TinyModem: software audio modems and packets with error correction. More...

Classes
struct	AX25Config
	Configuration of the AX.25 packet radio modem (AX25Encoder, AX25Decoder): Bell 202 AFSK with 1200 baud, NRZI and HDLC framing, as used by APRS. More...
class	AX25Frame
	Conversion between AX.25 frames and the monitor text format (SRC>DEST,DIGI1,DIGI2*:info) and the KISS framing. More...
class	AX25Decoder
	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...
class	AX25Encoder
	AX.25 packet radio modulator (APRS, 1200 baud AFSK). The written data is converted to AX.25 frames, which are sent with HDLC framing (flags, bit stuffing, frame check sequence) and NRZI coding. More...
class	FX25
	FX.25: AX.25 frames with Reed-Solomon forward error correction (as implemented by direwolf). The complete HDLC frame (flag, bit stuffed frame with FCS, flags as fill) is the data part of a Reed-Solomon code word, which is preceded by a 64 bit correlation tag that identifies the code. A receiver without FX.25 still decodes the HDLC frame in the data part. More...
class	IL2P
	IL2P (Improved Layer 2 Protocol, as implemented by direwolf): an AX.25 frame is sent as a scrambled header with Reed-Solomon parity and a scrambled payload in Reed-Solomon blocks, without HDLC framing and NRZI. Header type 1 compresses the addresses and the control field of frames with 2 addresses, header type 0 carries the complete AX.25 frame as payload. More...
struct	CSSConfig
	Configuration of the chirp spread spectrum modem (CSSEncoder, CSSDecoder), which works like LoRa in the audio band: each symbol is a linear chirp over the bandwidth, which starts at one of N = 2^SF frequencies and carries SF bits (SF = spreading factor). The signal can be received far below the noise level and is robust against frequency offsets, different clocks and echoes. It is not compatible with LoRa radios. More...
class	CSSFrame
	Frame format of the chirp spread spectrum modem: the bytes of the header code word (length and parity) and of the payload code word (data, CRC-16 and parity) are sent as SF bits per symbol, most significant bit first. The symbol value is the inverse Gray code of the bits, so that a detection in the neighboring FFT bin causes only 1 wrong bit. More...
class	CSSDecoder
	Chirp spread spectrum demodulator (LoRa-like): the PCM audio data is written to the decoder and the payload of the received frames with a correct CRC is written to the output. The input can be 8, 16 or 32 bit signed samples with any number of channels (only CSSConfig::channel is evaluated). More...
class	CSSEncoder
	Chirp spread spectrum modulator (LoRa-like): the written bytes are collected and sent as frame when CSSConfig::max_frame bytes are available or when you call endTransmission() (or flush()). A frame consists of the preamble (up chirps), 2 down chirps, the header and the payload. Each symbol is a chirp which starts at the frequency of its value and wraps around at the end of the band. The phase is continuous. More...
class	DataCodec
	Converts between characters and the data bits of a frame. More...
class	AsciiCodec
	ASCII 8-bit data (passthrough). More...
class	BinaryCodec
	Raw N-bit binary data: prints the bits as '0' and '1' followed by newline. More...
class	BaudotCodec
	Baudot (ITA2) 5-bit data. More...
class	CallerIDCodec
	Caller-ID (USA SDMF/MDMF) decoder. See http://melabs.com/resources/callerid.htm. More...
class	UICCodec
	UIC-751-3 ground-train or train-ground decoder. More...
class	PrintFilter
	Print which replaces non printable characters with '.'. More...
class	SampleRateConverter
	Converts the sample rate of a signal with a windowed sinc low pass filter (by default the cut off is at 45% of the lower sample rate). More...
class	SimpleFFT
	Radix 2 complex FFT with a precomputed twiddle table. More...
struct	DTMFConfig
	Configuration of the DTMF (touch tone) modem (DTMFEncoder, DTMFDecoder): each of the characters 0-9, *, #, A, B, C and D is sent as the sum of a row tone (697 - 941 Hz) and a column tone (1209 - 1633 Hz). More...
class	DTMFKeys
	The DTMF keypad: the tones and the characters of the 16 keys. More...
class	DTMFDecoder
	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...
class	DTMFEncoder
	DTMF (touch tone) modulator: each written character 0-9, *, #, A-D (also a-d) is sent as a tone pair of DTMFConfig::tone_ms followed by a pause of DTMFConfig::pause_ms. A ',' adds a pause of DTMFConfig::comma_ms, all other characters are ignored. The tones fade in and out within 2 ms to avoid clicks. More...
