problem in LL SPI example code

[HDaji.1]

I have been testing Examples_LL code (SPI_TwoBoards_FullDuplex_DMA_Master_Init ) in STM32Cube_FW_G4_V1.4.0 package.

Here is my problem:

I modified the original code such that I only need one board.

/* Enable the SPI1 peripheral */
 Activate_SPI();
 
 /* Wait for the end of the transfer and check received data */
 /* LED blinking FAST during waiting time */
 //WaitAndCheckEndOfTransfer();
 /* USER CODE END 2 */
 
 /* Infinite loop */
 /* USER CODE BEGIN WHILE */
 while (1)
 {
 /* USER CODE END WHILE */
 LL_mDelay(1);
 //while (ubTransmissionComplete != 1)
 //{
 //}
 
 LL_DMA_EnableChannel(DMA1, LL_DMA_CHANNEL_3);
 
 /* USER CODE BEGIN 3 */
 }

In the while loop, I keeps calling LL_DMA_EnableChannel, expecting to see repeated transmitting SPI message.

I used PicoScope to monitor SCLK and MOSI lines signal as showed below (D3 and D4). I expected repeated signals in those two lines, which did not happen. As showed in the picture below SPI transmission only happens once.

 

Another weird thing is that I define uint8_t aTxBuffer[] = {0x01, 0x02, 0x03, 0x04}; so I expect SPI to transmit 4 bytes out in MOSI line. What I captured is

 D3 is clock and D4 is MOSI. Obviously, the signals are far off from what is expected.

In fact, I did something similar with Nucleo-F411RE and example code SPI_TwoBoards_FullDuplex_DMA in package STM32Cube_FW_F4_V1.26.0, for which there is no problem. The only difference I notice is the function call to transmit SPI data: in F4 package it is called LL_DMA_EnableStream, while in G4 LL_DMA_EnableChannel.

I cannot find LL_DMA_EnableStream in STM32G4 HAL and low-layer drivers manual. BTW, the function descriptions in both HAL and low-layer driver manuals are sometimes too simple to be helpful.

[Amel NASRI]

Hi @HDaji.1​ ,

DMA peripheral isn't the same when comparing STM32G4 to STM32F4.

You can review the following 2 application notes to understand more about the difference between both of them:

• AN4031: Using the STM32F2, STM32F4 and STM32F7 Series DMA controller 
• AN2548: Using the STM32F0/F1/F3/Gx/Lx Series DMA controller

Now, as you have only one board, why don't you use the example STM32Cube_FW_G4\Projects\NUCLEO-G474RE\Examples_LL\SPI\SPI_OneBoard_HalfDuplex_DMA?

-Amel

[HDaji.1]

@Amel NASRI​ Thanks for your info.

I just want to transmit a few bytes to another device through SPI the fastest as the MCU can do.

[HDaji.1]

Purely based on example code in SPI_TwoBoards_FullDuplex_DMA: one possible way, to achieve repeated sending out a few bytes through SPI, could be to disable the DMA channel after SPI transmission has completed and re-enable it later. However, it seems not as efficient as the case in F4, whereby one enabling function does the job.