initial commit

2022-03-10 21:25:48 +01:00 · 2022-03-10 21:25:48 +01:00 · ffd073f1fd
commit ffd073f1fd
parent 92880173c3
17 changed files with 2581 additions and 0 deletions
--- a/ADSBLowLevelEncoder.py
+++ b/ADSBLowLevelEncoder.py
@ -0,0 +1,102 @@
+from CustomDecorators import *
+import numpy
+
+@Singleton
+class ADSBLowLevelEncoder:
+    """
+    Hamming and Manchester Encoding example
+
+    Author: Joel Addison
+    Date: March 2013
+
+    Functions to do (7,4) hamming encoding and decoding, including error detection
+    and correction.
+    Manchester encoding and decoding is also included, and by default will use
+    least bit ordering for the byte that is to be included in the array.
+    """
+
+    def __init__(self):
+        self.adsb_frame_preamble = [0xA1,0x40]
+        self.adsb_frame_pause = [0]*70
+###############################################################
+# Further work on fork
+# Copyright (C) 2017 David Robinson
+    def extract_bit(self, byte, pos):
+        """
+        Extract a bit from a given byte using MS ordering.
+        ie. B7 B6 B5 B4 B3 B2 B1 B0
+        """
+        return (byte >> pos) & 0x01
+
+    def manchester_encode(self, byte):
+        """
+        Encode a byte using Manchester encoding. Returns an array of bits.
+        Adds two start bits (1, 1) and one stop bit (0) to the array.
+        """
+        manchester_encoded = []
+
+        # Encode byte
+        for i in range(7, -1, -1):
+            if self.extract_bit(byte, i):
+                manchester_encoded.extend([0,1])
+            else:
+                manchester_encoded.extend([1,0])
+
+        return manchester_encoded
+
+    def frame_1090es_ppm_modulate(self, even, odd = []):
+        """
+        Args:
+            even and odd: The data frames that need to be converted to PPM
+        Returns:
+            The bytearray of the PPM data
+        """
+        ppm = [ ]
+
+        length_even = len(even)
+        length_odd  = len(odd)
+
+        if (length_even != 0):
+            ppm.extend(self.adsb_frame_pause)      # pause
+            ppm.extend(self.adsb_frame_preamble)   # preamble
+            
+            for i in range(length_even):
+                word16 = numpy.packbits(self.manchester_encode(~even[i]))
+                ppm.extend(word16[0:2])
+            
+            ppm.extend(self.adsb_frame_pause)  # pause
+
+        if (length_odd != 0):
+            ppm.extend(self.adsb_frame_pause)        # pause
+            ppm.extend(self.adsb_frame_preamble)     # preamble
+
+            for i in range(length_odd):
+                word16 = numpy.packbits(self.manchester_encode(~odd[i]))
+                ppm.extend(word16[0:2])
+
+            ppm.extend(self.adsb_frame_pause)  # pause
+        
+        return bytearray(ppm)
+
+    def hackrf_raw_IQ_format(self, ppm):
+        """
+        Args:
+            ppm: this is some data in ppm (pulse position modulation) which will be converted into
+                 hackRF raw IQ sample format, ready to be broadcasted
+            
+        Returns:
+            bytearray: containing the IQ data
+        """
+        signal = []
+        bits = numpy.unpackbits(numpy.asarray(ppm, dtype=numpy.uint8))
+        for bit in bits:
+            if bit == 1:
+                I = 127
+                Q = 127
+            else:
+                I = 0
+                Q = 0
+            signal.append(I)
+            signal.append(Q)
+
+        return bytearray(signal)
--- a/AbstractTrajectorySimulatorBase.py
+++ b/AbstractTrajectorySimulatorBase.py
@ -0,0 +1,97 @@
+""" Abstract base class for a trajectory simulation
+
+This class provides basic services that will generate and feed broadcasting
+thread with appropriate messages.
+
+2 abstract methods need to be overriden in derived classes :
+- refresh_delay which should return the simulation timestep in seconds
+- update_aircraftinfos which is reponsible for animating the aircraftinfos
+  object at each time step, thus making the simulation "alive"
+
+mutex protection occurs when calling replace_message
+
+This program is free software: you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later
+version.
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+You should have received a copy of the GNU General Public License along with
+this program. If not, see <http://www.gnu.org/licenses/>.
+"""
+
+import time
+import abc
+import threading
+
+from ModeS import ModeS
+
+class AbstractTrajectorySimulatorBase(threading.Thread,abc.ABC):
+    def __init__(self,mutex,broadcast_thread,aircraftinfos):
+        super().__init__()
+        self._mutex = mutex
+        self._broadcast_thread = broadcast_thread
+        self._aircraftinfos = aircraftinfos
+
+        self._modeSencoder = ModeS(df=17,icao=self._aircraftinfos.icao,ca=self._aircraftinfos.capability)
+
+        self._do_stop = False
+    
+    # Thread core function
+    def run(self):
+
+        is_first_step = True
+        while not self._do_stop:
+            encoder_changed = False
+            # check if modeS encoder needs update
+            if self._aircraftinfos.icao_changed or self._aircraftinfos.capability_changed or is_first_step:
+                self._modeSencoder.icao = self._aircraftinfos.icao
+                self._modeSencoder.ca = self._aircraftinfos.capability
+                encoder_changed = True
+
+            if encoder_changed or self._aircraftinfos.callsign_changed:
+                self.df_callsign = self._modeSencoder.callsign_encode(self._aircraftinfos.callsign)        
+                self._broadcast_thread.replace_message("identification",self.df_callsign)
+
+            if encoder_changed or self._aircraftinfos.squawk_changed:
+                self.frame_6116 = self._modeSencoder.modaA_encode(self._aircraftinfos.squawk)
+                self._broadcast_thread.replace_message("register_6116",self.frame_6116)
+
+            # message generation only if needed
+            if encoder_changed or self._aircraftinfos.on_surface_changed \
+                or self._aircraftinfos.lat_changed or self._aircraftinfos.lon_changed or self._aircraftinfos.alt_msl_changed \
+                or self._aircraftinfos.type_code_changed or self._aircraftinfos.surveillance_status_changed or self._aircraftinfos.nicsupb_changed \
+                or self._aircraftinfos.timesync_changed:
+                if not self._aircraftinfos.on_surface:
+                    (self.df_pos_even, self.df_pos_odd) = self._modeSencoder.df_encode_airborne_position(self._aircraftinfos.lat_deg, self._aircraftinfos.lon_deg, self._aircraftinfos.alt_msl_ft, \
+                        self._aircraftinfos.type_code, self._aircraftinfos.surveillance_status, self._aircraftinfos.nicsupb, self._aircraftinfos.timesync)
+                    self._broadcast_thread.replace_message("airborne_position",self.df_pos_even,self.df_pos_odd)
+                    self._broadcast_thread.replace_message("surface_position",[], [])                        
+                else:
+                    (self.df_pos_even, self.df_pos_odd) = self._modeSencoder.df_encode_surface_position(self._aircraftinfos.lat_deg, self._aircraftinfos.lon_deg, self._aircraftinfos.alt_msl_ft, \
+                        self._aircraftinfos.type_code, self._aircraftinfos.surveillance_status, self._aircraftinfos.nicsupb, self._aircraftinfos.timesync)
+                    self._broadcast_thread.replace_message("surface_position",self.df_pos_even,self.df_pos_odd)
+                    self._broadcast_thread.replace_message("airborne_position",[], [])
+
+            if encoder_changed or self._aircraftinfos.speed_changed or self._aircraftinfos.track_angle_changed or self._aircraftinfos.vspeed_changed:
+                self.df_velocity = self._modeSencoder.df_encode_ground_velocity(self._aircraftinfos.speed_kt, self._aircraftinfos.track_angle_deg, self._aircraftinfos.vspeed_ftpmin) 
+                self._broadcast_thread.replace_message("airborne_velocity",self.df_velocity)
+
+            is_first_step = False
+            self.update_aircraftinfos()         # update_aircraftinfos() : abstract method that need to be implemented i nderived classes
+            time.sleep(self.refresh_delay())    # refresh_delay()        : abstract method that need to be implemented i nderived classes
+
+        # upon exit, reset _do_stop flag in case there is a new start
+        self._do_stop = False
+
+    def stop(self):
+        self._do_stop = True
+
+    @abc.abstractmethod
+    def refresh_delay(self):
+        ...
