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  #1  
Old 03-26-2017, 08:03 PM
jwyatt jwyatt is offline
 
Join Date: Feb 2006
Location: Goodhue, MN
Posts: 148
Lightbulb AF-4000: dual-band ADS-B In with stratux

I have put a few flights on this system now and it works as I hoped, so I wanted to share this with the community.

BACKGROUND
My requirements for an ADS-B system were:
  • traffic & weather on AF-4500s (meaning, GDL-90 protocol via RS-232)
  • traffic, weather & position data to Foreflight (wifi or bluetooth)
  • dual-band receiver (I wanted to see as much traffic as possible even when out of reach of a ground station)
  • Out type (UAT vs. ES) wasn't a concern, as either type would meet my needs
  • Out would need to provide a 2020-compliant GPS, as I don't have an IFR navigator

I looked at the GTX-345 as an easy In/Out solution, but since Garmin didn't include the ability to send traffic & weather out an RS232 port using the GDL-90 protocol, it would not display on my 4500 as I wanted. So, I decided to split the Out/In equipment -- this also means I can change/upgrade the In equipment as appropriate in the future, without affecting the Out equipment. I settled on installing a GTX-335 with the GPS option in place of my GTX-327.

For the In portion, I built and installed the open-source Stratux receiver. This can be built as a single- or dual-band receiver, as you desire. I built the dual-band stratux, since my biggest complaint with the other available solutions that work with the 4500 (Freeflight, Navworx) is that they are UAT-only. Since most of the Out-equipped aircraft are going for 1090ES equipment, having UAT-only In capability was a handicap to me. I bought all the parts on Amazon for about $160, including the required cables to connect it to my belly-mounted DeltaPop UAT antenna for better reception.

You can see the list of parts I used here (updated with currently-available Amazon items): ( http://a.co/3LkGrBc )

BUILDING THE STRATUX
The official stratux website ( stratux.me/ ) has software and instructions for assembling the unit in it's typical configuration. It's not difficult, and there are several blogs chronicling the build, too. I would recommend getting it up and running in the typical configuration first, to be sure it's all working, and then making the few modifications to make it work with the AF-4000. (This should also work with any other EFIS that accepts the GDL-90 protocol, too.)

Note -- I'm running the 1.1b1 version; there is a newer version now but I haven't tested it yet to make sure everything is still functional.

Once you've installed it, check that the filesystem has expanded (this is automatic in new stratux builds, but older versions require you to run this command:
Code:
sudo raspbi-config
select the "expand filesystem" option, then reboot the system).

At this point, you should be able to test it with your tablet and verify the stratux is working.

ENABLING STRATUX SERIAL OUTPUT
( Read post #14 of this thread for a valuable note. )

For serial output to the 4500 (I believe you do need to have the "s" model 4500, I'm not sure whether traffic will work on the earlier units), stratux builds (1.1b1 or later) have support built in for a certain type of USB to serial adapter, the CP2102. If you pick something else, just be sure that it also provides RS232 level conversion; many of the units for sale are TTL level, which is a lower voltage and may not work with the 4500 serial port (though I didn't test it).

In order for the stratux to know that you want it to use the serial module as an output, you do need to make one minor tweak to the programming, which requires downloading some software from the chipset maker, and setting the "Product Description" field to "Stratux Serialout". See my notes on this on the stratux reddit group in these threads:...note that I used the Windows software; there is a linux package to do this but it's not preloaded on stratux.


Once the stratux recognizes the serialout, you'll have an additional field in the web interface's settings menu where you'll be able to set the serial speed. For the 4500 you want to set it to 115200.

You'll want to connect to serial port 1 or 3 on the 4500, according to the AFS crew -- ports 2 and 4 aren't capable of handling the higher speed data. Choose "ADSB 115K" as the port config in the admin menu. You'll want to be sure you have the latest AFS software as well, since the 115k support is a recent addition. You only need to connect the ground, and stratux Tx -> AFS Rx lines, not the AFS Tx line.

