Request to make the Avare PFD work with the Stratux MPU9250 or BMP280 AHRS

[Mike Dwyer]

Why?   For around $120 we could have an ADS-B In and an Attitude indicator.  Much like a Dynon D10a EFIS.

I've been playing with the MPU9250 or BMP280 (appears to be the same thing) AHRS (Attitude Heading Reference System).  This thing is available for $15!  It is an add on for the Stratux ADS-b In box.  

So far the only Android application that talks to it is the Stratux Interface on it's AHRS page.

The Stratux display while being an awesome Attitude indicator is no Dynon D10A.

If Avare was to make their PFD listen to the data that comes from the Stratux with AHRS, they would have the first decent App that gets AHRS data.

I will be posting a video on the Stratux AHRS performance soon on YouTube http://www.youtube.com/channel/UCLfVhmCxFkbRukDN_vuT9ag

Happy Flying,

Mike Dwyer Q200

Long live Avare!

[John W SBA]

> $120 we could have an ADS-B In and an Attitude indicator

I'm a big fan of this theory, but disappointed by AHRS experiments with
the FlightBox Plus bought recently. It worked great on the ground at
home, but was very difficult to calibrate on the ramp. In flight it
drifts randomly. Orientation of the box is crucial, but even when
physically aligned with the longitudinal axis and calibrated in that
position it is inaccurate. It could be helpful in conjunction with
panel instruments for inadvertent cloud entry concurrent with primary
HSI failure, but more likely just a distraction in maintaining straight
and level.

My impressions are:
1. Nobody on the small all-volunteer Apps4Av "Core Developer Team" (CDT)
currently has the interest or time to explore adding StratuX AHRS to Avare.
2. The current state of StratuX AHRS is not worth the effort.
3. There doesn't seem to be any current work on improving StratuX AHRS.
4. A collaboration between the Apps4Av CDT and the StratuX CDT is
probably the best hope for a future reliable and accurate StratuX AHRS.
5. Other inexpensive solutions may appear in coming months, and if so
any CDT efforts might best be directed to those unless StratuX improves.

> the Stratux Interface on it's AHRS page.

I found it possible to run that in a split display on my cheapo
non-rooted Samsung tablet, or to run it on one of my Samsung phones.
After trying both, I stopped experimenting due to the accuracy and
reliability issues noted above.

> is no Dynon D10A.

Exactly. An AHRS that is routinely +/-15 degrees is of questionable
value, imo. I'd much prefer to see any CDT work going toward other
Avare work.

Happy Flying, Mike :)

> Long live Avare!

Strongly concur! :D

[Peter A. Gustafson]

Thanks for this info John, I've also got a few of these FlighBox systems (one was demo, one was purchased). I will try to recruit some students this fall to look into reliability of the signal... which once demonstrated may make it worth further development effort in avare.

Pete

[John W SBA]

> I've also got a few of these FlighBox systems

Have you found any of them to be accurate and reliable enough for
situational awareness in IMC?

> I will try to recruit some students this fall to look into reliability

That would be great, Pete. :)

If it would be helpful, perhaps I could try to recruit UCSB, Cal Poly
and/or SBCC students here to join your effort?

> may make it worth further development effort in avare.

I'm curious whether sensor(s), calibration, gps cross-reference and
correction or some combination is how commercial products get reliable
results. If anyone in the StratuX development community would be
interested, perhaps some sort of collaboration could be helpful?

The Flightbox Plus has some sort of altimeter function that I've not
explored. Do you foresee any purpose in requesting addition of that
data to Avare in the future?

[Mike Dwyer]

I flew yesterday with the $15 Stratux AHRS on a Samsung S4 and a Dynon D10.  I shot video of straight and level, banking, and climbing.  

See Youtube Link      https://www.youtube.com/watch?v=fT5qhoTR6_U   

Use the D10 as the gold standard.  You can see the Stratux AHRS in straight and level does fine.  On the ground it does fine.  But in a 30 degree bank the AHRS quickly returns to showing level flight!  When I roll back to level the AHRS shows an opposite bank.  When I climb or descend the ARHS doesn't really show much of anything.  I really think the Stratux folks got the Kalman Filter messed up and with some tweaking this AHRS could work but it sure isn't working now!

Happy Flying,

Mike Dwyer

[John W SBA]

> returns to showing level flight! ...shows an opposite bank.