+
+    @abc.abstractmethod
+    def update_aircraftinfos(self):
+        ...
--- a/AircraftInfos.py
+++ b/AircraftInfos.py
@ -0,0 +1,291 @@
+""" This class holds the aircraft states from the ADS-B point of view
+
+It is refreshed by the simulation thread (or sensor feed thread) and will
+be used to provide broadcasted informations
+
+This program is free software: you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later
+version.
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+You should have received a copy of the GNU General Public License along with
+this program. If not, see <http://www.gnu.org/licenses/>.
+"""
+
+import math
+
+class AircraftInfos:
+    def __init__(self,icao,callsign,squawk,
+                      lat_deg,lon_deg,alt_msl_ft,speed_kph,vspeed_ftpmin,maxloadfactor,track_angle_deg,
+                      timesync,capability,type_code,surveillance_status,nicsupb,on_surface):
+
+        self._icao = int(icao,16)
+        self._oldicao = self._icao
+   
+        self._callsign = callsign
+        self._oldcallsign = self._callsign
+
+        self._squawk = squawk
+        self._oldsquawk = self._squawk
+
+        self._lat_deg = float(lat_deg)
+        self._oldlat_deg = self._lat_deg
+
+        self._lon_deg = float(lon_deg)
+        self._oldlon_deg = self._lon_deg
+
+        self._alt_msl_m = float(alt_msl_ft)*0.3048
+        self._oldalt_msl_m = self._alt_msl_m
+
+        self._speed_mps = float(speed_kph)/3.6
+        self._oldspeed_mps = self._speed_mps
+
+        self._vspeed_mps = float(vspeed_ftpmin)*0.00508
+        self._oldvspeed_mps = self._vspeed_mps
+
+        self._maxloadfactor = float(maxloadfactor)
+        self._oldmaxloadfactor = self._maxloadfactor
+
+        self._track_angle_deg = math.fmod(float(track_angle_deg),360.0)
+        self._oldtrack_angle_deg = self._track_angle_deg
+
+        self._timesync = int(timesync)
+        self._oldtimesync = self._timesync
+
+        self._capability = int(capability)
+        self._oldcapability = self._capability
+
+        self._type_code = int(type_code)
+        self._oldtype_code = self._type_code
+
+        self._surveillance_status = int(surveillance_status)
+        self._oldsurveillance_status = self._surveillance_status
+
+        self._nicsupb = int(nicsupb)
+        self._oldnicsupb = self._nicsupb
+
+        self._on_surface = on_surface
+        self._oldon_surface = self._on_surface
+
+    ################################################
+    @property
+    def icao(self):
+        return self._icao
+
+    @icao.setter
+    def icao(self,value):
+        self._oldicao = self._icao
+        self._icao = value
+    
+    @property
+    def icao_changed(self):
+        return self._icao != self._oldicao
+    ################################################
+    @property
+    def callsign(self):
+        return self._callsign
+
+    @callsign.setter
+    def callsign(self,value):
+        self._oldcallsign = self._callsign
+        self._callsign = value
+
+    @property
+    def callsign_changed(self):
+        return self._callsign != self._oldcallsign
+    ################################################
+    @property
+    def squawk(self):
+        return self._squawk
+
+    @squawk.setter
+    def squawk(self,value):
+        self._oldsquawk = self._squawk
+        self._squawk = value
+
+    @property
+    def squawk_changed(self):
+        return self._squawk != self._oldsquawk
+    ################################################
+    @property
+    def lat_deg(self):
+        return self._lat_deg
+
+    @lat_deg.setter
+    def lat_deg(self,value):
+        self._oldlat_deg = self._lat_deg
+        self._lat_deg = value
+
+    @property
+    def lat_changed(self):
+        return self._lat_deg != self._oldlat_deg
+    ################################################
+    @property
+    def lon_deg(self):
+        return self._lon_deg
+
+    @lon_deg.setter
+    def lon_deg(self,value):
+        self._oldlon_deg = self._lon_deg
+        self._lon_deg = value
+
+    @property
+    def lon_changed(self):
+        return self._lon_deg != self._oldlon_deg
+    ################################################
+    @property
+    def alt_msl_m(self):
+        return self._alt_msl_m
+
+    @property
+    def alt_msl_ft(self):
+        return self._alt_msl_m / 0.3048
+
+    @alt_msl_m.setter
+    def alt_msl_m(self,value):
+        self._oldalt_msl_m = self._alt_msl_m
+        self._alt_msl_m = value
+
+    @property
+    def alt_msl_changed(self):
+        return self._alt_msl_m != self._oldalt_msl_m
+    ################################################
+    @property
+    def speed_mps(self):
+        return self._speed_mps
+
+    @property
+    def speed_kt(self):
+        return self._speed_mps*1.94384449244
+
+    @speed_mps.setter
+    def speed_mps(self,value):
+        self._oldspeed_mps != self._speed_mps
+        self._speed_mps = value
+
+    @property
+    def speed_changed(self):
+        return self._speed_mps != self._oldspeed_mps
+    ################################################
+    @property
+    def vspeed_mps(self):
+        return self._vspeed_mps
+
+    @property
+    def vspeed_ftpmin(self):
+        return self._vspeed_mps * 196.850393701
+
+    @vspeed_mps.setter
+    def vspeed_mps(self,value):
+        self._oldvspeed_mps = self._vspeed_mps
+        self._vspeed_mps = value
+
+    @property
+    def vspeed_changed(self):
+        return self._vspeed_mps != self._oldvspeed_mps
+    ################################################
+    @property
+    def maxloadfactor(self):
+        return self._maxloadfactor
+
+    @maxloadfactor.setter
+    def maxloadfactor(self,value):
+        self._oldmaxloadfactor = self._maxloadfactor
+        self._maxloadfactor = value
+
+    @property
+    def maxloadfactor_changed(self):
+        return self._maxloadfactor != self._oldmaxloadfactor
+    ################################################
+    @property
+    def track_angle_deg(self):
+        return self._track_angle_deg
+
+    @track_angle_deg.setter
+    def track_angle_deg(self,value):
+        self._oldtrack_angle_deg = self._track_angle_deg
+        self._track_angle_deg = value
+
+    @property
+    def track_angle_changed(self):
+        return self._track_angle_deg != self._oldtrack_angle_deg
+    ################################################
+    @property
+    def timesync(self):
+        return self._timesync
+
+    @timesync.setter
+    def timesync(self,value):
+        self._oldtimesync = self._timesync
+        self._timesync = value
+
+    @property
