44 lines
1.1 KiB
Markdown
44 lines
1.1 KiB
Markdown
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# Airspy protocol
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## Ports
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* ??: server -> client feed
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## Format
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Textual format, similar to [raw](raw.md), but extended with MLAT and signal
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level data. Unlike raw format, lines are terminated with `0x0d 0x0a` (`\r\n`).
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## Frame structure
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* `0x2a` (`*`)
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* 7 or 14 byte frame (see [raw](raw.md))
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* `0x3b` (`;`)
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* 4 byte MLAT timestamp (see below)
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* `0x3b` (`;`)
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* 1 byte MLAT precision (see below)
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* `0x3b` (`;`)
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* 2 byte big-endian RSSI
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* `0x3b 0x0d 0x0a` (`;\r\n`)
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## MLAT timestamp
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The MLAT timestamp included in each frame is the big-endian value of a counter
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at the time of packet reception. The counter runs at a rate determined by the
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precision value multiplied by 2 MHz (e.g. `0x0a` means `10 * 2 MHz = 20 MHz`).
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This counter isn't calibrated to external time, but receiving software can
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calculate its offset from other receiving stations across multiple packets, and
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then use the differences between station receive timing to calculate signal
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source position.
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## Examples
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* `*5DA7DA1CE30DE5;D03B5A4B;0A;7AF3;\r\n`
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* `*8DA07CD89915908778A01E4B4C86;D03D33F9;0A;8437;\r\n`
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## Implementations
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* [Airspy ADSB decoder](http://airspy.com/download/)
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