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kevinh
04-02-2013, 09:30 PM
Hi ya'll,

So lately I've been recreationally making some software (http://www.diydrones.com/group/andropilot-users-group?xg_source=activity) for hobbyist drones. In the process I found a really cool software based ADS-B decoder. Someone has made a really cool open-source project (http://lemondronor.com/blog/indexphp/2013/4/cheap-ads-b-on-amateur-drones) that uses a $30 USB radio to decode ADS-B data. I've tried it out at home and it works great.

My desire is to use a Rasberry-Pi to convert this data into a form acceptable for aircraft avionics. Does anyone know of a document that specifies the protocol garmin or dynon expects for aircraft and/or weather data? With such a document I can easily make this project go.

I suspect the total cost to add ADS-B in to your RV with this project would be about $100.

kevinh
04-02-2013, 09:37 PM
alas - this is still cool but I just realized it is only supporting the 1090MHz stuff (http://en.wikipedia.org/wiki/Automatic_dependent_surveillance-broadcast#1090_MHz_extended_squitter_.281090ES.29) - so no weather and probably only traffic from 'big' airplanes. Bummer.

comfortcat
04-02-2013, 09:37 PM
Would the serial USB from the rPI be fast enough? what OS are you experimenting with?

12V, low cost solid state SD chip. Easy to update and next gen will be WiFi.

Cool!

Dkb

kevinh
04-02-2013, 10:34 PM
Yep - the USB on a low end ARM I have here for other purposes (approximately rPI class) had no problems.

Would the serial USB from the rPI be fast enough? what OS are you experimenting with?

12V, low cost solid state SD chip. Easy to update and next gen will be WiFi.

Cool!

Dkb

roee
04-03-2013, 01:10 AM
alas - this is still cool but I just realized it is only supporting the 1090MHz stuff (http://en.wikipedia.org/wiki/Automatic_dependent_surveillance-broadcast#1090_MHz_extended_squitter_.281090ES.29) - so no weather and probably only traffic from 'big' airplanes. Bummer.

Kevin, I'm not sure that's entirely true.

It is my understanding that the FAA's ADS-B ground based transceivers (GBT's) are supposed to re-broadcast traffic target information (TIS-B) between the 1090ES and UAT interfaces, essentially acting as a bridge. GBT's might even broadcast traffic information of non-ADS-B broadcasting targets as well that were acquired by radar (though I'm not certain about that capability being implemented). In any case, a 1090ES receiver should not be limited to knowing only about targets that are broadcasting on 1090ES (typically "big" airplanes), due to the bridging role played by the GBT's.

About weather (FIS-B), true, it is not supported on 1090ES. Only on UAT.

P.S. I think your idea is waaay cool, and when I get some time (after I get my airplane flying), I could definitely see picking it up and helping make it work (if you haven't already)! :D

roee
04-03-2013, 01:26 AM
P.S. I don't know what your technical background is, but if you have the right skills and are so inclined, you could implement a UAT receiver using the same approach these guys took to implement the 1090ES receiver. UAT uses a different band (978MHz), different modulation scheme, and different data protocol. But it sounds from the cursory description of this piece of hardware that it gives you all you need for the RF front end to support UAT as well. And beyond that, it's a soft decoder that you have to implement for the UAT standard.

Aiki_Aviator
04-03-2013, 07:40 AM
In Oz that is all we are getting. I would think that there are a lot of people down under that would like this project... me included :-)

alas - this is still cool but I just realized it is only supporting the 1090MHz stuff (http://en.wikipedia.org/wiki/Automatic_dependent_surveillance-broadcast#1090_MHz_extended_squitter_.281090ES.29) - so no weather and probably only traffic from 'big' airplanes. Bummer.

kevinh
04-03-2013, 08:12 AM
Good to know. Okay, I'd happily do this then. Anyone know of docs on the protocol Garmin or Dynon wants their traffic data in? (So I can have my widget emit data in the form they will display)

Kevin, I'm not sure that's entirely true.

It is my understanding that the FAA's ADS-B ground based transceivers (GBT's) are supposed to re-broadcast traffic target information (TIS-B) between the 1090ES and UAT interfaces, essentially acting as a bridge. GBT's might even broadcast traffic information of non-ADS-B broadcasting targets as well that were acquired by radar (though I'm not certain about that capability being implemented). In any case, a 1090ES receiver should not be limited to knowing only about targets that are broadcasting on 1090ES (typically "big" airplanes), due to the bridging role played by the GBT's.

