STM32H5 GPDMA software controlled double buffering

[pollkky]

Hello,

im in the process of trying to make a LED Matrix driver with the gpdma on my stm32h562. Currently, I have everything working with one buffer, but want to implement double buffering so i can fill one buffer with data, and read from the other.

I was looking around on the internet on how to implement this, but i found only one thread with the same problem, but i cant figure out how to implement the solution into my project, as there is no LLIx.nextLLI definition anywhere. Im using CubeMx to generate me code.
 

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * File Name          : linked_list.c
  * Description        : This file provides code for the configuration
  *                      of the LinkedList.
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2026 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 "linked_list.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "main.h"
#include "Colours.h"
#include "Buffers.h"
#include "Fonts.h"
/* USER CODE END Includes */

DMA_NodeTypeDef RGB_transfer1;
DMA_QListTypeDef RGB_queue;
DMA_NodeTypeDef RGB_transfer2;
DMA_NodeTypeDef ACTrans;
DMA_QListTypeDef ACtransQ;

/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */

extern uint32_t BsrrBuf1[BsrrBufXsize * BsrrBufYsize];
extern uint32_t BsrrBuf2[BsrrBufXsize * BsrrBufYsize];



uint32_t ACtransferLUT[] = {
		(1U << (4 + 16))	| (1U << (3 + 16)) 	| (1U << (2 + 16)) 	| (1U << (1 + 16)),
		(1U << (4)) 		| (1U << (3 + 16)) 	| (1U << (2 + 16)) 	| (1U << (1 + 16)),
		(1U << (4 + 16)) 	| (1U << (3)) 		| (1U << (2 + 16)) 	| (1U << (1 + 16)),
		(1U << (4)) 		| (1U << (3)) 		| (1U << (2 + 16)) 	| (1U << (1 + 16)),
		(1U << (4 + 16)) 	| (1U << (3 + 16)) 	| (1U << (2)) 		| (1U << (1 + 16)),
		(1U << (4)) 		| (1U << (3 + 16)) 	| (1U << (2)) 		| (1U << (1 + 16)),
		(1U << (4 + 16)) 	| (1U << (3)) 		| (1U << (2)) 		| (1U << (1 + 16)),
		(1U << (4)) 		| (1U << (3)) 		| (1U << (2)) 		| (1U << (1 + 16)),
		(1U << (4 + 16)) 	| (1U << (3 + 16)) 	| (1U << (2 + 16)) 	| (1U << (1)),
		(1U << (4)) 		| (1U << (3 + 16)) 	| (1U << (2 + 16)) 	| (1U << (1)),
		(1U << (4 + 16)) 	| (1U << (3)) 		| (1U << (2 + 16)) 	| (1U << (1)),
		(1U << (4)) 		| (1U << (3)) 		| (1U << (2 + 16)) 	| (1U << (1)),
		(1U << (4 + 16)) 	| (1U << (3 + 16)) 	| (1U << (2)) 		| (1U << (1)),
		(1U << (4)) 		| (1U << (3 + 16)) 	| (1U << (2)) 		| (1U << (1)),
		(1U << (4 + 16)) 	| (1U << (3)) 		| (1U << (2)) 		| (1U << (1)),
		(1U << (4)) 		| (1U << (3)) 		| (1U << (2)) 		| (1U << (1))
};

/* USER CODE END PTD */

/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */

/* USER CODE END PD */

/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */

/* USER CODE END PM */

/**
  * @brief  DMA Linked-list RGB_queue configuration
  * @param  None
  * @retval None
  */
HAL_StatusTypeDef MX_RGB_queue_Config(void)
{
  HAL_StatusTypeDef ret = HAL_OK;
  /* DMA node configuration declaration */
  DMA_NodeConfTypeDef pNodeConfig;

  /* Set node configuration ################################################*/
  pNodeConfig.NodeType = DMA_GPDMA_LINEAR_NODE;
  pNodeConfig.Init.Request = DMA_REQUEST_SW;
  pNodeConfig.Init.BlkHWRequest = DMA_BREQ_SINGLE_BURST;
  pNodeConfig.Init.Direction = DMA_MEMORY_TO_MEMORY;
  pNodeConfig.Init.SrcInc = DMA_SINC_INCREMENTED;
  pNodeConfig.Init.DestInc = DMA_DINC_FIXED;
  pNodeConfig.Init.SrcDataWidth = DMA_SRC_DATAWIDTH_WORD;
  pNodeConfig.Init.DestDataWidth = DMA_DEST_DATAWIDTH_WORD;
  pNodeConfig.Init.SrcBurstLength = 1;
  pNodeConfig.Init.DestBurstLength = 1;
  pNodeConfig.Init.TransferAllocatedPort = DMA_SRC_ALLOCATED_PORT0|DMA_DEST_ALLOCATED_PORT0;
  pNodeConfig.Init.TransferEventMode = DMA_TCEM_BLOCK_TRANSFER;
  pNodeConfig.Init.Mode = DMA_NORMAL;
  pNodeConfig.TriggerConfig.TriggerMode = DMA_TRIGM_SINGLE_BURST_TRANSFER ;
  pNodeConfig.TriggerConfig.TriggerPolarity = DMA_TRIG_POLARITY_RISING;
  pNodeConfig.TriggerConfig.TriggerSelection = GPDMA2_TRIGGER_TIM12_TRGO;
  pNodeConfig.DataHandlingConfig.DataExchange = DMA_EXCHANGE_NONE;
  pNodeConfig.DataHandlingConfig.DataAlignment = DMA_DATA_RIGHTALIGN_ZEROPADDED;
  pNodeConfig.SrcAddress = (uint32_t)&BsrrBuf1[0];
  pNodeConfig.DstAddress = ((uint32_t)&(GPIOC->BSRR));
  pNodeConfig.DataSize = 16384U;

