DTMF (touch tone) demodulator: the PCM audio data is written to the decoder and the received keys (0-9, *, #, A-D) are written to the output. The input can be 8, 16 or 32 bit signed samples with any number of channels (only DTMFConfig::channel is evaluated). More...

#include <DTMFDecoder.h>

Inheritance diagram for tinymodem::DTMFDecoder:

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Collaboration diagram for tinymodem::DTMFDecoder:

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Classes
struct	Window
	Goertzel filters of one window. More...

Public Member Functions
	DTMFDecoder ()=default
	DTMFDecoder (Print &out)
DTMFConfig	defaultConfig ()
	Provides a default configuration.
void	setAudioInfo (audio_tools::AudioInfo info) override
	Defines the format of the input audio data.
audio_tools::AudioInfo	audioInfo () override
bool	begin (DTMFConfig config)
	Starts the processing with the indicated configuration.
bool	begin () override
void	end () override
	Processes the remaining samples and reports the end of the carrier.
void	flush () override
	Processes the remaining samples (e.g. at the end of the input).
size_t	write (const uint8_t *data, size_t len) override
	Provide PCM data to the decoder.
bool	isCarrier () override
	true from the first key until the end of the transmission
bool	isFinished () override
	true if the decoding was stopped (rx_one)
char	currentKey ()
	The key which is currently received or 0.
DTMFConfig &	config ()
	The configuration which was provided in begin().
	operator bool () override
Public Member Functions inherited from tinymodem::ModemDecoder
void	setStatusOutput (Print &out)
	Defines the output for the ### CARRIER / ### NOCARRIER messages.
void	setQuiet (bool quiet)
	Suppresses the status messages.
const char *	mime () override

Protected Member Functions
void	resetState ()
void	resetWindow (Window &w)
float	noise ()
	uniform random value in the range -0.5 to 0.5
void	addSample (float x, bool add_noise)
int	detect (Window &w)
void	decide (int key)
	Debouncing of the detected keys.
void	startOfCarrier ()
void	endOfCarrier ()
Protected Member Functions inherited from tinymodem::ModemDecoder
void	status (const char *fmt,...)

Static Protected Member Functions
static int	strongest (const float *amp)

Protected Attributes
DTMFConfig	cfg
bool	is_active = false
bool	is_finished = false
PcmInput	input
uint32_t	noise_seed = 1
int	window = 205
int	step = 51
float	coeff [TONES]
Window	windows [WINDOWS]
uint32_t	timeout = 0
float	twist = 6.3f
float	group_ratio = 4.0f
int	candidate = -1
int	hits = 0
int	held = -1
int	misses = 0
int	last_key = -1
float	last_level = 0
float	level = 0
bool	carrier = false
uint32_t	idle_samples = 0
unsigned	ndata = 0
Protected Attributes inherited from tinymodem::ModemDecoder
Print *	p_status = nullptr
bool	is_quiet = false

Static Protected Attributes
static constexpr int	TONES = 8
static constexpr int	WINDOWS = 4
static constexpr float	WINDOW_SEC = 205.0f / 8000.0f
static constexpr int	HITS = 3
static constexpr int	MISSES = 3
static constexpr float	ECHO_LEVEL = 0.5f
	the same key with a lower level (relative to the last one) is an echo
static constexpr float	ENERGY_RATIO = 0.3f
	part of the signal energy which must be in the two tones

Detailed Description

DTMF (touch tone) demodulator: the PCM audio data is written to the decoder and the received keys (0-9, *, #, A-D) are written to the output. The input can be 8, 16 or 32 bit signed samples with any number of channels (only DTMFConfig::channel is evaluated).

The 8 tones are measured with Goertzel filters over windows of 25.6 ms (205 samples at 8000 Hz). Four windows overlap, so that a new result is available every 6.4 ms. A key is detected when the strongest row and column tone are clearly above the other tones of their group (DTMFConfig::group_ratio_db), have a similar level (DTMFConfig::max_twist_db) and contain most of the signal energy. A key is reported after 3 consecutive detections and released after 3 windows without it. The same key is only reported again if it is at least half as strong as before: this ignores the echo at the end of a tone.

