PDM - Pulse Density Modulation
Description
Pulse Density Modulation (PDM) peripheral API.
PDM API functions provide full support for the PDM peripheral. The PDM peripheral accept PDM bitstreams and produce PCM encoded output.
Example PDM usage when interfacing to two PDM microphones:
Configure clocks and GPIO pins:
Initialize and start PDM, then read PCM samples from FIFO:
Data Structures |
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struct | PDM_Init_TypeDef |
PDM initialization structure.
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Functions |
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void | PDM_DeInit (PDM_TypeDef *pdm) |
De-initialize the PDM peripheral.
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void | PDM_Init (PDM_TypeDef *pdm, const PDM_Init_TypeDef *init) |
Initialize the PDM peripheral.
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void | PDM_Reset (PDM_TypeDef *pdm) |
Initialize PDM registers with reset values.
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void | PDM_Clear (PDM_TypeDef *pdm) |
Clear PDM filter.
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void | PDM_FifoFlush (PDM_TypeDef *pdm) |
Flush the PDM sample FIFO.
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void | PDM_IntClear (PDM_TypeDef *pdm, uint32_t flags) |
Clear one or more pending PDM interrupts.
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void | PDM_IntDisable (PDM_TypeDef *pdm, uint32_t flags) |
Disable one or more PDM interrupts.
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void | PDM_IntEnable (PDM_TypeDef *pdm, uint32_t flags) |
Enable one or more PDM interrupts.
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uint32_t | PDM_IntGet (PDM_TypeDef *pdm) |
Get pending PDM interrupt flags.
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uint32_t | PDM_IntGetEnabled (PDM_TypeDef *pdm) |
Get enabled and pending PDM interrupt flags.
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void | PDM_IntSet (PDM_TypeDef *pdm, uint32_t flags) |
Set one or more pending PDM interrupts.
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uint32_t | PDM_Rx (PDM_TypeDef *pdm) |
Read one entry from the PDM FIFO.
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void | PDM_Start (PDM_TypeDef *pdm) |
Start PDM operation (start the PDM filter).
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uint32_t | PDM_StatusGet (PDM_TypeDef *pdm) |
Get PDM STATUS register.
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void | PDM_Stop (PDM_TypeDef *pdm) |
Stop PDM operation (stop the PDM filter).
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Macros |
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#define | PDM_INIT_DEFAULT |
Default configuration for PDM.
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Enumerations |
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enum |
PDM_Ch3ClkPolarity_Typedef
{
pdmCh3ClkPolarityRisingEdge = _PDM_CFG0_CH3CLKPOL_NORMAL, pdmCh3ClkPolarityFallingEdge = _PDM_CFG0_CH3CLKPOL_INVERT } |
Configure CH3 CLK Polarity.
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enum |
PDM_Ch2ClkPolarity_Typedef
{
pdmCh2ClkPolarityRisingEdge = _PDM_CFG0_CH2CLKPOL_NORMAL, pdmCh2ClkPolarityFallingEdge = _PDM_CFG0_CH2CLKPOL_INVERT } |
Configure CH2 CLK Polarity.
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enum |
PDM_Ch1ClkPolarity_Typedef
{
pdmCh1ClkPolarityRisingEdge = _PDM_CFG0_CH1CLKPOL_NORMAL, pdmCh1ClkPolarityFallingEdge = _PDM_CFG0_CH1CLKPOL_INVERT } |
Configure CH1 CLK Polarity.
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enum |
PDM_Ch0ClkPolarity_Typedef
{
pdmCh0ClkPolarityRisingEdge = _PDM_CFG0_CH0CLKPOL_NORMAL, pdmCh0ClkPolarityFallingEdge = _PDM_CFG0_CH0CLKPOL_INVERT } |
Configure CH0 CLK Polarity.
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enum |
PDM_FifoValidWatermark_Typedef
{
pdmFifoValidWatermarkOne = _PDM_CFG0_FIFODVL_ONE, pdmFifoValidWatermarkTwo = _PDM_CFG0_FIFODVL_TWO, pdmFifoValidWatermarkThree = _PDM_CFG0_FIFODVL_THREE, pdmFifoValidWatermarkFour = _PDM_CFG0_FIFODVL_FOUR } |
Configure FIFO Data valid level water-mark.
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enum |
PDM_DataFormat_TypeDef
{
pdmDataFormatRight16 = _PDM_CFG0_DATAFORMAT_RIGHT16, pdmDataFormatDouble16 = _PDM_CFG0_DATAFORMAT_DOUBLE16, pdmDataFormatRight24 = _PDM_CFG0_DATAFORMAT_RIGHT24, pdmDataFormatFull32bit = _PDM_CFG0_DATAFORMAT_FULL32BIT, pdmDataFormatLeft16 = _PDM_CFG0_DATAFORMAT_LEFT16, pdmDataFormatLeft24 = _PDM_CFG0_DATAFORMAT_LEFT24, pdmDataFormatRaw32bit = _PDM_CFG0_DATAFORMAT_RAW32BIT } |
Configure PDM filter data output format.
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enum |
PDM_NumberOfChannels_TypeDef
{
pdmNumberOfChannelsOne = _PDM_CFG0_NUMCH_ONE, pdmNumberOfChannelsTwo = _PDM_CFG0_NUMCH_TWO, pdmNumberOfChannelsThree = _PDM_CFG0_NUMCH_THREE, pdmNumberOfChannelsFour = _PDM_CFG0_NUMCH_FOUR } |
Configure number of PDM channels.
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enum |
PDM_FilterOrder_TypeDef
{
pdmFilterOrderSecond = _PDM_CFG0_FORDER_SECOND, pdmFilterOrderThird = _PDM_CFG0_FORDER_THIRD, pdmFilterOrderFourth = _PDM_CFG0_FORDER_FOURTH, pdmFilterOrderFifth = _PDM_CFG0_FORDER_FIFTH } |
Configure order of the PDM filter.
