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Transponder properties

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Re: Transponder properties

Postby mickybadia » Sun Jun 11, 2017 6:35 pm

FYI, I have asked for the devel list's opinion, with a summary of the two current candidate options for a ground mode: (1) inputs/mode=3; (2) repurpose ident for flags. And a link to here.
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Re: Transponder properties

Postby sanhozay » Sun Jun 11, 2017 9:52 pm

OK, thanks. I'll explore the code changes in transponder.cxx but I'm away a few days this week so it might take a week or so.
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Re: Transponder properties

Postby sanhozay » Mon Jun 12, 2017 11:33 am

If you've seen the mailing list, the recommendation is that we go with a new boolean for the ground bit. I've started coding this and it will be property 1504 (05E0 in hex).

EDIT: I've got the bare bones of this working, simulating a squat switch only at this stage, but I can see the ground bit coming through the MP packet. If you want to test with ATC-Pie, let me know.
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Re: Transponder properties

Postby Maerchenprinz » Thu Jun 07, 2018 6:58 pm

Hallo everybody!

You must be really happy that someone brings up this topic again! :P
Anyway, I've spent the last two days trying to implement a simple "GROUND" mode into a transponder capable of only "A" and "C" (not "S");
Everything is working, except that /transponder/inputs/knob-mode=3 still answers ident-interrogations. So /transmitted-id remains, and does not change to -9999.
The idea with the "ground-bit" is reasonable and working, unfortunately only for S-mode (which is correct), all other knob-modes do what they should in both C- and S-types ... Everything works! Except...
So my suspicion is that there's just a little flaw in the source code, which e.g. changes /altitude or /airspeed-kt to -9999 in corresponding /knob-mode and /mode configurations, but not /transmitted-id.
Fortunately, I have a ( fiddly :) )workaround for this for my transponder.xml in mind ; Unfortunately, I don't think that there are many (new) devs willing (capable) to do that.
What do you think, is this a bug (as I see it) and can I file a bug-report, or is there anything I have missed, and this is correct behaviour?

Ciao,

Adrian
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Re: Transponder properties

Postby mickybadia » Fri Jun 08, 2018 6:21 am

Maerchenprinz wrote in Thu Jun 07, 2018 6:58 pm:I've spent the last two days trying to implement a simple "GROUND" mode into a transponder capable of only "A" and "C" (not "S");


The way I understand transponder modes, this is neither possible nor even meaningful in real life because the GND bit is a feature of the mode S.

Here is the expected prop-value spec by mode and capability. All prop's below come under instrumentation/transponder:
- transmitted-id (int)
- altitude (int)
- ident (bool)
- inputs/mode (int)
- ground-bit (bool) <-- INTRODUCED AFTER THIS THREAD
- airspeed-kt (int) <-- INTRODUCED AFTER THIS THREAD

For all transponders:
- off: transmitted-id < 0
- on: transmitted-id = "squawk code" integer as if to be read a decimal value
- if reporting altitude (modes C and S turned on): altitude = pressure-alt. value in feet
- otherwise (mode A): altitude = -9999
- ident = 0/1 (result of cockpit button press; up to the model to implement the timeout)

Modes A/C transponders:
- in all settings: inputs/mode = 1
- ground-bit and airspeed-kt irrelevant

For a mode S capable XPDR:
- in all settings: inputs/mode = 2
- airspeed-kt set to indicated airspeed
- ground-bit = 0/1 (this can be the result of squatting or manual setting)

For testing, the best is to check the property tree yourself against the spec, but for a real use case ATC-pie fully implements this. Just be careful what capability you set your radar to have (set to mode S without any cheats for actual account of the transmitted data). See the "display conventions" in the quick ref to interpret the stuff displayed on the scope.
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Re: Transponder properties

Postby Maerchenprinz » Fri Jun 08, 2018 11:17 am

Hi mickybadia!

Thanks for your reply! Sorry, I may have not pointed out clearly what I meant:
With "GROUND"-mode, I was referring to the FG-wiki page http://wiki.flightgear.org/Transponder#Knob.2FFunctional_Modes
3 - Ground mode, responds to altitude interrogation but does not broadcast an ID. This would typically be used while taxiing prior to takeoff.

- not a real bijectiv "GROUND"-mode identification (like sending a ground-bit): Is respond to "A"-interrogation deliberately turned off or does a faulty chiffrator form an invalid or no code?
- It is rather the "old" and rather inconvenient way of telling the controllers that you're still chilling 8) on ground or taxiing so that Approach and Departure controllers can ignore you with a clear conscience.
There were and are numerous transponder types around which have this option!

I'm only talking from the aircraft's transponder side and FG's internal representation; no real life ATC-, no ATC-Pie-, no FG-MP-side, no...

So either the FG-wiki page or the transponder.cxx/hxx is wrong. Having this /knob-mode=3 working as described in the wiki makes much more sense to me. But, beat me to it (Don't! Please! :) ), I wasn't capable of even finding the error in the code...

Thanks for all of your explanations; But after two :!: days of testing and cursing, I think I have tested and have thought through any possible property-configuration! As I said before (please discard "or is there anything I have missed"):

Maerchenprinz wrote in Thu Jun 07, 2018 6:58 pm:Fortunately, I have a ( fiddly :) )workaround for this for my transponder.xml in mind ; Unfortunately, I don't think that there are many (new) devs willing (capable) to do that.
What do you think, is this a bug (as I see it) and can I file a bug-report, or is there anything I have missed, and this is correct behaviour?