Distilled into four steps beyond the basic stratux build:
  • buy CP2102 module
  • program "Stratux Serialout" as Product Description
  • connect to stratux and set serial speed
  • wire to 4500 and set up serial port

ONE CODE CHANGE IN STRATUX
At this point it should work! The only quirk you'll notice is that ALL of the traffic targets on your 4500 will be displayed with the "yellow ball" alert icon. This is because stratux by default sends all targets with the "alert" flag turned on. If you reprogram stratux to leave that flag off, then the 4500 will use range and altitude information to manage the icons -- open diamond for far traffic, filled diamond for near traffic, and yellow ball for proximate traffic. There is a way to change this, but it does require you to modify one line of code and recompile the stratux package.

In /stratux/main/traffic.go, change
Code:
msg[1] = 0x10 | ti.Addr_type // Alert status, address type.
to
Code:
msg[1] = 0x00 | ti.Addr_type // Alert status, address type.
(in stratux 1.1b1, this is at line 248.)

You will need to recompile after editing! Here's what I've been using:
Code:
sudo su -
cd /stratux
make
stxstop && make install && systemctl daemon-reload && stxstart
I posted some more details on this in the stratux reddit group if needed. ( https://www.reddit.com/r/stratux/com...utput/dd6a9h8/ )

ADDITIONAL STRATUX TWEAKS
I'm using the DeltaPop UAT antenna mounted on the belly, and a splitter cable to feed both SDR's from the single antenna (BNC -> SMA cable, then an SMA -> (2) MCX Y-cable inside the stratux case). ( http://a.co/cpdxlXX )

Rather than powering from a 12V "cigarette lighter" plug or my panel-mount USB power jacks, I added a little 12VDC -> 5VDC converter that will do up to 3 amps, they're made for RC models and I've found it to work well and provide plenty of power for the stratux. I haven't noticed any interfering noise on the comm radios. ( http://a.co/dhDlAJl ) I'm drawing less than half an amp between 12 and 15 volts.


I brought the 12V power and data connections to a DB connector that I mounted to the side of the stratux case for better integration into the plane. The stratux still has its own GPS module on the glareshield; I think there may be a way to input NMEA data from my other GPS but I haven't worked it out yet. The whole thing fits inside the plastic stratux case, except that I had to desolder the header pins of the serial module, and solder wires to the board pads. I have one SMA connector feeding both radios, and use a short SMA -> BNC whip to connect to the ship's antenna cable (RG-400). I do have a whip antenna too, just for testing outside the plane during the build.


Alongside this project, I also added a second 4500s display to use as a fullscreen map, and the ARINC converter allowing the EFIS to drive the Trutrak autopilot. Combined, I've gained a lot of utility in my panel. My only remaining wish is for a way to push flight plans from the ipad to the 4500 like you can with the new 5000 series, since the Foreflight's flightplan editor is much more elegant than the internal 4500 one.

I'm happy with the setup so far. I use Foreflight on my ipad to display the same traffic and weather info; the display is prettier there, and the 4500 filters distant traffic so you see many more distant targets on the ipad, but it's handy to have the traffic and metar data on the panel display. I usually pick up 3 towers in the pattern, and 6 towers by ~2000AGL. Some screen captures from test flights (there's even a Pete Howell sighting)...



( h/t to Tcox750 who also built this and got it working with his AFS system, and added the part I forgot about the filesystem expand. )



( CLICK ANY PHOTO FOR FULL SIZE IMAGE )
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Joshua Wyatt | Goodhue, Minn.
RV-9A N627DW @ KRGK - Flying since 2012
rv9a.pacificrimsound.com

Last edited by jwyatt : 03-29-2017 at 09:15 PM. Reason: updating serial module info
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  #2  
Old 03-27-2017, 12:09 PM
Noah's Avatar
Noah Noah is offline
 
Join Date: Jun 2007
Location: Rhode Island
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Wow, great writeup! I've got a similar upgrade planned, so thanks for sharing the results of your labor! Right now I've got a GTX-330 feeding TIS-B traffic into my 4500. I wonder if I can maintain that connection or whether I need to abandon that input given the stratux input. Are you also displaying ADS-B weather on the 4500? Any photos of how that compares to XM on the 4500? Im still paying a subscription for XM. I wonder if i have enough ports to maintain that for a while while comparing it with ADS-B delivered weather.

