#include <Microphone_PDM.h>

Inheritance diagram for Microphone_PDM_Base:

Public Types
enum class	OutputSize { UNSIGNED_8 , SIGNED_16 , RAW_SIGNED_16 }

enum class	Range { RANGE_128 = 0 , RANGE_256 , RANGE_512 , RANGE_1024 , RANGE_2048 , RANGE_4096 , RANGE_8192 , RANGE_16384 , RANGE_32768 }

Public Member Functions
int	getSampleRate () const

Protected Member Functions
	Microphone_PDM_Base (size_t numSamples)

virtual	~Microphone_PDM_Base ()

void	copySamplesInternal (const int16_t src, uint8_t dst) const

virtual size_t	copySrcIncrement () const

Protected Attributes
pin_t	clkPin = A0

pin_t	datPin = A1

bool	stereoMode = false

int	sampleRate

OutputSize	outputSize = OutputSize::SIGNED_16

Range	range = Range::RANGE_2048

size_t	numSamples

Detailed Description

Class used for settings. You will not instantiate one of these; it's a base class of Microphone_PDM_MCU.

There are accessor methods for setting these settings in the Microphone_PDM class.

Member Enumeration Documentation

◆ OutputSize

enum class Microphone_PDM_Base::OutputSize

strong

Configuration for the size of the output data.

Enumerator
UNSIGNED_8	Output unsigned 8-bit values (adjusted by PDMRange)
SIGNED_16	Output signed 16-bit values (adjusted by PDMRange) (default)
RAW_SIGNED_16	Output values as signed 16-bit values as returned by MCU (unadjusted)

◆ Range

enum class Microphone_PDM_Base::Range

strong

Adjustment value so samples fill most of an 8 or 16 bit output size.

The setting is dependent on your microphone. The Adafruit microphone is 12-bit, so the default value of RANGE_2048 is correct.

Enumerator
RANGE_128	From -128 to 127 (8 bits)
RANGE_256	From -256 to 255 (9 bits)
RANGE_512	From -512 to 511 (10 bits)
RANGE_1024	From -1024 to 1023 (11 bits)
RANGE_2048	From -2048 to 2047 (12 bits) (default)
RANGE_4096	From -4096 to 4095 (13 bits)
RANGE_8192	From -8192 to 8191 (14 bits)
RANGE_16384	From -16384 to 16383 (15 bits)
RANGE_32768	From -32768 to 32767 (16 bits) (same as raw mode)

Constructor & Destructor Documentation

◆ Microphone_PDM_Base()

Microphone_PDM_Base::Microphone_PDM_Base ( size_t numSamples )

inlineprotected

You cannot instantiate one of these, it's only done by the subclass, which is a Microphone_PDM_* MCU-specific class.

Parameters

numSamples The value of BUFFER_SIZE_SAMPLES defined in the MCU-specific subclass

Member Function Documentation

◆ copySamplesInternal()

void Microphone_PDM_Base::copySamplesInternal	(	const int16_t *	src,
		uint8_t *	dst
	)		const

protected

Used internally. Use copySamples() externally.

Parameters

src	Pointer to the internal DMA buffer, which is always 16-bit samples
dst	Pointer to the destination buffer, which will be 8 or 16-bit samples, depending on outputSize

Also pays attention to range to determine how much to shift the samples, unless the output size is RAW_SIGNED_16, which does not do any transformation.

src and dst can be the same buffer to transform the data range in place.

◆ copySrcIncrement()

virtual size_t Microphone_PDM_Base::copySrcIncrement ( ) const

inlineprotectedvirtual

How much to increment src in copySamplesInternal. Used internally.

Returns: size_t number of bytes

This is almost always 1. The exception is if you are using 8000 Hz sampling on the nRF52. In this case, every other sample is skipped and the subclass overrides this to return 2.

Reimplemented in Microphone_PDM_nRF52.

◆ getSampleRate()

int Microphone_PDM_Base::getSampleRate ( ) const

inline

Return the sample rate (16000 or 32000) in samples per second.

Returns: int

The documentation for this class was generated from the following files:

src/Microphone_PDM.h
src/Microphone_PDM.cpp

Public Types

Public Member Functions

Protected Member Functions

Protected Attributes