Class to handle audio synthesis and playback using the MAX98357A DAC. More...

#include <AudioDevice.h>

Public Member Functions
	AudioDevice (int i2sBckPin, int i2sLrclkPin, int i2sDataPin, int spiClkPin, int spiMisoPin, int spiMosiPin, int spiCsPin)
	Constructor for AudioDevice class. More...

bool	begin ()
	Initialize the audio system and eSpeak-NG. More...

void	setVolume (int volume)
	Set the volume for audio playback. More...

void	setLanguage (uint8_t index)
	Set the language for text-to-speech conversion by index. More...

void	playText (const char *text)
	Convert text to speech and send it to the DAC. More...

void	playWav (String filename)
	Play a WAV file stored on the SD card. More...

void	selfTestSdReader ()
	Perform a built‑in self‑test of the Micro‑SD card interface. More...

void	sendTestTone (float freqHz=1000.0f, uint16_t durationMs=300, uint8_t amplitudePct=25)
	Play a short sine tone over I2S (self-test for speaker path). More...

Private Member Functions
bool	_initEspeak ()
	Initialize the eSpeak speech synthesizer and associated I2S interface. More...

bool	_initSpi ()
	Initialize the SPI bus and SD card. More...

void	_setupI2S ()
	Configure and start the ESP32 I2S peripheral for audio output. More...

Static Private Member Functions
static int	_synthCallback (short wav, int numsamples, espeak_EVENT events)
	Callback function for handling synthesized audio data. More...

Private Attributes
int	i2sDataPin_
	pins used for I2S

int	spiCsPin_
	pins used for SD Card Reader to read .wav files

Static Private Attributes
static int	volume_ = 100
	Master output volume as a percentage (0–100). More...

static const char *	language_ = AudioDevice::languages_[0]
	Pointer to the current eSpeak voice code (e.g., "en", "fr"). More...

static const char *	languages_ [10]
	Table of supported eSpeak voice identifiers. More...

Detailed Description

Class to handle audio synthesis and playback using the MAX98357A DAC.

Definition at line 58 of file AudioDevice.h.

Constructor & Destructor Documentation

◆ AudioDevice()

AudioDevice::AudioDevice	(	int	i2sBckPin,
		int	i2sLrclkPin,
		int	i2sDataPin,
		int	spiClkPin,
		int	spiMisoPin,
		int	spiMosiPin,
		int	spiCsPin
	)

inline

Constructor for AudioDevice class.

Parameters

i2sBckPin	The pin number for BCLK
i2sLrclkPin	The pin number for LRCLK
i2sDataPin	The pin number for DIN
spiClkPin	The pin number for SPI CLK
spiMisoPin	The pin number for MISO
spiMosiPin	The pin number for MSOI
spiCsPin	The pin number for CS

Definition at line 70 of file AudioDevice.h.

Member Function Documentation

◆ _initEspeak()

bool AudioDevice::_initEspeak ( )

inlineprivate

Initialize the eSpeak speech synthesizer and associated I2S interface.

Sets up the I2S peripheral, invokes espeak_Initialize() in retrieval mode, selects a default voice, and installs the synthesis callback. On failure, it reports an error via SerialIO and frees the I2S resources.

Returns: True if initialization succeeded, false otherwise.

Definition at line 322 of file AudioDevice.h.

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◆ _initSpi()

bool AudioDevice::_initSpi ( )

inlineprivate

Initialize the SPI bus and SD card.

Starts the SPI peripheral using the pins configured in the constructor, then attempts to mount the SD filesystem. If the card initialization fails, an error is printed. The SPI bus is ended before returning.

Returns: True if the SD card was successfully initialized, false otherwise.

Definition at line 351 of file AudioDevice.h.

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◆ _setupI2S()

void AudioDevice::_setupI2S ( )

inlineprivate

Configure and start the ESP32 I2S peripheral for audio output.