I have always figured that I would do the ES upgrade to the GTX-330 (connected to GNS430W) to get ADSB out. You are using a single belly mounted UAT antenna to feed both the UAT & ES receivers? That is working well? Interesting! I always figured I would need 2 receive antennae.

The connection between the IPAD and the stratux is wifi? Right now i use garmin pilot; I may have to change to foreflight to display the sratux info there.

Thanks again for the excellent and informative writeup!
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Noah F, RV-7A

All men dream, but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find that it was vanity: but the dreamers of the day are dangerous menů for they may act their dream with open eyes, to make it possible. -T.E. Lawrence

Last edited by Noah : 03-27-2017 at 12:49 PM.
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  #3  
Old 03-27-2017, 12:28 PM
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Sam Buchanan Sam Buchanan is offline
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Quote:
Originally Posted by Noah View Post
You are using a single belly mounted UAT antenna to feed both the UAT & ES receivers? That is working well? Interesting! I always figures I would need 2 receive antennae.
Same here, one inexpensive transponder antenna on the belly of the RV-6 feeding both receivers in the Stratux via a SMA splitter cable adapter..
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  #4  
Old 03-27-2017, 12:44 PM
Tcox750 Tcox750 is offline
 
Join Date: Nov 2012
Location: Kirkland, WA
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This is a picture of my 4500 using the Stratux and showing some weather and a traffic target.

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  #5  
Old 03-27-2017, 10:05 PM
jwyatt jwyatt is offline
 
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Location: Goodhue, MN
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Quote:
Originally Posted by Noah View Post
Right now I've got a GTX-330 feeding TIS-B traffic into my 4500. I wonder if I can maintain that connection or whether I need to abandon that input given the stratux input.
Not sure what the 4500 will do with traffic info from two sources. But the ADS-B traffic sent from the ground station should include everything you'd see via TIS-B on the 330 (If I understand it correctly).

Quote:
Originally Posted by Noah View Post
Are you also displaying ADS-B weather on the 4500? Any photos of how that compares to XM on the 4500?
I get weather -- NEXRAD, METARs and TAFs -- on the 4500, though I don't have any screenshots of it since my few flying days have been pretty clear lately. I like to have the metars in particular, because I don't have a nav receiver, and a bunch of airports in the area have their AWOS broadcasts on the VOR freq. I've been using ADS-B weather for a couple years on Foreflight.

Quote:
Originally Posted by Noah View Post
I have always figured that I would do the ES upgrade to the GTX-330 (connected to GNS430W) to get ADSB out. You are using a single belly mounted UAT antenna to feed both the UAT & ES receivers? That is working well? Interesting! I always figured I would need 2 receive antennae.
To be clear, I do have two belly antennas -- one for the GTX335 transponder, and one for the stratux, which feeds both the UAT and ES receivers. If you want to dig into it further, one of the guys who contributes to the stratux project has done some antenna testing and shown that you get acceptable reception on both bands whether your antenna is tuned for 1090 or 978. I figured 978 tuning is better since the 1090 transmissions are typically at higher power anyway. You can dig through his test reports on the stratux Github -- https://github.com/cyoung/stratux/issues/203

Quote:
Originally Posted by Noah View Post
The connection between the IPAD and the stratux is wifi? Right now i use garmin pilot; I may have to change to foreflight to display the sratux info there
Yes, Wifi to the iPad. There are new Pi boards with Bluetooth but support in stratux isn't there yet. I've used Foreflight, and also tested a WingX demo. Foreflight doesn't play with the AHRS in stratux, some of the others do. AFAIK, there is no support for stratux in Garmin Pilot (too bad, because it'll run on much cheaper tablets).
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  #6  
Old 03-28-2017, 11:48 AM
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Noah Noah is offline
 
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Thanks all! Yep, with no Stratux support, that'll be the end of my Garmin Pilot subscription!