Ciao,

Adrian
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Re: Transponder properties

Postby Isaak » Mon Nov 12, 2018 8:20 am

Hi there, I 'm fixing the transponder in the 777 currently. I've already implemented a functioning ident button locally, which I will push this evening (CET), but I 'm stuck at getting the correct transponder altitude. I 've already assigned the correct mode (2) to it (it was 0), and got the airspeed property to update correctly, but the instrumentation/transponder/altitude property keeps stuck at -9999, no matter what I do. I 'm not even able to update it manually because it seems tied to some other property, but I can't find out which one. The wiki page didn't help me much further. Enabling encode-mode-c and/or encode-mode-s in the altimeter configuration doesn't solve anything. Does anyone know which property-rule is preventing me from implementing a correctly functioning transponder?
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Re: Transponder properties

Postby WoodSTokk » Mon Nov 12, 2018 11:01 am

In the 'Systems/instrumentation.xml' set the following:
Code: Select all
    <altimeter>
        <name>altimeter</name>
        <number>0</number>
        <static-pressure>/systems/static/pressure-inhg</static-pressure>
        <encode-mode-c>false</encode-mode-c>
        <encode-mode-s>true</encode-mode-s>
    </altimeter>

    <transponder>
      <name type="string">transponder</name>
      <number type="int">0</number>
      <mode type="int">2</mode> <!-- 0 = Mode A, 1 = Mode C, 2 = Mode S -->
      <bus-volts type="double">8.0</bus-volts>
      <encoder-path type="string">/instrumentation/altimeter</encoder-path>
      <kt70-compatibility type="bool">0</kt70-compatibility>
    </transponder>
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Re: Transponder properties

Postby Isaak » Mon Nov 12, 2018 11:33 am

Thanks for the reply, will retry this evening!
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Re: Transponder properties

Postby Isaak » Mon Nov 12, 2018 5:12 pm

I 'm afraid it doesn't work. The altitude property stays at -9999. What I also find is that e.g. airspeed-kt doesn't get disabled when transponder/inputs/knob-mode changes. I 'll dig a bit deeper into the code, but I do think someone once implemented some transponder code that is competing with the default behaviour. I just need to point out where.
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Re: Transponder properties

Postby WoodSTokk » Mon Nov 12, 2018 11:32 pm

BEL ISAAK wrote in Mon Nov 12, 2018 5:12 pm:I 'm afraid it doesn't work. The altitude property stays at -9999. What I also find is that e.g. airspeed-kt doesn't get disabled when transponder/inputs/knob-mode changes. I 'll dig a bit deeper into the code, but I do think someone once implemented some transponder code that is competing with the default behaviour. I just need to point out where.

I have changed the transponder on the Citation II and Citation X from mode C to mode S for a while and as far as i know, it works, but i will double check it.
Is your working copy of the aircraft everywhere in the net so that i can investicate it?

EDIT:
Have now checked the Citation II and all works correct in the property tree.
I dont know if the correct values are also transmitted over MP protocol.

XPDR Off:
Image
XPDR Standby:
Image
XPDR On:
Image
XPDR Altitude:
Image
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Re: Transponder properties

Postby Isaak » Tue Nov 13, 2018 10:10 am

It's the official 777 I 'm working on, you can download it through the launcher or pull from svn. I 've tested various knob-modes, but can't get the altitude reporting to work. I did get the airspeed working by modifying altimeter and transponder config though (not yet committed because I don't want to commit non-functioning code). I 'll only have time on Thursday and Friday to continue my investigation, but please feel free to check it out too. I 'll take a look at the citation II to see if there are any differences. I have the feeling that there's some code competing with the default behaviour, but can't locate it.
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Re: Transponder properties

Postby WoodSTokk » Tue Nov 13, 2018 1:21 pm

BEL ISAAK wrote in Tue Nov 13, 2018 10:10 am:It's the official 777 I 'm working on, you can download it through the launcher or pull from svn. I 've tested various knob-modes, but can't get the altitude reporting to work. I did get the airspeed working by modifying altimeter and transponder config though (not yet committed because I don't want to commit non-functioning code). I 'll only have time on Thursday and Friday to continue my investigation, but please feel free to check it out too. I 'll take a look at the citation II to see if there are any differences. I have the feeling that there's some code competing with the default behaviour, but can't locate it.


Its a problem in the xml-file of the animation.
The mode-switch on the 777 change the property '/instrumentation/transponder/mode-switch'
insteed of '/instrumentation/transponder/inputs/knob-mode'.
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Re: Transponder properties

Postby Isaak » Tue Nov 13, 2018 2:41 pm

Yes, I did correct that locally, but when I overrode the knob-mode property manually, nothing changed. I 'll look into it again on Thursday. Thanks for pointing me in the right direction already ;)
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Re: Transponder properties

Postby Octal450 » Tue Nov 13, 2018 5:09 pm

Wait what?
for me, overwriting knob-mode is needed, am I understanding that it should be mode-switch instead? or is knob-mode correct?

I am asking since I am modelling the Airbus XPNDR and the the GTX-327 garmin.

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