Fixing DJI's Compass Problem

[ianwood]

Gents, good news. Terry from DJI HQ has come onto PhantomPilots to help us try to diagnose the compass declination issue. He's looking for beta testers to help them collect data. He posted in the P2 forum but he wants both P2 and P2V so if you're interested in helping out, please sign up here:

Beta Testers requested to fix Compass Issue: viewtopic.php?f=19&t=11555

 

[wkf94025]

Ian, Terry,

Are we useless to the cause if we lack iOSD Mark II? I (and many others) only have iOSD Mini.

kelly

 

[ianwood]

Ian, Terry,

Are we useless to the cause if we lack iOSD Mark II? I (and many others) only have iOSD Mini.

kelly

It's possible but definitely respond in the other thread and let them know you have a mini.

Everyone who has the compass declination issue sign up on Terry's thread!

 

[phantomguy]

Not SURE if I have a "problem" either. I may? Often when I head out to the field, if I fly it up and straight ahead for 40 feet or so and let go of the sticks? The PV2 will drift to the right about 10 feet or so, then curl back towards me by about 5-8 feet or so. It rarely just stays put in the same horizontal plane/line that I flew it down. Now cut to about 10 minutes later during a flight. If I repeat that same straight flight pattern? That drift to the right/curve back pattern almost all but disappears. It's as if the electronics inside have fully "warmed up" or adjusted to where I am (usually exact same park each day) and are working "better". I also tested doing a recalibration "dance" after it first happened the other day, and that, along with the warming up during the flight seemed to eliminate the issue for the rest of that day. Major issue? Not for me, but I can see how it can be an issue for others.

 

[ianwood]

Not SURE if I have a "problem" either. I may? Often when I head out to the field, if I fly it up and straight ahead for 40 feet or so and let go of the sticks? The PV2 will drift to the right about 10 feet or so, then curl back towards me by about 5-8 feet or so. It rarely just stays put in the same horizontal plane/line that I flew it down. Now cut to about 10 minutes later during a flight. If I repeat that same straight flight pattern? That drift to the right/curve back pattern almost all but disappears. It's as if the electronics inside have fully "warmed up" or adjusted to where I am (usually exact same park each day) and are working "better". I also tested doing a recalibration "dance" after it first happened the other day, and that, along with the warming up during the flight seemed to eliminate the issue for the rest of that day. Major issue? Not for me, but I can see how it can be an issue for others.

That sounds consistent with what everyone is seeing. Where are you located?

 

[BigBadFun]

Ian - thank you very much for chasing this, awesome work on the collecting of reports. Thanks also to Terry from DJI for hearing our voices... great to have you involved.

The Phantom has so much potential and I can't wait to fly it without having to panic about it j-hooking into a mountain. New Zealand has a really high magnetic declination which is shame as I think it might have the highest average Phantom ownership per capita in the world!

 

[Vicrimo]

Add me to the list. I'm in the Los Angeles area and the pv2 always j hooks and never flys straight at all

 

[AviZ]

Far North of NSW East coast Australia

Hi I live on the Far North of NSW around Byron Bay East coast Australia ( 28°38'45.22"S - 153°37'39.55"E )

I ran the tests being careful with the controls and noticed it hooking to the left when moving away and to the right when returning.

Was surprised I had not noticed this before I put it down to the wind From what I been able find out my declination is +12

I tried doing a complete recalibrating the phantom and redid the test Same thing again...

Thanks IAN for trying to sort this problem out

I hope DJI take your suggestions and do something to make a fix

 

[ianwood]

Updating this thread. DJI is looking into the problem. There are 5 of us identified as testers who will each be using an iOSD Mark II to record raw flight data so that DJI can use it to analyze the problem. We will also be analyzing the data to see what we can learn as well.

There are 87 forum users reporting the problem so far.

 

[nhoover]

Thanks Ian! I really hope this gets some results. I am getting more and more annoyed with this problem.

 

[woknwoll]

I live in Wyong about 70k north of Sydney Au and I have had my Vision for just over three weeks now and have always had problems trying to fly a straight line but I just put that down to learning as I have never flown any RC planes at all. I did the update to the 3 firmware and immediately had real problems.

The camera kept saying no SD card and I tried two cards ( which subsequently proved to be bricked by the camera) and tried to fly anyway.

It wouldn't hover at all, kept going up and down and going in giant circles and I ended up crashing it try it land it between the fences and sheds here,

I reloaded the 1.0,8 firmware which is older than what was originally on the Vision and the camera works again, it evens now shows video on my $65 Chinese 7 inch tablet which it never did before although it worked fine with my Ipad.

The toilet bowl thingo that is mentioned frequently on this forum was still evident and I tried some of the remedies suggested but even waiting for the cirlces to stabilise I just ran out of battery and had to land. Tried this a number of times without any positive result.

However, just playing around with it I found that if I take off up to about 5 metres and then turn the Vision to face west the toilet bowl effect is reduced to less than a foot and the Vision maintains a stable hover.

I tried this last night running flat three batteries powering off and on each time and with consistent results every time.

Now I know little about navigation but with facing the Vision in a particular direction having this affect would tend to suggest to me that the compass is involved in what is causing the toilet bowl events.

I am off now to a large clear area where I can see if this has any change to being able to fly in a straight line but I am curious if anyone else has tried this turning the Vision to see if it stabilises or if it just an anomaly with my toys.

edit. Bugger, it has just started to rain.

 

[Dalite]

ianwood, here are a few more things to give some consideration to.

The GPS module uses battery backes RAM (BBRAM) to store last fix info, TCXO Calibrations, Almanac Data and RTC info.

