SPI GPIOs don't work (except SCK) using DMA

[simo zz]

Hi, 

I am using an STM32H7RSxx device and I need to use the SPI6 (both full and half duplex) with the DMA.

The problem I am facing on is the MOSI pin doesn't transmit anything.Only the SCK is working.

Despite having configured it for SPI6 Alternate Function (according to datasheet)

  // SPI6 pins
  // SCLK, MISO, MISO, NSS
  GPIO_InitStruct.Pin = LL_GPIO_PIN_4 | LL_GPIO_PIN_5 | LL_GPIO_PIN_6 | LL_GPIO_PIN_7;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_ALTERNATE;
  GPIO_InitStruct.Speed = LL_GPIO_SPEED_FREQ_VERY_HIGH;
  GPIO_InitStruct.OutputType = LL_GPIO_OUTPUT_PUSHPULL;
  GPIO_InitStruct.Pull = LL_GPIO_PULL_UP;
  GPIO_InitStruct.Alternate = LL_GPIO_AF_8;
  LL_GPIO_Init(GPIOA, &GPIO_InitStruct);

it always stays to low level.

What is strange is the fact that if I use PB5 as SPI6 MOSI 

I can see as the pin stays at high level in idle state, but low for the rest of transmission, and this is quiet confusing.

If I am not blind at all, the TRM and datasheet does not say anything about it..

Of course the DMA transmission buffer is not zero.

I have read on another post that the order of initialization can matter, but honestly, I could not figure out the solution.

I attached a small working example of what I am doing, I hope I will receive some hint.

Thanks,

s.

[TDK]

Almost certainly a cache problem. Try disabling data cache while you are debugging.

The posted code doesn't seem to use SPI at all.

[simo zz]

Hello @TDK. 

Thanks, interesting the cache hint. I will try as soon as possible.

The SPI DMA transfer is triggered from EXTI13_IRQHandler() in stm32h7rsxx_it.c.

As a push button handling is quiet horrible without a timer de-bounce delay but does the job for testing purpose only.

s.