AX.25 packet radio demodulator (APRS, 1200 baud AFSK). The PCM audio data is written to the decoder and the received frames with a correct frame check sequence are written to the output: as monitor text lines (SRC>DEST,DIGI:info) or as KISS frames (see AX25Config::format). More...

#include <AX25Decoder.h>

Inheritance diagram for tinymodem::AX25Decoder:

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Collaboration diagram for tinymodem::AX25Decoder:

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Classes
struct	Phasor
	Rotating phasor of a tone: avoids sin() and cos() per sample. More...

Public Member Functions
	AX25Decoder ()=default
	AX25Decoder (Print &out)
AX25Config	defaultConfig ()
	Provides a default configuration: APRS (1200 baud AFSK).
void	setAudioInfo (audio_tools::AudioInfo info) override
	Defines the format of the input audio data.
audio_tools::AudioInfo	audioInfo () override
bool	begin (AX25Config config)
	Starts the processing with the indicated configuration.
bool	begin () override
void	end () override
	Reports the statistics.
void	flush () override
	Provides a frame which is held back during an FX.25 block.
size_t	write (const uint8_t *data, size_t len) override
	Provide PCM data to the decoder.
bool	isCarrier () override
	true while a frame is received
bool	isFinished () override
	The decoder never stops.
size_t	frameCount ()
	Number of received frames with a correct frame check sequence.
size_t	errorCount ()
	Number of frames with a wrong frame check sequence.
size_t	fx25Count ()
	Number of received FX.25 frames.
size_t	il2pCount ()
	Number of received IL2P frames.
size_t	correctedCount ()
	Number of bytes which were corrected by FX.25 and IL2P.
AX25Config &	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 ()
float	noise ()
	uniform random value in the range -0.5 to 0.5
void	addSample (float x)
void	recalculate ()
	Avoids the accumulation of rounding errors.
void	hdlc (int bit)
void	processFrame ()
void	deliverPending ()
void	fx25 (int bit)
	FX.25: correlation tag and Reed-Solomon block.
void	il2p (int raw)
	IL2P: sync word, header and payload.
void	deliver (const uint8_t *frame, int len)
	Writes a received frame (without FCS) to the output.
Protected Member Functions inherited from tinymodem::ModemDecoder
void	status (const char *fmt,...)

Static Protected Member Functions
static int	popcount (uint32_t v)

Protected Attributes
AX25Config	cfg
bool	is_active = false
PcmInput	input
uint32_t	noise_seed = 1
size_t	frames = 0
size_t	errors = 0
size_t	fx25_frames = 0
size_t	il2p_frames = 0
size_t	corrected_bytes = 0
int	window = 40
audio_tools::Vector< float >	products
int	pos = 0
float	sums [4] = {0, 0, 0, 0}
Phasor	mark
Phasor	space
uint32_t	sample_count = 0
float	pll_step = 0.025f
float	pll = 0
bool	last_tone = false
bool	bit_tone = false
uint8_t	history = 0
int	ones = 0
bool	in_frame = false
uint8_t	frame [AX25Frame::MAX_FRAME+2]
int	frame_len = 0
uint8_t	current = 0
int	current_bits = 0
char	text [AX25Frame::MAX_FRAME *2]
uint8_t	pending [AX25Frame::MAX_FRAME]
int	pending_len = 0
int	fx_tag = 0
uint64_t	fx_accum = 0
uint8_t	fx_block [FX25::BLOCK_SIZE]
int	fx_len = 0
int	fx_bits = 0
int	fx_total = 0
int	il_state = 0
uint32_t	il_accum = 0
bool	il_inverted = false
int	il_len = 0
int	il_bits = 0
int	il_need = 0
uint8_t	il_raw_header [IL2P::HEADER_SIZE+IL2P::HEADER_PARITY]
uint8_t	il_header [IL2P::HEADER_SIZE]
uint8_t	il_payload [IL2P_MAX_ENCODED]
int	il_corrected = 0
Protected Attributes inherited from tinymodem::ModemDecoder
Print *	p_status = nullptr
bool	is_quiet = false

