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ModeS.py
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ModeS.py
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from ModeSLocation import ModeSLocation
import math
import numpy
from CustomDecorators import *
###############################################################
# Further work on fork
# Copyright (C) 2017 David Robinson
class ModeS:
"""This class handles the ModeS ADSB manipulation
"""
def __init__(self,df,icao,ca):
self._location = ModeSLocation()
self.df = df # as far as I understand specification, this should be :
# 17 if the broadcast source is an aircraft
# 18 if the broadcast source is some other ADSB facility (tower)
self.icao = icao # 24 bits icao registration code
self.ca = ca # capability see §3.1.2.5.2.2.1
# (will usually be 5 for level 2 transponder and airborne)
self._charmap = "#ABCDEFGHIJKLMNOPQRSTUVWXYZ#####_###############0123456789######"
self._crc_poly = 0x01FFF409
self._crc_lookup_T0 = [0]*256
crc = 0x1000000
i = 1
while(i < 256):
if crc & 0x1000000:
crc <<= 1
crc = crc ^ self._crc_poly
else:
crc <<= 1
for j in range(i):
self._crc_lookup_T0[i ^ j] = (crc ^ self._crc_lookup_T0[j])
i <<= 1
def df_frame_start(self):
"""
This will build the usual df frame start and reserve a full frame with "0" for the reste of message
"""
frame = bytearray(14)
frame[0] = (self.df << 3) | self.ca
frame[1] = ((self.icao >> 16) & 0xff)
frame[2] = ((self.icao >> 8) & 0xff)
frame[3] = ((self.icao) & 0xff)
return frame
# Ref :
# ICAO Annex 10 : Aeronautical Telecommunications
# Volume IV : Surveillance and Collision Avoidance Systems
# Figure C-1. Extended Squitter Airborne Position
# "Register 05_16"
#@Timed
def df_encode_airborne_position(self, lat, lon, alt, tc, ss, nicsb, timesync):
"""
This will encode even and odd frames from airborne position extended squitter message
tc = type code (§C2.3.1)
ss = surveillance status : 0 = no condition information
1 = permanent alert (emergency condition)
2 = temporary alert (change in Mode A identity code other than emergency condition)
3 = SPI condition
nicsb = NIC supplement-B (§C.2.3.2.5)
"""
#encode height information
enc_alt = self._location.encode_alt_modes(alt, False)
#encode that position
(evenenclat, evenenclon) = self._location.cpr_encode(lat, lon, False, False)
(oddenclat, oddenclon) = self._location.cpr_encode(lat, lon, True, False)
ff = 0
df_frame_even_bytes = self.df_frame_start()
# data
df_frame_even_bytes[4] = (tc<<3) | (ss<<1) | nicsb
df_frame_even_bytes[5] = (enc_alt>>4) & 0xff
df_frame_even_bytes[6] = (enc_alt & 0xf) << 4 | (timesync<<3) | (ff<<2) | (evenenclat>>15)
df_frame_even_bytes[7] = (evenenclat>>7) & 0xff
df_frame_even_bytes[8] = ((evenenclat & 0x7f) << 1) | (evenenclon>>16)
df_frame_even_bytes[9] = (evenenclon>>8) & 0xff
df_frame_even_bytes[10] = (evenenclon ) & 0xff
self.df_frame_write_crc(df_frame_even_bytes)
ff = 1
df_frame_odd_bytes = self.df_frame_start()
# data
df_frame_odd_bytes[4] = (tc<<3) | (ss<<1) | nicsb
df_frame_odd_bytes[5] = (enc_alt>>4) & 0xff
df_frame_odd_bytes[6] = (enc_alt & 0xf) << 4 | (timesync<<3) | (ff<<2) | (oddenclat>>15)