+    def timesync_changed(self):
+        return self._timesync != self._oldtimesync
+    ################################################
+    @property
+    def capability(self):
+        return self._capability
+
+    @capability.setter
+    def capability(self,value):
+        self._oldcapability = self._capability
+        self._capability = value
+
+    @property
+    def capability_changed(self):
+        return self._capability != self._oldcapability
+    ################################################
+    @property
+    def type_code(self):
+        return self._type_code
+
+    @type_code.setter
+    def type_code(self,value):
+        self._oldtype_code = self._type_code
+        self._type_code = value
+
+    @property
+    def type_code_changed(self):
+        return self._type_code != self._oldtype_code
+    ################################################
+    @property
+    def surveillance_status(self):
+        return self._surveillance_status
+
+    @surveillance_status.setter
+    def surveillance_status(self,value):
+        self._oldsurveillance_status = self._surveillance_status
+        self._surveillance_status = value
+
+    @property
+    def surveillance_status_changed(self):
+        return self._surveillance_status != self._oldsurveillance_status
+    ################################################
+    @property
+    def nicsupb(self):
+        return self._nicsupb
+
+    @nicsupb.setter
+    def nicsupb(self,value):
+        self._oldnicsupb = self._nicsupb
+        self._nicsupb = value
+
+    @property
+    def nicsupb_changed(self):
+        return self._nicsupb != self._oldnicsupb
+    ################################################
+    @property
+    def on_surface(self):
+        return self._on_surface
+
+    @on_surface.setter
+    def on_surface(self,value):
+        self._oldon_surface = self._on_surface
+        self._on_surface = value
+
+    @property
+    def on_surface_changed(self):
+        return self._on_surface != self._oldon_surface
--- a/CustomDecorators.py
+++ b/CustomDecorators.py
@ -0,0 +1,22 @@
+import time
+
+def Singleton(class_):
+    instances = {}
+    def getinstance(*args, **kwargs):
+        if class_ not in instances:
+            instances[class_] = class_(*args, **kwargs)
+        return instances[class_]
+    return getinstance
+
+def Timed(method):
+    def timed(*args, **kw):
+        ts = time.time()
+        result = method(*args, **kw)
+        te = time.time()
+        if 'log_time' in kw:
+            name = kw.get('log_name', method.__name__.upper())
+            kw['log_time'][name] = int((te - ts) * 1000)
+        else:
+            print('%r total execution time was %2.2f ms' % (method.__name__, (te - ts) * 1000))
+        return result
+    return timed
--- a/FixedTrajectorySimulator.py
+++ b/FixedTrajectorySimulator.py
@ -0,0 +1,27 @@
+""" simplest implementation of a trajectory simulation where the simulated
+aircraft is steady at the provided position
+
+mutex protection occurs when calling replace_message
+
+This program is free software: you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later
+version.
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+You should have received a copy of the GNU General Public License along with
+this program. If not, see <http://www.gnu.org/licenses/>.
+"""
+
+from AbstractTrajectorySimulatorBase import AbstractTrajectorySimulatorBase
+
+class FixedTrajectorySimulator(AbstractTrajectorySimulatorBase):
+    def __init__(self,mutex,broadcast_thread,aircrafinfos):
+        super().__init__(mutex,broadcast_thread,aircrafinfos)
+
+    def refresh_delay(self):
+        return 0.005
+
+    def update_aircraftinfos(self):
+        pass
--- a/HackRfBroadcastThread.py
+++ b/HackRfBroadcastThread.py
@ -0,0 +1,177 @@
+""" This class holds the aircraft states from the ADS-B point of view
+
+It is refreshed by the simulation thread (or sensor feed thread) and will
+be used to provide broadcasted informations
+
+This program is free software: you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later
+version.
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+You should have received a copy of the GNU General Public License along with
+this program. If not, see <http://www.gnu.org/licenses/>.
+"""
+
+#
+#   This class overrides threading.Thread and provides service to broacast
+#   ADS-B message though a HackRF device
+#   message updates are performed from a separate thread which will
+#   update/push messages thanks to the replace_message method
+#   thread loop will pump and broacast updated message (soft realtime)
+#
+#   mutex protection mecanism is implemented in
+#   replace_message() which is call from other thread
+#   broadcast_one_message() which is called from this thread
+#   in order to prevent concurrent access to broadcasted data buffers
+
+import time, datetime, math
+import threading
+
+from CustomDecorators import *
+from ADSBLowLevelEncoder import ADSBLowLevelEncoder
+from pyhackrf import *
+from ctypes import *
+
+class hackrf_tx_context(Structure):
+    _fields_ = [("buffer", POINTER(c_ubyte)),
+                ("last_tx_pos", c_int),
+                ("buffer_length", c_int) ]
+
+def hackrfTXCB(hackrf_transfer):
+    user_tx_context = cast(hackrf_transfer.contents.tx_ctx, POINTER(hackrf_tx_context))
+    tx_buffer_length = hackrf_transfer.contents.valid_length
+    left = user_tx_context.contents.buffer_length - user_tx_context.contents.last_tx_pos
+    addr_dest = addressof(hackrf_transfer.contents.buffer.contents)
+    addr_src = addressof(user_tx_context.contents.buffer.contents)
+
+    if (left > tx_buffer_length):
+        memmove(addr_dest,addr_src,tx_buffer_length)
+        user_tx_context.contents.last_tx_pos += tx_buffer_length
+        return 0
+    else:
+        memmove(addr_dest,addr_src,left)
+        memset(addr_dest+left,0,tx_buffer_length-left)
+        return -1
+
+@Singleton
+class HackRfBroadcastThread(threading.Thread):
+    def __init__(self,mutex,airborne_position_refresh_period = 150000):
+        super().__init__()
+        self._mutex = mutex
+
+        self._lowlevelencoder = ADSBLowLevelEncoder()
+
+        self._messages = {}
+        # key : "name of message" value : ["data to be broadcasted", datetime of last broadcast, delay_between 2 messages of this type]
+        self._messages["identification"] = [None, None, 10000000]    # max should be 15s
+        self._messages["register_6116"] = [None, None, 800000]       # TODO : specs says that interval should be randomized between [0.7s;0.9s] and max is 1.0s
