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.
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:
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:
ONE CODE CHANGE IN STRATUX
- buy CP2102 module
- program "Stratux Serialout" as Product Description
- connect to stratux and set serial speed
- wire to 4500 and set up serial port
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
msg = 0x10 | ti.Addr_type // Alert status, address type.
msg = 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:
sudo su -
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 )