DMA with SAI

[DYann.1]

Hello,

I would like to use DMA with SAI but I am having difficulty writing the code. Can you check if my code is correct and why I cannot retrieve the RX values ?

  /* USER CODE BEGIN 2 */

  HAL_SAI_RegisterCallback(&hsai_BlockA1, HAL_SAI_RX_HALFCOMPLETE_CB_ID, HAL_SAI_RxHalfCpltCallback);
  HAL_SAI_RegisterCallback(&hsai_BlockA1, HAL_SAI_RX_COMPLETE_CB_ID, HAL_SAI_RxCpltCallback);
  fresult= HAL_SAI_Init(&hsai_BlockA1);
  if (fresult != HAL_OK)
  	{
  	return HAL_ERROR;
  	}
  fresult = HAL_SAI_Receive_DMA(&hsai_BlockA1, (uint8_t *)playbuf_RX, (sizeof(playbuf_RX))/4);

  HAL_SAI_RegisterCallback(&hsai_BlockB1, HAL_SAI_TX_HALFCOMPLETE_CB_ID, HAL_SAI_TxHalfCpltCallback);
  HAL_SAI_RegisterCallback(&hsai_BlockB1, HAL_SAI_TX_COMPLETE_CB_ID, HAL_SAI_TxCpltCallback);
  fresult= HAL_SAI_Init(&hsai_BlockB1);
  if (fresult != HAL_OK)
	{
  	return HAL_ERROR;
	}

  fresult = HAL_SAI_Transmit_DMA(&hsai_BlockB1, (uint8_t *)playbuf , (sizeof(playbuf))/4);

With CubeMX I have configured 2 DMAs.

One to send the data and the other to read the data again.
I think I'm missing something for the callback but I don't know how to use it to retrieve the values.

Thank you for your helps. 

Regards.

[LCE]

Look at the examples, step by step:

1) What are they doing there in general?

2) How's RX set up and started?

3) How's TX set up, then started?

4) What's happening in the callbacks / ISRs? (which they hopefully use, meaning that DMA with interrupts is used)

[DYann.1]

Hi,

Thank you for your helps, I'll look for the documentation for that. I modified my code to know if the transmission is correct via the HAL_SAI_TxHalfCpltCallback function :

  while (1)
  {
    /* USER CODE END WHILE */
	void HAL_SAI_TxHalfCpltCallback (SAI_HandleTypeDef *hsai)
	  {HAL_GPIO_TogglePin(GPIOB, GPIO_PIN_3);
	   HAL_Delay(200);}

    /* USER CODE BEGIN 3 */
  }

So for me something is wrong with the transmission since the LED never flashes.

[LCE]

You got it completely wrong...
You are declaring a function within the while loop - and the compiler does not complain? Interesting.

[LCE]

And again, usually callback functions are not for you to call them, it's another function that does that, in the HAL case it should be called by the DMA / SAI complete ISR. Try to find where the callback is called within the HAL functions.

Maybe the interrupts you need are not active?

[LCE]

Maybe you should forget about audio for some time and work on the basics.

Make an LED blink.
Then turn it on / off if some GPIO input is high or low.
Then use that GPIO with an interrupt, and so on.

Start simple, and understand that first.

[DYann.1]

Hi,

I'm not sure if you're right, no errors during compilation :

I saw a tutorial and you can do this to find out if the transmission is going well. The proof is that I have no errors during compilation.

[DYann.1]

I think this function is useful to know if the transmission is going well. 

Why am I looking at this function ? Because the DMA is configured in circular. After I can check for RX.

Normally the interrupts is automatically generated by cubemx right ? How to check this interruption ?

[DYann.1]

---

@LCE wrote:

Maybe you should forget about audio for some time and work on the basics.

Make an LED blink.
Then turn it on / off if some GPIO input is high or low.
Then use that GPIO with an interrupt, and so on.

Start simple, and understand that first.

---

I'm a beginner but I've already done all this.

[DYann.1 · Accepted solution]

Now it's ok

I just to change the configuration and I configure the SAI in DMA only for transmission but not for reception.

[LCE]

Congratulations!

But how did you configure the SAI in RX?

You are mostly showing not so useful pictures, easier to read would be parts of the code with the (initially hidden) </> code insert button.
So it would be interesting to see the SAI inits, and the part where you start TX / RX.

But good that it's working now.