Noisy audio output with TAS2110 codec over SAI on STM32U5G9J-DK1

[Jinal]

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Hi,

On checking, I noticed a mismatch between the expected sampling frequency (44.1 kHz) and the actual frequency (46.875 kHz). Could this be the cause of the noise? Any suggestions on what might be going wrong?

For reference, I’m using SAI1_A with circular linked-list channel 12 of GPDMA1. The configuration details for SAI and GPDMA are provided below.
 

GPDMA Configuration: 

handle_GPDMA1_Channel12.Instance = GPDMA1_Channel12;

handle_GPDMA1_Channel12.InitLinkedList.Priority = DMA_HIGH_PRIORITY;

handle_GPDMA1_Channel12.InitLinkedList.LinkStepMode = DMA_LSM_FULL_EXECUTION;

handle_GPDMA1_Channel12.InitLinkedList.LinkAllocatedPort = DMA_LINK_ALLOCATED_PORT0;

handle_GPDMA1_Channel12.InitLinkedList.TransferEventMode = DMA_TCEM_LAST_LL_ITEM_TRANSFER;

handle_GPDMA1_Channel12.InitLinkedList.LinkedListMode = DMA_LINKEDLIST_CIRCULAR;



SAI Configuration:

hsai_BlockA1.Instance = SAI1_Block_A;

hsai_BlockA1.Init.Protocol = SAI_FREE_PROTOCOL;

hsai_BlockA1.Init.AudioMode = SAI_MODEMASTER_TX;

hsai_BlockA1.Init.DataSize = SAI_DATASIZE_16;

hsai_BlockA1.Init.FirstBit = SAI_FIRSTBIT_MSB;

hsai_BlockA1.Init.ClockStrobing = SAI_CLOCKSTROBING_FALLINGEDGE;

hsai_BlockA1.Init.Synchro = SAI_ASYNCHRONOUS;

hsai_BlockA1.Init.OutputDrive = SAI_OUTPUTDRIVE_DISABLE;

hsai_BlockA1.Init.NoDivider = SAI_MASTERDIVIDER_ENABLE;

hsai_BlockA1.Init.FIFOThreshold = SAI_FIFOTHRESHOLD_1QF;

hsai_BlockA1.Init.AudioFrequency = SAI_AUDIO_FREQUENCY_44K;

hsai_BlockA1.Init.SynchroExt = SAI_SYNCEXT_DISABLE;

hsai_BlockA1.Init.MckOutput = SAI_MCK_OUTPUT_DISABLE;

hsai_BlockA1.Init.MonoStereoMode = SAI_STEREOMODE;

hsai_BlockA1.Init.CompandingMode = SAI_NOCOMPANDING;

hsai_BlockA1.Init.TriState = SAI_OUTPUT_NOTRELEASED;

hsai_BlockA1.Init.PdmInit.Activation = DISABLE;

hsai_BlockA1.Init.PdmInit.MicPairsNbr = 1;

hsai_BlockA1.Init.PdmInit.ClockEnable = SAI_PDM_CLOCK1_ENABLE;

hsai_BlockA1.FrameInit.FrameLength = 32;

hsai_BlockA1.FrameInit.ActiveFrameLength = 16;

hsai_BlockA1.FrameInit.FSDefinition = SAI_FS_CHANNEL_IDENTIFICATION;

hsai_BlockA1.FrameInit.FSPolarity = SAI_FS_ACTIVE_LOW;

hsai_BlockA1.FrameInit.FSOffset = SAI_FS_BEFOREFIRSTBIT;

hsai_BlockA1.SlotInit.FirstBitOffset = 0;

hsai_BlockA1.SlotInit.SlotSize = SAI_SLOTSIZE_DATASIZE;

hsai_BlockA1.SlotInit.SlotNumber = 2;

hsai_BlockA1.SlotInit.SlotActive = 0x00000003;
LinkList configuration:

pNodeConfig.NodeType = DMA_GPDMA_LINEAR_NODE;

pNodeConfig.Init.Request = GPDMA1_REQUEST_SAI1_A;

pNodeConfig.Init.BlkHWRequest = DMA_BREQ_SINGLE_BURST;

pNodeConfig.Init.Direction = DMA_MEMORY_TO_PERIPH;

pNodeConfig.Init.SrcInc = DMA_SINC_INCREMENTED;

pNodeConfig.Init.DestInc = DMA_DINC_FIXED;

pNodeConfig.Init.SrcDataWidth = DMA_SRC_DATAWIDTH_HALFWORD;

pNodeConfig.Init.DestDataWidth = DMA_DEST_DATAWIDTH_BYTE;

pNodeConfig.Init.SrcBurstLength = 1;

pNodeConfig.Init.DestBurstLength = 1;

pNodeConfig.Init.TransferAllocatedPort = DMA_SRC_ALLOCATED_PORT0|DMA_DEST_ALLOCATED_PORT0;

pNodeConfig.Init.TransferEventMode = DMA_TCEM_BLOCK_TRANSFER;

pNodeConfig.TriggerConfig.TriggerPolarity = DMA_TRIG_POLARITY_MASKED;

pNodeConfig.DataHandlingConfig.DataExchange = DMA_EXCHANGE_NONE;

pNodeConfig.DataHandlingConfig.DataAlignment = DMA_DATA_RIGHTALIGN_ZEROPADDED;

pNodeConfig.SrcAddress = 0;

pNodeConfig.DstAddress = 0;

pNodeConfig.DataSize = 0;

 Thanks,

Jinal

[Saket_Om]

Hello @Jinal 

To help us further investigate the sampling frequency mismatch, could you please share the configuration details of your SAI kernel clock? For accurate 44.1 kHz audio output, the SAI kernel clock should be set to a frequency that is multiple of 44.1 kHz.