Static Protected Attributes
static constexpr int	IL2P_MAX_ENCODED = AX25Frame::MAX_FRAME + 2 * 16
static constexpr float	PLL_GAIN = 0.15f

Detailed Description

AX.25 packet radio demodulator (APRS, 1200 baud AFSK). The PCM audio data is written to the decoder and the received frames with a correct frame check sequence are written to the output: as monitor text lines (SRC>DEST,DIGI:info) or as KISS frames (see AX25Config::format).

The mark and space energy is measured with sliding correlators over one bit, a digital PLL recovers the bit clock, and the bits are NRZI and HDLC decoded. The input can be 8, 16 or 32 bit signed samples with any number of channels (only AX25Config::channel is evaluated).

FX.25 and IL2P frames are decoded in parallel (independent of AX25Config::layer2) and corrected with their Reed-Solomon codes. An FX.25 frame which is also received as standard AX.25 frame is provided only once.

Copyright: GPLv3

Constructor & Destructor Documentation

◆ AX25Decoder() [1/2]

tinymodem::AX25Decoder::AX25Decoder ( )

default

◆ AX25Decoder() [2/2]

tinymodem::AX25Decoder::AX25Decoder ( Print & out )

inline

Member Function Documentation

◆ addSample()

void tinymodem::AX25Decoder::addSample ( float x )

inlineprotected

◆ audioInfo()

audio_tools::AudioInfo tinymodem::AX25Decoder::audioInfo ( )

inlineoverride

◆ begin() [1/2]

bool tinymodem::AX25Decoder::begin ( )

inlineoverride

◆ begin() [2/2]

bool tinymodem::AX25Decoder::begin ( AX25Config config )

inline

Starts the processing with the indicated configuration.

◆ config()

AX25Config & tinymodem::AX25Decoder::config ( )

inline

The configuration which was provided in begin().

◆ correctedCount()

size_t tinymodem::AX25Decoder::correctedCount ( )

inline

Number of bytes which were corrected by FX.25 and IL2P.

◆ defaultConfig()

AX25Config tinymodem::AX25Decoder::defaultConfig ( )

inline

Provides a default configuration: APRS (1200 baud AFSK).

◆ deliver()

void tinymodem::AX25Decoder::deliver	(	const uint8_t *	frame,
		int	len )

inlineprotected

Writes a received frame (without FCS) to the output.

◆ deliverPending()

void tinymodem::AX25Decoder::deliverPending ( )

inlineprotected

◆ end()

void tinymodem::AX25Decoder::end ( )

inlineoverride

Reports the statistics.

◆ errorCount()

size_t tinymodem::AX25Decoder::errorCount ( )

inline

Number of frames with a wrong frame check sequence.

◆ flush()

void tinymodem::AX25Decoder::flush ( )

inlineoverridevirtual

Provides a frame which is held back during an FX.25 block.

Implements tinymodem::ModemDecoder.

◆ frameCount()

size_t tinymodem::AX25Decoder::frameCount ( )

inline

Number of received frames with a correct frame check sequence.

◆ fx25()

void tinymodem::AX25Decoder::fx25 ( int bit )

inlineprotected

FX.25: correlation tag and Reed-Solomon block.

◆ fx25Count()

size_t tinymodem::AX25Decoder::fx25Count ( )

inline

Number of received FX.25 frames.

◆ hdlc()

void tinymodem::AX25Decoder::hdlc ( int bit )

inlineprotected

◆ il2p()

void tinymodem::AX25Decoder::il2p ( int raw )

inlineprotected

IL2P: sync word, header and payload.

◆ il2pCount()

size_t tinymodem::AX25Decoder::il2pCount ( )

inline

Number of received IL2P frames.