> climb or descend the ARHS doesn't really show much of anything

That's even worse than what I saw, but that was a very short flight
after lots of tweaking and manually leveling the box. Clearly not ready
for even VFR judging by these results.

> Kalman Filter messed up

Haven't read up on this, but does it include GPS cross-reference? Seems
to me that well-placed acceleration sensors that are calibrated for
their specs and combined with WAAS GPS variations could be at least good
enough for VFR and emergency IFR backup redundancy.

> with some tweaking this AHRS could work

Sure would be great if somebody takes it on. Doesn't seem like anyone
in the StratuX world is working on it at present.

Anyway, thanks for the report.

Happy Flying -j

[Mike Saathoff]

I have the AHRS module and normally have a MUCH better experience. Your video kind of worried me until someone pointed out that the Stratux uses GPS to manage drift and that there was no GPS lock in the video you posted.

[Diane Cook]

On Mon, Jul 30, 2018, 1:36 PM Mike Saathoff <saatho...@gmail.com> wrote:

I have the AHRS module and normally have a MUCH better experience.  Your video kind of worried me until someone pointed out that the Stratux uses GPS to manage drift and that there was no GPS lock in the video you posted. 

--
You received this message because you are subscribed to the Google Groups "Apps4Av Forum" group.
To unsubscribe from this group and stop receiving emails from it, send an email to apps4av-foru...@googlegroups.com.
To post to this group, send email to apps4a...@googlegroups.com.
Visit this group at https://groups.google.com/group/apps4av-forum.
To view this discussion on the web visit https://groups.google.com/d/msgid/apps4av-forum/87b33b8d-5498-4a90-a023-b6655e401579%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[John W SBA]

> Stratux uses GPS to manage drift

This is great news for me! Maybe I'll try again with my FlightBox Plus.
Perhaps after I've found a final mounting spot for it, I'll relocate
the internal sensors so it shows level in flight. Manually leveling it
was the only way I could get it to work, despite repeatedly using the
web-based menu to calibrate it. It also needed to have one end or the
other aligned with the direction of level flight. I wonder if it's
possible to mount the sensors externally on a gymbal I could easily
adjust for best performance.

Diane Cook, FYI the reply you posted didn't seem to contain anything
other than the previous message.

[Mike Saathoff]

This is how I use it. I've only about 5 hours so far but it has been nearly a flawless match to my vacuum horizon for that period. I would VERY much like it if the ability to add a Stratux horizon was an option. Heck, even if you felt the Stratux wasn't up to the task isn't it the same method for connecting to the Stratus?

[Cal Simmons]

Use the following procedure to eliminate the need for Gimbal Mounting.

I recall that the Web Based calibration is used to indicate which axis is forward as follows.  Hold the unit with the axis that will be forward when mounted so that it is up by pitching the unit up 90 degrees.  Select the Menu->Settings->Set AHRS Sensor Orientation, Then pitch unit up 90 degrees so that the forward mounting direction points to the sky and Press "Set Forward Direction".

Once that is done you can mount the unit.  Then with the unit still press "Calibrate Gyros"  this will allow the unit to remove bias from the gyros and estimate the true zero point for rotation in each axis.

Then with the unit mounted, select Menu-> GPS/AHRS to bring up the attitude indicator.  With the Aircraft Level Press "Reset / Level " to compensate for slight differences in the mounting attitude of the AHRS sensors.

[John W SBA]

> Use the following procedure to eliminate the need for Gimbal Mounting.

Wow, thanks Cal for posting this. I'm going to try recalibration using
your steps, and maybe start a new Topic with a title easy for new users
to find.

> Hold the unit with the axis that will be forward when mounted
> so that it is up by pitching the unit up 90 degrees.

In reading the FlightBox directions and web interface options, my
impression was that the only two mounting possibilities were with the
box horizontal and one end or the other pointing forward. In my
experience, it also had to be completely level in that position *before*
calibration. To be clear, are you saying that *any* position can be
made to work for accurate AHRS?

I'd given up on AHRS and mounted the box vertically by using 3M pull tab
velcro on the pilot side windshield of my C172. In that position it
doesn't obscure visibility since my normal eye line in flight is mostly
blocked there anyway. I can see in that general direction out the side
window, and can also lean forward to look past the box.