+        self._messages["airborne_position"] = [None, None, airborne_position_refresh_period]   # max should be 0.2s
+        self._messages["surface_position"] = [None, None, 150000]    # max should be 0.2s
+        self._messages["airborne_velocity"] = [None, None, 1200000]  # max should be 1.3s
+
+        # Initialize pyHackRF library
+        result = HackRF.initialize()
+        if (result != LibHackRfReturnCode.HACKRF_SUCCESS):
+            print("Error :",result, ",", HackRF.getHackRfErrorCodeName(result))
+
+        # Initialize HackRF instance (could pass board serial or index if specific board is needed)
+        self._hackrf_broadcaster = HackRF()
+
+        # Do requiered settings
+        # so far hard-coded e.g. gain and disabled amp are specific to hardware test setup
+        # with hackrf feeding a flight aware dongle through cable + attenuators (-50dB)
+        result = self._hackrf_broadcaster.open()
+        if (result != LibHackRfReturnCode.HACKRF_SUCCESS):
+            print("Error :",result, ",", HackRF.getHackRfErrorCodeName(result))
+
+        result = self._hackrf_broadcaster.setSampleRate(2000000)
+        if (result != LibHackRfReturnCode.HACKRF_SUCCESS):
+            print("Error :",result, ",", HackRF.getHackRfErrorCodeName(result))
+
+        result = self._hackrf_broadcaster.setBasebandFilterBandwidth(HackRF.computeBaseBandFilterBw(2000000))
+        if (result != LibHackRfReturnCode.HACKRF_SUCCESS):
+            print("Error :",result, ",", HackRF.getHackRfErrorCodeName(result))
+
+        #result = self.hackrf_broadcaster.setFrequency(868000000)   # free frequency for over the air brodcast tests
+        result = self._hackrf_broadcaster.setFrequency(1090000000)   # do not use 1090MHz for actual over the air broadcasting
+                                                                    # only if you use wire feed (you'll need attenuators in that case)
+        if (result != LibHackRfReturnCode.HACKRF_SUCCESS):
+            print("Error :",result, ",", HackRF.getHackRfErrorCodeName(result))
+
+        result = self._hackrf_broadcaster.setTXVGAGain(4)            # week gain (used for wire feed + attenuators)
+        if (result != LibHackRfReturnCode.HACKRF_SUCCESS):
+            print("Error :",result, ",", HackRF.getHackRfErrorCodeName(result))
+
+        result = self._hackrf_broadcaster.setAmplifierMode(LibHackRfHwMode.HW_MODE_OFF)
+        if (result != LibHackRfReturnCode.HACKRF_SUCCESS):
+            print("Error :",result, ",", HackRF.getHackRfErrorCodeName(result))        
+
+        self._tx_context = hackrf_tx_context()
+
+        self._do_stop = False
+
+    # do hackRF lib and instance cleanup at object destruction time
+    def __del__(self):
+        result = self._hackrf_broadcaster.close()
+        if (result != LibHackRfReturnCode.HACKRF_SUCCESS):
+            print("Error :",result, ",", HackRF.getHackRfErrorCodeName(result))
+
+        result = HackRF.deinitialize()
+        if (result != LibHackRfReturnCode.HACKRF_SUCCESS):
+            print("Error :",result, ",", HackRF.getHackRfErrorCodeName(result))
+
+    def stop(self):
+        self._do_stop = True
+
+    # updates the next data to be broadcaster for a given message type
+    def replace_message(self,type,frame_even,frame_odd = []):
+        frame_ppm = self._lowlevelencoder.frame_1090es_ppm_modulate(frame_even, frame_odd)
+        frame_IQ = self._lowlevelencoder.hackrf_raw_IQ_format(frame_ppm)
+
+        # this will usuallyy be called from another thread, so mutex lock mecanism is used during update
+        self._mutex.acquire()
+        self._messages[type][0] = frame_IQ
+        self._mutex.release()
+
+    def broadcast_one_message(self,data): 
+        self._tx_context.last_tx_pos = 0  
+        self._mutex.acquire()        
+        self._tx_context.buffer_length = len(data)
+        self._tx_context.buffer = (c_ubyte*self._tx_context.buffer_length).from_buffer_copy(data)
+        # TODO : need to evaluate if mutex protection is requiered during full broadcast or
+        #        could be reduced to buffer filling (probably can be reduced)
+        #        reduced version is when next line mutex.release() is uncommented and
+        #        mutex release at the end of this method is commented
+
+        self._mutex.release()
+
+        result = self._hackrf_broadcaster.startTX(hackrfTXCB,self._tx_context)
+
+        if (result != LibHackRfReturnCode.HACKRF_SUCCESS):
+            print("Error :",result, ",", HackRF.getHackRfErrorCodeName(result))
+
+        while self._hackrf_broadcaster.isStreaming():
+            time.sleep(0.00001)
+
+        result = self._hackrf_broadcaster.stopTX()
+        if (result != LibHackRfReturnCode.HACKRF_SUCCESS):
+            print("Error :",result, ",", HackRF.getHackRfErrorCodeName(result))
+         
+        #self.mutex.release() 
+
+    def run(self):
+        while not self._do_stop:
+            for k,v in self._messages.items():
+                now = datetime.datetime.now(datetime.timezone.utc)
+                # Time throttling : messages are broadcasted only at provided time intervall
+                # TODO : implement UTC syncing mecanism (requiered that the actual host clock is UTC synced)
+                #        which can be implemented to some accuracy level with ntp or GPS + PPS mecanisms
+                if (v[0] != None and len(v[0]) > 0) and (v[1] == None or (now - v[1]) >= datetime.timedelta(seconds=v[2] // 1000000,microseconds=v[2] % 1000000)):
+                    self.broadcast_one_message(v[0])
+                    v[1] = now
+            time.sleep(0.0001)  # this loop will run at 10 kHz max
+
+        # upon exit, reset _do_stop flag in case there is a new start
+        self._do_stop = False
--- a/ModeS.py
+++ b/ModeS.py
@ -0,0 +1,343 @@
+from ModeSLocation import ModeSLocation
+import math
+import numpy
+###############################################################
+# 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.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)
+
+    def df_frame_start(self):
+        """
+        This will build the usual df frame start
+        """        
+        frame = []
+        frame.append((self.df << 3) | self.ca)
+        frame.append((self.icao >> 16) & 0xff)
+        frame.append((self.icao >> 8) & 0xff)
+        frame.append((self.icao) & 0xff)
+        return frame
+
+    def df_frame_append_crc(self,frame):
+        frame_str = "{0:02x}{1:02x}{2:02x}{3:02x}{4:02x}{5:02x}{6:02x}{7:02x}{8:02x}{9:02x}{10:02x}".format(*frame[0:11])
