SAI Synchronous Slave with BDMA (CubeMX)

[TCash.1]

Hello All, I am trying to get Full Duplex I2S working with a STM32H7 and a PCM3168A.

The STM has 2 SAI blocks (SAI1 A/B) (A in master mode and B in synchronous slave) for sending data to the PCM for the DAC part of the PCM. I use this to transmit 4 Mono signals. This works with double-buffered circular DMA.

I then have 2 SAI block (SAI4 A/B) both configured as synchronous slaves. both synchronized to SAI1. These should receive data from the ADC portion of the PCM. I want to setup a circular DMA transfer for this as well, to take data from the PCM and transfer continuously to a buffer.

I can start a DMA transfer with

status = HAL_SAI_Receive_DMA(&hsai_BlockA4, (uint8_t*)&adc0DMA, ADCDMABUFFERSIZE);
 

And status returns HAL_OK. But I only ever see 0's in the adc0DMA buffer. I can see I2S data on the incoming SD data line. I also have global interrupts enabled for the SAI, but the following generated handlers are never called when I set a breakpoint:

void BDMA_Channel0_IRQHandler(void)
{
  /* USER CODE BEGIN BDMA_Channel0_IRQn 0 */
 
  /* USER CODE END BDMA_Channel0_IRQn 0 */
  HAL_DMA_IRQHandler(&hdma_sai4_a);
  /* USER CODE BEGIN BDMA_Channel0_IRQn 1 */
 
  /* USER CODE END BDMA_Channel0_IRQn 1 */
}
 
/**
  * @brief This function handles BDMA channel1 global interrupt.
  */
void BDMA_Channel1_IRQHandler(void)
{
  /* USER CODE BEGIN BDMA_Channel1_IRQn 0 */
 
  /* USER CODE END BDMA_Channel1_IRQn 0 */
  HAL_DMA_IRQHandler(&hdma_sai4_b);
  /* USER CODE BEGIN BDMA_Channel1_IRQn 1 */
 
  /* USER CODE END BDMA_Channel1_IRQn 1 */
}
 
/**
  * @brief This function handles SAI4 global interrupt.
  */
void SAI4_IRQHandler(void)
{
  /* USER CODE BEGIN SAI4_IRQn 0 */
 
  /* USER CODE END SAI4_IRQn 0 */
  HAL_SAI_IRQHandler(&hsai_BlockA4);
  HAL_SAI_IRQHandler(&hsai_BlockB4);
  /* USER CODE BEGIN SAI4_IRQn 1 */
 
  /* USER CODE END SAI4_IRQn 1 */
}

Am I missing an initial setup step that is not auto-generated? From what I understand SAI4 should be in sync to SAI1 with the frame signal. I know SAI1 is working and is generating signal on the PCM.

Connections:

Master-Clock, Bit-Clock, and Frame-Signal come from SAI1 and attach to the PCM (Both ADC and DAC sections as both are in "slave" mode on the PCM device).

SAI1_SD_A and SAI1_SD_B come from SAI1 and attach to the PCM.

SAI4_SD_A and SAI4_SD_B come from the PCM and attach to SAI4.

SAI1:

 SAI4:

 

Any help or suggestions would be appreciated.

Thanks,

-Trevor

[TCash.1 · Accepted solution]

I found out my issue - I had not enabled "External Synchro Out" in the .ioc configuration on the master , (SAI1). After enabling that the slaves began to work.

I also ended up switching from SAI4 to SAI2 for the slave. Because only the BDMA was attached to SAI4 and that uses memory region D3.