Initial version of the encoder.
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434
ADSB_Encoder.py
Executable file
434
ADSB_Encoder.py
Executable file
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#!/usr/bin/env python
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#
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##########################################################################
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# Copyright 2010, 2012 Nick Foster
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#
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# This file is part of gr-air-modes
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#
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# gr-air-modes is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3, or (at your option)
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# any later version.
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#
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# gr-air-modes is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with gr-air-modes; see the file COPYING. If not, write to
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# the Free Software Foundation, Inc., 51 Franklin Street,
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# Boston, MA 02110-1301, USA.
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#
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import math
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def encode_alt_modes(alt, bit13):
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mbit = False
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qbit = True
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encalt = (int(alt) + 1000) / 25
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if bit13 is True:
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tmp1 = (encalt & 0xfe0) << 2
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tmp2 = (encalt & 0x010) << 1
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else:
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tmp1 = (encalt & 0xff8) << 1
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tmp2 = 0
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return (encalt & 0x0F) | tmp1 | tmp2 | (mbit << 6) | (qbit << 4)
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latz = 15
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def nz(ctype):
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return 4 * latz - ctype
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def dlat(ctype, surface):
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if surface == 1:
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tmp = 90.0
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else:
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tmp = 360.0
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nzcalc = nz(ctype)
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if nzcalc == 0:
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return tmp
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else:
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return tmp / nzcalc
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def nl(declat_in):
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if abs(declat_in) >= 87.0:
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return 1.0
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return math.floor( (2.0*math.pi) * math.acos(1.0- (1.0-math.cos(math.pi/(2.0*latz))) / math.cos( (math.pi/180.0)*abs(declat_in) )**2 )**-1)
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def dlon(declat_in, ctype, surface):
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if surface:
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tmp = 90.0
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else:
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tmp = 360.0
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nlcalc = max(nl(declat_in)-ctype, 1)
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return tmp / nlcalc
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#encode CPR position
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def cpr_encode(lat, lon, ctype, surface):
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if surface is True:
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scalar = 2.**19
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else:
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scalar = 2.**17
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#encode using 360 constant for segment size.
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dlati = dlat(ctype, False)
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yz = math.floor(scalar * ((lat % dlati)/dlati) + 0.5)
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rlat = dlati * ((yz / scalar) + math.floor(lat / dlati))
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#encode using 360 constant for segment size.
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dloni = dlon(lat, ctype, False)
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xz = math.floor(scalar * ((lon % dloni)/dloni) + 0.5)
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yz = int(yz) & (2**17-1)
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xz = int(xz) & (2**17-1)
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return (yz, xz) #lat, lon
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###############################################################
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# Copyright (C) 2015 Junzi Sun (TU Delft)
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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# the polynominal generattor code for CRC
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GENERATOR = "1111111111111010000001001"
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def hex2bin(hexstr):
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"""Convert a hexdecimal string to binary string, with zero fillings. """
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scale = 16
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num_of_bits = len(hexstr) * math.log(scale, 2)
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binstr = bin(int(hexstr, scale))[2:].zfill(int(num_of_bits))
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return binstr
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def bin2int(binstr):
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"""Convert a binary string to integer. """
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return int(binstr, 2)
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def crc(msg, encode=False):
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"""Mode-S Cyclic Redundancy Check
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Detect if bit error occurs in the Mode-S message
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Args:
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msg (string): 28 bytes hexadecimal message string
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encode (bool): True to encode the date only and return the checksum
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Returns:
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string: message checksum, or partity bits (encoder)
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"""
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msgbin = list(hex2bin(msg))
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if encode:
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msgbin[-24:] = ['0'] * 24
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# loop all bits, except last 24 piraty bits
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for i in range(len(msgbin)-24):
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# if 1, perform modulo 2 multiplication,
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if msgbin[i] == '1':
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for j in range(len(GENERATOR)):
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# modulo 2 multiplication = XOR
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msgbin[i+j] = str((int(msgbin[i+j]) ^ int(GENERATOR[j])))
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# last 24 bits
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reminder = ''.join(msgbin[-24:])
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return reminder
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###############################################################
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'''
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Copyright 2015 Wolfgang Nagele
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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'''
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def bin2dec(buf):
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if 0 == len(buf): # Crap input
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return -1
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return int(buf, 2)
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# Ported from: http://www.radarspotters.eu/forum/index.php?topic=5617.msg41293#msg41293
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def get_parity(msg, extended):
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msg_length = len(msg)
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payload = msg[:msg_length - 24]
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parity = msg[msg_length - 24:]
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data = bin2dec(payload[0:32])
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if extended:
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data1 = bin2dec(payload[32:64])
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data2 = bin2dec(payload[64:]) << 8
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hex_id = bin2dec(parity) << 8
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for i in range(0, len(payload)):
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if ((data & 0x80000000) != 0):
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data ^= 0xFFFA0480
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data <<= 1
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if extended:
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if ((data1 & 0x80000000) != 0):
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data |= 1
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data1 <<= 1
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if ((data2 & 0x80000000) != 0):
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data1 = data1 | 1
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data2 <<= 1
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return data
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#return (data ^ hex_id) >> 8
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###############################################################
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"""
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Hamming and Manchester Encoding example
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Author: Joel Addison
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Date: March 2013
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Functions to do (7,4) hamming encoding and decoding, including error detection
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and correction.