df_frame_odd_bytes[7] = (oddenclat>>7) & 0xff
df_frame_odd_bytes[8] = ((oddenclat & 0x7f) << 1) | (oddenclon>>16)
df_frame_odd_bytes[9] = (oddenclon>>8) & 0xff
df_frame_odd_bytes[10] = (oddenclon ) & 0xff
self.df_frame_write_crc(df_frame_odd_bytes)
return (df_frame_even_bytes, df_frame_odd_bytes)
# Ref :
# ICAO Annex 10 : Aeronautical Telecommunications
# Volume IV : Surveillance and Collision Avoidance Systems
# Figure C-1. Extended Squitter Surface Position
# "Register 06_16"
def df_encode_surface_position(self, lat, lon, alt, tc, ss, nicsb, timesync):
# TODO
exit(-1)
# Ref :
# ICAO Annex 10 : Aeronautical Telecommunications
# Volume IV : Surveillance and Collision Avoidance Systems
# Figure C-3. Extended Squitter Status
# "Register 07_16"
#@Timed
def df_encode_extended_squitter_status(self, trs = 0x0, ats = 0x0):
df_frame = self.df_frame_start()
df_frame[4] = ((trs << 6) & 0x3 | (ats << 5) & 0x1)
self.df_frame_write_crc(df_frame)
return df_frame
#From https://github.com/jaywilhelm/ADSB-Out_Python on 2019-08-18
#@Timed
def df_encode_ground_velocity(self, ground_velocity_kt, track_angle_deg, vertical_rate):
#1-5 downlink format
#6-8 CA capability
#9-32 ICAO
#33-88 DATA -> 33-87 w/ 33-37 TC
#89-112 Parity
track_angle_rad = numpy.deg2rad(track_angle_deg)
V_EW = ground_velocity_kt*numpy.sin(track_angle_rad)
V_NS = ground_velocity_kt*numpy.cos(track_angle_rad)
if(V_EW >= 0):
S_EW = 0
else:
S_EW = 1
if(V_NS >= 0):
S_NS = 0
else:
S_NS = 1
V_EW = int(abs(V_EW))+1
V_NS = int(abs(V_NS))+1
S_Vr = 0
Vr = int(vertical_rate)+1
if(vertical_rate < 0):
Vr = -Vr
S_Vr = 1
tc = 19 #33-37 1-5 type code
st = 0x01 #38-40 6-8 subtype, 3 air, 1 ground speed
ic = 0 # #41 9 intent change flag
resv_a = 0#1 #42 10
NAC = 2#0 #43-45 11-13 velocity uncertainty
#S_EW = 1#1 #46 14
#V_EW = 97#9 #47-56 15-24
#S_NS = 0#1 #57 25 north-south sign
#V_NS = 379#0xA0 #58-67 26-35 160 north-south vel
VrSrc = 1#0 #68 36 vertical rate source
#S_Vr = 1#1 #69 37 vertical rate sign
#Vr = 41#0x0E #70-78 38-46 14 vertical rate
RESV_B = 0 #79-80 47-48
S_Dif = 0 #81 49 diff from baro alt, sign
Dif = 0x1c#0x17 #82-88 50-66 23 diff from baro alt
dfvel = self.df_frame_start()
# data
dfvel[4] = ((tc << 3) | st)
dfvel[5] = ((ic << 7) | (resv_a << 6) | (NAC << 3) | (S_EW << 2) | ((V_EW >> 8) & 0x03))
dfvel[6] = (0xFF & V_EW)
dfvel[7] = ((S_NS << 7) | ((V_NS >> 3))) #& 0x7F))
dfvel[8] = (((V_NS << 5) & 0xE0) | (VrSrc << 4) | (S_Vr << 3) | ((Vr >> 6) & 0x03))
dfvel[9] = (((Vr << 2) & 0xFC) | (RESV_B))
dfvel[10] = ((S_Dif << 7) | (Dif))
self.df_frame_write_crc(dfvel)
return dfvel
#From https://github.com/jaywilhelm/ADSB-Out_Python on 2019-08-25
# TODO the callsign must be 8
def callsign_encode(self, csname):
#Pad the callsign to be 8 characters
csname = csname.ljust(8, '_')
if len(csname) > 8 or len(csname) <= 0:
print ("Name length error")
return None
csname = csname.upper()
tc = 1 # §C.2.3.4
ec = 1 # §C.2.3.4
dfname = self.df_frame_start()
# data
dfname[4] = (tc << 3) | (ec)
dfname[5] = (0xFC & (int(self._charmap.find(csname[0])) << 2)) | (0x03 & (int(self._charmap.find(csname[1])) >> 4))
