decode

Documentation

Index

• func NextPowerOf2(v int) int
• func Quantize(input []float64, output []byte)
• type AlphaMaxBetaMinLUT
  • func NewAlphaMaxBetaMinLUT() (lut AlphaMaxBetaMinLUT)
  • func (lut AlphaMaxBetaMinLUT) Execute(input []byte, output []float64)
• type Decoder
  • func NewDecoder(cfg PacketConfig, decimation int, fastMag bool) (d Decoder)
  • func (d Decoder) Decode(input []byte) []int
  • func (d Decoder) Filter(input, output []float64)
  • func (d Decoder) Log()
  • func (d Decoder) Pack(input []byte, slices [][]byte)
  • func (d Decoder) Search(slices [][]byte, preamble []byte) (indexes []int)
  • func (d Decoder) Slice(indices []int) (pkts [][]byte)
• type Demodulator
• type MagLUT
  • func NewSqrtMagLUT() (lut MagLUT)
  • func (lut MagLUT) Execute(input []byte, output []float64)
• type PacketConfig
  • func (cfg PacketConfig) Decimate(decimation int) PacketConfig

Functions

func NextPowerOf2

func NextPowerOf2(v int) int

func Quantize

func Quantize(input []float64, output []byte)

Bit-value is determined by the sign of each sample after filtering.

Types

type AlphaMaxBetaMinLUT

type AlphaMaxBetaMinLUT []float64

Alpha*Max + Beta*Min Magnitude Approximation Lookup Table.

func NewAlphaMaxBetaMinLUT

func NewAlphaMaxBetaMinLUT() (lut AlphaMaxBetaMinLUT)

Pre-computes absolute values with most common DC offset for rtl-sdr dongles.

func (AlphaMaxBetaMinLUT) Execute

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

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

type Decoder

type Decoder struct {
	Cfg PacketConfig

	Decimation int
	DecCfg     PacketConfig

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

Decoder contains buffers and radio configuration.

func NewDecoder

func NewDecoder(cfg PacketConfig, decimation int, fastMag bool) (d Decoder)

Create a new decoder with the given packet configuration.

func (Decoder) Decode

func (d Decoder) Decode(input []byte) []int

Decode accepts a sample block and performs various DSP techniques to extract a packet.

func (Decoder) Filter

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

Matched filter for Manchester coded signals. Output signal's sign at each sample determines the bit-value since Manchester symbols have odd symmetry.

func (Decoder) Log

func (d Decoder) Log()

func (Decoder) Pack

func (d Decoder) Pack(input []byte, slices [][]byte)

Packs quantized signal into slices such that the first rank represents sample offsets and the second represents the value of each symbol from the given offset.

func (Decoder) Search

func (d Decoder) Search(slices [][]byte, preamble []byte) (indexes []int)

For each sample offset look for the preamble. Return a list of indexes the preamble is found at. Indexes are absolute in the unsliced quantized buffer.

func (Decoder) Slice

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

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

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 MagLUT

type MagLUT []float64

Default Magnitude Lookup Table

func NewSqrtMagLUT

func NewSqrtMagLUT() (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 PacketConfig

type PacketConfig struct {
	DataRate int

	BlockSize, BlockSize2       int
	SymbolLength, SymbolLength2 int
	SampleRate                  int

	PreambleSymbols, PacketSymbols int
	PreambleLength, PacketLength   int
	Preamble                       string

	BufferLength int

	CenterFreq uint32
}

PacketConfig specifies packet-specific radio configuration.

func (PacketConfig) Decimate

func (cfg PacketConfig) Decimate(decimation int) PacketConfig