class	FSKDecoder
	FSK demodulator: PCM audio data is written to the decoder and the decoded data is written to the output that was defined with setOutput(). Supported input formats are 8, 16 or 32 bit signed integer samples with any number of channels (only config.channel is evaluated). The decoding is compatible with minimodem –tx. More...
class	FSKDemodulator
	FSK bit and frame analysis (port of minimodem's fsk.c). Instead of a full FFT we use the Goertzel algorithm from the AudioTools to determine the magnitude of the mark and space bands. The bands are defined like the FFT bins of minimodem, so the results are equivalent. More...
class	FSKEncoder
	FSK modulator: converts the written characters into 16 bit PCM audio which is written to the defined output. The generated signal is compatible with minimodem –rx. More...
struct	GGWaveProtocol
	Transmission protocol of ggwave (https://github.com/ggerganov/ggwave): the ids and parameters are identical to the original. The tones are multiples of sample_rate / samplesPerFrame (46.875 Hz at 48 kHz). More...
struct	GGWaveConfig
	Configuration of the ggwave compatible modem (GGWaveEncoder, GGWaveDecoder). Each message (up to 140 bytes) starts and ends with a marker and is protected by Reed-Solomon codes. Each byte is sent as 2 of 16 tones which are transmitted at the same time. More...
class	GGWaveDecoder
	ggwave compatible demodulator: the PCM audio data is written to the decoder and the payload of the received messages is written to the output. The input can be 8, 16 or 32 bit signed samples with any number of channels (only GGWaveConfig::channel is evaluated). More...
class	GGWaveEncoder
	ggwave compatible modulator: the written bytes are collected into messages of up to 140 bytes. A message is sent when it is full or when you call endTransmission() (or flush()). The generated audio is identical to the audio of ggwave (variable length format). More...
struct	MFSKConfig
	Configuration of the multi-tone FSK modem (MFSKEncoder, MFSKDecoder). Each symbol is one of tones tones and carries log2(tones) bits. The tones are base_freq + i * tone_spacing. More...
class	MFSKDecoder
	Multi-tone FSK demodulator: PCM audio data is written to the decoder and the decoded bytes are written to the output. The input can be 8, 16 or 32 bit signed samples with any number of channels (only MFSKConfig::channel is evaluated). More...
class	MFSKEncoder
	Multi-tone FSK modulator: converts the written bytes into 16 bit PCM audio. Each symbol is one of MFSKConfig::tones tones and carries log2(tones) bits (Gray coded, most significant bit first). More...
class	FSKToneGenerator
	Default sine generator of the encoders: like minimodem it keeps the phase continuous when the frequency is changed (continuous phase FSK) and restarts it at phase 0 after silence (frequency 0). More...
class	ToneOutput
	Writes tones of a SoundGenerator as 16 bit PCM with the requested number of channels and volume to a Print. More...
class	SampleOutput
	Writes float samples (-1.0 to 1.0) as 16 bit PCM with the requested number of channels and volume to a Print. More...
class	PcmInput
	Assembles the PCM frames from the written bytes and provides the samples of the selected channel as float (-1.0 to 1.0). Supports 8, 16 and 32 bit signed samples. More...
class	ByteQueue
	FIFO for received data which grows when needed: e.g. one decoding step can produce more data than expected (like a Caller-ID message). More...
class	ModemEncoder
	Common API of the modulators (FSKEncoder, MFSKEncoder): the written data is converted to 16 bit PCM audio which is written to the output. More...
class	ModemDecoder
	Common API of the demodulators (FSKDecoder, MFSKDecoder): PCM audio data is written to the decoder and the decoded data is written to the output. Status messages (### CARRIER and ### NOCARRIER) are written to the status output. More...
struct	ModemConfig
	Configuration of the FSK modem. The fields correspond to the command line options of minimodem. Call setMode() to select one of the predefined baud modes ("1200", "300", "rtty", "tdd", "same", "callerid", "uic-train", "uic-ground", "V.21" or any number N for a Bell-like N bps modem) first and then change the individual fields. Fields which are left at 0 (or -1) are derived automatically when the encoder or decoder is started. More...
class	BasicModemStream
