Module: PWN::SDR::Decoder::ADSB

Defined in:
lib/pwn/sdr/decoder/adsb.rb

Overview

ADS-B (1090 MHz Mode-S / 978 MHz UAT) true-air decoder.

Prefer PWN::FFI::RTLSdr,AdalmPluto,HackRF at ≥2 Msps and run a pure-Ruby Mode-S preamble correlator + 112-bit PPM slicer over magnitude samples. Falls back to Base.run_detector energy mode when no I/Q source is available. Offline SBS-1 CSV → .parse_line.

Defined Under Namespace

Classes: DemodIQ

Constant Summary collapse

SBS_FIELDS = 
%i[
  msg_type tx_type session_id aircraft_id icao24 flight_id
  date_gen time_gen date_log time_log callsign altitude_ft
  ground_speed_kt track_deg lat lon vertical_rate_fpm squawk
  alert emergency spi on_ground
].freeze
PREAMBLE =

8 μs Mode-S preamble at 2 Msps → 16 samples: 1 0 1 0 0 0 0 1 0 1 0 0 0 0 0 0

[1, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0].map(&:to_f).freeze
SAMPLES_PER_US =

@ 2 Msps

2
MODE_S_CRC_POLY =

CRC-24 (Mode-S) generator 0x1FFF409 (poly over GF(2), 24-bit)

0x1FFF409

Class Method Summary collapse

Class Method Details

.ais_char(opts = {}) ⇒ Object 



183
184
185
186
187
 
# File 'lib/pwn/sdr/decoder/adsb.rb', line 183

public_class_method def self.ais_char(opts = {})
  code = opts[:code]
  table = '#ABCDEFGHIJKLMNOPQRSTUVWXYZ##### ###############0123456789######'
  table[code] || ' '
end

.authors ⇒ Object

Author(s)

0day Inc. support@0dayinc.com



248
249
250
 
# File 'lib/pwn/sdr/decoder/adsb.rb', line 248

public_class_method def self.authors
  "AUTHOR(S):\n  0day Inc. <support@0dayinc.com>\n"
end

.crc24(opts = {}) ⇒ Object

Supported Method Parameters

crc = PWN::SDR::Decoder::ADSB.crc24(bits: Array<0|1>) CRC over all bits except the final 24 (which hold the parity).



119
120
121
122
123
124
125
126
127
128
129
130
131
132
 
# File 'lib/pwn/sdr/decoder/adsb.rb', line 119

public_class_method def self.crc24(opts = {})
  bits = opts[:bits] || []
  return nil if bits.length < 32

  # Mode-S CRC-24: left-shift register fed by every message bit
  # (including the 24 parity bits). A valid frame leaves residual 0.
  reg = 0
  bits.each do |b|
    reg <<= 1
    reg |= (b & 1)
    reg ^= MODE_S_CRC_POLY if reg.anybits?(0x1000000)
  end
  reg & 0xFFFFFF
end

.crc_ok?(opts = {}) ⇒ Boolean

Supported Method Parameters

ok = PWN::SDR::Decoder::ADSB.crc_ok?(bits: Array<0|1>)

Returns:

  • (Boolean) 


137
138
139
140
141
142
 
# File 'lib/pwn/sdr/decoder/adsb.rb', line 137

public_class_method def self.crc_ok?(opts = {})
  bits = opts[:bits] || []
  return false unless [56, 112].include?(bits.length)

  crc24(bits: bits).zero?
end

.decode(opts = {}) ⇒ Object

Supported Method Parameters

PWN::SDR::Decoder::ADSB.decode( freq_obj: 'required - freq_obj returned from PWN::SDR::GQRX.init_freq' )



207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
 
# File 'lib/pwn/sdr/decoder/adsb.rb', line 207

public_class_method def self.decode(opts = {})
  freq_obj = opts[:freq_obj]
  hz  = PWN::SDR.hz_to_i(freq: freq_obj[:freq])
  uat = hz.between?(977_000_000, 979_000_000)
  proto = uat ? 'ADSB-UAT978' : 'ADSB-1090ES'
  rate  = (opts[:sample_rate] || freq_obj[:iq_rate] || 2_000_000).to_i
  PWN::SDR::Decoder::Base.run_iq(
    freq_obj: freq_obj,
    protocol: proto,
    sample_rate: rate,
    source: opts[:source],
    file: opts[:file],
    demod: DemodIQ.new(rate: rate),
    note: 'Mode-S 2 Mbit/s PPM — true-air path uses RTL-SDR/Pluto I/Q; detector fallback characterises squitter density only.',
    describe: proc { |b| { modulation: 'PPM', frame_len_us: 120, classification: b[:duration_ms] < 5 ? 'squitter' : 'interrogation-train' } }
  )
end