+        frame_crc = self.bin2int(self.modes_crc(frame_str + "000000", encode=True))
+        frame.append((frame_crc >> 16) & 0xff)
+        frame.append((frame_crc >> 8) & 0xff)
+        frame.append((frame_crc) & 0xff)
+
+    # Ref :
+    # ICAO Annex 10 : Aeronautical Telecommunications
+    # Volume IV : Surveillance and Collision Avoidance Systems
+    # Figure C-1. Extended Squitter Airborne Position
+    # "Register 05_16"
+
+    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)
+        """
+
+        location = ModeSLocation()
+        enc_alt =	location.encode_alt_modes(alt, False)
+        
+        #encode that position
+        (evenenclat, evenenclon) = location.cpr_encode(lat, lon, False, False)
+        (oddenclat, oddenclon)   = location.cpr_encode(lat, lon, True, False)
+
+        ff = 0
+        df_frame_even_bytes = self.df_frame_start()
+        # data
+        df_frame_even_bytes.append((tc<<3) | (ss<<1) | nicsb)
+        df_frame_even_bytes.append((enc_alt>>4) & 0xff)
+        df_frame_even_bytes.append((enc_alt & 0xf) << 4 | (timesync<<3) | (ff<<2) | (evenenclat>>15))
+        df_frame_even_bytes.append((evenenclat>>7) & 0xff)
+        df_frame_even_bytes.append(((evenenclat & 0x7f) << 1) | (evenenclon>>16))
+        df_frame_even_bytes.append((evenenclon>>8) & 0xff)
+        df_frame_even_bytes.append((evenenclon   ) & 0xff)
+
+        self.df_frame_append_crc(df_frame_even_bytes)
+
+        ff = 1
+        df_frame_odd_bytes = self.df_frame_start()
+        # data
+        df_frame_odd_bytes.append((tc<<3) | (ss<<1) | nicsb)
+        df_frame_odd_bytes.append((enc_alt>>4) & 0xff)
+        df_frame_odd_bytes.append((enc_alt & 0xf) << 4 | (timesync<<3) | (ff<<2) | (oddenclat>>15))
+        df_frame_odd_bytes.append((oddenclat>>7) & 0xff)
+        df_frame_odd_bytes.append(((oddenclat & 0x7f) << 1) | (oddenclon>>16))
+        df_frame_odd_bytes.append((oddenclon>>8) & 0xff)
+        df_frame_odd_bytes.append((oddenclon   ) & 0xff)
+
+        self.df_frame_append_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"
+    def df_encode_extended_squitter_status(self, trs = 0x0, ats = 0x0):
+        df_frame = self.df_frame_start()
+
+        df_frame.append((trs << 6) & 0x3 | (ats << 5) & 0x1)
+        df_frame.extend([0]*6)
+
+        self.df_frame_append_crc(df_frame)
+        return df_frame
+    
+    #From https://github.com/jaywilhelm/ADSB-Out_Python on 2019-08-18
+    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.append((tc << 3) | st)
+        dfvel.append((ic << 7) | (resv_a << 6) | (NAC << 3) | (S_EW << 2) | ((V_EW >> 8) & 0x03))
+        dfvel.append(0xFF & V_EW)
+        dfvel.append((S_NS << 7) | ((V_NS >> 3))) #& 0x7F))
+        dfvel.append(((V_NS << 5) & 0xE0) | (VrSrc << 4) | (S_Vr << 3) | ((Vr >> 6) & 0x03))        
+        dfvel.append(((Vr  << 2) & 0xFC) | (RESV_B))
+        dfvel.append((S_Dif << 7) | (Dif))
+
+        self.df_frame_append_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
+
+        map = "#ABCDEFGHIJKLMNOPQRSTUVWXYZ#####_###############0123456789######"
+
+        dfname = self.df_frame_start()
+        # data
+        dfname.append((tc << 3) | (ec))
+        dfname.append((0xFC & (int(map.find(csname[0])) << 2)) | (0x03 & (int(map.find(csname[1])) >> 6)))
+        dfname.append((0xF0 & (int(map.find(csname[1])) << 4)) | (0x0F & (int(map.find(csname[2])) >> 2)))
+        dfname.append((0xF0 & (int(map.find(csname[2])) << 6)) | (0x3F & (int(map.find(csname[3])) >> 0)))
+        dfname.append((0xFC & (int(map.find(csname[4])) << 2)) | (0x03 & (int(map.find(csname[5])) >> 4)))
+        dfname.append((0xF0 & (int(map.find(csname[5])) << 4)) | (0x0F & (int(map.find(csname[6])) >> 2)))
+        dfname.append((0xF0 & (int(map.find(csname[6])) << 6)) | (0x3F & (int(map.find(csname[7])) >> 0)))
+
+        self.df_frame_append_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"
+
+    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.append((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.append(emergency << 5 | squawk_bits >> 8)
+        frame.append(squawk_bits & 0xFF)
+
+        frame.extend([0]*4)
+
+        self.df_frame_append_crc(frame)
+
+        return frame
+
+###############################################################
+# Copyright (C) 2015 Junzi Sun (TU Delft)
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+###############################################################
+
+# the polynominal generattor code for CRC
+        
+    def modes_crc(self, msg, encode=False):
+        """Mode-S Cyclic Redundancy Check
+        Detect if bit error occurs in the Mode-S message
+        Args:
+            msg (string): 28 bytes hexadecimal message string
+            encode (bool): True to encode the date only and return the checksum
+        Returns:
+            string: message checksum, or partity bits (encoder)
+        """
+
+        GENERATOR = "1111111111111010000001001" # polynomial coefficients
+        
+        msgbin = list(self.hex2bin(msg))
+
+        if encode:
+            msgbin[-24:] = ['0'] * 24
+
+        # loop all bits, except last 24 piraty bits
+        for i in range(len(msgbin)-24):
+            # if 1, perform modulo 2 multiplication,
+            if msgbin[i] == '1':
+                for j in range(len(GENERATOR)):
+                    # modulo 2 multiplication = XOR
+                    msgbin[i+j] = str((int(msgbin[i+j]) ^ int(GENERATOR[j])))
+
+        # last 24 bits
+        reminder = ''.join(msgbin[-24:])
+        return reminder
+
+    def hex2bin(self, hexstr):
+        """Convert a hexdecimal string to binary string, with zero fillings. """
+        scale = 16
+        num_of_bits = len(hexstr) * math.log(scale, 2)
+        binstr = bin(int(hexstr, scale))[2:].zfill(int(num_of_bits))
+        return binstr
+
+    def bin2int(self, binstr):
+        """Convert a binary string to integer. """
+        return int(binstr, 2)
--- a/ModeSLocation.py
+++ b/ModeSLocation.py
@ -0,0 +1,110 @@
+import math
+
+class ModeSLocation:
+    """This class does ModeS/ADSB Location calulations"""
+
+    def __init__(self):
+        self.latz = 15
+    
+##########################################################################
+
+# Copyright 2010, 2012 Nick Foster
+# # This file is part of gr-air-modes
+# 
+# gr-air-modes is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+# 
+# gr-air-modes is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with gr-air-modes; see the file COPYING.  If not, write to
+# the Free Software Foundation, Inc., 51 Franklin Street,
+# Boston, MA 02110-1301, USA.