◆ isCarrier()

bool tinymodem::AX25Decoder::isCarrier ( )

inlineoverridevirtual

true while a frame is received

Implements tinymodem::ModemDecoder.

◆ isFinished()

bool tinymodem::AX25Decoder::isFinished ( )

inlineoverridevirtual

The decoder never stops.

Implements tinymodem::ModemDecoder.

◆ noise()

float tinymodem::AX25Decoder::noise ( )

inlineprotected

uniform random value in the range -0.5 to 0.5

◆ operator bool()

tinymodem::AX25Decoder::operator bool ( )

inlineoverride

◆ popcount()

int tinymodem::AX25Decoder::popcount ( uint32_t v )

inlinestaticprotected

◆ processFrame()

void tinymodem::AX25Decoder::processFrame ( )

inlineprotected

◆ recalculate()

void tinymodem::AX25Decoder::recalculate ( )

inlineprotected

Avoids the accumulation of rounding errors.

◆ resetState()

void tinymodem::AX25Decoder::resetState ( )

inlineprotected

◆ setAudioInfo()

void tinymodem::AX25Decoder::setAudioInfo ( audio_tools::AudioInfo info )

inlineoverride

Defines the format of the input audio data.

◆ write()

size_t tinymodem::AX25Decoder::write	(	const uint8_t *	data,
		size_t	len )

inlineoverride

Provide PCM data to the decoder.

Member Data Documentation

◆ bit_tone

bool tinymodem::AX25Decoder::bit_tone = false

protected

◆ cfg

AX25Config tinymodem::AX25Decoder::cfg

protected

◆ corrected_bytes

size_t tinymodem::AX25Decoder::corrected_bytes = 0

protected

◆ current

uint8_t tinymodem::AX25Decoder::current = 0

protected

◆ current_bits

int tinymodem::AX25Decoder::current_bits = 0

protected

◆ errors

size_t tinymodem::AX25Decoder::errors = 0

protected

◆ frame

uint8_t tinymodem::AX25Decoder::frame[AX25Frame::MAX_FRAME+2]

protected

◆ frame_len

int tinymodem::AX25Decoder::frame_len = 0

protected

◆ frames

size_t tinymodem::AX25Decoder::frames = 0

protected

◆ fx25_frames

size_t tinymodem::AX25Decoder::fx25_frames = 0

protected

◆ fx_accum

uint64_t tinymodem::AX25Decoder::fx_accum = 0

protected

◆ fx_bits

int tinymodem::AX25Decoder::fx_bits = 0

protected

◆ fx_block

uint8_t tinymodem::AX25Decoder::fx_block[FX25::BLOCK_SIZE]

protected

◆ fx_len

int tinymodem::AX25Decoder::fx_len = 0

protected

◆ fx_tag

int tinymodem::AX25Decoder::fx_tag = 0

protected

◆ fx_total

int tinymodem::AX25Decoder::fx_total = 0

protected

◆ history

uint8_t tinymodem::AX25Decoder::history = 0

protected

◆ il2p_frames

size_t tinymodem::AX25Decoder::il2p_frames = 0

protected

◆ IL2P_MAX_ENCODED

int tinymodem::AX25Decoder::IL2P_MAX_ENCODED = AX25Frame::MAX_FRAME + 2 * 16

staticconstexprprotected

◆ il_accum

uint32_t tinymodem::AX25Decoder::il_accum = 0

protected

◆ il_bits

int tinymodem::AX25Decoder::il_bits = 0

protected

◆ il_corrected

int tinymodem::AX25Decoder::il_corrected = 0

protected

◆ il_header

uint8_t tinymodem::AX25Decoder::il_header[IL2P::HEADER_SIZE]

protected

◆ il_inverted

bool tinymodem::AX25Decoder::il_inverted = false

protected

◆ il_len

int tinymodem::AX25Decoder::il_len = 0

protected

◆ il_need

int tinymodem::AX25Decoder::il_need = 0

protected

◆ il_payload

uint8_t tinymodem::AX25Decoder::il_payload[IL2P_MAX_ENCODED]