Can the RY835AI chipset be omitted? I have no use for an extra AHRS or GPS within the Stratux.
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Highest Regards,

Noah F, RV-7A

All men dream, but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find that it was vanity: but the dreamers of the day are dangerous menů for they may act their dream with open eyes, to make it possible. -T.E. Lawrence
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  #7  
Old 03-28-2017, 08:42 PM
jwyatt jwyatt is offline
 
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Quote:
Originally Posted by Noah View Post
Can the RY835AI chipset be omitted? I have no use for an extra AHRS or GPS within the Stratux.
No need for the RY835 if you don't want AHRS. (And AHRS is sort of a work in progress, with some EFBs not compatible.). The USB gps pucks work well for basic position, which you'll want in order to feed your tablet unless you have internal gps.
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rv9a.pacificrimsound.com
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  #8  
Old 03-29-2017, 11:03 AM
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Noah Noah is offline
 
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Thanks again for the feedback! As far as I can tell, porting ADS-B IN Data to the AFS should provide a couple of benefits over just viewing on the IPAD:

1. Because the AFS-4500 is integrated with ship's audio, ADS-B traffic should include audible alerts ("TRAFFIC"!) whereas they might not be immediately noticed visually on the IPAD (is this correct?)
2. The AFS is in my primary viewing area whereas the IPAD is somewhat peripherally located - so I may not immediately see something on the IPAD
3. The AFS provides means for a redundant display of both wx & traffic

Having said that, viewing distant weather data is not easy or intuitive on the AFS 4500 - at least using XM. I can't see any nexrad data beyond about 500 miles, and I do many trips where I cover a lot more than that in a day. Similarly, using the AFS-4500 to check METARS along the route is clunky at best (I need to initiate a "direct to" or hit "nearest" to select an airport along/near my route on the 4500, then I can access it's METAR/TAF - one at a time). I can't "play" or animate nexrad motion. I can't scroll the display away from my present position. All of these add up to making weather access time consuming and annoying. Is this weather interface on the 4500 any different with ADS-B derived weather data than it is for XM?? I would think that the IPAD would become the primary weather device due to the more intuitive interface while the 4500 would be the backup. Have you found this to be the case? Can AIRMETS be viewed on the 4500? Or just on the IPAD?

And I would expect that the 4500 would be the primary device for traffic due to its more selective (decluttered) display, and due to it's audible alerts - which to me are the real key. Would you agree?
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Highest Regards,

Noah F, RV-7A

All men dream, but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find that it was vanity: but the dreamers of the day are dangerous menů for they may act their dream with open eyes, to make it possible. -T.E. Lawrence
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Old 03-29-2017, 12:44 PM
jwyatt jwyatt is offline
 
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Quote:
Originally Posted by Noah View Post
1. Because the AFS-4500 is integrated with ship's audio, ADS-B traffic should include audible alerts ("TRAFFIC"!) whereas they might not be immediately noticed visually on the IPAD (is this correct?)
...
And I would expect that the 4500 would be the primary device for traffic due to its more selective (decluttered) display, and due to it's audible alerts - which to me are the real key. Would you agree?
I'm definitely using the 4500 as primary traffic display, since it's right in front of me. I haven't heard it generate any audio alerts, however. I don't see a "traffic" audio file in the package available from the AFS website either, so I'm honestly unsure whether it does audio alerts. Maybe Rob or one of the gang from AFS will see this and confirm?