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Manchester encoding and decoding is also included, and by default will use
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least bit ordering for the byte that is to be included in the array.
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"""
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def extract_bit(byte, pos):
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"""
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Extract a bit from a given byte using MS ordering.
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ie. B7 B6 B5 B4 B3 B2 B1 B0
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"""
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return (byte >> pos) & 0x01
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def manchester_encode(byte):
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"""
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Encode a byte using Manchester encoding. Returns an array of bits.
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Adds two start bits (1, 1) and one stop bit (0) to the array.
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"""
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# Add start bits (encoded 1, 1)
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# manchester_encoded = [0, 1, 0, 1]
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manchester_encoded = []
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# Encode byte
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for i in range(7, -1, -1):
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if extract_bit(byte, i):
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manchester_encoded.append(0)
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manchester_encoded.append(1)
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else:
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manchester_encoded.append(1)
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manchester_encoded.append(0)
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# Add stop bit (encoded 0)
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# manchester_encoded.append(1)
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# manchester_encoded.append(0)
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return manchester_encoded
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###############################################################
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# Copyright (C) 2017 Linar Yusupov
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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import numpy
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#from scipy.signal import hilbert
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def df17_pos_rep_encode(ca, icao, tc, ss, nicsb, alt, time, lat, lon, surface):
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format = 17
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enc_alt = encode_alt_modes(alt, surface)
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#print "Alt(%r): %X " % (surface, enc_alt)
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#encode that position
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(evenenclat, evenenclon) = cpr_encode(lat, lon, False, surface)
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(oddenclat, oddenclon) = cpr_encode(lat, lon, True, surface)
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#print "Even Lat/Lon: %X/%X " % (evenenclat, evenenclon)
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#print "Odd Lat/Lon: %X/%X " % (oddenclat, oddenclon)
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ff = 0
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df17_even_bytes = []
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df17_even_bytes.append((format<<3) | ca)
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df17_even_bytes.append((icao>>16) & 0xff)
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df17_even_bytes.append((icao>> 8) & 0xff)
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df17_even_bytes.append((icao ) & 0xff)
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# data
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df17_even_bytes.append((tc<<3) | (ss<<1) | nicsb)
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df17_even_bytes.append((enc_alt>>4) & 0xff)
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df17_even_bytes.append((enc_alt & 0xf) << 4 | (time<<3) | (ff<<2) | (evenenclat>>15))
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df17_even_bytes.append((evenenclat>>7) & 0xff)
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df17_even_bytes.append(((evenenclat & 0x7f) << 1) | (evenenclon>>16))
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df17_even_bytes.append((evenenclon>>8) & 0xff)
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df17_even_bytes.append((evenenclon ) & 0xff)
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df17_str = "{0:02x}{1:02x}{2:02x}{3:02x}{4:02x}{5:02x}{6:02x}{7:02x}{8:02x}{9:02x}{10:02x}".format(*df17_even_bytes[0:11])
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#print df17_str , "%X" % bin2int(crc(df17_str+"000000", encode=True)) , "%X" % get_parity(hex2bin(df17_str+"000000"), extended=True)
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df17_crc = bin2int(crc(df17_str+"000000", encode=True))
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df17_even_bytes.append((df17_crc>>16) & 0xff)
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df17_even_bytes.append((df17_crc>> 8) & 0xff)
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df17_even_bytes.append((df17_crc ) & 0xff)
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ff = 1
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df17_odd_bytes = []
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df17_odd_bytes.append((format<<3) | ca)
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df17_odd_bytes.append((icao>>16) & 0xff)
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df17_odd_bytes.append((icao>> 8) & 0xff)
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df17_odd_bytes.append((icao ) & 0xff)
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# data
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df17_odd_bytes.append((tc<<3) | (ss<<1) | nicsb)
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df17_odd_bytes.append((enc_alt>>4) & 0xff)
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df17_odd_bytes.append((enc_alt & 0xf) << 4 | (time<<3) | (ff<<2) | (oddenclat>>15))
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df17_odd_bytes.append((oddenclat>>7) & 0xff)
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df17_odd_bytes.append(((oddenclat & 0x7f) << 1) | (oddenclon>>16))
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df17_odd_bytes.append((oddenclon>>8) & 0xff)