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Function Documentation
◆ PDM_DeInit()
void PDM_DeInit | ( | PDM_TypeDef * |
pdm
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De-initialize the PDM peripheral.
This function will stop the PDM filter and set PDM control registers to their reset values.
- Parameters
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[in] pdm
A pointer to the PDM peripheral register block.
◆ PDM_Init()
void PDM_Init | ( | PDM_TypeDef * |
pdm,
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const PDM_Init_TypeDef * |
init
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Initialize the PDM peripheral.
This function will configure basic settings in PDM according to values in the initialization data structure.
Notice that enabling of PDM clock, setup of PDM pins and setup of PRS is not covered by this function.
- Parameters
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[in] pdm
A pointer to the PDM peripheral register block. [in] init
A pointer to the initialization structure used to configure the PDM.
◆ PDM_Reset()
void PDM_Reset | ( | PDM_TypeDef * |
pdm
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Initialize PDM registers with reset values.
- Parameters
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[in] pdm
A pointer to the PDM peripheral register block.
◆ PDM_Clear()
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inline |
Clear PDM filter.
- Parameters
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[in] pdm
A pointer to the PDM peripheral register block.
◆ PDM_FifoFlush()
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inline |
Flush the PDM sample FIFO.
- Parameters
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[in] pdm
A pointer to the PDM peripheral register block.
◆ PDM_IntClear()
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inline |
Clear one or more pending PDM interrupts.
- Parameters
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[in] pdm
A pointer to the PDM peripheral register block. [in] flags
Pending PDM interrupt sources to clear. Use one or more valid interrupt flags for the PDM module. The flags are PDM_IFC_DV, PDM_IFC_DVL, PDM_IFC_OF and PDM_IFC_UF.
◆ PDM_IntDisable()
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inline |
Disable one or more PDM interrupts.
- Parameters
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[in] pdm
A pointer to the PDM peripheral register block. [in] flags
PDM interrupt sources to disable. Use one or more valid interrupt flags for the PDM module. The flags are PDM_IEN_DV, PDM_IEN_DVL, PDM_IEN_OF and PDM_IEN_UF.
◆ PDM_IntEnable()
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inline |
Enable one or more PDM interrupts.
- Note
- Depending on the use, a pending interrupt may already be set prior to enabling the interrupt. To ignore a pending interrupt, consider using PDM_IntClear() prior to enabling the interrupt.
- Parameters
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[in] pdm
A pointer to the PDM peripheral register block. [in] flags
PDM interrupt sources to enable. Use one or more valid interrupt flags for the PDM module. The flags are PDM_IEN_DV, PDM_IEN_DVL, PDM_IEN_OF and PDM_IEN_UF.
◆ PDM_IntGet()
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inline |
Get pending PDM interrupt flags.
- Note
- Event bits are not cleared by the use of this function.
- Parameters
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[in] pdm
A pointer to the PDM peripheral register block.
- Returns
- PDM interrupt sources pending. Returns one or more valid interrupt flags for PDM module. The flags are PDM_IF_DV, PDM_IF_DVL, PDM_IF_OF and PDM_IF_UF.
◆ PDM_IntGetEnabled()
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inline |
Get enabled and pending PDM interrupt flags.
Useful for handling more interrupt sources in the same interrupt handler.
- Note
- Interrupt flags are not cleared by the use of this function.
- Parameters
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[in] pdm
A pointer to the PDM peripheral register block.
- Returns
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Pending and enabled PDM interrupt sources Return value is the bitwise AND of
- the enabled interrupt sources in PDM_IEN and
- the pending interrupt flags PDM_IF
◆ PDM_IntSet()
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inline |
Set one or more pending PDM interrupts.
- Parameters
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[in] pdm
A pointer to the PDM peripheral register block. [in] flags
PDM interrupt sources to set to pending. Use one or more valid interrupt flags for the PDM module. The flags are PDM_IFS_DV, PDM_IFS_DVL, PDM_IFS_OF and PDM_IFS_UF.
◆ PDM_Rx()
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inline |
Read one entry from the PDM FIFO.
- Note
- This function will wait until a sample is available in the FIFO. Depending on PDM configuration, a FIFO entry can consist of one or two samples.
- Parameters
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[in] pdm
A pointer to the PDM peripheral register block.
- Returns
- The entry read from the FIFO.
◆ PDM_Start()
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inline |
Start PDM operation (start the PDM filter).
- Parameters
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[in] pdm
A pointer to the PDM peripheral register block.
◆ PDM_StatusGet()
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inline |
Get PDM STATUS register.
- Parameters
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[in] pdm
A pointer to the PDM peripheral register block.
- Returns
- STATUS register value.
◆ PDM_Stop()
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inline |
Stop PDM operation (stop the PDM filter).
- Parameters
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[in] pdm
A pointer to the PDM peripheral register block.
Macro Definition Documentation
◆ PDM_INIT_DEFAULT
#define PDM_INIT_DEFAULT |
Default configuration for PDM.
Stereo Ch0/1, 16bit samples, 44,100 Hz sampling rate, 32 times oversampling (requires 1,411,209 Hz PDM clock).
Enumeration Type Documentation
◆ PDM_Ch3ClkPolarity_Typedef
◆ PDM_Ch2ClkPolarity_Typedef
◆ PDM_Ch1ClkPolarity_Typedef
◆ PDM_Ch0ClkPolarity_Typedef
◆ PDM_FifoValidWatermark_Typedef
◆ PDM_DataFormat_TypeDef
Configure PDM filter data output format.