.decode_modes(opts = {}) ⇒ Object

Supported Method Parameters

h = PWN::SDR::Decoder::ADSB.decode_modes(bits: Array<0|1> of length 56 or 112)



147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
 
# File 'lib/pwn/sdr/decoder/adsb.rb', line 147

public_class_method def self.decode_modes(opts = {})
  bits = opts[:bits] || []
  return nil unless [56, 112].include?(bits.length)

  # DF (5) + CA (3) + ICAO (24) + ...
  df = PWN::SDR::Decoder::DSP.bits_to_int(bits: bits[0, 5])
  icao = format('%06X', PWN::SDR::Decoder::DSP.bits_to_int(bits: bits[8, 24]))
  out = {
    protocol: 'ADSB',
    df: df,
    icao24: icao,
    bits: bits.length,
    raw_hex: bits.each_slice(4).map { |n| PWN::SDR::Decoder::DSP.bits_to_int(bits: n).to_s(16) }.join.upcase
  }
  # DF17/18 ME field (56 bits starting at bit 32)
  if [17, 18].include?(df) && bits.length >= 88
    tc = PWN::SDR::Decoder::DSP.bits_to_int(bits: bits[32, 5])
    out[:type_code] = tc
    if tc.between?(1, 4)
      # aircraft identification — 8× 6-bit AIS chars
      cs = bits[40, 48].each_slice(6).map { |ch| ais_char(code: PWN::SDR::Decoder::DSP.bits_to_int(bits: ch)) }.join.strip
      out[:callsign] = cs
    elsif tc.between?(9, 18) || tc.between?(20, 22)
      out[:altitude_ft] = modes_altitude(bits12: bits[40, 12])
    end
  end
  bits_s = []
  bits_s << "ICAO=#{out[:icao24]}"
  bits_s << "DF=#{df}"
  bits_s << "CS=#{out[:callsign]}" if out[:callsign]
  bits_s << "ALT=#{out[:altitude_ft]}ft" if out[:altitude_ft]
  bits_s << "TC=#{out[:type_code]}" if out[:type_code]
  out[:summary] = "ADSB #{bits_s.join(' ')}"
  out
end

.help ⇒ Object

Display Usage for this Module



254
255
256
257
258
259
260
261
262
263
264
265
266
267
 
# File 'lib/pwn/sdr/decoder/adsb.rb', line 254

public_class_method def self.help
  puts "USAGE (true-air I/Q via PWN::FFI + detector fallback):
    #{self}.decode(
      freq_obj: 'required - freq_obj returned from PWN::SDR::GQRX.init_freq',
      source:   'optional - :auto|:rtlsdr|:adalm_pluto|:file',
      file:     'optional - .cu8/.cs16 capture at ≥2 Msps'
    )

    #{self}.decode_modes(bits: [0,1,...])   # 56/112 Mode-S bits
    #{self}.parse_line(line: 'MSG,3,1,1,ABCDEF,1,...')

    #{self}.authors
  "
end

.modes_altitude(opts = {}) ⇒ Object 



189
190
191
192
193
194
195
196
197
198
199
200
 
# File 'lib/pwn/sdr/decoder/adsb.rb', line 189

public_class_method def self.modes_altitude(opts = {})
  bits12 = opts[:bits12]
  return nil unless bits12.is_a?(Array) && bits12.length == 12

  # Gillham / 25 ft encoding — simplified (bit 7 is Q)
  q = bits12[7]
  if q == 1
    n = PWN::SDR::Decoder::DSP.bits_to_int(bits: bits12[0, 7] + bits12[8, 4])
    return (n * 25) - 1000
  end
  nil
end

.parse_line(opts = {}) ⇒ Object

Supported Method Parameters

PWN::SDR::Decoder::ADSB.parse_line(line: 'MSG,3,1,1,ABCDEF,...')



228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
 
# File 'lib/pwn/sdr/decoder/adsb.rb', line 228

public_class_method def self.parse_line(opts = {})
  line = opts[:line].to_s
  return { protocol: 'ADSB-UAT', summary: line.strip } unless line.start_with?('MSG,')

  f   = line.split(',', -1)
  out = { protocol: 'ADSB' }
  SBS_FIELDS.each_with_index { |k, i| out[k] = f[i] unless f[i].to_s.empty? }
  bits = []
  bits << "ICAO=#{out[:icao24]}" if out[:icao24]
  bits << "CS=#{out[:callsign].to_s.strip}" if out[:callsign]
  bits << "ALT=#{out[:altitude_ft]}ft" if out[:altitude_ft]
  bits << "POS=#{out[:lat]},#{out[:lon]}" if out[:lat] && out[:lon]
  bits << "GS=#{out[:ground_speed_kt]}kt" if out[:ground_speed_kt]
  bits << "SQK=#{out[:squawk]}" if out[:squawk]
  out[:summary] = "ADSB #{bits.join(' ')}".strip
  out
end