STM32G441 SPI1 transmit with DMA1 and DMAMUX cannot get it to transmit

[Nickelgrass]

I am trying to send some bytes over an SPI via DMA on bare metal STM32G441. But there is nothing being sent and I cant find why. I only used DMA on ST32F devices that do not have the DMAMUX. Please note that SCK and MISO are not used here. I looked at a generated code from CubeIDE which does not seem to do anything else. I expected the SPI to send 1000 bytes.

Here is my code. The comment shows what is happening in each line as I am not using CMSIS. The bit definitions are corresponding to the bits: bit5 = (1<<5) for example. 

 

 

 

 

volatile uint8_t buf[1000] = {0b11001000};

// initialize
RCC->AHB1ENR |= bit0|bit2;		// enable DMA1 and DMAMUX clocks
RCC->AHB2ENR |= bit0; // enable GPIOA clock
RCC->APB2ENR |= bit12; // enable SPI1 clock

GPIOA->MODER &= ~(0b11<<14);
GPIOA->MODER |= (0b10<<14); // PA7 alternate function
GPIOA->AFRL |= (5<<28); // PA7 SPI1 MOSI
GPIOA->OSPEEDR |= (0b11<<14); // MOSI speed high

DMA1_Channel1->CCR = 0; // disable DMA
DMA1_Channel1->CPAR = (uint32_t)&SPI1->DR; // peripheral SPI1
DMA1_Channel1->CMAR = (uint32_t)&buf; // memory array
DMA1_Channel1->CCR |= (bit4|bit7|(0b11<<12)); // memory to peripheral, memory increment, very high priority

DMAMUX1_Channel0->CCR = 11; // DMAMUX SPI1TX

SPI1->CR1 |= (bit2|(0b100<<3)|bit8|bit9|bit14); // SPI1 master, f/32, SSI, SSM, bidirectional mode
SPI1->CR2 |= bit1; // SPITX DMA enable

// send bytes
SPI1->CR1 &= ~bit6; // SPI1 disable
DMA1_Channel1->CCR &= ~bit0;	// disable DMA
DMA1_Channel1->CNDTR = 1000; // reload amount
DMA1_Channel1->CCR |= bit0; // DMA1 enable
SPI1->CR1 |= bit6; // SPI1 enable

 

 

 

 

How can I trigger the DMA? The SPI on its own works fine. Am thankfull for any tip.

[TDK]

DMA1_Channel1->CCR |= (bit4|bit7|(0b11<<12)); // memory to peripheral, memory increment, very high priority

DMAMUX1_Channel0->CCR = 11; // DMAMUX SPI1TX

SPI1->CR1 |= (bit2|(0b100<<3)|bit8|bit9|bit14); // SPI1 master, f/32
SPI1->CR2 |= bit1;

// send bytes
SPI1->CR1 &= ~bit6; // SPI1 disable
DMA1_Channel1->CCR = 0; // disable DMA

The second write to CCR undoes everything you wrote to it up above, so it's no longer configured. Probably you wanted to clear bit 0 (which was already off anyway), not all of them.

Using standard CMSIS header defines will make your code a lot easier to read and debug.

 

[Nickelgrass]

Thanks for the answer. Corrected the second write but still no output. Does the DMAMUX have to be triggerd somehow differently?

[TDK]

No, just what you have should work. Might want to recheck all your bits. Might want to look at the register values/field in a debugger to verify they look correct. This is where the CMSIS definitions would be helpful.

[waclawek.jan]

> there is nothing being sent

How do you know?

Polled (nonDMA) operation works?

Read our and check/post content of SPI, DMAMUX, DMA and relevant GPIO registers, just before enabling transmission, and also after it.

JW

[Nickelgrass]

Thanks for the reply. I looked with a logicanalyzer. Sending without DMA works. With DMA nothing is transmitted. 

I will check the contents of the registers if they are what they should be. 

[TDK]

Could also be that your buffer is not accessible by DMA, but again, looking at register flags would indicate an error.

[Nickelgrass]

Thanks everyone for the replies. It turns out the problem seems to have been the datawidth set in the DMA. I set it to 16 bit both and now it works. Its just a minor adjustment to use 16 instead of 8 bits. So all fine now. 

[waclawek.jan]

I don't think this is it. While the FIFO and data packing makes SPI a bit more complex than in the older STM32 and the description in RM is far from being clean and concise, I can find nothing which would justify 8-bit PSIZE in DMA not to work with SPI set to 8-bit. IMO you've inadvertently changed also something else which made it working.

JW

 

[Nickelgrass]

Hm... yes that could very well be. Although I am afraid I cannot recall what it may have been.