	Arduino Stream API for a modem (encoder and decoder): the written characters are modulated to the audio output and the audio input is demodulated into characters that can be read. You can use only the output (transmit only), only the input (receive only) or both. More...
class	ModemStream
	Arduino Stream API for the minimodem compatible FSK modem: print() transmits, read() receives. See BasicModemStream. More...
class	MFSKStream
	Arduino Stream API for the multi-tone FSK modem: print() transmits, read() receives. See BasicModemStream. More...
class	AX25Stream
	Arduino Stream API for the AX.25 packet radio modem (APRS): print() transmits the frames, read() provides the received frames, both as monitor text lines or KISS frames. See BasicModemStream. More...
class	PSKStream
	Arduino Stream API for the PSK modem (PSK31 to PSK500): print() transmits, read() receives. See BasicModemStream. More...
class	OFDMStream
	Arduino Stream API for the OFDM modem: print() collects the data, flush() sends it as frame, read() receives. See BasicModemStream. More...
class	GGWaveStream
	Arduino Stream API for the ggwave compatible modem: print() collects the data (up to 140 bytes), flush() sends it as message, read() receives. See BasicModemStream. More...
class	OliviaStream
	Arduino Stream API for the Olivia and Contestia modems (compatible with fldigi): print() transmits, flush() completes the last block, read() receives. See BasicModemStream. More...
class	CSSStream
	Arduino Stream API for the chirp spread spectrum modem (LoRa-like): print() collects the data, flush() sends it as frame, read() receives. See BasicModemStream. More...
class	MorseStream
	Arduino Stream API for Morse code (International or American): print() transmits, read() receives. See BasicModemStream. More...
class	DTMFStream
	Arduino Stream API for the DTMF (touch tone) modem: print() sends the keys 0-9, *, #, A-D, read() provides the received keys. See BasicModemStream. More...
class	BasicModemStreamRTOS
	BasicModemStream which receives in a separate task (FreeRTOS on ESP32 and RP2040, a std::thread on the desktop): the task reads the audio input and decodes it, so the decoding does not block your loop() and no audio is lost while loop() is busy. available(), read() and peek() only access the received data and can be called from any task. More...
class	ModemStreamRTOS
	ModemStream (FSK) which receives in a separate task. See BasicModemStreamRTOS. More...
class	MFSKStreamRTOS
	MFSKStream (multi-tone FSK) which receives in a separate task. See BasicModemStreamRTOS. More...
class	AX25StreamRTOS
	AX25Stream (APRS) which receives in a separate task. See BasicModemStreamRTOS. More...
class	PSKStreamRTOS
	PSKStream which receives in a separate task. See BasicModemStreamRTOS. More...
class	OFDMStreamRTOS
	OFDMStream which receives in a separate task. See BasicModemStreamRTOS. More...
class	GGWaveStreamRTOS
	GGWaveStream which receives in a separate task. See BasicModemStreamRTOS. More...
class	OliviaStreamRTOS
	OliviaStream which receives in a separate task. See BasicModemStreamRTOS. More...
class	CSSStreamRTOS
	CSSStream which receives in a separate task. See BasicModemStreamRTOS. More...
class	MorseStreamRTOS
	MorseStream which receives in a separate task. See BasicModemStreamRTOS. More...
class	DTMFStreamRTOS
	DTMFStream which receives in a separate task. See BasicModemStreamRTOS. More...
struct	MorseConfig
	Configuration of the Morse code modem (MorseEncoder, MorseDecoder): a tone which is switched on and off (CW). The speed is defined in words per minute (PARIS): a unit (the length of a dot) is 1.2 / wpm seconds. More...
class	MorseCode
	The Morse code tables and timing. A code is a string of '.' (dot), '-' (dash), '_' (long dash of the American L), '=' (longer dash of the American 0) and ' ' (space within a character of American Morse). More...
class	MorseDecoder
	Morse code demodulator (CW): the PCM audio data is written to the decoder and the decoded characters (upper case) are written to the output. The input can be 8, 16 or 32 bit signed samples with any number of channels (only MorseConfig::channel is evaluated). More...
class	MorseEncoder
	Morse code modulator (CW): each written character is sent as dots and dashes of a tone with the timing of the alphabet (International: dot 1, dash 3, element space 1, letter space 3, word space 7 units). A space (or a character which is not in the alphabet) is a word space. The tone is switched on and off with a raised cosine ramp of MorseConfig::ramp_ms. More...
struct	OFDMConfig