  /* Build RGB_transfer1 Node */
  ret |= HAL_DMAEx_List_BuildNode(&pNodeConfig, &RGB_transfer1);

  /* Insert RGB_transfer1 to Queue */
  ret |= HAL_DMAEx_List_InsertNode_Tail(&RGB_queue, &RGB_transfer1);

  /* Set node configuration ################################################*/
  pNodeConfig.SrcAddress = (uint32_t)&BsrrBuf2[0];

  /* Build RGB_transfer2 Node */
  ret |= HAL_DMAEx_List_BuildNode(&pNodeConfig, &RGB_transfer2);

  /* Insert RGB_transfer2 to Queue */
  ret |= HAL_DMAEx_List_InsertNode_Tail(&RGB_queue, &RGB_transfer2);

  ret |= HAL_DMAEx_List_SetCircularModeConfig(&RGB_queue, &RGB_transfer1);

   return ret;
}

/**
  * @brief  DMA Linked-list ACtransQ configuration
  * @param  None
  * @retval None
  */
HAL_StatusTypeDef MX_ACtransQ_Config(void)
{
  HAL_StatusTypeDef ret = HAL_OK;
  /* DMA node configuration declaration */
  DMA_NodeConfTypeDef pNodeConfig;

  /* Set node configuration ################################################*/
  pNodeConfig.NodeType = DMA_GPDMA_LINEAR_NODE;
  pNodeConfig.Init.Request = DMA_REQUEST_SW;
  pNodeConfig.Init.BlkHWRequest = DMA_BREQ_SINGLE_BURST;
  pNodeConfig.Init.Direction = DMA_MEMORY_TO_MEMORY;
  pNodeConfig.Init.SrcInc = DMA_SINC_INCREMENTED;
  pNodeConfig.Init.DestInc = DMA_DINC_FIXED;
  pNodeConfig.Init.SrcDataWidth = DMA_SRC_DATAWIDTH_WORD;
  pNodeConfig.Init.DestDataWidth = DMA_DEST_DATAWIDTH_WORD;
  pNodeConfig.Init.SrcBurstLength = 1;
  pNodeConfig.Init.DestBurstLength = 1;
  pNodeConfig.Init.TransferAllocatedPort = DMA_SRC_ALLOCATED_PORT0|DMA_DEST_ALLOCATED_PORT0;
  pNodeConfig.Init.TransferEventMode = DMA_TCEM_BLOCK_TRANSFER;
  pNodeConfig.Init.Mode = DMA_NORMAL;
  pNodeConfig.TriggerConfig.TriggerMode = DMA_TRIGM_SINGLE_BURST_TRANSFER ;
  pNodeConfig.TriggerConfig.TriggerPolarity = DMA_TRIG_POLARITY_RISING;
  pNodeConfig.TriggerConfig.TriggerSelection = GPDMA1_TRIGGER_TIM2_TRGO;
  pNodeConfig.DataHandlingConfig.DataExchange = DMA_EXCHANGE_NONE;
  pNodeConfig.DataHandlingConfig.DataAlignment = DMA_DATA_RIGHTALIGN_ZEROPADDED;
  pNodeConfig.SrcAddress = (uint32_t)&ACtransferLUT[0];
  pNodeConfig.DstAddress = ((uint32_t)&(GPIOB->BSRR));
  pNodeConfig.DataSize = 64U;

  /* Build ACTrans Node */
  ret |= HAL_DMAEx_List_BuildNode(&pNodeConfig, &ACTrans);

  /* Insert ACTrans to Queue */
  ret |= HAL_DMAEx_List_InsertNode_Tail(&ACtransQ, &ACTrans);

  ret |= HAL_DMAEx_List_SetCircularMode(&ACtransQ);

   return ret;
}

 

[Khaled_DHIF]

Hello ​@pollkky ,

Your linked-list setup already alternates between BsrrBuf1 and BsrrBuf2. What is still needed is a completion callback to know which buffer DMA has just finished, so the CPU can refill the other one.

 

volatile uint8_t rgb_active_buf = 0;   // For example: 0 = BsrrBuf1, 1 = BsrrBuf2


void HAL_DMA_TransferCompleteCallback(DMA_HandleTypeDef *hdma)
{
    if (hdma == &hdma_gpdma1_channelX)   // replace with your handle
    {
        rgb_active_buf ^= 1U;            // switch to the other buffer
    }
}


// Then, whenever you prepare new LED data:


if (rgb_active_buf == 0)
{
    // DMA is using BsrrBuf1, so CPU may fill BsrrBuf2
}
else
{
    // DMA is using BsrrBuf2, so CPU may fill BsrrBuf1
}

kind regards, 

DHIF Khaled