HAL_I2S_TransmitDMA in circular mode (STM32H503) doesn't run continuously

[chriskuku]

I have set up a DMA on an I2S device with an STM32H503CBU6. The idea is, that the DMA runs continuously on a single bufferaddress (one word, containing the left and right channels for the external I2S-DAC). When the DMA transfer of that 1 word is complete it should start over again by itself.

At present the goal is not achieved with the following setup:

uint16_t ram_loc[2] = {0,0};
int main(void)
{

  

  /* MCU Configuration--------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();



  /* Configure the system clock */
  SystemClock_Config();

 

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_GPDMA1_Init();
  MX_ICACHE_Init();
  MX_I2C1_Init();
  MX_I2S2_Init();
  MX_TIM1_Init();
  
      HAL_I2S_Transmit_DMA(&hi2s2, ram_loc,1); // since circular is configured,
                                               // am I right that the DMA keeps alive itself?
  /* USER CODE END 2 */

  /* Infinite loop */
 
     while (1)
     {

    	// for testing, increment ram_loc (L+R) by one every 10ms
    	// which should produce a (sawtooth) ramp.
    	//
    	 HAL_Delay(10);
    	 ram_loc[0]++,ram_loc[1]++;
    	 if(ram_loc[0] == 65535)
    		 ram_loc[0]=ram_loc[1]=0;
	
    }
 
}

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Some things I'm not sure about: how is the DMA data organized. Since it is an I2S audio stream with L+R signals, I assume they are two words of 16bits, sent in one 32bit DMA chunk. Or is it 32bit data in a 32bit frame? BTW, what does "frame" actually stand for?
What is the "Port 0" that appears, when I choose "circular" mode in the DMA channel 4 setup?

I2S2_WS  - PA3
I2S2_CK  - PA5
I2S2_SDO - PB1

 I don't see any data on PB1. Timing is there (48KHz on PA5, WS on PA3).

[TDK]

You should initialize ram_loc with nonzero data, and make it volatile.

volatile uint16_t ram_loc[2] = {0xAAAA, 0xAAAA};

Clock is there. Data is probably there as well. It's not being updated because the compiler is free to optimize it away.

[chriskuku]

Would have been too nice, but:

volatile uint16_t ram_loc[2] = {0xAAAA, 0xAAAA};

../Core/Src/main.c: In function 'main':
../Core/Src/main.c:179:36: warning: passing argument 2 of 'HAL_I2S_Transmit_DMA' discards 'volatile' qualifier from pointer target type [-Wdiscarded-qualifiers]
  179 |       HAL_I2S_Transmit_DMA(&hi2s2, ram_loc,1); // since circular is configured,
      |                                    ^~~~~~~

And, thinking about it, the compiler shouldn't optimize a variable away, that is being passed to a function

and is being assigned (incremented) further down in the while loop in the code. Or am I wrong? And non-zero data? No, this can't be it. 

Data is data, whether zero or non-zero, it's an initialization.

[TDK]

 HAL_I2S_Transmit_DMA(&hi2s2, (uint16_t*)ram_loc,1)

Cast it to the proper type to avoid the warning.

[chriskuku]

---

@TDK wrote:

 HAL_I2S_Transmit_DMA(&hi2s2, (uint16_t*)ram_loc,1)

Cast it to the proper type to avoid the warning.

---

Did that, no change. Still no data. I'm wondering if it has to do sth. with circular and linked lists downstream in the DMA configuration in 

HAL_I2S_Transmit_DMA

The fact that the timing can be seen at the I2S2 pins cannot be interpreted as the DMA being running, can it?

[chriskuku]

I traced HAL_I2S_Transmit_DMA a bit. It runs into the following code:

  /* Enable the Tx DMA Stream/Channel */
  if ((hi2s->hdmatx->Mode & DMA_LINKEDLIST) == DMA_LINKEDLIST)
  {
    if (hi2s->hdmatx->LinkedListQueue != NULL)
    {
      /* Set DMA data size */
      hi2s->hdmatx->LinkedListQueue->Head->LinkRegisters[NODE_CBR1_DEFAULT_OFFSET] = hi2s->TxXferCount;

      /* Set DMA source address */
      hi2s->hdmatx->LinkedListQueue->Head->LinkRegisters[NODE_CSAR_DEFAULT_OFFSET] = (uint32_t)hi2s->pTxBuffPtr;

      /* Set DMA destination address */
      hi2s->hdmatx->LinkedListQueue->Head->LinkRegisters[NODE_CDAR_DEFAULT_OFFSET] = (uint32_t)&hi2s->Instance->TXDR;

      errorcode = HAL_DMAEx_List_Start_IT(hi2s->hdmatx);
    }

I'm wondering about the 

HAL_DMAEx_List_Start_IT(hi2s->hdmatx);

I cannot remember having enabled any interrupts. 

Could it be I have to add a LINKEDLIST (under Utilities in the IOC)?

[chriskuku · Accepted solution]

I got it running. I hadn't finished the necessary setup of the GPDMA.
Had to define a linked list with two nodes. And get some other parameters in the I2S interface (word length etc.) right. See attached IOC.