2016-02-13 22:38:40 +00:00
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# Beast protocol
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## Ports
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* 30005: server -> client feed
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2016-02-13 22:56:41 +00:00
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## Format
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All data is escaped: `0x1a` -> `0x1a 0x1a`. Note that synchronization is still
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complex, since `0x1a 0x31` may be the start of a frame or mid-data, depending
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on what preceded it. To synchronize, you must see, in order:
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* != `0x1a`
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* `0x1a`
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* {`0x31`, `0x32`, `0x33`}
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2016-02-13 22:56:41 +00:00
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Escaping makes frame length for a given type variable, up to
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`2 + (2 * data_length_sum)`
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2016-02-13 22:56:41 +00:00
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2016-02-13 23:12:48 +00:00
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## Frame structure
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* `0x1a`
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* 1 byte frame type (see types below)
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* 6 byte MLAT timestamp (see below)
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## Frame types
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* `0x31`: Mode-AC frame
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* 1 byte [RSSI](https://en.wikipedia.org/wiki/Received_signal_strength_indication)
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* 2 byte Mode-AC data
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* `0x32`: Mode-S short frame
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* 1 byte RSSI
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* 7 byte Mode-S short data
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* `0x33`: Mode-S long frame
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* 1 byte RSSI
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* 14 byte Mode-S long data
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* `0x34`: Status data
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* *Appears to only be used by Mode-S Beast hardware later versions*
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* ?? byte status data
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* ?? byte DIP switch configuration
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2016-02-13 23:12:48 +00:00
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## MLAT timestamp
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The MLAT timestamp included in each frame is the big-endian value of a 12 MHz
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counter at the time of packet reception. This counter isn't calibrated to
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external time, but receiving software can calculate its offset from other
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receiving stations across multiple packets, and then use the differences between
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station receive timing to calculate signal source position.
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2016-02-17 04:45:23 +00:00
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FlightAware's dump1090 fork sends `0x00 0x00 0x00 0x00 0x00 0x00` when it has
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no MLAT data.
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## RSSI
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FlightAware's dump1090 fork sends `0xff` when it has no RSSI data.
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2016-02-13 23:12:48 +00:00
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2016-02-13 23:22:24 +00:00
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## Examples
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* `0x1a 0x32 0x08 0x3e 0x27 0xb6 0xcb 0x6a 0x1a 0x1a 0x00 0xa1 0x84 0x1a 0x1a 0xc3 0xb3 0x1d`
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* `0x1a`: Frame start
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* `0x32`: Mode-S short frame
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* `0x08 0x3e 0x27 0xb6 0xcb 0x6a`: MLAT counter value
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* Decimal: 9063047285610
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* `0x1a 0x1a`: Signal level
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* Unescaped: `0x1a`
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* Decimal: 26
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* 26 / 255 * 100% = 10%
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* `0x00 0xa1 0x84 0x1a 0x1a 0xc3 0xb3 0x1d`: Mode-S short data
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* Unescaped: `0x00 0xa1 0x84 0x1a 0xc3 0xb3 0x1d`
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2016-02-13 22:38:40 +00:00
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## Implementations
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* [Mode-S Beast hardware](http://modesbeast.com/scope.html)
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* [FlightAware dump1090 fork](https://flightaware.com/adsb/piaware/install)
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2016-02-13 23:22:24 +00:00
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2016-02-13 22:38:40 +00:00
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## References
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* [Original description](http://wiki.modesbeast.com/Mode-S_Beast:Data_Output_Formats)
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