About weather (FIS-B), true, it is not supported on 1090ES. Only on UAT.

P.S. I think your idea is waaay cool, and when I get some time (after I get my airplane flying), I could definitely see picking it up and helping make it work (if you haven't already)! :D

rocketbob
04-03-2013, 08:17 AM
I still really like the 396/496. It would be really cool if one could reverse-engineer the GXM30 antenna protocol so that a Pi receiving ADS/B weather could be used instead. I suspect its no more than a USB-to-serial connection.

Kahuna
04-03-2013, 08:48 AM
I too am happy to help.
Been working on my Pi aprs iGate. This would be more fun.
I think I have some gld39 data captures laying around.

tc1234c
04-03-2013, 08:51 AM
Explored Flightradar24 further and found the following link:

http://www.flightradar24.com/hardware

Seems to be a very neat site.

KRviator
04-03-2013, 08:01 PM
ISTR the Dynon uses the standard GTX330 format for their ADS-B data, so any device that outputs this will show as traffic on their displays.

The GTX330 Manual (http://tinymicros.com/mediawiki/images/0/07/Garmin_GTX330_Transponder_Installation_Manual.pdf) covers the data output which appears to be a derivative of the ARINC429 protocol orperhaps ARINC 429 itself -I'm not an engineer so I leave that to you :p...

Anyway, it shows the labels used, threats, ranges etc. on pages 5-12 & 5-13.

kevinh
04-03-2013, 08:51 PM
Thanks! Now can anyone point me at ARNIC429 protocol docs? I can't find any on the web.

ISTR the Dynon uses the standard GTX330 format for their ADS-B data, so any device that outputs this will show as traffic on their displays.

The GTX330 Manual (http://tinymicros.com/mediawiki/images/0/07/Garmin_GTX330_Transponder_Installation_Manual.pdf) covers the data output which appears to be a derivative of the ARINC429 protocol orperhaps ARINC 429 itself -I'm not an engineer so I leave that to you :p...

Anyway, it shows the labels used, threats, ranges etc. on pages 5-12 & 5-13.

eddieseve
04-03-2013, 10:57 PM
Hi Kevin

Have a look at;

http://read.pudn.com/downloads111/ebook/462196/429P1-17_Errata1.pdf

Cheers

dynonsupport
04-05-2013, 10:39 AM
A technicality - our ADS-B box actually uses an unpublished format that gets traffic and wx together from the box - so you can't emulate the actual ADS-B connection. But, you're right, we also support traffic input via the TIS format on any of SkyView's serial ports. Anything that can spit out TIS can also be displayed on SkyView.

N363RV
04-05-2013, 06:05 PM
http://www.faa.gov/nextgen/implementation/programs/adsb/wsa/media/GDL90_Public_ICD_RevA.PDF

this spec tells you how to read the data. I hope this helps.

6 Gun
04-07-2013, 10:39 PM
This is real homebuilding keep up good work guys.

Jamie Aust
05-23-2013, 04:25 PM
Any update on this Kevin ?
I use a DVB-T stick and get many aircraft just with the included antenna, im going to make a bigger antenna for out side and see how that goes.
For $20 outlay, and the free software, this is FUN on the cheap !

Brantel
05-23-2013, 04:47 PM
Per Radomir's suggestion,

I bought one of the <$20 software definable radio sticks:

http://www.flightradar24.com/files/dvbt-stick-adsb-receiver-48_380.jpg
(http://www.flightradar24.com/dvbt-stick)
And had it running in about 15 minutes and it works surprizingly well!

Tons of work out on the net has been done with these radio's. I caught my short flight today by recieving my Mode S/ES squawk and uploading it to FlightRadar24 live. This is totally done via this receiver sniffing my Mode S/ES xponder signals... Little antenna stuck to the roof of my truck sitting on the ramp at the airport.

http://www.flightradar24.com/files/dvbt-stick-adsb-receiver-55_260.jpg

http://i39.tinypic.com/21blvuv.png


Pretty cool stuff but it is scary. If I can do this for a hobby, what prevents some terrorist from doing it and sticking one of these things on the nose of a missle?

SDR stick....If someone can write a software front end and decoder to be able to pull out the Mode S/ES aircraft buzzing around, there should be someone that is smart enough to write one for the 978 band and decode the FIS-B data.