Also, Foreflight has a quirk with the GDL90 traffic where some targets occasionally lose their heading data--position still shows, but heading doesn't (so it displays as a diamond rather than an arrow). The 4500 keeps displaying the heading data and vector line, which I believe is valuable information when evaluating potential conflicts.
I have submitted notes, screenshots, and logs on this issue to Foreflight a few weeks back -- they said they would look into it but I haven't heard anything yet. The issue should affect users of other GDL90 devices too (like Freeflight). If anyone else has noticed this, please submit to team@foreflight.com so they know it affects multiple users (emphazise the GDL90 part, not the stratux part, or they may brush it off as an "unsupported device").

Quote:
Originally Posted by Noah View Post
...viewing distant weather data is not easy or intuitive on the AFS 4500 - at least using XM. I can't see any nexrad data beyond about 500 miles, and I do many trips where I cover a lot more than that in a day. Similarly, using the AFS-4500 to check METARS along the route is clunky at best (I need to initiate a "direct to" or hit "nearest" to select an airport along/near my route on the 4500, then I can access it's METAR/TAF - one at a time). I can't "play" or animate nexrad motion. I can't scroll the display away from my present position. All of these add up to making weather access time consuming and annoying.
...
Can AIRMETS be viewed on the 4500?
100% agree. These are all limitations with the 4500, I believe the display interaction is the same as with XM-supplied data. You can zoom out to the widest range, but it takes significant time to redraw the map, and as you noted it's still a limited distance without the ability to slew. I think the newer 5000 series is a step up on these items, but I had to do this on a budget, and a 5000 upgrade for me would also require new AHRS, magnetometer, changes to pitot/static routing, etc, making it fairly costly. If I strike it rich, I could upgrade just the new MFD to a 5400 to get the more advanced mapping, leaving my PFD alone to avoid the need to replace hardware.

AFS documentation (at least the most recent manual, v7.4) shows these products available from ADS-B:
  • NEXRAD (last frame only, no animation)
  • METAR (text, flag on airport symbol; note colors are different than Foreflight)
  • TAF (raw only, not a decoded format)
  • TFR (drawn on map)
  • Lightning
  • Winds Aloft

I'm using the 4500 for nearby weather info and looking up reports for nearby & destination stations, and Foreflight for longer-range info, planning, additional products like AIRMET and PIREPs, and radar animations. Stratux does have a "replay" feature like the official Stratus receiver, that will cache an amount of received FIS-B data while your tablet is sleeping, and dump it to the app once it wakes up.
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  #10  
Old 03-29-2017, 01:18 PM
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Noah Noah is offline
 
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Quote:
Originally Posted by jwyatt View Post
I haven't heard it generate any audio alerts, however. I don't see a "traffic" audio file in the package available from the AFS website either, so I'm honestly unsure whether it does audio alerts. Maybe Rob or one of the gang from AFS will see this and confirm?
Now that you mention it, the "TRAFFIC" alerts I get are the British lady's voice - meaning that they come from the GTX-330, not the AFS-4500 as I had thought. Shoot, that is a bummer since the audible attention getter is the most important feature of a traffic alert to me.

Quote:
Originally Posted by jwyatt View Post
AFS documentation (at least the most recent manual, v7.4) shows these products available from ADS-B:
  • NEXRAD (last frame only, no animation)
  • METAR (text, flag on airport symbol; note colors are different than Foreflight)
  • TAF (raw only, not a decoded format)
  • TFR (drawn on map)
  • Lightning
  • Winds Aloft
Have you verified that all of these come through on the 4500? (I never paid for Lightning or Winds Aloft from XM, so I have no idea how they display).

Quote:
Originally Posted by jwyatt View Post
I'm using the 4500 for nearby weather info and looking up reports for nearby & destination stations, and Foreflight for longer-range info, planning, additional products like AIRMET and PIREPs, and radar animations.
This is how I figure I would use it too.
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Highest Regards,

Noah F, RV-7A

All men dream, but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find that it was vanity: but the dreamers of the day are dangerous menů for they may act their dream with open eyes, to make it possible. -T.E. Lawrence
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