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November 30, 2025
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HAL_DCMI_FrameEventCallback is not called in dcmi snapshot mode

  • November 30, 2025
  • 1 reply
  • 134 views

 

I'm using an ov2640 camera.

When I use HAL_DCMI_Start_DMA(&hdcmi, DCMI_MODE_CONTINUOUS, (uint32_t)camBuf0, (CAM_W * CAM_H) / 2);, HAL_DCMI_FrameEventCallback is called,

but when I use HAL_DCMI_Start_DMA(&hdcmi, DCMI_MODE_SNAPSHOT, (uint32_t)camBuf0, (CAM_W * CAM_H) / 2);, HAL_DCMI_FrameEventCallback is never called. Why is this happening? Below are the relevant settings.

I'm using an STM32H743 MCU.

 

static void MX_DCMI_Init(void)
{

 /* USER CODE BEGIN DCMI_Init 0 */

 /* USER CODE END DCMI_Init 0 */

 /* USER CODE BEGIN DCMI_Init 1 */

 /* USER CODE END DCMI_Init 1 */
 hdcmi.Instance = DCMI;
 hdcmi.Init.SynchroMode = DCMI_SYNCHRO_HARDWARE;
 hdcmi.Init.PCKPolarity = DCMI_PCKPOLARITY_RISING;
 hdcmi.Init.VSPolarity = DCMI_VSPOLARITY_LOW;
 hdcmi.Init.HSPolarity = DCMI_HSPOLARITY_LOW;
 hdcmi.Init.CaptureRate = DCMI_CR_ALL_FRAME;
 hdcmi.Init.ExtendedDataMode = DCMI_EXTEND_DATA_8B;
 hdcmi.Init.JPEGMode = DCMI_JPEG_DISABLE;
 hdcmi.Init.ByteSelectMode = DCMI_BSM_ALL;
 hdcmi.Init.ByteSelectStart = DCMI_OEBS_ODD;
 hdcmi.Init.LineSelectMode = DCMI_LSM_ALL;
 hdcmi.Init.LineSelectStart = DCMI_OELS_ODD;
 if (HAL_DCMI_Init(&hdcmi) != HAL_OK)
 {
 Error_Handler();
 }
 /* USER CODE BEGIN DCMI_Init 2 */

 /* USER CODE END DCMI_Init 2 */

}

void HAL_DCMI_MspInit(DCMI_HandleTypeDef* hdcmi)
{
 GPIO_InitTypeDef GPIO_InitStruct = {0};
 if(hdcmi->Instance==DCMI)
 {
 /* USER CODE BEGIN DCMI_MspInit 0 */

 /* USER CODE END DCMI_MspInit 0 */
 /* Peripheral clock enable */
 __HAL_RCC_DCMI_CLK_ENABLE();

 __HAL_RCC_GPIOE_CLK_ENABLE();
 __HAL_RCC_GPIOA_CLK_ENABLE();
 __HAL_RCC_GPIOC_CLK_ENABLE();
 __HAL_RCC_GPIOD_CLK_ENABLE();
 __HAL_RCC_GPIOG_CLK_ENABLE();
 __HAL_RCC_GPIOB_CLK_ENABLE();
 /**DCMI GPIO Configuration
 PE4 ------> DCMI_D4
 PE5 ------> DCMI_D6
 PE6 ------> DCMI_D7
 PA4 ------> DCMI_HSYNC
 PA6 ------> DCMI_PIXCLK
 PC6 ------> DCMI_D0
 PC7 ------> DCMI_D1
 PD3 ------> DCMI_D5
 PG10 ------> DCMI_D2
 PG11 ------> DCMI_D3
 PB7 ------> DCMI_VSYNC
 */
 GPIO_InitStruct.Pin = GPIO_PIN_4|GPIO_PIN_5|GPIO_PIN_6;
 GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
 GPIO_InitStruct.Pull = GPIO_PULLUP;
 GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
 GPIO_InitStruct.Alternate = GPIO_AF13_DCMI;
 HAL_GPIO_Init(GPIOE, &GPIO_InitStruct);

 GPIO_InitStruct.Pin = GPIO_PIN_4|GPIO_PIN_6;
 GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
 GPIO_InitStruct.Pull = GPIO_PULLUP;
 GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
 GPIO_InitStruct.Alternate = GPIO_AF13_DCMI;
 HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

 GPIO_InitStruct.Pin = GPIO_PIN_6|GPIO_PIN_7;
 GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
 GPIO_InitStruct.Pull = GPIO_PULLUP;
 GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
 GPIO_InitStruct.Alternate = GPIO_AF13_DCMI;
 HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);

 GPIO_InitStruct.Pin = GPIO_PIN_3;
 GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
 GPIO_InitStruct.Pull = GPIO_PULLUP;
 GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
 GPIO_InitStruct.Alternate = GPIO_AF13_DCMI;
 HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);

 GPIO_InitStruct.Pin = GPIO_PIN_10|GPIO_PIN_11;
 GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
 GPIO_InitStruct.Pull = GPIO_PULLUP;
 GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
 GPIO_InitStruct.Alternate = GPIO_AF13_DCMI;
 HAL_GPIO_Init(GPIOG, &GPIO_InitStruct);

 GPIO_InitStruct.Pin = GPIO_PIN_7;
 GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
 GPIO_InitStruct.Pull = GPIO_PULLUP;
 GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
 GPIO_InitStruct.Alternate = GPIO_AF13_DCMI;
 HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

 /* DCMI DMA Init */
 /* DCMI Init */
 hdma_dcmi.Instance = DMA1_Stream1;
 hdma_dcmi.Init.Request = DMA_REQUEST_DCMI;
 hdma_dcmi.Init.Direction = DMA_PERIPH_TO_MEMORY;
 hdma_dcmi.Init.PeriphInc = DMA_PINC_DISABLE;
 hdma_dcmi.Init.MemInc = DMA_MINC_ENABLE;
 hdma_dcmi.Init.PeriphDataAlignment = DMA_PDATAALIGN_WORD;
 hdma_dcmi.Init.MemDataAlignment = DMA_MDATAALIGN_WORD;
 hdma_dcmi.Init.Mode = DMA_CIRCULAR;
 hdma_dcmi.Init.Priority = DMA_PRIORITY_VERY_HIGH;
 hdma_dcmi.Init.FIFOMode = DMA_FIFOMODE_ENABLE;
 hdma_dcmi.Init.FIFOThreshold = DMA_FIFO_THRESHOLD_FULL;
 hdma_dcmi.Init.MemBurst = DMA_MBURST_SINGLE;
 hdma_dcmi.Init.PeriphBurst = DMA_PBURST_SINGLE;
 if (HAL_DMA_Init(&hdma_dcmi) != HAL_OK)
 {
 Error_Handler();
 }

 __HAL_LINKDMA(hdcmi,DMA_Handle,hdma_dcmi);

 /* DCMI interrupt Init */
 HAL_NVIC_SetPriority(DCMI_IRQn, 0, 0);
 HAL_NVIC_EnableIRQ(DCMI_IRQn);
 /* USER CODE BEGIN DCMI_MspInit 1 */

 /* USER CODE END DCMI_MspInit 1 */

 }

}

 

 

    This topic has been closed for replies.
    Best answer by Saket_Om

    Hello @eunoia 

    DMA should not be set to DMA_CIRCULAR for DCMI_MODE_SNAPSHOT.

    1 reply

    Saket_OmAnswer
    Technical Moderator
    December 2, 2025

    Hello @eunoia 

    DMA should not be set to DMA_CIRCULAR for DCMI_MODE_SNAPSHOT.