+# 
+###############################################################
+# Further work on fork
+# Copyright (C) 2017 David Robinson
+    def encode_alt_modes(self, alt, bit13):
+        # need to better understand as the >50175 feet not working
+        mbit = False
+        qbit = True
+        # For altitudes -1000<=X<=50175 feet, set bit 8 AKA the Q bit to true which means 25 feet resoulution
+        # For >50175 set the qbit to False and use 100 feet resoultion
+        if alt > 50175:
+            qbit = False
+            encalt = int((int(alt) + 1000) / 100)
+        else:
+            qbit = True
+            encalt = int((int(alt) + 1000) / 25)
+
+        if bit13 is True:
+            tmp1 = (encalt & 0xfe0) << 2
+            tmp2 = (encalt & 0x010) << 1
+
+        else:
+            tmp1 = (encalt & 0xff8) << 1
+            tmp2 = 0
+
+        return (encalt & 0x0F) | tmp1 | tmp2 | (mbit << 6) | (qbit << 4)
+
+
+
+    def nz(self, ctype):
+        """
+        Number of geographic latitude zones between equator and a pole. It is set to NZ = 15 for Mode-S CPR encoding
+        https://adsb-decode-guide.readthedocs.io/en/latest/content/cpr.html
+        """
+        return 4 * self.latz - ctype
+
+    def dlat(self, ctype, surface):
+        if surface == 1:
+            tmp = 90.0
+        else:
+            tmp = 360.0
+
+        nzcalc = self.nz(ctype)
+        if nzcalc == 0:
+            return tmp
+        else:
+            return tmp / nzcalc
+
+    def nl(self, declat_in):
+        if abs(declat_in) >= 87.0:
+            return 1.0
+        return math.floor( (2.0*math.pi) / math.acos(1.0- (1.0-math.cos(math.pi/(2.0*self.latz))) / math.cos( (math.pi/180.0)*abs(declat_in) )**2 ))
+
+    def dlon(self, declat_in, ctype, surface):
+        if surface:
+            tmp = 90.0
+        else:
+            tmp = 360.0
+        nlcalc = max(self.nl(declat_in)-ctype, 1)
+        return tmp / nlcalc
+
+    # encode CPR position
+    # https://adsb-decode-guide.readthedocs.io/en/latest/content/cpr.html
+    # compact position reporting
+    def cpr_encode(self, lat, lon, ctype, surface):
+        if surface is True:
+            scalar = 2.**19
+        else:
+            scalar = 2.**17
+
+        #encode using 360 constant for segment size.
+        dlati = self.dlat(ctype, False)
+        yz = math.floor(scalar * ((lat % dlati)/dlati) + 0.5)
+        rlat = dlati * ((yz / scalar) + math.floor(lat / dlati))
+        
+        #encode using 360 constant for segment size.
+        dloni = self.dlon(lat, ctype, False)
+        xz = math.floor(scalar * ((lon % dloni)/dloni) + 0.5)
+        
+        yz = int(yz) & (2**17-1)
+        xz = int(xz) & (2**17-1)
+        
+        return (yz, xz) #lat, lon
--- a/PseudoCircleTrajectorySimulator.py
+++ b/PseudoCircleTrajectorySimulator.py
@ -0,0 +1,51 @@
+""" simplest implementation of a trajectory simulation where the simulated
+aircraft is flying a pseudo circle around center position at max load factor
+
+mutex protection occurs when calling replace_message
+
+This program is free software: you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later
+version.
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+You should have received a copy of the GNU General Public License along with
+this program. If not, see <http://www.gnu.org/licenses/>.
+"""
+
+import datetime, math
+from AbstractTrajectorySimulatorBase import AbstractTrajectorySimulatorBase
+
+class PseudoCircleTrajectorySimulator(AbstractTrajectorySimulatorBase):
+    def __init__(self,mutex,broadcast_thread,aircrafinfos):
+        super().__init__(mutex,broadcast_thread,aircrafinfos)
+        self._starttime = datetime.datetime.now(datetime.timezone.utc)
+        
+        self._lasttime = self._starttime
+
+        self._lat0 = aircrafinfos.lat_deg
+        self._lon0 = aircrafinfos.lon_deg
+
+    def refresh_delay(self):
+        return 0.005
+
+    def update_aircraftinfos(self):
+        now = datetime.datetime.now(datetime.timezone.utc)
+        elapsed = (now - self._lasttime).total_seconds()
+        turn_rate = self.getTurnRate()
+        R = self.getTurnRadius()
+        Rlat = (R/6371000.0)*(180.0/math.pi)
+        ta = self._aircraftinfos.track_angle_deg - (turn_rate*elapsed)*(180.0/math.pi)
+        ta = math.fmod(ta,360.0)
+        self._aircraftinfos.track_angle_deg = ta
+        self._aircraftinfos.lat_deg = self._lat0 - Rlat*math.sin(self._aircraftinfos.track_angle_deg*math.pi/180.0)
+        self._aircraftinfos.lon_deg = self._lon0 + Rlat/math.cos(self._aircraftinfos.lat_deg*math.pi/180.0)*math.cos(self._aircraftinfos.track_angle_deg*math.pi/180.0)
+        self._lasttime = now
+
+    def getTurnRate(self):
+        tr = (9.81/self._aircraftinfos.speed_mps)*math.sqrt(self._aircraftinfos.maxloadfactor**2.0 - 1.0)
+        return tr
+
+    def getTurnRadius(self):
+        return self._aircraftinfos.speed_mps/self.getTurnRate()
--- a/README.md
+++ b/README.md
@ -0,0 +1,100 @@
+# realtime ADS-B out
+
+## Foreword
+
+This project is inspired and reuse several parts of several other ADS-B / mode S projects amongst which:
+
+- https://github.com/lyusupov/ADSB-Out
+- https://github.com/nzkarit/ADSB-Out and https://github.com/pynstrom/adsb-out
+- https://github.com/bistromath/gr-air-modes
+- https://github.com/junzis/pyModeS
+
+All those repositories are published under GNU General Public License v3.0. This is also the license chosen for this repository.
+Please let me know if you have issues or require more explicit citations about reused source code.
+
+## Project goals
+
+The initial project goals are oriented towards:
+
+- completing the set of broadcastable messages that have already been implemented "adsb-out" in referenced projects.
+- fixing bugs / adding features in existing code.
+- producing a software architecture that better suit my understanding/habits.
+- beeing able to live feed HackRF through a libhackrf python wrapper layer, rather than generating an IQ sample files that would later be hackrf_transfer'd.
+
+## HackRF python wrapper
+
+HackRF python wrapper `pyhackrf.py` is included in this repository but is also proposed to be merged into hackRF main repository: https://github.com/greatscottgadgets/hackrf/pull/1058  
+If the pull request get accepted, file `pyhackrf.py` will be removed from this repo.  
+This repo only uses TX feature of the python wrapper, but RX is also possible (see examples in the PR)
+
+At time of writting this guide, I also believe there is a regression in `libhackrf` which should be solved by PR: https://github.com/greatscottgadgets/hackrf/pull/1057  
+This is still under review from greatscottgadgets maintainers but code in this repo is tested with the PR included.  
+I have not tested it with older/officiel releases of hackrf drivers/dev lib versions.
+
+## Software architecture
+
+The workflow is divided between 3 execution threads:
+
+- main thread wich performs all initializations and control user inputs (mainly start / stop simulation for now)
+- hackrf broadcasting thread which pump encoded messages and send them over the air with a predefined schedule
+- trajectory simulation thread which feed brodcasting thread with encoded messages matching a real time simulated trajectory
+
+The message encoding is splitted into mode S "frame encoding" and "low level encoding" which handles PPM modulation and conversion to hackRF IQ sample format.  
+Software source code structure tries to reflect those 2 different layers.
+
+So far only "simple" simulated trajectories are available, but one can easily extend/fork behaviour to e.g. have a flight informations coming from a flight simulator (X-plane would be pretty well suited for that purpose through it's UDP aircraft state broadcast facility) or use actual sensors to feed live data.
+
+## Usage and RF broadcast disclaimer
+
+Usage can be demonstrated together with `dump1090-mutability` or `dump1090-fa` and associated webservers or text message views.
+
+Repository source code is tuned for a 1090 MHz brodcast with **direct wire feed** to a receiver SDR dongle (no over the air broadcast).  
+The hardware setup I'm using is pictured below. Please note the RF attenuators (-20dB and -30dB).  
+The extra 1090MHz filter is probably not requiered as the flight aware dongle already features 1090 MHz filtering.
+My HackRF is fitted with a 0.5 ppm TCXO
+
+![test setup image](./test-setup.jpg "test setup")
+
+The default hackrf settings in repo are :
+- 1090 MHz
+- LNA amplificator disabled
+- TX gain 4dB
+- Sample rate needs to be 2MHz as this matches the ADS-B specification where PPM symbols last for 0.5 µs.
+
+Actual ADS-B brodcast frequency is 1090MHz which in most if not all places is a reserved band.  
+Some critical **flight safety feature** do rely on actual ADS-B broadcasts.  
+Unless you have special authorisations, **you should NEVER broadcast over the air at this frequency**.
+
+If you can't use a wired RF feeding between hackRF and your SDR receiver for your test setup, you can easily modify source code in order to use a "fake" free frequency (e.g. 868MHz) and setup dump1090 accordingly to match this "fake" frequency by adding switch `--freq 868000000` to your usual `dump1090` command line. Increasing TX gain may be needed in that use case.
+
+By the way, I believe that the fact that one with 200$ hardware would actually be able to broadcast at 1090MHz and produce some fake ADS-B aircraft tracks highlights a serious weakness in ADS-B design.  
+Those forged broadcasts may be used to spoof ATC, trigger TCAS or other malicious behaviours.
+
+## Command line examples
+
+`./realtime-adsb-out.py --callsign 'FCKPUTIN' --alt 4500 --speed 600 --trajectorytype circle --maxloadfactor 1.03`
+
+will generate a pseudo circular trajectory, flown at 4500 ft, 600 km/h and a load factor of 1.03.
+
+![circle mode example image](./adsb-out-circle.png "circle mode example")
+
+`./realtime-adsb-out.py --callsign 'FCKPUTIN' --alt 4500  --trajectorytype random`
+
+will generate a random trajectory in a ~30s at specified (here default) speed around center lat / lon (default here too).  
+track angle is randomized, speed is randomized, altitude is randomized. The default position frame broadcast period can be lowered in order to
+produce a large numer of tracks in a given area
+
+![random mode example image](./adsb-out-random.png "random mode example")
+
+## Reference documentation
+
+All reference documentation from the repositories mentionned in the foreword.
+
+https://mode-s.org/
+
+*ICAO Annex 10, Aeronautical Telecommunications, Volume IV - Surveillance Radar and Collision Avoidance Systems* which at time of writing can be retrieved here:
+- english version https://www.bazl.admin.ch/bazl/en/home/specialists/regulations-and-guidelines/legislation-and-directives/anhaenge-zur-konvention-der-internationalen-zivilluftfahrtorgani.html
+- french version https://www.bazl.admin.ch/bazl/fr/home/experts/reglementation-et-informations-de-base/bases-legales-et-directives/annexes-a-la-convention-de-l-organisation-internationale-de-l-av.html  
+
+*ICAO doc 9871 edition 1* which can be retrieved here (There is an edition 2 of this document but all seems to be behing paywalls):
+- [ICAO doc 9871 edition 1](http://www.aviationchief.com/uploads/9/2/0/9/92098238/icao_doc_9871_-_technical_provisions_for_mode_s_-_advanced_edition_1.pdf)
--- a/RandomTrajectorySimulator.py
+++ b/RandomTrajectorySimulator.py
@ -0,0 +1,45 @@
+""" simplest implementation of a trajectory simulation where the simulated
+aircraft is randomly distributed inside a circle
+
+mutex protection occurs when calling replace_message
+
+This program is free software: you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later
+version.
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+You should have received a copy of the GNU General Public License along with
+this program. If not, see <http://www.gnu.org/licenses/>.
+"""
+
+import random
+import datetime, math
+from AbstractTrajectorySimulatorBase import AbstractTrajectorySimulatorBase
+
+class RandomTrajectorySimulator(AbstractTrajectorySimulatorBase):
+    def __init__(self,mutex,broadcast_thread,aircrafinfos):
+        super().__init__(mutex,broadcast_thread,aircrafinfos)
+        self._starttime = datetime.datetime.now(datetime.timezone.utc)
+        
+        self._lat0 = aircrafinfos.lat_deg
+        self._lon0 = aircrafinfos.lon_deg
+
+        self._max_alt_m = aircrafinfos.alt_msl_m
+        self._max_speed_mps = aircrafinfos.speed_mps
+
+    def refresh_delay(self):
+        return 0.005
+
+    def update_aircraftinfos(self):
+        
+        d0 = self._max_speed_mps * 30.0
+        Rlat = (d0/6371000.0)*(180.0/math.pi)
+        Rlon = Rlat/math.cos(self._lat0*math.pi/180.0)
+        self._aircraftinfos.track_angle_deg = random.uniform(0,360.0)
+        self._aircraftinfos.lat_deg = self._lat0 - random.uniform(-Rlat,Rlat)
+        self._aircraftinfos.lon_deg = self._lon0 + random.uniform(-Rlon,Rlon)
+
+        self._aircraftinfos.alt_msl_m = random.uniform(1.0,self._max_alt_m)
+        self._aircraftinfos.speed_mps = random.uniform(0.0,self._max_speed_mps)
--- a/WaypointsTrajectorySimulator.py
+++ b/WaypointsTrajectorySimulator.py
@ -0,0 +1,32 @@
+""" implementation of a trajectory simulation where the simulated aircraft
+is following a preplanned trajectory
+
+mutex protection occurs when calling replace_message
+
+This program is free software: you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later
+version.
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+You should have received a copy of the GNU General Public License along with
+this program. If not, see <http://www.gnu.org/licenses/>.
+"""
+
+import time
+
+from AbstractTrajectorySimulatorBase import AbstractTrajectorySimulatorBase
+
+class WaypointsTrajectorySimulator(AbstractTrajectorySimulatorBase):
+    def __init__(self,mutex,broadcast_thread,aircrafts_info,waypoints_file):
+        super().__init__(mutex,broadcast_thread)
+
+
+    def refresh_delay(self):
+        return 0.005
+
+
+    # TODO : implement waypoint simulation...
+    #def update_aircraftinfos(self):
+    #    pass
--- a/adsb-out-circle.png
+++ b/adsb-out-circle.png
--- a/adsb-out-random.png
+++ b/adsb-out-random.png
--- a/pyhackrf.py
+++ b/pyhackrf.py
--- a/realtime-adsb-out.py
+++ b/realtime-adsb-out.py
@ -0,0 +1,156 @@
+#!/usr/bin/env python3
+
+""" This file hold the main function which read user inputs
+initialize and launch the simulation
+
+This program is free software: you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later
+version.