	Configuration of the OFDM modem (OFDMEncoder, OFDMDecoder): the data is transmitted in parallel on carriers subcarriers with differential QPSK (2 bits per carrier and symbol). Each symbol has a cyclic prefix (guard interval) against echoes. More...
class	OFDMTable
	Sine and cosine of 2 * PI * i / size. More...
class	OFDMDecoder
	OFDM demodulator: the PCM audio data is written to the decoder and the decoded frames are written to the output. The input can be 8, 16 or 32 bit signed samples with any number of channels (only OFDMConfig::channel is evaluated). More...
class	OFDMEncoder
	OFDM modulator: the written bytes are collected into frames (up to OFDMConfig::max_frame bytes) which are transmitted with differential QPSK on all carriers. A frame is sent when it is full or when you call endTransmission() (or flush()). More...
struct	OliviaConfig
	Configuration of the Olivia and Contestia modems (OliviaEncoder, OliviaDecoder): MFSK with 2 to 256 tones and a strong forward error correction (Walsh-Hadamard codes over blocks of 64 or 32 symbols), as designed by Pawel Jalocha and implemented by fldigi. More...
class	OliviaCodec
	The forward error correction of Olivia and Contestia (as in fldigi): each character of a block of bitsPerSymbol() characters is a Walsh-Hadamard code word of 64 (Contestia: 32) bits, which is scrambled and spread diagonally over the 64 (32) symbols of the block. More...
class	OliviaDecoder
	Olivia and Contestia demodulator (compatible with fldigi): the PCM audio data is written to the decoder and the decoded characters are written to the output. The input can be 8, 16 or 32 bit signed samples with any number of channels (only OliviaConfig::channel is evaluated). More...
class	OliviaEncoder
	Olivia and Contestia modulator (compatible with fldigi): the written characters are collected in blocks of bitsPerSymbol() characters, which are FEC encoded into 64 (Contestia: 32) symbols. Each symbol is a tone with a raised cosine envelope over two symbol periods, so consecutive symbols overlap by half. More...
struct	PacketStatistics
	Statistics of the received packets. More...
struct	PacketFormat
	Constants of the packet format. More...
class	PacketEncoder
	Splits the written data into packets with a CRC-16 and Reed-Solomon forward error correction, which are framed with HDLC-style flags (0x7E) and byte stuffing, and writes them to the output (e.g. a ModemStream). More...
class	PacketDecoder
	Receives the packets of a PacketEncoder: the written bytes (e.g. the output of a modem decoder) are deframed, corrected and checked, and the payload of the valid packets is written to the output. More...
class	PacketStream
	Reliable data transfer over any Stream (e.g. a ModemStream, an MFSKStream or a Serial): the written data is sent in packets with CRC-16 and Reed-Solomon forward error correction, and only correct data can be read. Corrupted packets which can't be corrected are dropped. More...
struct	PSKConfig
	Configuration of the PSK modem (PSKEncoder, PSKDecoder): differential PSK with cosine shaped transitions like PSK31, compatible with fldigi. More...
class	Varicode
	The PSK31 Varicode (as extended by fldigi to all 256 byte values): frequent characters have short codes. A code starts and ends with 1 and contains no "00": the characters are separated by "00". More...
class	MFSKVaricode
	The IZ8BLY MFSK Varicode (as used by fldigi for 8PSK): a code starts with 1 and does not contain "001", so a character ends when "001" is received (the 1 starts the next character). More...
class	QPSKCode
	Rate 1/2 convolutional code with K=5 (polynomials 0x17 and 0x19) of QPSK31 (fldigi) and a soft decision Viterbi decoder. More...
class	PSKDecoder
	PSK demodulator (BPSK, QPSK and 8PSK compatible with fldigi): the PCM audio data is written to the decoder and the decoded bytes are written to the output. The input can be 8, 16 or 32 bit signed samples with any number of channels (only PSKConfig::channel is evaluated). More...
class	PSKEncoder
	PSK modulator (compatible with fldigi): the written bytes are Varicode encoded and each symbol is a phase step with a cosine shaped transition from the previous phase. More...
class	RSCodec
	Reed-Solomon code over GF(256) with the polynomial 0x11d and lengths which are defined at runtime. The generator roots are alpha^fcr to alpha^(fcr+ecc-1): fcr = 0 is used by ggwave (Mike Lubinets' library) and IL2P, fcr = 1 by FX.25. The parity bytes follow the message, the first byte is the highest power (like Phil Karn's library). More...

Typedefs
using	GGWaveRS = RSCodec

Enumerations
enum class	AX25Format { TEXT , KISS }
enum class	AX25Layer2 { AX25 , FX25 , IL2P }
enum	GGWaveProtocolId { GGWAVE_AUDIBLE_NORMAL = 0 , GGWAVE_AUDIBLE_FAST = 1 , GGWAVE_AUDIBLE_FASTEST = 2 , GGWAVE_ULTRASOUND_NORMAL = 3 , GGWAVE_ULTRASOUND_FAST = 4 , GGWAVE_ULTRASOUND_FASTEST = 5 , GGWAVE_DT_NORMAL = 6 , GGWAVE_DT_FAST = 7 , GGWAVE_DT_FASTEST = 8 }
	Protocol ids of ggwave: the values are identical to ggwave's ggwave_ProtocolId. The mono-tone protocols (MT, 9 - 11) are not supported. More...
enum class	DataFormat { ASCII , BAUDOT , BINARY , CALLERID , UIC_TRAIN , UIC_GROUND }
	Data encoding which is used for the payload of a frame. More...
enum class	MorseAlphabet { INTERNATIONAL , AMERICAN }
	Morse code alphabet. More...
enum class	PSKModulation { BPSK , QPSK , PSK8 }
	Modulation of the PSK modem. More...

Functions
uint64_t	bitReverse (uint64_t value, unsigned bits)
	Reverses the ordering of the bits on an integer.
uint64_t	bitWindow (uint64_t value, unsigned offset, unsigned bits)
	Gets "bits" bits from "value" starting "offset" bits from the start.
unsigned	grayEncode (unsigned value)
	Gray code of a value: neighbouring tones differ in a single bit.
unsigned	grayDecode (unsigned gray)
	Inverse of grayEncode().
uint16_t	crc16 (const uint8_t *data, size_t len, uint16_t crc=0xFFFF)
	CRC-16-CCITT (polynomial 0x1021, initial value 0xFFFF).

Detailed Description

TinyModem: software audio modems and packets with error correction.

Typedef Documentation

◆ GGWaveRS

using tinymodem::GGWaveRS = RSCodec

Reed-Solomon code of ggwave: the generator roots are alpha^0 to alpha^(ecc-1)

Enumeration Type Documentation

◆ AX25Format

enum class tinymodem::AX25Format

strong

Format of the data which is written to the AX25Encoder and provided by the AX25Decoder

Enumerator
TEXT	one frame per line in the monitor format: SRC>DEST,DIGI1,DIGI2:info
KISS	KISS frames (0xC0 0x00 frame 0xC0), used by APRS and packet radio applications

◆ AX25Layer2

enum class tinymodem::AX25Layer2

strong

Frame format which is transmitted by the AX25Encoder: the AX25Decoder receives all formats

Enumerator
AX25	HDLC framing (standard AX.25).
FX25	FX.25: HDLC frame with Reed-Solomon FEC (compatible with AX.25).
IL2P	IL2P: Improved Layer 2 Protocol with Reed-Solomon FEC.

◆ DataFormat

enum class tinymodem::DataFormat

strong

Data encoding which is used for the payload of a frame.

Enumerator
ASCII	ASCII 8-N-1 (or 7-N-1).
BAUDOT	Baudot 5 bit (RTTY, TDD).
BINARY	print the raw data bits as '0'/'1' (receive only)
CALLERID	Bell 202 Caller-ID (SDMF/MDMF, receive only).
UIC_TRAIN	UIC-751-3 train to ground (receive only).
UIC_GROUND	UIC-751-3 ground to train (receive only).

◆ GGWaveProtocolId

enum tinymodem::GGWaveProtocolId

Protocol ids of ggwave: the values are identical to ggwave's ggwave_ProtocolId. The mono-tone protocols (MT, 9 - 11) are not supported.

Enumerator
GGWAVE_AUDIBLE_NORMAL
GGWAVE_AUDIBLE_FAST
GGWAVE_AUDIBLE_FASTEST
GGWAVE_ULTRASOUND_NORMAL
GGWAVE_ULTRASOUND_FAST
GGWAVE_ULTRASOUND_FASTEST
GGWAVE_DT_NORMAL
GGWAVE_DT_FAST
GGWAVE_DT_FASTEST

◆ MorseAlphabet

enum class tinymodem::MorseAlphabet

strong

Morse code alphabet.

Enumerator
INTERNATIONAL	International Morse code (ITU-R M.1677): dots and dashes of 3 units.
AMERICAN	American Morse code (railroad telegraph): dashes of 2 units, long dashes and spaces within some characters

◆ PSKModulation

enum class tinymodem::PSKModulation

strong

Modulation of the PSK modem.

Enumerator
BPSK	1 bit per symbol, PSK31 Varicode
QPSK	2 bits per symbol: rate 1/2 convolutional code (K=5) on 1 data bit per symbol, PSK31 Varicode
PSK8	3 bits per symbol without FEC, MFSK Varicode

Function Documentation

◆ bitReverse()

uint64_t tinymodem::bitReverse	(	uint64_t	value,
		unsigned	bits )

inline

Reverses the ordering of the bits on an integer.

◆ bitWindow()

uint64_t tinymodem::bitWindow	(	uint64_t	value,
		unsigned	offset,
		unsigned	bits )

inline

Gets "bits" bits from "value" starting "offset" bits from the start.

◆ crc16()

uint16_t tinymodem::crc16	(	const uint8_t *	data,
		size_t	len,
		uint16_t	crc = 0xFFFF )

inline

CRC-16-CCITT (polynomial 0x1021, initial value 0xFFFF).

◆ grayDecode()

unsigned tinymodem::grayDecode ( unsigned gray )

inline

Inverse of grayEncode().

◆ grayEncode()

unsigned tinymodem::grayEncode ( unsigned value )

inline

Gray code of a value: neighbouring tones differ in a single bit.

Classes

Typedefs

Enumerations

Functions

Detailed Description

Typedef Documentation

◆ GGWaveRS

Enumeration Type Documentation

◆ AX25Format

◆ AX25Layer2

◆ DataFormat

◆ GGWaveProtocolId

◆ MorseAlphabet

◆ PSKModulation

Function Documentation

◆ bitReverse()

◆ bitWindow()

◆ crc16()

◆ grayDecode()

◆ grayEncode()