kopia lustrzana https://github.com/cyoung/stratux
125 wiersze
3.2 KiB
Markdown
125 wiersze
3.2 KiB
Markdown
# dump978
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Experimental demodulator/decoder for 978MHz UAT signals.
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## A note about future development
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I'm in Europe which doesn't use UAT, so there won't be much spontaneous
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development going on now that the demodulator is at a basic "it works" stage.
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I'm happy to look at signal or message captures and help with further
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development, but it really needs to be driven by whoever is actually using the
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code to receive UAT!
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## Demodulator
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dump978 is the demodulator. It expects 8-bit I/Q samples on stdin at
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2.083334MHz, for example:
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````
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$ rtl_sdr -f 978000000 -s 2083334 -g 48 - | ./dump978
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````
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It outputs one one line per demodulated message, in the form:
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````
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+012345678..; this is an uplink message
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-012345678..; this is a downlink message
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````
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For parsers: ignore everything between the first semicolon and newline that
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you don't understand, it will be used for metadata later. See reader.[ch] for
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a reference implementation.
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## Decoder
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To decode messages into a readable form use uat2text:
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````
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$ rtl_sdr -f 978000000 -s 2083334 -g 48 - | ./dump978 | ./uat2text
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````
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## Sample data
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Around 1100 sample messages are in the file sample-data.txt.gz. They are the
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output of the demodulator from various RF captures I have on hand. This file
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can be fed to uat2text etc:
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$ zcat sample-data.txt.gz | ./uat2text
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When testing, this is much easier on your CPU (and disk space!) than starting
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from the raw RF captures.
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## Filtering for just uplink or downlink messages
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As the uplink and downlink messages start with different characters, you can
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filter for just one type of message very easily with grep:
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````
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# Uplink messages only:
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$ zcat sample-data.txt.gz | grep "^+" | ./uat2text
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# Downlink messages only:
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$ zcat sample-data.txt.gz | grep "^-" | ./uat2text
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````
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## Map generation via uat2json
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uat2json writes aircraft.json files in the format expected by dump1090's
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map html/javascript.
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To set up a live map feed:
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1) Get a copy of dump1090, we're going to reuse its mapping html/javascript:
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````
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$ git clone https://github.com/mutability/dump1090 dump1090-copy
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````
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2) Put the html/javascript somewhere your webserver can reach:
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````
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$ mkdir /var/www/dump978map
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$ cp -a dump1090-copy/public_html/* /var/www/dump978map/
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````
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3) Create an empty "data" subdirectory
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````
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$ mkdir /var/www/dump978map/data
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````
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4) Feed uat2json from dump978:
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````
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$ rtl_sdr -f 978000000 -s 2083334 -g 48 - | \
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./dump978 | \
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./uat2json /var/www/dump978map/data
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````
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5) Go look at http://localhost/dump978map/
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## uat2esnt: convert UAT ADS-B messages to Mode S ADS-B messages.
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Warning: This one is particularly experimental.
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uat2esnt accepts 978MHz UAT downlink messages on stdin and
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generates 1090MHz Extended Squitter messages on stdout.
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The generated messages mostly use DF18 with CF=6, which is
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for rebroadcasts of ADS-B messages (ADS-R).
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The output format is the "AVR" text format; this can be
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fed to dump1090 on port 30001 by default. Other ADS-B tools
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may accept it too - e.g. VRS seems to accept most of it (though
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it ignores DF18 CF=5 messages which are generated for
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non-ICAO-address callsign/squawk information.
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You'll want a pipeline like this:
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````
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$ rtl_sdr -f 978000000 -s 2083334 -g 48 - | \
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./dump978 | \
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./uat2esnt | \
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nc -q1 localhost 30001
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````
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