tinymodem::IL2P Class Reference

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...

#include <AX25FEC.h>

Classes
struct	Blocks
	Partitioning of the payload into Reed-Solomon blocks. More...

Static Public Member Functions
static int	encode (const uint8_t *frame, int len, bool max_fec, uint8_t *out)
static int	decodeHeader (const uint8_t *received, uint8_t *hdr, int *corrected=nullptr)
static int	decodeFrame (const uint8_t *hdr, const uint8_t *encoded, uint8_t *frame, int frame_size, int *corrected=nullptr)
static int	payloadLength (const uint8_t *hdr)
static bool	maxFec (const uint8_t *hdr)
static void	scramble (const uint8_t *in, uint8_t *out, int len)
	Scrambles a block (the scrambler output is delayed by 5 bits).
static void	descramble (const uint8_t *in, uint8_t *out, int len)

Static Public Attributes
static constexpr uint8_t	PREAMBLE = 0x55
static constexpr uint32_t	SYNC_WORD = 0xF15E48
static constexpr int	HEADER_SIZE = 13
static constexpr int	HEADER_PARITY = 2
static constexpr int	MAX_PAYLOAD = 1023
static constexpr int	MAX_ENCODED

Static Protected Member Functions
static bool	blocks (int len, bool max_fec, Blocks &p)
static int	encodePayload (const uint8_t *payload, int len, bool max_fec, uint8_t *out)
static bool	decodePayload (const uint8_t *in, int len, bool max_fec, uint8_t *payload, int *corrected)
static int	scrambleBit (int in, int &state)
static void	setField (uint8_t *hdr, int bit, int lsb_index, int width, int value)
static int	getField (const uint8_t *hdr, int bit, int lsb_index, int width)
static int	encodePid (uint8_t pid)
static uint8_t	decodePid (int pid)
static const uint8_t *	uFrames ()
	U frame control fields (without poll/final) in the order of IL2P.
static int	type1Header (const uint8_t *frame, int len, bool max_fec, uint8_t *hdr)
static int	type1Frame (const uint8_t *hdr, uint8_t *frame)

Detailed Description

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.

Copyright

GPLv3

Member Function Documentation

blocks()

bool tinymodem::IL2P::blocks ( int len, bool max_fec, Blocks & p )

inlinestaticprotected

decodeFrame()

int tinymodem::IL2P::decodeFrame ( const uint8_t * hdr, const uint8_t * encoded, uint8_t * frame, int frame_size, int * corrected = nullptr )

inlinestatic

Decodes the frame from the decoded header and the encoded payload: returns the frame length (without FCS) or 0 if invalid

decodeHeader()

int tinymodem::IL2P::decodeHeader ( const uint8_t * received, uint8_t * hdr, int * corrected = nullptr )

inlinestatic

Corrects and descrambles a received header (15 bytes): returns the encoded payload length or -1 if the header is invalid

decodePayload()

bool tinymodem::IL2P::decodePayload ( const uint8_t * in, int len, bool max_fec, uint8_t * payload, int * corrected )

inlinestaticprotected

decodePid()

uint8_t tinymodem::IL2P::decodePid ( int pid )

inlinestaticprotected

descramble()

void tinymodem::IL2P::descramble ( const uint8_t * in, uint8_t * out, int len )

inlinestatic

encode()

int tinymodem::IL2P::encode ( const uint8_t * frame, int len, bool max_fec, uint8_t * out )

inlinestatic

Encodes a frame (without FCS) into header and payload (without the sync word): returns the length or 0 if the frame can't be encoded

encodePayload()

int tinymodem::IL2P::encodePayload ( const uint8_t * payload, int len, bool max_fec, uint8_t * out )

inlinestaticprotected

encodePid()

int tinymodem::IL2P::encodePid ( uint8_t pid )

inlinestaticprotected

getField()

int tinymodem::IL2P::getField ( const uint8_t * hdr, int bit, int lsb_index, int width )

inlinestaticprotected

maxFec()

bool tinymodem::IL2P::maxFec ( const uint8_t * hdr )

inlinestatic

payloadLength()

int tinymodem::IL2P::payloadLength ( const uint8_t * hdr )

inlinestatic

scramble()

void tinymodem::IL2P::scramble ( const uint8_t * in, uint8_t * out, int len )

inlinestatic

Scrambles a block (the scrambler output is delayed by 5 bits).

scrambleBit()

int tinymodem::IL2P::scrambleBit ( int in, int & state )

inlinestaticprotected

setField()

void tinymodem::IL2P::setField ( uint8_t * hdr, int bit, int lsb_index, int width, int value )

inlinestaticprotected

type1Frame()

int tinymodem::IL2P::type1Frame ( const uint8_t * hdr, uint8_t * frame )

inlinestaticprotected

AX.25 frame (addresses, control, pid) of a type 1 header: returns the length or 0 if invalid

type1Header()

int tinymodem::IL2P::type1Header ( const uint8_t * frame, int len, bool max_fec, uint8_t * hdr )

inlinestaticprotected

Type 1 header of a frame with 2 addresses: returns the position of the payload in the frame or -1 if a type 1 header is not possible

uFrames()

const uint8_t * tinymodem::IL2P::uFrames ( )

inlinestaticprotected

U frame control fields (without poll/final) in the order of IL2P.

Member Data Documentation

HEADER_PARITY

int tinymodem::IL2P::HEADER_PARITY = 2

staticconstexpr

HEADER_SIZE

int tinymodem::IL2P::HEADER_SIZE = 13

staticconstexpr

MAX_ENCODED

int tinymodem::IL2P::MAX_ENCODED

staticconstexpr

Initial value:

=
      HEADER_SIZE + HEADER_PARITY + MAX_PAYLOAD + 5 * 16

MAX_PAYLOAD

int tinymodem::IL2P::MAX_PAYLOAD = 1023

staticconstexpr

PREAMBLE

uint8_t tinymodem::IL2P::PREAMBLE = 0x55

staticconstexpr

SYNC_WORD

uint32_t tinymodem::IL2P::SYNC_WORD = 0xF15E48

staticconstexpr

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

• src/modem/AX25FEC.h