STM32H7 Workaround for DMA data transfer > SPI fifo-buffer

HansPLJ · ‎2025-01-13

Hi!

I am working on a project where we are using DMA driven SPI-transmissions. I am using LPTIM1 to synchronize readouts of multiple SPI busses.

The setup works when the transmissions is equal or below 128 bits (for SPI1-SPI3).

When HAL_DMA_MuxSyncConfigTypeDef.RequestNumber is above 4 (at DMA_PDATAALIGN_WORD and DMA_MDATAALIGN_WORD) it will not work.

From what I can understand this is due to the size of the fifo registers of the SPI-peripheral.

Is there a workaround for this?

This is my current setup:

DMA_InitTypeDef txDMAinit;
DMA_InitTypeDef rxDMAinit;

spiHandle.Init.Mode = SPI_MODE_MASTER;
spiHandle.Init.Direction = SPI_DIRECTION_2LINES;
spiHandle.Init.DataSize = SPI_DATASIZE_32BIT;
spiHandle.Init.CLKPolarity = SPI_POLARITY_LOW;
spiHandle.Init.CLKPhase = SPI_PHASE_1EDGE;
spiHandle.Init.NSS = SPI_NSS_HARD_OUTPUT;
spiHandle.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_16;
spiHandle.Init.FirstBit = SPI_FIRSTBIT_MSB;
spiHandle.Init.TIMode = SPI_TIMODE_DISABLE;
spiHandle.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
spiHandle.Init.CRCPolynomial = 0x0;
spiHandle.Init.NSSPMode = SPI_NSS_PULSE_ENABLE;
spiHandle.Init.NSSPolarity = SPI_NSS_POLARITY_LOW;
spiHandle.Init.FifoThreshold = SPI_FIFO_THRESHOLD_01DATA;
spiHandle.Init.TxCRCInitializationPattern = SPI_CRC_INITIALIZATION_ALL_ZERO_PATTERN;
spiHandle.Init.RxCRCInitializationPattern = SPI_CRC_INITIALIZATION_ALL_ZERO_PATTERN;
spiHandle.Init.MasterSSIdleness = SPI_MASTER_SS_IDLENESS_04CYCLE;
spiHandle.Init.MasterInterDataIdleness = SPI_MASTER_INTERDATA_IDLENESS_00CYCLE;
spiHandle.Init.MasterReceiverAutoSusp = SPI_MASTER_RX_AUTOSUSP_DISABLE;
spiHandle.Init.MasterKeepIOState = SPI_MASTER_KEEP_IO_STATE_DISABLE;
spiHandle.Init.IOSwap = SPI_IO_SWAP_DISABLE;

if(HAL_SPI_Init(&m_spiHandle)!= HAL_OK)
{
return StatusCode::STATUS_ERROR;
}

txDMAinit.Direction = DMA_MEMORY_TO_PERIPH;
txDMAinit.PeriphInc = DMA_PINC_DISABLE;
txDMAinit.MemInc = DMA_MINC_ENABLE;
txDMAinit.PeriphDataAlignment = DMA_PDATAALIGN_WORD;
txDMAinit.MemDataAlignment = DMA_MDATAALIGN_WORD;
txDMAinit.Mode = DMA_CIRCULAR;
txDMAinit.Priority = DMA_PRIORITY_MEDIUM;
txDMAinit.FIFOMode = DMA_FIFOMODE_ENABLE;
txDMAinit.FIFOThreshold = DMA_FIFO_THRESHOLD_1QUARTERFULL;

rxDMAinit.Direction = DMA_PERIPH_TO_MEMORY;
rxDMAinit.PeriphInc = DMA_PINC_DISABLE;
rxDMAinit.MemInc = DMA_MINC_ENABLE;
rxDMAinit.PeriphDataAlignment = DMA_PDATAALIGN_WORD;
rxDMAinit.MemDataAlignment = DMA_MDATAALIGN_WORD;
rxDMAinit.Mode = DMA_CIRCULAR;
rxDMAinit.Priority = DMA_PRIORITY_MEDIUM;
rxDMAinit.FIFOMode = DMA_FIFOMODE_ENABLE;
rxDMAinit.FIFOThreshold = DMA_FIFO_THRESHOLD_1QUARTERFULL;

pSyncConfig.SyncSignalID = HAL_DMAMUX1_SYNC_LPTIM1_OUT;
pSyncConfig.SyncPolarity = HAL_DMAMUX_SYNC_FALLING;
pSyncConfig.SyncEnable = ENABLE;
pSyncConfig.EventEnable = DISABLE;
pSyncConfig.RequestNumber = 8;

hdma_spi1_tx.Instance = DMA1_Stream4;
hdma_spi1_tx.Init = txDMAinit;
hdma_spi1_tx.Init.Request = DMA_REQUEST_SPI1_TX;

HAL_DMA_Init(&hdma_spi1_tx);

if((HAL_DMAEx_ConfigMuxSync(&hdma_spi1_tx, &pSyncConfig)) != HAL_OK)
{
return StatusCode::STATUS_ERROR;
}

__HAL_LINKDMA(&m_spiHandle,hdmatx,hdma_spi1_tx);

hdma_spi1_rx.Instance = DMA1_Stream1;
hdma_spi1_rx.Init = rxDMAinit;
hdma_spi1_rx.Init.Request = DMA_REQUEST_SPI1_RX;

HAL_DMA_Init(&hdma_spi1_rx);

if((HAL_DMAEx_ConfigMuxSync(&hdma_spi1_rx, &pSyncConfig)) != HAL_OK)
{
return StatusCode::STATUS_ERROR;
}

__HAL_LINKDMA(&m_spiHandle,hdmarx,hdma_spi1_rx);

It only works for pSyncConfig.RequestNumber <= 4.

Any suggestions for a workaround would be appreciated!

Best regards,

Hans-Petter

waclawek.jan · ‎2025-01-13

> it will not work

Elaborate.

JW

SofLit · ‎2025-01-13

@HansPLJ please use </> button to paste a code. See this post. I've edited your post

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.
PS: Be polite in your reply. Otherwise, it will be reported as inappropriate and you will be permanently blacklisted from my help/support.

HansPLJ · ‎2025-01-13

Thanks for your reply! I will try to elaborate

When Im using pSyncConfig.RequestNumber = 4, I am getting the expected behavior. At the current stage I am looping back MOSI to MISO and I am reading what I am sending. This is happening at the rate of LPTIM sync event at 16 kHz.

After setting up the SPI, DMA and LPTIM I am using this function:

#define SIZE_BUFFER       96
uint32_t __attribute__((section (".axi_sram1"))) RxBuff[SIZE_BUFFER];
uint32_t __attribute__((section (".axi_sram1"))) TxBuff[SIZE_BUFFER];

HAL_SPI_TransmitReceive_DMA(&hal.spi1.getHandle(), (uint8_t*)TxBuff, (uint8_t*)RxBuff, (uint16_t)SIZE_BUFFER);
HAL_LPTIM_PWM_Start(&hal.lptim1.getHandle(), LPTIM1_PERIODS, LPTIM1_PULSE_PERIODS);

From oscilloscope: