Stratux AHRS With Avare

[John Wiley]

Update 7/2019: I've updated the Apps4Av website article on this topic.

First off, note that both Stratux (not Stratus) and Avare are "open source" and updates are frequently available. These updates typically require users to install such updates, and for Stratux updates can be found at this link.  Be sure to note the difference between the red "Pre-release" and green "Latest release" labels there (pre-release not yet fully tested).  Stratux v1.5 includes significant improvements to AHRS along with other features & fixes. Brief directions for installing Stratux updates may be found at this link and on the websites of Crew Dog, Open Flight Solutions, and other Stratux providers. When posting a question or comment about Stratux AHRS on this Forum, it will be helpful to specify the versions of Android, Avare, and Stratux you are using.

As of this writing, although GPS and other features like traffic work perfectly, AHRS has not been fully implemented for the Stratux receiver in Avare.  The PFD screen (de-selected in Prefs on my devices) has not yet been updated to utilize all the AHRS information provided by a fully-equipped Stratux.  But AHRS from a Stratux could be useful on a secondary device (i.e. phone), since Stratux WiFi feeds multiple devices.  So for example, you could fly Avare on your main screen and add an old Android phone or other device displaying the full set of Stratux capabilities via their web browser interface. There's an interesting YouTube video demonstrating that at this link. At the end of that video, the author notes that the AHRS worked best when he closed all other apps (including Avare) on the Android device.

On many recent Android devices there's a dual-screen feature where two apps can be active and shown next to each other.  Despite warning notices that Avare won't work in that mode, it has for me (though I've not yet tried it on a long flight).  I mention this because it is possible to display the Stratux AHRS in split screen alongside Avare (see below). Note that this may tax the CPU on your device, and requires a recent Android device that has split screen capability.

So mainly this topic is about my brief flight test of the AHRS of my stock FlightBox+ pre-built Stratux.  I've flown this unit several times and been quite pleased with the features and reliability - especially for the price!  I gather that some people building their own get similar results (and sometimes maybe better) for less money, while other builders report problems and hassles.  My pre-built was a breeze to set up and use (see Apps4Av website here) - other than the AHRS (in mid-2018).

I finally found time to take it up for a brief test flight on the glare shield of a C-172, and have just posted a video of that on the Apps4Av uTube Channel here: https://youtu.be/zhRgQmvpz4c   >Play Video
 
As you can see in the video, it tracked quite well (once I finally got it calibrated), but that was a brief test.  The calibration was confusing at first.  I placed it on the C-172 glare shield with those consumer self-adhesive "pull/stretch to remove w/o residue" 3M velcro strips.  In that location on the passenger side, glare from the white case on the windshield isn't a problem (esp. w/polarized sunglasses that I wear). If glare had been a problem, I was thinking about attaching a bit of dark window screen with 1/2" standoffs. That could retain good cooling airflow while reducing solar heating of the case and preserving its reflective white color.

I mounted the Stratux with the antennae at the rear to minimize obstruction of forward view and tilted the 1090 antenna horizontal. With C-172 glare shield forward slope, only the thin UAT antenna is significantly in my sight line (and passenger side makes it even less noticeable). The 1090 still seems to work fine in that orientation since I'm only interested in nearby traffic. Default orientation is opposite, so AHRS initially showed reverse of actual attitude (i.e. left bank shows as right).  The instructions say to point the forward end up, which in my case means stand the box on end with the antennae down.  In the Stratux built-in (offline) "web" page Settings, you then tap a button and it sets that as the forward direction.

Then (using that same FlightBox built-in Stratux web page) I used the Calibrate button in Settings to set the level.  It didn't work in flight, even though it had on the ground.  Instead it consistently showed a bank equivalent to the tilt where it was mounted on the glare shield.  To get it showing level when calibrated in straight and level flight, I had to first level the box by putting something under the low outboard side.  The forward tilt of the box didn't seem to matter.

The flight was in light to moderate turbulence, flying at 80kias to enable holding a Samsung S7 phone camera pointed at another S7 held against the panel next to the instruments.  That S7 is displaying t he FlightBox Stratux AHRS "web" page on the Android Firefox app.  As you can see in the video, I did level climbing and descending turns that didn't go 360 degrees.  I was trying to keep sun glare & reflections off the glass.

I have displayed AHRS in flight before on an 8" Samsung tablet mounted to the yoke.  I used the split screen option in Landscape (horizontal) mode, with Avare on one side and AHRS in Firefox beside it.  Both apps worked perfectly during that brief test.  While this is a way to have AHRS and Avare on the same screen, it's far from optimal.  Note also that it won't work on older Android devices or those lacking the split screen feature.  Due to the Stratux AHRS screen formatting, it also required using much more of the screen space than would be ideal.  I'm hoping at some point we'll see at least that html code added as a screen option (PFD?) in Avare. That would eliminate the need to use split screen.  Even better would be an option to display a tiny version of it in an Avare window on the Map screen.  An AHRS window on Map would eliminate the need to switch Avare screens.

Potential Stratux AHRS problems I've yet to explore are:
*Any long-term drift in the calibration.
*Finding a way to get it showing level when mounted on the glare shield tilt (maybe just pre-calibrate on the ground or in calm air?).
*Any drift induced by extended turns, such as constant turns through 360 degrees.

New features I'd like to see:
*Quick methods to re-calibrate in flight, and/or auto-calibration when straight and level flight is detected.
*Integration with Avare and means of displaying AHRS on the Avare Map screen.
*After integrating Stratux AHRS into Avare, a Calibrate option on the Map screen AHRS display.

My own use for Stratux AHRS would be quite limited.  Flying VFR, my only reference to it would be loss of visual reference coupled with concurrent primary instrument failure.  Unlikely.  But in that scenario, I'd still only use it as a visual aid in my modified scan.  I'd probably switch primarily to Avare for heading and track, any functioning panel secondary instruments, and GNS430. That said, AHRS in a Map window could be very helpful by adding approximate attitude at a glance.  My preference for Avare has to do with the simplicity and reliability it's proven to have over several years, and the fact I usually fly with at least two running it that function perfectly for hours on their internal battery power.

My hope is that the promised improvements in Stratux code and perhaps new/better sensors will eventually make it more comparable to a panel digital AHRS.  If not, not much expense to try it out.  Meanwhile, I'll report back on anything new from subsequent and hopefully longer tests.

So do you have different preferences or experiences to share? By adding your comments and requests here, everyone benefits from the discussion and that increases the chances that someone may add to the Avare and Stratux AHRS capabilities.

[Cal Simmons]

I could use a pointer.  I have updated my Stratus and added the AHRS module.  I have installed the beta version of Avare that incorporates the External I/O function within Avare.  I have tried it on a Kindle Fire, a Samsung S7, and a Samsung TabA.  Seems to work well.  But the S7 phone is displaying relative altitude for ADSB traffic (+/-feet).  While the two tablets are displaying absolute altitude (feet Pa).  The phone started displaying relative altitude when I installed the AHRS module and updated the Stratux Firmware.  I was surprised to see the two tablets display the absolute altitude while all three were connected to the same Stratux at the same time all running the beta Avare application.  

Can anyone tell me what determines how the ADSB traffic altitude is displayed in Avare (Relative vs Absolute) and how I can configure it to display according to my personal preference?

On Monday, April 30, 2018 at 3:20:13 PM UTC-6, John Wiley wrote:

First off, this topic Subject is misleading.  As of this writing, there's no AHRS in Avare.  The PFD screen (de-selected in Prefs on my devices) is demo only and doesn't distinguish between centrifugal force & gravity (hence shows bank even when driving a car).  But it could be useful on a secondary device (i.e. phone), since Stratux WiFi feeds multiple devices.  Also, on many recent Android devices there's a dual-screen feature where two apps can be active and shown next to each other.  Despite warning notices that Avare won't work in that mode, it has for me (though I've not yet tried it on a long flight).  I mention this because it is possible to display the Stratux AHRS in split screen alongside Avare (see below).

So mainly this topic is about my brief flight test of the AHRS of my stock FlightBox+ pre-built Stratux.  I've flown this unit several times and been quite pleased with the features and reliability - especially for the price!  I gather that some people building their own get similar results (and sometimes maybe better) for less money, while other builders report problems and hassles.  Mine was a breeze to set up and use (see Apps4Av website here) - other than the AHRS.

I finally found time to take it up for a brief test flight on the glare shield of a C-172 a few days ago, and have just posted a video of that on the Apps4Av uTube Channel here: https://youtu.be/zhRgQmvpz4c   >Play Video

[Stevo Keano]

Have you found a way to zero the Avare PFD Attitude indicator? My Stratux has the AHRS and working great; but Avare mount us not 90° to the horizontal, so Avare PFD shows 10° descent when flying horizontal... AHRS shows pitch and bank correctly in ForeFlight.

[Mike Dwyer]

Yes but it's nothing to do with Avare.  The Stratux web page has a Zero button.  When your flying straight and level hit the Zero button on the Stratux web page.  But before you start the plane, make sure you do the "front" Stratux calibration on the settings screen of Stratux.  I'm using the latest Stratux load (stratux-v1.5b2-8f4a52d739.img) and Version 8.1.1 Avare. On Avare I have selected use internal GPS only. I've turned on the Avare PFD feature that takes the data streaming over Wifi from the Stratux ADS-B box and presents a attitude indication display. The Roll is selected to be reversed in the Avare GPS settings.

See my results for a 45 minute flight, then the next flight everything stayed working without having to re-zero it.

One time I did have the Stratux not bolted down. After landing and having it bounced around, it needed re-zeroing. So make sure the Stratux is securly held down.

Check out my results: https://www.youtube.com/watch?v=LQ7msyX0W4E

Mike

[Phil P]

Try using Stratux Manager to recalibrate the AHRS gyros when parked level. Not the horizon zero, the gyro calibrate.