provided that the following conditions are met:
  *
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  *    this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright notice,
  *    this list of conditions and the following disclaimer in the documentation
  *    and/or other materials provided with the distribution.
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  *    contributors to this software may be used to endorse or promote products
  *    derived from this software without specific written permission.
  * 4. This software, including modifications and/or derivative works of this
  *    software, must execute solely and exclusively on microcontroller or
  *    microprocessor devices manufactured by or for STMicroelectronics.
  * 5. Redistribution and use of this software other than as permitted under
  *    this license is void and will automatically terminate your rights under
  *    this license.
  *
  * THIS SOFTWARE IS PROVIDED BY STMICROELECTRONICS AND CONTRIBUTORS "AS IS"
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/* Includes ------------------------------------------------------------------*/
#include "usart.h"

#include "gpio.h"
#include "dma.h"

/* USER CODE BEGIN 0 */

/* USER CODE END 0 */

UART_HandleTypeDef huart1;
DMA_HandleTypeDef hdma_usart1_rx;
DMA_HandleTypeDef hdma_usart1_tx;

/* USART1 init function */

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|UART_ADVFEATURE_DMADISABLEONERROR_INIT;
  huart1.AdvancedInit.OverrunDisable = UART_ADVFEATURE_OVERRUN_DISABLE;
  huart1.AdvancedInit.DMADisableonRxError = UART_ADVFEATURE_DMA_DISABLEONRXERROR;
  if (HAL_UART_Init(&huart1) != HAL_OK)
  {
    Error_Handler();
  }

}

void HAL_UART_MspInit(UART_HandleTypeDef* uartHandle)
{

  GPIO_InitTypeDef GPIO_InitStruct;
  if(uartHandle->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_NORMAL;
    hdma_usart1_rx.Init.Priority = DMA_PRIORITY_VERY_HIGH;
    hdma_usart1_rx.Init.FIFOMode = DMA_FIFOMODE_DISABLE;
    if (HAL_DMA_Init(&hdma_usart1_rx) != HAL_OK)
    {
      Error_Handler();
    }

    __HAL_LINKDMA(uartHandle,hdmarx,hdma_usart1_rx);

    hdma_usart1_tx.Instance = DMA2_Stream7;
    hdma_usart1_tx.Init.Channel = DMA_CHANNEL_4;
    hdma_usart1_tx.Init.Direction = DMA_MEMORY_TO_PERIPH;
    hdma_usart1_tx.Init.PeriphInc = DMA_PINC_DISABLE;
    hdma_usart1_tx.Init.MemInc = DMA_MINC_ENABLE;
    hdma_usart1_tx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
    hdma_usart1_tx.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
    hdma_usart1_tx.Init.Mode = DMA_NORMAL;
    hdma_usart1_tx.Init.Priority = DMA_PRIORITY_LOW;
    hdma_usart1_tx.Init.FIFOMode = DMA_FIFOMODE_DISABLE;
    if (HAL_DMA_Init(&hdma_usart1_tx) != HAL_OK)
    {
      Error_Handler();
    }

    __HAL_LINKDMA(uartHandle,hdmatx,hdma_usart1_tx);

    /* Peripheral interrupt init */
    HAL_NVIC_SetPriority(USART1_IRQn, 5, 0);
    HAL_NVIC_EnableIRQ(USART1_IRQn);
  /* 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   
    PB14     ------> USART1_TX
    PB15     ------> USART1_RX
    */
    HAL_GPIO_DeInit(GPIOB, GPIO_PIN_14|GPIO_PIN_15);

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

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

  }
  /* USER CODE BEGIN USART1_MspDeInit 1 */

  /* USER CODE END USART1_MspDeInit 1 */
}

/* USER CODE BEGIN 1 */

/* USER CODE END 1 */

/**
  * @}
  */

/**
  * @}
  */

/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/

thank you.

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