protocol

Documentation

Index

• Constants
• func NextPowerOf2(v int) int
• func RegisterParser(name string, parserFn NewParserFunc)
• type Data
  • func NewData(data []byte) (d Data)
• type Decoder
  • func NewDecoder() Decoder
  • func (d *Decoder) Allocate()
  • func (d Decoder) Decode(input []byte) chan Message
  • func (d Decoder) Filter(input []float64, output []byte)
  • func (d Decoder) Log()
  • func (d *Decoder) RegisterProtocol(p Parser)
  • func (d *Decoder) Search(preamble []byte) []int
  • func (d Decoder) Slice(indices []int) (pkts []Data)
• type Demodulator
• type Digest
  • func NewDigest(msg Message) Digest
• type FilterChain
  • func (fc *FilterChain) Add(filter MessageFilter)
  • func (fc FilterChain) Match(msg Message) bool
• type LogMessage
  • func (msg LogMessage) Record() (r []string)
  • func (msg LogMessage) String() string
  • func (msg LogMessage) StringNoOffset() string
• type MagLUT
  • func NewMagLUT() (lut MagLUT)
  • func (lut MagLUT) Execute(input []byte, output []float64)
• type Message
• type MessageFilter
• type NewParserFunc
• type PacketConfig
• type Parser
  • func NewParser(name string, symbolLength int) (Parser, error)

Constants

const (
	TimeFormat = "2006-01-02T15:04:05.000"
)

Functions

func NextPowerOf2

func NextPowerOf2(v int) int

func RegisterParser

func RegisterParser(name string, parserFn NewParserFunc)

Given a name and a parser, register a parser for use. Later used by underscore improting each parser package:

import _ "github.com/bemasher/rtlamr/scm"

Types

type Data

type Data struct {
	Idx   int
	Bits  string
	Bytes []byte
}

Used by parsers to interpret received bits/bytes into their appropriate fields.

func NewData

func NewData(data []byte) (d Data)

type Decoder

type Decoder struct {
	Cfg PacketConfig

	Signal    []float64
	Quantized []byte
	// contains filtered or unexported fields
}

Decoder contains buffers and radio configuration.

func NewDecoder

func NewDecoder() Decoder

func (*Decoder) Allocate

func (d *Decoder) Allocate()

Calculate lengths and allocate internal buffers.

func (Decoder) Decode

func (d Decoder) Decode(input []byte) chan Message

Decode accepts a sample block and returns a channel of messages.

func (Decoder) Filter

func (d Decoder) Filter(input []float64, output []byte)

Matched filter for Manchester coded signals. Output signal's sign at each sample determines the bit-value due to Manchester symbol odd symmetry.

func (Decoder) Log

func (d Decoder) Log()

func (*Decoder) RegisterProtocol

func (d *Decoder) RegisterProtocol(p Parser)

Using a single decoder, register protocols to pass off decoded packets to.

func (*Decoder) Search

func (d *Decoder) Search(preamble []byte) []int

Return a list of indices into the quantized signal at which a valid preamble exists.

1. Pack the quantized signal into bytes.
2. Build a list of indices by eliminating bytes that contain no bits matching the first bit of the preamble.
3. Continue eliminating indices at which the preamble cannot exist.
4. Convert indices from byte-based to sample-based.
5. Check each of these indices for the preamble.

func (Decoder) Slice

func (d Decoder) Slice(indices []int) (pkts []Data)

Given a list of indices the preamble exists at, sample the appropriate bits of the signal's bit-decision. Pack bits of each index into an array of bytes and return each packet.

type Demodulator

type Demodulator interface {
	Execute([]byte, []float64)
}

A Demodulator knows how to demodulate an array of uint8 IQ samples into an array of float64 samples.

type Digest

type Digest struct {
	MsgType   string
	MeterType uint8
	MeterID   uint32
	Checksum  string
}

Uniquely identifies a message spanning two sample blocks.

func NewDigest

func NewDigest(msg Message) Digest

type FilterChain

type FilterChain []MessageFilter

A FilterChain takse a list of filters and applies them iteratively to messages sent through the chain.

func (*FilterChain) Add

func (fc *FilterChain) Add(filter MessageFilter)

func (FilterChain) Match

func (fc FilterChain) Match(msg Message) bool

type LogMessage

type LogMessage struct {
	Time   time.Time `xml:",attr"`
	Offset int64     `xml:",attr"`
	Length int       `xml:",attr"`
	Type   string    `xml:",attr"`
	Message
}

A LogMessage associates a message with a point in time and an offset and length into a binary sample file.

func (LogMessage) Record

func (msg LogMessage) Record() (r []string)

func (LogMessage) String

func (msg LogMessage) String() string

func (LogMessage) StringNoOffset

func (msg LogMessage) StringNoOffset() string

type MagLUT

type MagLUT []float64

Default Magnitude Lookup Table

func NewMagLUT

func NewMagLUT() (lut MagLUT)

Pre-computes normalized squares with most common DC offset for rtl-sdr dongles.

func (MagLUT) Execute

func (lut MagLUT) Execute(input []byte, output []float64)

Calculates complex magnitude on given IQ stream writing result to output.

type Message

type Message interface {
	csv.Recorder
	MsgType() string
	MeterID() uint32
	MeterType() uint8
	Checksum() []byte
}

type MessageFilter

type MessageFilter interface {
	Filter(Message) bool
}

type NewParserFunc

type NewParserFunc func(symbolLength int) Parser

type PacketConfig

type PacketConfig struct {
	Protocol string
	Preamble string

	DataRate int

	BlockSize, BlockSize2    int
	ChipLength, SymbolLength int
	SampleRate               int

	PreambleSymbols, PacketSymbols int
	PreambleLength, PacketLength   int

	BufferLength int
	CenterFreq   uint32
}

PacketConfig specifies packet-specific radio configuration.

type Parser

type Parser interface {
	Parse([]Data, chan Message, *sync.WaitGroup)
	SetDecoder(*Decoder)
	Cfg() PacketConfig
}

A Parser converts slices of bytes to messages.

func NewParser

func NewParser(name string, symbolLength int) (Parser, error)

Given a name and symbolLength, lookup the parser and make a new one.