dfname[6] = (0xF0 & (int(self._charmap.find(csname[1])) << 4)) | (0x0F & (int(self._charmap.find(csname[2])) >> 2))
dfname[7] = (0xF0 & (int(self._charmap.find(csname[2])) << 6)) | (0x3F & (int(self._charmap.find(csname[3])) >> 0))
dfname[8] = (0xFC & (int(self._charmap.find(csname[4])) << 2)) | (0x03 & (int(self._charmap.find(csname[5])) >> 4))
dfname[9] = (0xF0 & (int(self._charmap.find(csname[5])) << 4)) | (0x0F & (int(self._charmap.find(csname[6])) >> 2))
dfname[10] = (0xF0 & (int(self._charmap.find(csname[6])) << 6)) | (0x3F & (int(self._charmap.find(csname[7])) >> 0))
self.df_frame_write_crc(dfname)
return dfname
# Ref :
# ICAO Annex 10 : Aeronautical Telecommunications
# Volume IV : Surveillance and Collision Avoidance Systems
# Figure C-8a. Extended Squitter Aircraft Status
# "Register 61_16"
#@Timed
def modaA_encode(self,modeA_4096_code = "7000", emergency_state = 0x0):
frame = self.df_frame_start()
# data
format_tc = 28
st = 0x01 # 0 : No information
# 1 : Emergency/Priority Status and Mode A Code
# 2 : TCAS/ACAS RA Broadcast -> Figure C-8b : fields have different meaning
# 3-7 : reserved
frame[4] = ((format_tc << 3) | st)
# Encode Squawk
# ABCD (A:0-7, B:0-7, C:0-7, D:0-7)
# A = a4,a2,a1
# B = b4,b2,b1
# C = c4,c2,c1
# D = d4,d2,d1
# bits = c1,a1,c2,a2,c4,a4,0,b1,d1,b2,d2,b4,d4
if isinstance(modeA_4096_code,int):
squawk_str = '{:04d}'.format(modeA_4096_code)
elif isinstance(modeA_4096_code,str):
squawk_str = modeA_4096_code
else:
print("squawk must be provided as decimal int or 4 digits string")
exit(-1)
if (len(squawk_str) == 4):
test_digits = True
for i in range(4):
test_digits = test_digits and (squawk_str[i] >= '0' and squawk_str[i] <= '7')
if not test_digits:
print("all 4 squawk digits must be in 0-7 range")
exit(-1)
else:
print("squawk must be 4 digits string")
exit(-1)
a = "{0:03b}".format(int(squawk_str[0]))
b = "{0:03b}".format(int(squawk_str[1]))
c = "{0:03b}".format(int(squawk_str[2]))
d = "{0:03b}".format(int(squawk_str[3]))
a4 = int(a[0])
a2 = int(a[1])
a1 = int(a[2])
b4 = int(b[0])
b2 = int(b[1])
b1 = int(b[2])
c4 = int(c[0])
c2 = int(c[1])
c1 = int(c[2])
d4 = int(d[0])
d2 = int(d[1])
d1 = int(d[2])
squawk_bits = d4 | b4 << 1 | d2 << 2 | b2 << 3 | d1 << 4 | b1 << 5 | a4 << 7 | c4 << 8 | a2 << 9 | c2 << 10 | a1 << 11 | c1 << 12
emergency = emergency_state
if squawk_str == "7700":
emergency = 0x1
elif squawk_str == "7600":
emergency = 0x4
elif squawk_str == "7500":
emergency = 0x5
frame[5] = (emergency << 5 | squawk_bits >> 8)
frame[6] = (squawk_bits & 0xFF)
self.df_frame_write_crc(frame)
return frame
#@Timed
def df_frame_write_crc(self,frame):
crc = self.crc24_lu(frame[0:11])
frame[11] = crc >> 16
frame[12] = (crc >> 8) & 0xFF
frame[13] = crc & 0xFF
#@Timed
# CRC24 without lookup table
def crc24(self,msg):
crc = 0x0
for b in msg:
crc ^= (b << 16)
for i in range(8):
crc <<= 1
if crc & 0x1000000: crc ^= self._crc_poly
return crc & 0xFFFFFF
#@Timed
# CRC24 with lookup table (about 3x faster than non lookup version)
def crc24_lu(self,msg):
#print("len:",len(msg))
crc = 0x0
for b in msg:
tmp = (crc ^ (b << 16)) >> 16
crc = ((crc << 8) ^ self._crc_lookup_T0[tmp & 0xff])
return crc & 0xFFFFFF