A transmission ends after DTMFConfig::rx_timeout_ms without a key: this is reported with ### NOCARRIER.

Copyright: GPLv3

Constructor & Destructor Documentation

◆ DTMFDecoder() [1/2]

tinymodem::DTMFDecoder::DTMFDecoder ( )

default

◆ DTMFDecoder() [2/2]

tinymodem::DTMFDecoder::DTMFDecoder ( Print & out )

inline

Member Function Documentation

◆ addSample()

void tinymodem::DTMFDecoder::addSample	(	float	x,
		bool	add_noise )

inlineprotected

◆ audioInfo()

audio_tools::AudioInfo tinymodem::DTMFDecoder::audioInfo ( )

inlineoverride

◆ begin() [1/2]

bool tinymodem::DTMFDecoder::begin ( )

inlineoverride

◆ begin() [2/2]

bool tinymodem::DTMFDecoder::begin ( DTMFConfig config )

inline

Starts the processing with the indicated configuration.

◆ config()

DTMFConfig & tinymodem::DTMFDecoder::config ( )

inline

The configuration which was provided in begin().

◆ currentKey()

char tinymodem::DTMFDecoder::currentKey ( )

inline

The key which is currently received or 0.

◆ decide()

void tinymodem::DTMFDecoder::decide ( int key )

inlineprotected

Debouncing of the detected keys.

◆ defaultConfig()

DTMFConfig tinymodem::DTMFDecoder::defaultConfig ( )

inline

Provides a default configuration.

◆ detect()

int tinymodem::DTMFDecoder::detect ( Window & w )

inlineprotected

Evaluates a completed window: returns the key index (row * 4 + column) or -1

◆ end()

void tinymodem::DTMFDecoder::end ( )

inlineoverride

Processes the remaining samples and reports the end of the carrier.

◆ endOfCarrier()

void tinymodem::DTMFDecoder::endOfCarrier ( )

inlineprotected

◆ flush()

void tinymodem::DTMFDecoder::flush ( )

inlineoverridevirtual

Processes the remaining samples (e.g. at the end of the input).

Implements tinymodem::ModemDecoder.

◆ isCarrier()

bool tinymodem::DTMFDecoder::isCarrier ( )

inlineoverridevirtual

true from the first key until the end of the transmission

Implements tinymodem::ModemDecoder.

◆ isFinished()

bool tinymodem::DTMFDecoder::isFinished ( )

inlineoverridevirtual

true if the decoding was stopped (rx_one)

Implements tinymodem::ModemDecoder.

◆ noise()

float tinymodem::DTMFDecoder::noise ( )

inlineprotected

uniform random value in the range -0.5 to 0.5

◆ operator bool()

tinymodem::DTMFDecoder::operator bool ( )

inlineoverride

◆ resetState()

void tinymodem::DTMFDecoder::resetState ( )

inlineprotected

◆ resetWindow()

void tinymodem::DTMFDecoder::resetWindow ( Window & w )

inlineprotected

◆ setAudioInfo()

void tinymodem::DTMFDecoder::setAudioInfo ( audio_tools::AudioInfo info )

inlineoverride

Defines the format of the input audio data.

◆ startOfCarrier()

void tinymodem::DTMFDecoder::startOfCarrier ( )

inlineprotected

◆ strongest()

int tinymodem::DTMFDecoder::strongest ( const float * amp )

inlinestaticprotected

◆ write()

size_t tinymodem::DTMFDecoder::write	(	const uint8_t *	data,
		size_t	len )

inlineoverride

Provide PCM data to the decoder.