In that location the box is standing on end with the antennae up, and
the side of the box pointing approximately forward. If I could
calibrate it there and get the excellent results reported, it would be
great having a usable backup AHRS.

> Select the Menu->Settings->Set AHRS Sensor Orientation

> Then pitch unit up 90 degrees so that the forward mounting
> direction points to the sky

I briefly tried that today in the aircraft on the ramp, and it didn't
work. I held it horizontally with the side that's foreward in flight
pointed up.

> and Press "Set Forward Direction".

Did that.

> Once that is done you can mount the unit.

Did that.

> Then with the unit still press "Calibrate Gyros"

Did that.

> With the Aircraft Level Press "Reset / Level "

Did that.

Has anyone mounted a StratuX as I described, and been able to get good
results?

[John W SBA]

> I mount mine vertically on the pilot side windshield

Excellent! I brought it home to mess with, and will go over your steps
again to hopefully get it working. Hopefully there's nothing
fundamentally different from homebuilt StratuX about the FlightBox Plus.

> We're getting a little off topic for Avare

Actually, a year or more ago there was discussion here about the
relative lack of StratuX information and dialog in other online venues.
Also about the fact that a relatively large proportion of StratuX users
are Avare users. So we made some effort to include StratuX here, and on
our other online resources. I'm going to start a new Topic and re-post
some of this new info there.

> happy to walk you through it in a different forum or format.

I'd greatly appreciate that. Please join me for that in the new Topic
if you're willing. If not, I can try to summarize and paraphrase there.
If you have links for StratuX info & discussion, please post them in
that Topic. Might you also be willing to do one or more uTube videos I
could link to from our uTube Channel?

See you in the new Topic...

Happy Flying -j

[John W SBA]

Hi Mike,
Thanks SO much for offering your expertise and help with this! Since
the Apps4Av open source community is all-volunteer, the only way we can
continue to improve the apps and documentation is by all sharing what we
learn, our suggestions, and especially bug reports. In terms of sharing
what we learn, it's very important to keep this discussion about StratuX
on the Forum where everyone can see it and add their comments,
questions, suggestions, experiences, and requests. I hope others will
join us in sharing and organizing info and discussion on this Topic (and
everything else of interest here).

> Orient it in the same direction you plan on mounting it

OK, so to get StratuX AHRS working in Avare, first I decide on initial
placement in the aircraft and then do initial setup at home.

I'm going to integrate Steps into this reply as a first draft so we can
edit them and then make a new post with StratuX setup instructions. I'm
thinking to make that a new Topic with that title, then add links to
that and other specific sub-Topics from this general StratuX Topic.

Step 1. Select a location in the aircraft where you initially plan to
mount the StratuX receiver. Note that the ADSB UAT ground transmissions
are vertically polarized, so best reception is with the StratuX antennae
vertical or mostly so. It's relatively easy to change the location
later as you experiment with your preferred placement, and then repeat
these setup Steps.
a. Most pilots may choose the glareshield ("dashboard" in car
language), with the StratuX flat with the fan pointing up and the
antennae end either pointed in the direction of straight and level
flight, or the opposite.
b. In some aircraft, pilots prefer mounting the Stratux vertically on
the pilot side windshield using removable 3M pull-tab strips (either
double-sided adhesive or adhesive/velcro on the windshield and StratuX.

Step 2. At home or elsewhere indoors, orient the StratuX as it will be
in the aircraft (e.g. flat as in 1.a. above).

> Confirm you got the orientation right with the settings
> by manually moving.

I'm not clear on this "Step 3." By "moving" do you mean only tilting,
and not walking around with it? When I tried AHRS with my FlightBox
StratuX mounted vertically (pilot side windshield) in the aircraft
yesterday, the AHRS was at a 45 degree angle upside down and didn't seem
to move when I moved the StatuX box. I'll try that again here at home
later and report, but for now I hope you can clarify whether I'm
understanding correctly that it will show movement regardless of how
crazy the initial attitude indication is. Also that it will do so
without GPS detecting movement that will add data to that provided by
the motion sensors (accelerometers?).

> Next calibrate it perfectly still in that orientation.

So to clarify, this "Step 4" will be the first calibration step you
outlined in the prior discussion? Could you write that out as a Step
and post it here, or would you prefer to just describe it again?