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+You should have received a copy of the GNU General Public License along with
+this program. If not, see <http://www.gnu.org/licenses/>.
+"""
+
+import sys, time, math
+import threading
+
+from AircraftInfos import AircraftInfos
+from FixedTrajectorySimulator import FixedTrajectorySimulator
+from PseudoCircleTrajectorySimulator import PseudoCircleTrajectorySimulator
+from RandomTrajectorySimulator import RandomTrajectorySimulator
+from WaypointsTrajectorySimulator import WaypointsTrajectorySimulator
+from HackRfBroadcastThread import HackRfBroadcastThread
+
+from getopt import getopt, GetoptError
+
+def usage(msg=False):
+    if msg:print(msg)
+    print("Usage: %s [options]\n" % sys.argv[0])
+    print("-h | --help              Display help message.")
+    print("--icao <opt>             Callsign in hex, Default:0x508035")
+    print("--callsign <opt>         Callsign (8 chars max), Default:DEADBEEF")
+    print("--squawk <opt>           4-digits 4096 code squawk, Default:7000")
+    print("--trajectorytype <opt>   Type of simulated trajectory amongst :")
+    print("                           fixed       : steady aircraft")
+    print("                           circle      : pseudo circular flight")
+    print("                           random      : random positions inside circle area")    
+    print("                           waypoints   : fly long flight path")
+    print("                           Default:fixed")
+    print("--lat <opt>              Latitude for the plane in decimal degrees, Default:50.44994")
+    print("--long <opt>             Longitude for the place in decimal degrees. Default:30.5211")
+    print("--altitude <opt>         Altitude in decimal feet, Default:1500.0")
+    print("--speed <opt>            Airspeed in decimal kph, Default:300.0")
+    print("--vspeed <opt>           Vertical speed en ft/min, positive up, Default:0")
+    print("--maxloadfactor          Specify the max load factor for aircraft simulation. Default:1.45")
+    print("--trackangle <opt>       Track angle in decimal degrees. Default:0")
+    print("--timesync <opt>         0/1, 0 indicates time not synchronous with UTC, Default:0")
+    print("--capability <opt>       Capability, Default:5")
+    print("--typecode <opt>         ADS-B message type, Default:11")
+    print("--sstatus <opt>          Surveillance status, Default:0")
+    print("--nicsupplementb <opt>   NIC supplement-B, Default:0")
+    print("--surface                Aircraft located on ground, Default:False")
+    print("--waypoints <opt>        Waypoints file for waypoints trajectory")
+    print("--posrate <opt>          position frame broadcast period in µs, Default: 150000")
+    print("")
+    #print("see usage.md for additionnal information")
+
+    sys.exit(2)
+
+def main():
+
+    # Default values
+    icao_aa = '0x508035'
+    callsign = 'DEADBEEF'
+    squawk = '7000'
+
+    alt_ft  = 1500.0
+    lat_deg = 50.44994
+    lon_deg = 30.5211
+    speed_kph = 300.0
+    vspeed_ftpmin = 0.0
+    maxloadfactor = 1.45
+    track_angle_deg = 0.0
+    capability = 5
+    type_code = 11
+    surveillance_status = 0
+    timesync = 0
+    nicsup = 0
+    on_surface = False
+    trajectory_type = 'fixed'
+    waypoints_file = None
+    posrate = 150000
+
+    try:
+        (opts, args) = getopt(sys.argv[1:], 'h', \
+            ['help','icao=','callsign=','squawk=','trajectorytype=','lat=','long=','altitude=','speed=','vspeed=','maxloadfactor=','trackangle=',
+            'timesync=','capability=','typecode=','sstatus=','nicsupplementb=','surface','posrate='
+            ])
+    except GetoptError as err:
+        usage("%s\n" % err)
+
+    if len(opts) != 0:
+        for (opt, arg) in opts:
+            if opt in ('-h', '--help'):usage()
+            elif opt in ('--icao'):icao_aa = arg
+            elif opt in ('--callsign'):callsign = arg
+            elif opt in ('--squawk'):squawk = arg
+            elif opt in ('--trajectorytype'):trajectory_type = arg
+            elif opt in ('--lat'):lat_deg = float(arg)
+            elif opt in ('--long'):lon_deg = float(arg)
+            elif opt in ('--altitude'):alt_ft = float(arg)
+
+            elif opt in ('--speed'):speed_kph = float(arg)
+            elif opt in ('--vspeed'):vspeed_ftpmin = float(arg)
+            elif opt in ('--maxloadfactor'):maxloadfactor = float(arg)
+            
+            elif opt in ('--trackangle'):track_angle_deg = float(arg)
+
+            elif opt in ('--timesync'):timesync = int(arg)
+            elif opt in ('--capability'):capability = int(arg)
+            elif opt in ('--typecode'):type_code = int(arg)
+            elif opt in ('--sstatus'):surveillance_status = int(arg)
+            elif opt in ('--nicsupplementb'):nicsup = int(arg)
+            elif opt in ('--surface'):on_surface = True
+            elif opt in ('--posrate'):posrate = int(arg)
+            else:usage("Unknown option %s\n" % opt)
+
+    aircraftinfos = AircraftInfos(icao_aa,callsign,squawk, \
+                                  lat_deg,lon_deg,alt_ft,speed_kph,vspeed_ftpmin,maxloadfactor,track_angle_deg, \
+                                  timesync,capability,type_code,surveillance_status,nicsup,on_surface)
+
+    # TODO : the mutex would better be implemented as an object attribute in broadcast thread
+    mutex = threading.Lock()
+
+    brodcast_thread = HackRfBroadcastThread(mutex,posrate) # posrate would usally be used with random mode to generate load of tracks
+
+    if trajectory_type == 'fixed':
+        trajectory_simulator = FixedTrajectorySimulator(mutex,brodcast_thread,aircraftinfos)
+    elif trajectory_type == 'circle':
+        trajectory_simulator = PseudoCircleTrajectorySimulator(mutex,brodcast_thread,aircraftinfos)
+    elif trajectory_type == 'random':
+        trajectory_simulator = RandomTrajectorySimulator(mutex,brodcast_thread,aircraftinfos)        
+    elif trajectory_type == 'waypoints':
+        print("WaypointsTrajectorySimulator not implemented yet")
+        exit(-1)
+        trajectory_simulator = WaypointsTrajectorySimulator(mutex,brodcast_thread,aircraftinfos,waypoints_file)
+
+    while(val:=input("Type \'s + Enter\' to start the adsb-out simulation, and type \'s + Enter\' again to stop it:\n") != 's'):
+        time.sleep(0.05)
+
+    trajectory_simulator.start()
+    brodcast_thread.start()
+    # user input loop. Todo : implement other commands ? (in that case don't forget to check if mutex protection is needed)
+    while(val:=input("") != 's'):
+        time.sleep(0.05)
+    trajectory_simulator.stop()
+    brodcast_thread.stop()
+    trajectory_simulator.join()
+    brodcast_thread.join()
+
+    print("reatime-adsb-out simulation is finished")
+
+if __name__ == "__main__":
+    main()
--- a/test-setup.jpg
+++ b/test-setup.jpg