Loss of all satellites on HERE 2 GNSS in-flight

Hello @philip
We had a issue with HERE2 GNSS today. According to the log, there was complete loss of satellites for very short period and we almost had a fly-away. Log also says Ublox detected at baud 115200 just after the loss of satellites including EKF error due to loss of satellites. I’ll attach the log below. Please have a look. Board voltage seems to be alright, there was no short or anything. We flew the aircraft before an hour with stable satellite count. We have been flying this aircraft from a long time and never had a issue.


It’s surely looks like a reboot because of ublox message that’s being logged.

The ublox message comes up when a new connection is found. So if you boot up and then plug in a GPS the message comes up. Maybe check the the GPS connections are solid.

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Seems to be a loose cable from the GPS maybe, or underpower from the FC. Time ago I have some dificults because I had 2 sonar sensor connected directly to the FC (taking the power of the sonar from the FC), and at the moment of the takeoff the pix reeboot every time. I know this is not the case, but if you have some electronics getting power from thr FC (like the RC), will be better to use a BEC and avoid this kind of problem. Some RC RX increase the power consumption as they going away, so near to you maybe works fine, but at the moment you go far, bingo!


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Cables look good. Power consumption is minimal. Only telemetry and GPS are connected.

What kind of telemetry? Some telemetry like DragonLink draw a lot of current…

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Sik radio 100mW!

oh, ok, yes, not to much power…

This happend just one time? or is a daily problem?

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Happened one time today in whole 7 years of flying! :joy:
Have been in GPS glitch, low sat counts. But this is first time.

Please double check all your cables. Looks like power or wiring to me.

Did you loose the compass as well?

CAN? Or Serial?

There is a reason that dual GPS has been added for the last 4 years or so :slight_smile:

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I would check the cables… if the stick of the GPS is foldable, 7 years of folding the GPS cable may be can damage it.

Hey @philip
This is the board voltage graph and servo rail voltage. I’m using serial with AC3.6.10. We have got CAN running but can’t use it on customers aircraft without full long period tests. Yes, I agree with Dual GPS solution. Is it possible for you to have a look at the log once, please? The cable looks really sturdy and there’s no wiring issue. The compass data is logged without any power cut. Is there a way to check voltage on HERE2 across time?
Thank you!

If you used CAN as the secondary GPS you would have redundancy and still have your serial gps as primary…

I suspect your cable is damaged or something.

Not sure why you are looking at servo rail, it’s got nothing to do with GPS…

Hello @philip
I have attached both board voltage and servo rail voltage just for reference. I checked the cable thoroughly. It really looks good. I’m also planning to solder the wire on GPS side if you insist. As per the graph, there was no loss of compass data which makes me doubt about power loss on GPS. I really cannot use dual GPS since our aircraft is small and extra weight matters a lot.
Thank you!

Hello @philip
Changed the cable, with fresh cable I had kept the aircraft outside to check whether there is loss of satellite. Looks like there is loss of all satellites at one point again and i can see ublox initializing and ublox config happening again.


Can you keep that cable and cube, and try another Here2. Do the same test

Then try that Here2 on another cube and repeat the same test.

Whichever bit is faulty, should show the fault.

Once you have confirmation, we will RMA it and further investigate


Yes. Doing it now! I had one more system running parallelly. I’ll swap here2 now.

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I just had the very same issue happening to me. Here2 updated to the latest fw following the instructions, set in i2c and plugged into the GPS port. Cube Blue running 3.6.10.

In the figure over here you have the GPS accuracy as long as the compass. The compass was alive during all the time we had the disconnection that lasted probably 5 to 6 seconds.

Since I upgraded the fw on the GPS I noticed that the MAV on the ground would sometimes say that the UBLOX had been recognized and the parameters were saved, but it always did it in the first minutes as the EKF converged and never showed that message again.

Here is my telemetry (I have randomized the GPS): https://plot.dron.ee/cEQy

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My here2 isn’t updated. But I’m running AC3.6.10.
I’m tried fresh cable and got this issue once. I’m trying to find out which part is actually the culprit whether it’s here2, cable or carrier board. Updating to lastest arducopter version is the only change I have made. Hope firmware isn’t the issue.
@philip I’m also wondering why GPS failsafe trigger before it started flying away at high speed till it gets back location.