> Do not calibrate it in a moving airplane, use "reset level"

Step 5. After mounting the StratuX in the aircraft, use the StratuX web
page interface to set the receiver for level using the "Reset Level"
option. [ADD menu location]

> GPS signal/lock when flying as its used to correct any drift.

Step 6. In straight and level flight, ensure you have GPS acquired as
indicated by your track moving on a chart in Avare. Note that in Avare
-> Map -> Menu -> Preferences -> GPS -> GPS Position Source you *MUST*
have All Available or Avare IO Module Only selected. Otherwise GPS
could be acquired in Avare via your Android device's internal GPS, even
with the StratuX off or not connected.

> I have been able to have a horizon that matches within a very
> few degrees of my vacuum horizon for about 5 hours of flying

I'm very encouraged by your experience, so thank you for sharing it!
Also for your kindness in helping me to clarify and document this. I
hope others reading this will chime in too, whether they've had success
with StratuX AHRS or not.

[John W SBA]

> The big problem I had at first was not calibrating.

Looks like you may have put the AHRS on my FlightBox back in play. :)

I did the calibration as outlined and hand held it in the car today.
Yes, my wife was driving. Though it wasn't mounted so it's hard to be
sure until flying it, my strong impression is that the AHRS was rock
solid. It doesn't show bank in turns on the road, but does show changes
in pavement angle. Best of all, I was holding it in approximately the
position it's velcro mounted on the pilot side window. I'm eager to fly
it and make a new video to post.

Thank you!

---

On 8/3/18 12:13 PM, Mike wrote:
> The big problem I had at first was not calibrating. I assumed the "reset
> level" was doing this for me, it was not. The the thing drifted in a
> unusable fashion in a few seconds to minutes. The documentation
should be
> explicitly clear that this is a required prerequisite for use.
>
> I've been asking as a feature request that they X out the interface until
> it is both initially calibrated and has a GPS lock. People using it
> without doing both of these actions are responsible for virtually all the
> complaints

[Mike Dwyer]

After my first video showing poor performance of the Stratux AHRS, several people wrote me to say that I needed a GPS attached to the Stratux for it to work.  I'd like to report that I purchased a $10 GPS from the Chinese and re-did my flight test with much better results.  I was using a Samsung S4 phone and found that when I had Avare running in the background and the Stratux AHRS running I was getting only a few minutes of operation until the dreaded "GPS Lost" light popped on.  I was tracking 10 satellites so I think the use of both APPs at the same time overwhelmed my processor.  I closed Avare and had no more issues with the Stratux AHRS display.  

My new youtube video at this link: https://www.youtube.com/watch?v=trjkhJSjTgM&t=4s

The video shows the performance of the Stratux AHRS compared to the Dynon EFIS.  The Stratux AHRS was quite good.  If you lose GPS lock when straight and level, no issue.  If you lose GPS lock in a bank, big issue.  You then have to roll level, not climbing or descending then re-calibrate the display.  The Stratux AHRS really needs to Latch the "GPS Lock" warning so you know it happened.

For a $25 add on to the Stratux ADS-B In, the device is pretty cool.

Mike Dwyer

[Mike Saathoff]

Yep, this has been my experience also comparing to my vacuum AHRS even on two hour and somewhat bumpy flights.  I REALLY wish the Avare PFD could use the Stratux data or even better yet, a sizable corner button AHRS layer. Finally, the AHRS needs to stop or red X if GPS lock is lost. With that said beggars can't be choosers.  I LOVE the AVARE application and I'm a lousy programmer so the best I can do is "Pretty please with sugar on top? "

[Zubair Khan]

Sure, sounds like stratux is quite comparable to in aircraft gyros. However I am worried people may start using it in IMC with Avare.
Z


Sent from ProtonMail mobile



-------- Original Message --------

--

You received this message because you are subscribed to the Google Groups "Apps4Av Forum" group.
To unsubscribe from this group and stop receiving emails from it, send an email to apps4av-foru...@googlegroups.com.
To post to this group, send email to apps4a...@googlegroups.com.
Visit this group at https://groups.google.com/group/apps4av-forum.

To view this discussion on the web visit https://groups.google.com/d/msgid/apps4av-forum/8f7bb562-5bed-41ea-b1f3-f8c3158e735a%40googlegroups.com.