Trigger SPI6 DMA transfer using external pin via DMAMUX

[gotthard]

 

Hello,

I'm working with the STM32H723 and need to interface with an external ADC that provides a DRDY (PG2 pin) signal. I'd like to initiate an SPI transfer via DMA whenever the DRDY pin goes low. The ADC is connected to SPI6, and I understand that only BDMA can be used with this peripheral.

My main question is:
How can I configure DMAMUX to trigger a BDMA transfer for SPI6 when the DRDY pin goes low?

I'm using STM32CubeMX for configuration. I’ve looked through existing forum posts and the STM documentation, but haven’t found a clear example or explanation for this setup. Any guidance, examples, or tips to get started would be greatly appreciated.

Thanks in advance!

[waclawek.jan]

According to DMAMUX2 and BDMA connections table in RM0468, exti_syscfg_exti2 is an input to the DMAMUX generator, as dmamux2_gen21, so this should be doable by selecting PG2 in the EXTI2 selector in SYSCFG and setting up DMA generation in DMAMUX2. I don't use Cube, so can't help with that; but I'd assume there's some clicking related to these facts in CubeMX. Maybe somebody versed in CubeMX will chime in with the details.

I presume you already know how to set up SPI with DMA - I do not know that, SPI in 'H7 is an overcomplicated beast and I don't use the 'H7.

JW

 

[gotthard]

My configuration is as follows:

 

/* Local variables */
HAL_DMA_MuxRequestGeneratorConfigTypeDef pRequestGeneratorConfig = { 0 };

/* DMA controller clock enable */
__HAL_RCC_BDMA_CLK_ENABLE();

/* Configure DMA request hdma_bdma_generator0 on BDMA_Channel1 */
hdma_bdma_generator0.Instance = BDMA_Channel1;
hdma_bdma_generator0.Init.Request = BDMA_REQUEST_GENERATOR0;
hdma_bdma_generator0.Init.Direction = DMA_MEMORY_TO_PERIPH;
hdma_bdma_generator0.Init.PeriphInc = DMA_PINC_DISABLE;
hdma_bdma_generator0.Init.MemInc = DMA_MINC_ENABLE;
hdma_bdma_generator0.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
hdma_bdma_generator0.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
hdma_bdma_generator0.Init.Mode = DMA_NORMAL;
hdma_bdma_generator0.Init.Priority = DMA_PRIORITY_LOW;
if (HAL_DMA_Init(&hdma_bdma_generator0) != HAL_OK) {
Error_Handler();
}

/* Configure the DMAMUX request generator for the selected BDMA channel */
pRequestGeneratorConfig.SignalID = HAL_DMAMUX2_REQ_GEN_EXTI2;
pRequestGeneratorConfig.Polarity = HAL_DMAMUX_REQ_GEN_FALLING;
pRequestGeneratorConfig.RequestNumber = 1;
if (HAL_DMAEx_ConfigMuxRequestGenerator(&hdma_bdma_generator0,
&pRequestGeneratorConfig) != HAL_OK) {
Error_Handler();
}

hdma_spi6_tx.Instance = BDMA_Channel0;
hdma_spi6_tx.Init.Request = BDMA_REQUEST_SPI6_TX;
hdma_spi6_tx.Init.Direction = DMA_MEMORY_TO_PERIPH;
hdma_spi6_tx.Init.PeriphInc = DMA_PINC_DISABLE;
hdma_spi6_tx.Init.MemInc = DMA_MINC_ENABLE;
hdma_spi6_tx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
hdma_spi6_tx.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
hdma_spi6_tx.Init.Mode = DMA_NORMAL;
hdma_spi6_tx.Init.Priority = DMA_PRIORITY_HIGH;

HAL_DMA_Init(&hdma_spi6_tx);
__HAL_LINKDMA(&hspi6, hdmatx, hdma_spi6_tx);

MX_SPI6_Init();

HAL_DMAEx_EnableMuxRequestGenerator(&hdma_bdma_generator0);
HAL_SPI_Transmit_DMA(&hspi6, dmaBuffer, 10);

 

My SPI width is configured to 8 bits and I would like to transmit 10x8 bits. When request generator is enabled I see that only 8 bits are transferred when EXTI2 pin goes low and this happens 10 times and then it stops. 

How to achieve 10x8 bits in a single transfer when EXTI2 is low? Also, I would like to point out that my chip select is constantly tied low. 

 

[waclawek.jan]

I don't use Cube/HAL, but I'd guess here

pRequestGeneratorConfig.RequestNumber = 1;

you have to set 10.

JW

[gotthard]

Unfortunately, it did not work. Only 8 bits were transferred. 

[waclawek.jan]

Read out and check/post content of relevant DMA and DMAMUX registers.

> hdma_bdma_generator0.Instance = BDMA_Channel1;

> hdma_spi6_tx.Instance = BDMA_Channel0;

As I've said, I don't use Cube, but how do these things add up?

JW