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df17_odd_bytes.append((oddenclon ) & 0xff)
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df17_str = "{0:02x}{1:02x}{2:02x}{3:02x}{4:02x}{5:02x}{6:02x}{7:02x}{8:02x}{9:02x}{10:02x}".format(*df17_odd_bytes[0:11])
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df17_crc = bin2int(crc(df17_str+"000000", encode=True))
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df17_odd_bytes.append((df17_crc>>16) & 0xff)
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df17_odd_bytes.append((df17_crc>> 8) & 0xff)
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df17_odd_bytes.append((df17_crc ) & 0xff)
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return (df17_even_bytes, df17_odd_bytes)
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def frame_1090es_ppm_modulate(even, odd):
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ppm = [ ]
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for i in range(48): # pause
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ppm.append( 0 )
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ppm.append( 0xA1 ) # preamble
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ppm.append( 0x40 )
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for i in range(len(even)):
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word16 = numpy.packbits(manchester_encode(~even[i]))
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ppm.append(word16[0])
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ppm.append(word16[1])
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for i in range(100): # pause
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ppm.append( 0 )
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ppm.append( 0xA1 ) # preamble
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ppm.append( 0x40 )
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for i in range(len(odd)):
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word16 = numpy.packbits(manchester_encode(~odd[i]))
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ppm.append(word16[0])
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ppm.append(word16[1])
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for i in range(48): # pause
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ppm.append( 0 )
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#print '[{}]'.format(', '.join(hex(x) for x in ppm))
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return bytearray(ppm)
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def hackrf_raw_IQ_format(ppm):
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"""
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real_signal = []
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bits = numpy.unpackbits(numpy.asarray(ppm, dtype=numpy.uint8))
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for bit in bits:
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if bit == 1:
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I = 127
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else:
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I = 0
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real_signal.append(I)
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analytic_signal = hilbert(real_signal)
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#for i in range(len(real_signal)):
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# print i, real_signal[i], int(analytic_signal[i])
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"""
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signal = []
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bits = numpy.unpackbits(numpy.asarray(ppm, dtype=numpy.uint8))
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for bit in bits:
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if bit == 1:
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I = 127
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Q = 127
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else:
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I = 0
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Q = 0
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signal.append(I)
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signal.append(Q)
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return bytearray(signal)
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if __name__ == "__main__":
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from sys import argv, exit
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argc = len(argv)
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if argc != 5:
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print
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print 'Usage: '+ argv[0] +' <ICAO> <Latitude> <Longtitude> <Altitude>'
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print
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print ' Example: '+ argv[0] +' 0xABCDEF 12.34 56.78 9999.0'
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print
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exit(2)
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icao = int(argv[1], 16)
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lat = float(argv[2])
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lon = float(argv[3])
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alt = float(argv[4])
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ca = 5
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tc = 11
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ss = 0
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nicsb = 0
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time = 0
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surface = False
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(df17_even, df17_odd) = df17_pos_rep_encode(ca, icao, tc, ss, nicsb, alt, time, lat, lon, surface)
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#print ''.join(format(x, '02x') for x in df17_even)
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#print ''.join(format(x, '02x') for x in df17_odd)
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df17_array = frame_1090es_ppm_modulate(df17_even, df17_odd)
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#OutFile = open("filename.bin", "wb")
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#OutFile.write(df17_array)
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samples_array = hackrf_raw_IQ_format(df17_array)
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SamplesFile = open("HRF_samples.iq", "wb")
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SamplesFile.write(samples_array)
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###############################################################
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