Dave62
05-23-2013, 05:04 PM
This is way over my head:eek: However it is where the world is at! If you can figure out how to display ADS-B info on either a 430 or a 396/496 I and many more in the certified world would be interested. I dont think the FAA can regulate what we do with data:D. The world it is a changen. Thanks for you knowledge and work.
Dave 62 (Swift driver)

Snowflake
05-23-2013, 06:25 PM
Pretty cool stuff but it is scary. If I can do this for a hobby, what prevents some terrorist from doing it and sticking one of these things on the nose of a missle?
Really? The better solution would be to put a GPS in the nose of a missile. Let's hope this technology stays open and free rather than closed by big companies looking to make a buck off it instead.

Brantel
05-23-2013, 06:31 PM
Really? The better solution would be to put a GPS in the nose of a missile. Let's hope this technology stays open and free rather than closed by big companies looking to make a buck off it instead.

A GPS only gives the bad guys the position, speed etc. of their own vehicle. This technology could give their vehicle guidance and the ability to lock on to a specific target and from a really long distance. I have picked up targets well over 100 miles away even with this crappy antenna that came with the radio.

There are people right here on this forum today with the skills to write the code to pull this off.

Many folks in the Software/IT/Security business have been screaming that ADS-B is a nighmare waiting to happen and this pretty much shows you how easy it would be to exploit.

The FAA has long known that the availability of their radar data is a security threat. That is why they delay the data by 5 minutes. There is no way for them to control the ADS-B out data being transmitted more and more everyday.

It is scary really!

Trust me, I want it to remain open as well but we all know that if it can be exploited, someone will do it....there are some real smart nut jobs out there that are more than a few fries short of a happy meal!

walkman
05-24-2013, 12:04 PM
Many folks in the Software/IT/Security business have been screaming that ADS-B is a nighmare waiting to happen and this pretty much shows you how easy it would be to exploit.
!

It's not just this issue. Consider that many of the devices we fly with now, such as our EFIS systems are based on standard OS. GRT for example is a Debian Linux box with USB and Ethernet, the iFly is a windows box. Consider that we also update them via wireless or USB etc over unsecured connections. I don't know whether the various devices typically check SHA1 hashes or similar before updating themselves. What happens when one connects a malware infected android device (very insecure) via Bluetooth or USB or Ethernet to your EFIS system? Are the vendors even cogniscent of the issues?

I know one of the things on my list this summer is to poke at my gear with the arsenal of tools in my lab and see what I can find.

Jamie Aust
05-25-2013, 03:32 PM
Per Radomir's suggestion,

I bought one of the <$20 software definable radio sticks:

http://www.flightradar24.com/files/dvbt-stick-adsb-receiver-48_380.jpg
(http://www.flightradar24.com/dvbt-stick)
And had it running in about 15 minutes and it works surprizingly well!

Tons of work out on the net has been done with these radio's. I caught my short flight today by recieving my Mode S/ES squawk and uploading it to FlightRadar24 live. This is totally done via this receiver sniffing my Mode S/ES xponder signals... Little antenna stuck to the roof of my truck sitting on the ramp at the airport.

http://www.flightradar24.com/files/dvbt-stick-adsb-receiver-55_260.jpg

http://i39.tinypic.com/21blvuv.png


Pretty cool stuff but it is scary. If I can do this for a hobby, what prevents some terrorist from doing it and sticking one of these things on the nose of a missle?

SDR stick....If someone can write a software front end and decoder to be able to pull out the Mode S/ES aircraft buzzing around, there should be someone that is smart enough to write one for the 978 band and decode the FIS-B data.

If someone is going to give this a crack, I would like to see the output be sent in Garmin format via RS232 please. :):)

Jamie Aust
09-17-2013, 03:32 PM
If anyone is still working on this could you please reply, im looking for some log files ( garmin TIS )if anyone wants to share, please PM me and I will give you my email.

Hi ya'll,

So lately I've been recreationally making some software (http://www.diydrones.com/group/andropilot-users-group?xg_source=activity) for hobbyist drones. In the process I found a really cool software based ADS-B decoder. Someone has made a really cool open-source project (http://lemondronor.com/blog/indexphp/2013/4/cheap-ads-b-on-amateur-drones) that uses a $30 USB radio to decode ADS-B data. I've tried it out at home and it works great.

My desire is to use a Rasberry-Pi to convert this data into a form acceptable for aircraft avionics. Does anyone know of a document that specifies the protocol garmin or dynon expects for aircraft and/or weather data? With such a document I can easily make this project go.

