FlightBox is a modular, event-based processing framework for aviation-related data, writen in Python. It can be used, e.g., to receive GNSS/GPS, ADS-B and FLARM signals, process them, and provide a data stream to navigation systems, like SkyDemon. These systems then can show surrounding aircraft positions in their moving map displays.
For receiving ADS-B and FLARM signals, two DVB-T USB dongles with a certain chip set, which are compatible to the rtl-sdr tools (http://sdr.osmocom.org/trac/wiki/rtl-sdr), are required.
Currently, the default configuration assumes that the FlightBox files are located at /home/pi/opt/flightbox, and OGN receiver tools in /home/pi/opt/rtlsdr-ogn. There is a watchdog script called flightbox_watchdog.py, which starts and monitors all required processes except the dump1090 daemon (required for receiving ADS-B data). This watchdog can, e.g., be executed by a cronjob to automatically start the framework after boot and make sure it keeps running.
Below are requirements from the hardware and software perspective. Note that a system with reduced features, like only receiving ADS-B, works, too.
sudo pip3 install <PACKAGENAME>)
FlightBox is implemented in a modular way to allow adding additional data sources (input modules), data processing steps (transformation modules), and output interfaces (output modules) in a simply way. The modules that are currently implemented are described in the following subsections.
The data flows through a central data structure called data_hub. Input and transformation modules can inject data into the system by creating a data_hub_item and handing it over to the data hub. Output and transformation modules can subscribe to certain data_hub_item types, like nmea or sbs1. A data_hub_worker processes all incoming data hub items and forwards them to the registered output and transformation modules as desired.
The system needs to know the current position to provide it to a connected navigation system and to calculate collision avoidance information. To determine the current position, the input_serial_gnss module connects to a serial GNSS (GPS) receiver that is, e.g., connected via USB. Each message received from the NMEA data stream is inserted into the data hub (type nmea).
To receive FLARM signals from other aircraft, the input_setwork_ogn_server module implements a very simple APRS-IS (http://www.aprs-is.net) server to which the receiver software of the Open Glider Network (OGN) Project (http://wiki.glidernet.org/) can connect. For this, both ogn_rf and ogn_decode (available at http://wiki.glidernet.org/wiki:manual-installation-guide) need to be started after the FlightBox processes are running. Every OGN/APRS message is inserted into the data hub (type ogn).
The OGN tools need a configuration file. Please note that in this configuration file the own position, which is needed to calculate the absolute positions of FLARM targets, has to be set to 0. The current location from the GNSS input module will be used by FlightBox for calculation. Below is an example configuration file that uses the second rtl-sdr device:
RF:
{
Device = 1; # [index] 0 = 1st USB stick, 1 = 2nd USB stick, etc.
FreqCorr = +0; # [ppm] correction factors, measure it with gsm_scan or kalibrate
PipeName = "opt/rtlsdr-ogn/ogn-rf.fifo"; # path to pipe that is used to exchange data between ogn_rf and ogn_decode
# path is relative to location from which ogn_rf and ogn_decode are started
} ;
Position:
{ Latitude = +0.0000; # [deg] Antenna coordinates
Longitude = +0.0000; # [deg]
Altitude = 0; # [m] Altitude above sea leavel
GeoidSepar = 48; # [m] Geoid separation: FLARM transmits GPS altitude, APRS uses means Sea level altitude
} ;
APRS:
{ Call = "FlightBox"; # APRS callsign (max. 9 characters)
# Please refer to http://wiki.glidernet.org/receiver-naming-convention
Server = "localhost:14580"; # IP address and port at which an APRS-IS server is listening
} ;To receive ADS-B transponder signals from other aircraft, the input_network_sbs1 module implements a client that connects to a server that delivers ADS-B data via the SBS1 protocol (usually available on port 30003). There are many implementations for decoding ADS-B data, like dump1090. A popular fork of dump1090 is available at https://github.com/mutability/dump1090, which provides everything to run the tool as a daemon. After starting the daemon, the input_network_sbs1 module can connect to dump1090's SBS1 server interface. Every SBS1 message is inserted into the data hub (type sbs1).
AIR Connect (http://www.air-avionics.com/air/index.php/en/products/apps-and-interface-systems/air-connect-interface-for-apps) is a popular interface for providing serial data, like FLARM NMEA messages, via a network connection to a variety of navigation systems and apps. The output_network_airconnect module implements a server that allows apps to connect and receive position and traffic information from the FlightBox system. The module consumes NMEA and FLARM messages (types nmea and flarm) from the data hub and forwards them to the connected clients.
To process all GNSS, OGN, and SBS1 data and generate a FLARM data stream (containing position and traffic information), the module transformation_sbs1ognnmea implements all required processing steps. Therefore, the module consumes NMEA, OGN, and SBS1 messages (types nmea, ogn, sbs1) from the data hub and inserts FLARM messages (type flarm) back to the data hub after processing.
TODO
In case you have any problems, questions, ideas for improvement, would like to contribute to this project, or just find this piece of software useful, please do not hesitate to get in touch with the author. :-)