PDM 2 PCM DMA buffer size confusion

[kcire L.]

Hello,

I have a PDM MEMS microphone that I am reading in I2S master receive mode. I am trying to take this data and put it in a FIFO buffer and then output the data over UART using DMA. I must be confusing the buffer sizes because I get mostly zeros except for 64 Bytes of supposed data. Can someone please help me figure out where my issue is. Code is below. Thanks for any help.

uint16_t pdmRxBuf[128];
uint16_t audio_out[64];
uint16_t MidBuffer[16];
 
void FifoWrite(uint16_t data)
{
	fifoBuf[fifo_w_ptr] = data;
	fifo_w_ptr++;
}
 
uint16_t FifoRead()
{
	uint16_t val = fifoBuf[fifo_r_ptr];
	fifo_r_ptr++;
	return val;
}
 
 
 
 HAL_I2S_Receive_DMA(&hi2s2, &pdmRxBuf[0],64);
 
  HAL_UART_Transmit_DMA(&huart2, (uint8_t *) audio_out, 128);
 
  /* USER CODE END 2 */
 
 
 
  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
 
 
  while (1)
  {
 
	  if (rxstate==1)
	  {
	       	PDM_Filter(&pdmRxBuf[0],&MidBuffer[0], &PDM1_filter_handler);
	       	for (int i=0; i<16;i++)
	       	{ FifoWrite(MidBuffer[i]);
	       	}
	       	if (fifo_w_ptr-fifo_r_ptr > 128)
	       	{
	       		fifo_read_enabled=1;
	       	}
	       	rxstate=0;
 
	       }
 
	       if (rxstate==2)
	       {
	       	PDM_Filter(&pdmRxBuf[64],&MidBuffer[0], &PDM1_filter_handler);
	       	for (int i=0; i<16;i++)
	       	{
	       		FifoWrite(MidBuffer[i]);
	       	}
	       	rxstate=0;
 
	       }
 
	       if(half_complete == 1)
	       {
	 			for (int i=0; i<32;i=i+1)
	 			{
	 				uint16_t data = FifoRead();
	 				audio_out[i] = data;
	 			}
	 			half_complete = 0;
	       }
	       if(full_complete == 1)
	       {
	 			for (int i=32; i<64;i=i+1)
	 			{
	 				uint16_t data = FifoRead();
	 				audio_out[i] = data;
	 			}
	 			full_complete = 0;
	       }
 
 
    /* USER CODE END WHILE */
 
    /* USER CODE BEGIN 3 */
  }
 
  /* USER CODE END 3 */
}
 
 
 
void HAL_UART_TxHalfCpltCallback(UART_HandleTypeDef *huart)
{
	 half_complete = 1;
}
 
void HAL_UART_TxCpltCallback(UART_HandleTypeDef *huart)
{
	 full_complete = 1;
}
 
void HAL_I2S_RxHalfCpltCallback (I2S_HandleTypeDef *hi2s) {
	rxstate = 1;
}
 
void HAL_I2S_RxCpltCallback (I2S_HandleTypeDef *hi2s)
{
	rxstate = 2;
}