I suspect the total cost to add ADS-B in to your RV with this project would be about $100.

zaitcev
01-05-2014, 07:50 PM
SDR stick....If someone can write a software front end and decoder to be able to pull out the Mode S/ES aircraft buzzing around, there should be someone that is smart enough to write one for the 978 band and decode the FIS-B data.

I don't think RTL can cut it. Althought in theory Neuquist allows to decode a clean FSK signal at 1 mbit/s while sampling at 2.8 s/s (maximum rate for RTL), in practice the available software fails miserably when trying that. At least it did not work for me, although I gave up just after looking at the samples and waterfall. Just about anything out there requires significant oversampling for each bit or else the output is junk.

I got the RTL SDR getting me 1090ES with homemade software (http://zaitcev.livejournal.com/220516.html) easily (well, using a pre-existing SDR receiver), but UAT is a problem. The only thing that would do that is a real SDR like Ettus (https://www.ettus.com/product/details/UB200-KIT).

mculver
01-05-2014, 09:22 PM
This is cheap and extremely cool technology! Costs just $12 or so plus shipping at www.amazon.com/gp/product/B00C37AZXK. All the software is readily available for free, although some of the applications described in this thread do indeed require custom code.

I hooked one of these up to a Raspberry Pi, which is currently sitting in my kitchen in Seattle, letting me watch Seattle traffic from anywhere (which is currently Central America).

100% fun, 100% what homebuilding is all about :)

zaitcev
01-22-2014, 08:33 AM
SDR stick....If someone can write a software front end and decoder to be able to pull out the Mode S/ES aircraft buzzing around, there should be someone that is smart enough to write one for the 978 band and decode the FIS-B data.
I was motivated by this thread to give UAT another go, but it was an abject failure. I tried to forego normal signal analysis and just look at phases for adjacent samples, and possibly detect packet headers if timing is right. Something about this technique is wrong, or I'm missing something important about pushing RTL chip too far. It may be that I'm just not receiving anything, however. If anyone wants to give it a go and let me know if any syncs are seen, code is here:
https://github.com/zaitcev/ruat

Radomir
01-22-2014, 10:13 AM
There's tons of airports that have GBT on them -- I'd go to one of them and test things out there.. you're guaranteed to receive the signal.

Note: GBT's message has inverted preamble of an airplanes transceiver. Preamble's ones and zeros are opposite of what airplane sends out.

Find the UAT MOPS online (if you haven't already) as it has pretty good description of what the signal looks like. Depending on where you're doing your testing, it's possible you're not receiving anything useful.

digidocs
01-22-2014, 10:34 AM
Zaitcev,

What problem are you seeing with the RTL? Is the device dropping samples at 2.8Msps? Also, are you getting I and Q sample pairs at that rate or just "real" samples?

I don't have the UAT MOPS in front of me, but I seem to remember that the signal total bandwidth is 1.3MHz (ie: +/- 0.65MHz from center). One thing to check is that any upstream analog filtering in the RTL has a bandwidth greater than this.

If the analog bandwidth is good and you can reliably get samples at the above rate, it should be possible to decode the signal. Realistically, you're probably going to have to upsample your original signal into the 6.25+Msps range to make it possible to recover the bit timing.

I was able to decode a 1-bit 6.25Msps UAT datastream in software so I know that at least that can work.

Neat project.

David

compjtc
01-23-2014, 08:46 AM
Agreed, pretty neat project.

I've been wanting to put together a device that can display FIS-B information for quite a while now. Sure I could spend the dollars on a GDL 39, but where would the fun in that be?

Let us know if you have any luck. :)

digidocs
02-06-2014, 09:21 PM
I've posted the source code for a 978MHz UAT FSK software receiver and FIS-B data/weather decoder here:

https://code.google.com/p/lone-star-ads-b/ (https://code.google.com/p/lone-star-ads-b/source/browse/#git%2Fuat-decode)

I was able to use this code with a homebrewed 978MHz receiver to decode the UAT datastream and FIS-B weather radar. Perhaps it would be a useful to someone who is developing a similar setup.

If there is enough interest, I'll upload the hardware design as well.

David

YellowJacket RV9
02-06-2014, 11:32 PM
I've posted the source code for a 978MHz UAT FSK software receiver and FIS-B data/weather decoder here:

https://code.google.com/p/lone-star-ads-b/ (https://code.google.com/p/lone-star-ads-b/source/browse/#git%2Fuat-decode)

I was able to use this code with a homebrewed 978MHz receiver to decode the UAT datastream and FIS-B weather radar. Perhaps it would be a useful to someone who is developing a similar setup.