Sets the sample rate, bit depth, channel format, DMA buffer counts and lengths, and assigns the BCK, LRCLK and data pins. This must be called before any audio is transmitted via I2S. The configuration uses a mono (right channel only) stream at 22.05 kHz and 16‑bit samples.

Definition at line 375 of file AudioDevice.h.

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◆ _synthCallback()

static int AudioDevice::_synthCallback	(	short *	wav,
		int	numsamples,
		espeak_EVENT *	events
	)

inlinestaticprivate

Callback function for handling synthesized audio data.

Parameters

wav	Pointer to the audio data buffer
numsamples	Number of samples in the buffer
events	Pointer to eSpeak event data

Returns: 0 to continue, 1 to end synthesis

Definition at line 408 of file AudioDevice.h.

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◆ begin()

bool AudioDevice::begin ( )

inline

Initialize the audio system and eSpeak-NG.

Returns: True if initialization is successful, otherwise false

Definition at line 77 of file AudioDevice.h.

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◆ playText()

void AudioDevice::playText ( const char * text )

inline

Convert text to speech and send it to the DAC.

Parameters

text	The text to be converted to speech

Definition at line 112 of file AudioDevice.h.

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◆ playWav()

void AudioDevice::playWav ( String filename )

inline

Play a WAV file stored on the SD card.

Opens a .wav file from the Micro‑SD card reader and streams its PCM audio data to the DAC via the I2S interface. The method expects the file to use the standard 44‑byte WAV header for PCM 16‑bit mono samples at 22.05 kHz. If the file cannot be opened or the file size is shorter than a valid header, an error is reported over the serial port and no audio is played.

The SPI bus is initialized for each invocation and closed on return. This method blocks while the audio is playing.

Parameters

filename Relative path to the .wav file on the SD card (e.g., "/my_sounds/hello.wav").

Definition at line 141 of file AudioDevice.h.

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◆ selfTestSdReader()

void AudioDevice::selfTestSdReader ( )

inline

Perform a built‑in self‑test of the Micro‑SD card interface.

This method brings up the SPI bus on the configured pins, toggles the chip‑select line, and issues a few dummy transfers to verify basic connectivity. It then attempts to initialize the SD card. If a card is present, it reports the card type (e.g., SD, SDHC), approximate capacity in megabytes, and whether a filesystem is detected. The results are printed over the serial interface. If no card is inserted, a warning is emitted but the SPI bus is still validated.

Definition at line 196 of file AudioDevice.h.

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◆ sendTestTone()

void AudioDevice::sendTestTone	(	float	freqHz = `1000.0f`,
		uint16_t	durationMs = `300`,
		uint8_t	amplitudePct = `25`
	)

inline

Play a short sine tone over I2S (self-test for speaker path).

Parameters

freqHz	Tone frequency in Hz (e.g., 1000)
durationMs	Duration in milliseconds (e.g., 300)
amplitudePct	0..100, percent of full-scale (default 25%)

Definition at line 239 of file AudioDevice.h.

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◆ setLanguage()

void AudioDevice::setLanguage ( uint8_t index )

inline

Set the language for text-to-speech conversion by index.

Parameters

index The index of the language code (0 to 9)

Definition at line 101 of file AudioDevice.h.

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◆ setVolume()

void AudioDevice::setVolume ( int volume )

inline

Set the volume for audio playback.

Parameters

volume Volume level (0 to 100)

Definition at line 91 of file AudioDevice.h.

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

Audio_Card/AudioDevice.h

Public Member Functions

Private Member Functions

Static Private Member Functions

Private Attributes

Static Private Attributes

Detailed Description

Constructor & Destructor Documentation

◆ AudioDevice()

Member Function Documentation

◆ _initEspeak()

◆ _initSpi()

◆ _setupI2S()

◆ _synthCallback()

◆ begin()

◆ playText()

◆ playWav()

◆ selfTestSdReader()

◆ sendTestTone()

◆ setLanguage()

◆ setVolume()