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STM32H7 triggering a SPI TX transmission via DMA with a synch event on EXTI0

Associate II

Hi All,

Looking at the STM32H7 Ref manual it seems the DMAMUX would allow for a DMA channel to be synchronized with an external event on the EXTI0 input.

I would like to use this capability to trigger an SPI transmission to an ADC (since this would allow me to avoid time consuming tasks in the ISR routines )

I figured I would be able to configure the SPI2 TX in DMA mode and enable the DMA request synchronization settings so I have the following configuration.

SPI2 TX is assigned to DMA1 Stream 0. and the DMA Request synchronization settings are setup for

Enable Synchronization

Synchronization signal EXTI0

SignalPolarity: Synchronize on falling edge

Request Number: 1

The SPI initialization is as follows

hdma_spi2_tx.Instance = DMA1_Stream0;
    hdma_spi2_tx.Init.Request = DMA_REQUEST_SPI2_TX;
    hdma_spi2_tx.Init.Direction = DMA_MEMORY_TO_PERIPH;
    hdma_spi2_tx.Init.PeriphInc = DMA_PINC_DISABLE;
    hdma_spi2_tx.Init.MemInc = DMA_MINC_DISABLE;
    hdma_spi2_tx.Init.PeriphDataAlignment = DMA_PDATAALIGN_HALFWORD;
    hdma_spi2_tx.Init.MemDataAlignment = DMA_MDATAALIGN_HALFWORD;
    hdma_spi2_tx.Init.Mode = DMA_CIRCULAR; //DMA_NORMAL;
    hdma_spi2_tx.Init.Priority = DMA_PRIORITY_MEDIUM;
    hdma_spi2_tx.Init.FIFOMode = DMA_FIFOMODE_DISABLE;
    if (HAL_DMA_Init(&hdma_spi2_tx) != HAL_OK)
    pSyncConfig.SyncSignalID = HAL_DMAMUX1_SYNC_EXTI0;
    pSyncConfig.SyncPolarity = HAL_DMAMUX_SYNC_FALLING;
    pSyncConfig.SyncEnable = ENABLE;
    pSyncConfig.EventEnable = DISABLE;
    pSyncConfig.RequestNumber = 1;
    if (HAL_DMAEx_ConfigMuxSync(&hdma_spi2_tx, &pSyncConfig) != HAL_OK)

The EXTI input is configured as follows

GPIO_InitStruct.Pin = SPI2_EXTI_SYNC_Pin;

The EXTI input is PA0 and it is driven via a PWM signal from the High resolution timer output pin connected to PA0.

I have verified that I am getting a pulse every 1 us on the EXTI input - however the SPI DMA TX is not being triggered.

Any thoughts on if this is an appropriate way to achieve the desired outcome or am I missing something?



Associate II

Would it be possible your share you basic code for DMAMUX SPI transfer. I am having issues using DMAMUX1 to work with LPTIM1 output to do an SP transfer.