protected

◆ il_raw_header

uint8_t tinymodem::AX25Decoder::il_raw_header[IL2P::HEADER_SIZE+IL2P::HEADER_PARITY]

protected

◆ il_state

int tinymodem::AX25Decoder::il_state = 0

protected

◆ in_frame

bool tinymodem::AX25Decoder::in_frame = false

protected

◆ input

PcmInput tinymodem::AX25Decoder::input

protected

◆ is_active

bool tinymodem::AX25Decoder::is_active = false

protected

◆ last_tone

bool tinymodem::AX25Decoder::last_tone = false

protected

◆ mark

Phasor tinymodem::AX25Decoder::mark

protected

◆ noise_seed

uint32_t tinymodem::AX25Decoder::noise_seed = 1

protected

◆ ones

int tinymodem::AX25Decoder::ones = 0

protected

◆ pending

uint8_t tinymodem::AX25Decoder::pending[AX25Frame::MAX_FRAME]

protected

◆ pending_len

int tinymodem::AX25Decoder::pending_len = 0

protected

◆ pll

float tinymodem::AX25Decoder::pll = 0

protected

◆ PLL_GAIN

float tinymodem::AX25Decoder::PLL_GAIN = 0.15f

staticconstexprprotected

◆ pll_step

float tinymodem::AX25Decoder::pll_step = 0.025f

protected

◆ pos

int tinymodem::AX25Decoder::pos = 0

protected

◆ products

audio_tools::Vector<float> tinymodem::AX25Decoder::products

protected

◆ sample_count

uint32_t tinymodem::AX25Decoder::sample_count = 0

protected

◆ space

Phasor tinymodem::AX25Decoder::space

protected

◆ sums

float tinymodem::AX25Decoder::sums[4] = {0, 0, 0, 0}

protected

◆ text

char tinymodem::AX25Decoder::text[AX25Frame::MAX_FRAME *2]

protected

◆ window

int tinymodem::AX25Decoder::window = 40

protected

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

src/modem/AX25Decoder.h

Classes

Public Member Functions

Protected Member Functions

Static Protected Member Functions

Protected Attributes

Static Protected Attributes

Detailed Description

Constructor & Destructor Documentation

◆ AX25Decoder() [1/2]

◆ AX25Decoder() [2/2]

Member Function Documentation

◆ addSample()

◆ audioInfo()

◆ begin() [1/2]

◆ begin() [2/2]

◆ config()

◆ correctedCount()

◆ defaultConfig()

◆ deliver()

◆ deliverPending()

◆ end()

◆ errorCount()

◆ flush()

◆ frameCount()

◆ fx25()

◆ fx25Count()

◆ hdlc()

◆ il2p()

◆ il2pCount()

◆ isCarrier()

◆ isFinished()

◆ noise()

◆ operator bool()

◆ popcount()

◆ processFrame()

◆ recalculate()

◆ resetState()

◆ setAudioInfo()

◆ write()

Member Data Documentation

◆ bit_tone

◆ cfg

◆ corrected_bytes

◆ current

◆ current_bits

◆ errors

◆ frame

◆ frame_len

◆ frames

◆ fx25_frames

◆ fx_accum

◆ fx_bits

◆ fx_block

◆ fx_len

◆ fx_tag

◆ fx_total

◆ history

◆ il2p_frames

◆ IL2P_MAX_ENCODED

◆ il_accum

◆ il_bits

◆ il_corrected

◆ il_header

◆ il_inverted

◆ il_len

◆ il_need

◆ il_payload

◆ il_raw_header

◆ il_state

◆ in_frame

◆ input

◆ is_active

◆ last_tone

◆ mark

◆ noise_seed

◆ ones

◆ pending

◆ pending_len

◆ pll

◆ PLL_GAIN