If there is enough interest, I'll upload the hardware design as well.

David

Yes please share! Nice work

Chris

LifeofReiley
02-07-2014, 08:32 AM
I've posted the source code for a 978MHz UAT FSK software receiver and FIS-B data/weather decoder here:

https://code.google.com/p/lone-star-ads-b/ (https://code.google.com/p/lone-star-ads-b/source/browse/#git%2Fuat-decode)

I was able to use this code with a homebrewed 978MHz receiver to decode the UAT datastream and FIS-B weather radar. Perhaps it would be a useful to someone who is developing a similar setup.

If there is enough interest, I'll upload the hardware design as well.

David

Hi David... nice work. Way over my head, amazing stuff! :) Please keep an update going here.

bullojm1
02-07-2014, 08:49 AM
Hi David,

What FSK decoder did you use in order to get the binary input required for your decoder?

rocketbob
02-07-2014, 08:50 AM
Awesome work David!

digidocs
02-07-2014, 12:51 PM
Update:

I added the schematic and board layout to the google code project above. You can navigate to the hardware directory or just follow this link:

https://code.google.com/p/lone-star-ads-b/source/browse/#git%2Fhardware (https://code.google.com/p/lone-star-ads-b/source/browse/#git%2Fhardware)

I did this work in 2011 and I'm not sure where the board is at the moment. If I can find it, I'll post some pictures of the receiver itself. In the meantime, the hardware theory of operation from the Readme is reproduced below. There's also a weather radar map produced by the full setup. The black areas are places were the data was not received during the time I was recording.

Theory of Operation

The 978 MHz signal from the antenna enters from CONN1 and passes through an impedance matching network formed by L2 and C4. A receiver IC originally designed for use with cordless phones is used to decode the 1.0417Mbps FSK signal. Internally, the IC downconverts and demodulates the incoming 978MHz signal, however the internal bit slicer is disabled because its time constant is not appropriate for the UAT datastream. Instead, the raw discriminator output (availble in test mode) is fed through a low pass filter formed by L1 and C27 and then on to the TS3021 comparator. A MCP4725 I2C DAC is used to provide an adjustable reference level to the comparator for accurate bit slicing. The output of the DAC which is the raw FSK datastream is then output via J1. J1 is intended to be connected to a USB capture device sampling the 1-bit value at 6.25Msps. Here a Cypress EZ-USB FX2LP was used to perform this function.

http://i1277.photobucket.com/albums/y486/digidocs/test_zps2d0ed321.png

David

kevinh
02-07-2014, 12:56 PM
wow - super cool David!

zaitcev
01-15-2015, 01:28 PM
Two updates:

- With help from an actual EE engineer (Mr. Oliver Jowett), I was able to receive UAT signals with RTL-SDR. Of course the whole premise of ruat is to only receive packets that accidentially clock just right, but that is at least something. Now the decoding and error correction are needed. If you know what "systematic RS 256-ary code with 8-bit code word symbols" is and how to compute RS(92,72), you could be of a big help. I can verify a polynomial CRC, but not recover errors.

- The cheapest real receiver on the market, capable to receive UAT link, appears to be so-called "AirSpy", $200. The next cheapest is HackRF, $300. The HackRF is also a transmitter, so you can have a whole DIY 2020 ADS-B/FIS-B system, except that would be grossly illegal.

I found that I'm unable to reproduce David Carr's receiver, so I ordered AirSpy.

digidocs
01-15-2015, 09:19 PM
Awesome work! Glad to hear you made some progress with the USB dongles.

The entire code for a working UAT RS error corrector is included in the repository I posted above. There are even example files that you can use to get going/test things out.

David

iken
01-17-2015, 07:08 AM
Good job Zaitcev! I think the project 'lone-star-ads-b' shows the decoding of Reed-Solomon, in file decode.c around line 296, the func name is "fec_msg()" as David said above, and there is more decode/encode func in the c lib 'fec-3.0'.

Hope that helps.

Ken

Gash
01-17-2015, 10:03 AM
This is one of the reasons why I love VAF. What an incredible group of smart and talented people! You guys are amazing.

Mike S
01-17-2015, 10:18 AM
Ken, welcome to VAF:D