2016-02-13 23:55:12 +00:00
|
|
|
# Airspy ADSB protocol
|
2016-02-13 23:35:34 +00:00
|
|
|
|
|
|
|
|
## Ports
|
|
|
|
|
|
|
|
|
|
* ??: server -> client feed
|
|
|
|
|
|
|
|
|
|
## Format
|
|
|
|
|
|
|
|
|
|
Textual format, similar to [raw](raw.md), but extended with MLAT and signal
|
2016-02-13 23:55:12 +00:00
|
|
|
level data. Unlike raw format, lines are terminated with `\r\n` (`0x0d 0x0a`).
|
2016-02-13 23:35:34 +00:00
|
|
|
|
|
|
|
|
|
|
|
|
|
## Frame structure
|
2016-02-13 23:55:12 +00:00
|
|
|
* `*` (`0x2a`)
|
2016-02-13 23:35:34 +00:00
|
|
|
* 7 or 14 byte frame (see [raw](raw.md))
|
2016-02-13 23:55:12 +00:00
|
|
|
* `;` (`0x3b`)
|
2016-02-13 23:35:34 +00:00
|
|
|
* 4 byte MLAT timestamp (see below)
|
2016-02-13 23:55:12 +00:00
|
|
|
* `;` (`0x3b`)
|
2016-02-13 23:35:34 +00:00
|
|
|
* 1 byte MLAT precision (see below)
|
2016-02-13 23:55:12 +00:00
|
|
|
* `;` (`0x3b`)
|
2016-02-13 23:35:34 +00:00
|
|
|
* 2 byte big-endian RSSI
|
2016-02-13 23:55:12 +00:00
|
|
|
* `;\r\n` (`0x3b 0x0d 0x0a`)
|
2016-02-13 23:35:34 +00:00
|
|
|
|
|
|
|
|
|
|
|
|
|
## MLAT timestamp
|
|
|
|
|
The MLAT timestamp included in each frame is the big-endian value of a counter
|
|
|
|
|
at the time of packet reception. The counter runs at a rate determined by the
|
|
|
|
|
precision value multiplied by 2 MHz (e.g. `0x0a` means `10 * 2 MHz = 20 MHz`).
|
|
|
|
|
This counter isn't calibrated to external time, but receiving software can
|
|
|
|
|
calculate its offset from other receiving stations across multiple packets, and
|
|
|
|
|
then use the differences between station receive timing to calculate signal
|
|
|
|
|
source position.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
## Examples
|
|
|
|
|
|
|
|
|
|
* `*5DA7DA1CE30DE5;D03B5A4B;0A;7AF3;\r\n`
|
2016-02-13 23:55:12 +00:00
|
|
|
* `*` (`0x2a`): Frame start
|
|
|
|
|
* `5DA7DA1CE30DE5`: Mode-S short data
|
|
|
|
|
* Decoded: `0x5d 0xa7 0xda 0x1c 0xe3 0x0d 0xe5`
|
|
|
|
|
* `;` (`0x3b`): Delimiter
|
|
|
|
|
* `D03B5A4B`: MLAT counter
|
|
|
|
|
* Decoded: `0xd0 0x3b 0x5a 0x4b`
|
|
|
|
|
* Decimal: 3493550667
|
|
|
|
|
* `;` (`0x3b`): Delimiter
|
|
|
|
|
* `0A`: MLAT precision
|
|
|
|
|
* Decoded: `0x0a`
|
|
|
|
|
* Decimal: 10
|
|
|
|
|
* 10 * 2 MHz = 20 MHz MLAT counter clock
|
|
|
|
|
* `;` (`0x3b`): Delimiter
|
|
|
|
|
* `7AF3`: RSSI
|
|
|
|
|
* Decoded: `0x7a 0xf3`
|
|
|
|
|
* Decimal: 31475
|
|
|
|
|
* 31475 / 65536 * 100% = 48%
|
|
|
|
|
* `;` (`0x3b`): Delimiter
|
|
|
|
|
* `\r\n` (`0x0d 0x0a`): Frame end
|
|
|
|
|
|
2016-02-13 23:35:34 +00:00
|
|
|
* `*8DA07CD89915908778A01E4B4C86;D03D33F9;0A;8437;\r\n`
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
## Implementations
|
|
|
|
|
|
|
|
|
|
* [Airspy ADSB decoder](http://airspy.com/download/)
|