Member Data Documentation

◆ candidate

int tinymodem::DTMFDecoder::candidate = -1

protected

◆ carrier

bool tinymodem::DTMFDecoder::carrier = false

protected

◆ cfg

DTMFConfig tinymodem::DTMFDecoder::cfg

protected

◆ coeff

float tinymodem::DTMFDecoder::coeff[TONES]

protected

◆ ECHO_LEVEL

float tinymodem::DTMFDecoder::ECHO_LEVEL = 0.5f

staticconstexprprotected

the same key with a lower level (relative to the last one) is an echo

◆ ENERGY_RATIO

float tinymodem::DTMFDecoder::ENERGY_RATIO = 0.3f

staticconstexprprotected

part of the signal energy which must be in the two tones

◆ group_ratio

float tinymodem::DTMFDecoder::group_ratio = 4.0f

protected

◆ held

int tinymodem::DTMFDecoder::held = -1

protected

◆ HITS

int tinymodem::DTMFDecoder::HITS = 3

staticconstexprprotected

◆ hits

int tinymodem::DTMFDecoder::hits = 0

protected

◆ idle_samples

uint32_t tinymodem::DTMFDecoder::idle_samples = 0

protected

◆ input

PcmInput tinymodem::DTMFDecoder::input

protected

◆ is_active

bool tinymodem::DTMFDecoder::is_active = false

protected

◆ is_finished

bool tinymodem::DTMFDecoder::is_finished = false

protected

◆ last_key

int tinymodem::DTMFDecoder::last_key = -1

protected

◆ last_level

float tinymodem::DTMFDecoder::last_level = 0

protected

◆ level

float tinymodem::DTMFDecoder::level = 0

protected

◆ MISSES

int tinymodem::DTMFDecoder::MISSES = 3

staticconstexprprotected

◆ misses

int tinymodem::DTMFDecoder::misses = 0

protected

◆ ndata

unsigned tinymodem::DTMFDecoder::ndata = 0

protected

◆ noise_seed

uint32_t tinymodem::DTMFDecoder::noise_seed = 1

protected

◆ step

int tinymodem::DTMFDecoder::step = 51

protected

◆ timeout

uint32_t tinymodem::DTMFDecoder::timeout = 0

protected

◆ TONES

int tinymodem::DTMFDecoder::TONES = 8

staticconstexprprotected

◆ twist

float tinymodem::DTMFDecoder::twist = 6.3f

protected

◆ window

int tinymodem::DTMFDecoder::window = 205

protected

◆ WINDOW_SEC

float tinymodem::DTMFDecoder::WINDOW_SEC = 205.0f / 8000.0f

staticconstexprprotected

◆ WINDOWS

int tinymodem::DTMFDecoder::WINDOWS = 4

staticconstexprprotected

◆ windows

Window tinymodem::DTMFDecoder::windows[WINDOWS]

protected

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

src/modem/DTMFDecoder.h

Classes

Public Member Functions

Protected Member Functions

Static Protected Member Functions

Protected Attributes

Static Protected Attributes

Detailed Description

Constructor & Destructor Documentation

◆ DTMFDecoder() [1/2]

◆ DTMFDecoder() [2/2]

Member Function Documentation

◆ addSample()

◆ audioInfo()

◆ begin() [1/2]

◆ begin() [2/2]

◆ config()

◆ currentKey()

◆ decide()

◆ defaultConfig()

◆ detect()

◆ end()

◆ endOfCarrier()

◆ flush()

◆ isCarrier()

◆ isFinished()

◆ noise()

◆ operator bool()

◆ resetState()

◆ resetWindow()

◆ setAudioInfo()

◆ startOfCarrier()

◆ strongest()

◆ write()

Member Data Documentation

◆ candidate

◆ carrier

◆ cfg

◆ coeff

◆ ECHO_LEVEL

◆ ENERGY_RATIO

◆ group_ratio

◆ held

◆ HITS

◆ hits

◆ idle_samples

◆ input

◆ is_active

◆ is_finished

◆ last_key

◆ last_level

◆ level

◆ MISSES

◆ misses

◆ ndata

◆ noise_seed

◆ step

◆ timeout

◆ TONES

◆ twist

◆ window

◆ WINDOW_SEC

◆ WINDOWS

◆ windows