ASTERIX

[k2fc]

This PR adds ASTERIX i/o support.

The following command line arguments are added:
--net-ai-port
--net-ao-port
--net-asterix-reduce

Additionally --net-connector has the following formats added:
asterix_in
asterix_out

Currently, only CAT021 (ADS-B) messages are supported. The following CAT021 items work:

Item Number	Description	Notes
10	Data Source Identification	Hard Coded to output SAC=0 SIC=1. Discarded on input. Required field per Asterix spec
40	Target Report Descriptor
71	Time of Applicability for position	Input only
130	Position in WGS-84 Coordinates	Output and input
131	Position in WGS-84 Coordinates (High-Resolution)	Input only
72	Time of Applicability for velocity	Input only
150	Air Speed
151	True Airspeed
80	Target Address
73	Time of Message Reception of Position
74	Time of Message Reception of Velocity - High Precision	Input Only
75	Time of Message Reception for Velocity
76	Time of Message Reception for Velocity – High Precision	Input Only
140	Geometric Height
90	Quality Indicators	I do not fully understand these, so it's probably not correct
210	MOPS Version	I do not fully understand these, so it's probably not correct
70	Mode 3/A Code
230	Roll Angle
145	Flight Level
152	Magnetic Heading
200	Target Status	I do not fully understand these, so it's probably not correct (especially Nav Modes)
155	Barometric Vertical Rate
157	Geometric Vertical Rate
160	Airborne Ground Vector
77	Time of Report Transmission
170	Target Identification (Callsign)
20	Emitter Category	I do not fully understand this, so it's probably not correct
220	Met Information	Ouput only. I tried to add COMM_B code to decode met information, but I have not decoded any. Unknown if this works. readsb can still continue to derive the met information on its own, but it won't be sent over ASTERIX.
8	Aircraft Operational Status	I do not fully understand this. It may be correct, but I wouldn't bet money on it.
400	Receiver ID	Output only. Only 8 bits are available. I simply took the last 8 bits of mm->receiverId... it should probably be a hash.

MLAT messages are not passed. I don't have access to MLAT data to work with, but MLAT data should be exchanged as CAT020.

Known issues

Most issues are caused by my lack of understanding on some of the internals.

• Quality indicators seem to intermittently show up. When they do, they seem to match what my main instance of readsb (beast format) shows, but they quickly revert to n/a.
• ADS-B version always shows as v15... not sure why.
• I have seen TIS-B ground targets appear at ~1500ft intermittently, but haven't tracked down the cause yet.

[k2fc]

The ASTERIX CAT021 spec document:
https://www.eurocontrol.int/sites/default/files/2021-12/asterix-adsbtr-cat021-part12-v2-6.pdf

[wiedehopf]

I will start looking at the overall diff of these changes once this PR doesn't change for a day or two.

Asterix seems like an overcomplicated badly documented protocol.

Also lol: NOTE: This edition is NOT backwards compatible
to category 021 edition 2.1 or earlier

I'm sorry i'm not enthusiastic about merging stuff but it's usually things i don't need / find interesting and that's just a chore.
I'll try though just don't expect this to happen quickly.
I don't have any big changes to readsb planned so ... at least rebasing shouldn't be much necessary for you and you can just continue to work based on your fork.

I suppose it might be worth to merge the basic skeleton ... i'll see about that the next couple days.

[wiedehopf]

So this kinda needs a rebase.
But i'll try and make a diff and just make one big patch i guess.

Is the merged version working for you?

[wiedehopf]

So i want this as one big commit i'm making right now.
It is just a diff from the current state.a
Plus some whitespace fixes (trailing space / indent).

I'll see how i can attribute you.
Will try just messing with a commit ;)

[wiedehopf]

https://github.com/wiedehopf/readsb/tree/asterix

Ok please test this, make a new branch on your side and make a new PR using this commit i made.
That should give you all the attribution properly.

I'll close this PR, feel free to just copy the text from the new PR.

[wiedehopf]

@k2fc i'm trying to merge this but i'd like it to show properly on github that it was your PR ... but due to rebase and stuff anyhow it's complicated.
You mind getting that branch over to you? I can change the branch name if that's an issue.

[wiedehopf]

@k2fc This is merged, but it won't show as merged here as i wanted to flatten all the work in progress commits a bit.

Merged as: 8dfb94b

I tried to get you to pull that branch so i can just merge it and it shows as PR on here but there was no response.
If that's important to you, i can still make that happen.

[wiedehopf]

Keeping this PR open even though it's merged for some visibility of the feature :)