The module requires a voltage above 1.8 VDC to retain this info

If the backup battery is below that threshold, every flight is a cold start. The TCXO calibrations and Almanac data download are time consuming. And the NAZA may not have the computing power to deviate from its task manager cycle to assimilate the most up to date info immediately. It may have to cycle back to he read timer tic sequentially, meaning latency in getting correct compass and GPS info.

Now here is the kicker... I have never measured a backup battery in my Phantoms above .5VDC.

The compass data goes straight to the GPS module, from the lowest point to the highest point through a 5 wire ribbon cable near 9" long. That is nearly 4' of antenna to capture any interference and further complicate. I don't think that is in pay in the numbers you are gathering, but it could cause enough of a deviation to mask the true numbers, if interference is factored into the mix.

I believe you are seeing the TCXO and real time clock ((RTC) calibrations in real time, due to low backup battery voltages. The wider the declination, the more complex the calibrations.

The references to lookup tables makes me think that others have had to second guess OBD II routines in the past also.

 

[sar104]

ianwood, here are a few more things to give some consideration to.

The GPS module uses battery backes RAM (BBRAM) to store last fix info, TCXO Calibrations, Almanac Data and RTC info.

The module requires a voltage above 1.8 VDC to retain this info

If the backup battery is below that threshold, every flight is a cold start. The TCXO calibrations and Almanac data download are time consuming. And the NAZA may not have the computing power to deviate from its task manager cycle to assimilate the most up to date info immediately. It may have to cycle back to he read timer tic sequentially, meaning latency in getting correct compass and GPS info.

Now here is the kicker... I have never measured a backup battery in my Phantoms above .5VDC.

The compass data goes straight to the GPS module, from the lowest point to the highest point through a 5 wire ribbon cable near 9" long. That is nearly 4' of antenna to capture any interference and further complicate. I don't think that is in pay in the numbers you are gathering, but it could cause enough of a deviation to mask the true numbers, if interference is factored into the mix.

I believe you are seeing the TCXO and real time clock ((RTC) calibrations in real time, due to low backup battery voltages. The wider the declination, the more complex the calibrations.

The references to lookup tables makes me think that others have had to second guess OBD II routines in the past also.

That's an interesting thought, but if it were an interference issue then I would not have expected to see such consistent flight deviation as a function of declination, but rather just increasing random deviation.

 

[Dalite]

Take away the interference issue. I just included that possibility to point out the percentages of those affected may be higher, but not reported as it manifests itself as a different problem, when it is merely complicating the compass problem discussed in ths thread.

ianwood, here are a few more things to give some consideration to.

The GPS module uses battery backes RAM (BBRAM) to store last fix info, TCXO Calibrations, Almanac Data and RTC info.

The module requires a voltage above 1.8 VDC to retain this info

If the backup battery is below that threshold, every flight is a cold start. The TCXO calibrations and Almanac data download are time consuming. And the NAZA may not have the computing power to deviate from its task manager cycle to assimilate the most up to date info immediately. It may have to cycle back to he read timer tic sequentially, meaning latency in getting correct compass and GPS info.

Now here is the kicker... I have never measured a backup battery in my Phantoms above .5VDC.

The compass data goes straight to the GPS module, from the lowest point to the highest point through a 5 wire ribbon cable near 9" long. That is nearly 4' of antenna to capture any interference and further complicate. I don't think that is in pay in the numbers you are gathering, but it could cause enough of a deviation to mask the true numbers, if interference is factored into the mix.

I believe you are seeing the TCXO and real time clock ((RTC) calibrations in real time, due to low backup battery voltages. The wider the declination, the more complex the calibrations.

The references to lookup tables makes me think that others have had to second guess OBD II routines in the past also.

That's an interesting thought, but if it were an interference issue then I would not have expected to see such consistent flight deviation as a function of declination, but rather just increasing random deviation.

 

[nhoover]

Fired up my brand new P2V+ yesterday. After calibration, it was sad to see such a pronounced hover rotation (TBE) and J-curves at the start of each of the 4 flights. It does seem to go away, maybe quicker than with the P2V. But here in N Calif, I cannot just take off and fly accurately. They really need to fix this!

 

[Navman]

20 miles South of Portland Oregon
Latitude: 45° 14' 28.9" N
Longitude: 122° 40' 35.7" W
Declination 16
P2 arrived 10 days ago with 2.0 CCW TBE starts small, gets bigger and faster
Upgraded to 3.2 same problem
H3 3D gimbal
iOSD mini
AVL58

 

[JimDE]

I had this with versions 2.0 and 3.0 .... Along with a very slow satellite lock. I went back to ver 1.08 and do not experience it.

 

[perrys]

You can add another user to your numbers. i'm in eastern Australia and have only noticed this problem since upgrading firmware to 2.0 and then 3.0. If i keep flying the vision, it sometimes tells me that the compass needs calibration but it still happens after a successful calibration. It usually flies to the left of where it should and also does the circle in the hover.

 

[slapface]

So mine went back to dji, they said they fixed it (changed the flight controller), did a test flight on a tether and it flew great. Right out of the box from the repair it flew the infamous j-hook.
I called and they said send video.
I sent video.
This is the response if received:

"Unfortunately this is not an issue this can be dependent on weight, wind and magnetic interference/radio frequency in the area. At no time do we recommend not keep control of the unit with both hands there will be times you need to adjust the flight path.

Rob E.
DJI Technology,
Systems Administrator."

--- remember, my phantom 2 vision did NOT do this when it was new in November 2013. It only did this after a firmware update.
It is not a location thing either, it didn't happen in November in exactly the same place as it is doing it now (and everywhere).

So is this a bogus response to a real problem?

 

[RemE]

Rumor has it that the testers have some software that is working better??

Is this so?? Update?