Is HAL_SPI_Transmit_DMA faster than HAL_SPI_Transmit?

[DMårt]

Hi!

Is HAL_SPI_Transmit_DMA faster than HAL_SPI_Transmit?

If yes: Do I need to enable DMA for the SPI to make this work?

[Rookie38]

Hello,

Yes, transferring larger amounts of data is faster using DMA. The data transfer process is outsourced to the DMA controller and the MCU can continue working. Again, yes, DMA must be configured for use with the specific SPI bus. You should give a look at the CubeRepository examples:

For example for STM32F4 Series:

..\STM32Cube\Repository\STM32Cube_FW_F4_V1.26.1\Projects\STM32F429I-Discovery\Examples\SPI

There are three examples for SPI communication via polling, interrupt and DMA available.

[DMårt]

Thank you. I tried with HAL_SPI_Transmit_DMA and it was much slower than HAL_SPI_Transmit.

In this case, I transfered maximum 1 to 4 bytes of data.

[MM..1]

Your question isnt right. Speed of SPI is defined aka clock. Little change is interword times when is used IRQ vs DMA.

Your code must have fail when dont work...

[DMårt]

Yes. But isin't DMA SPI the same as regular SPI without time out?

[MM..1]

Speed is same because SPI have FIFO

[PMath.4 · Accepted solution]

Setting up DMA takes time so will always be slower for small transfers. For larger transfers DMA is better but only if there is something else you want to do while the transfer is happening. Otherwise speed will be the same.

[DMårt]

So there no reason to call SPI_DMA then if I want to transmit data?