Pixhawk Issue

A 3DR developer recently tuned my Pixhawk, it flies great, but when he did he also setup my battery failsafe.  Shortly afterwards I was hovering approximately 5 meters away and about 6 feet when the Pixhawk started beeping continuously and started to climb.  Stick inputs had no effect until I switched from Stabilize to Loiter then I was able to gain control for a couple of seconds but then it started beeping again and started to climb so I switched it to AltHold lowered the throttle and let it drop giving it throttle to arrest the decent just before hitting the ground.

The battery was still about 15.2 volts but I thought it might have been related to the battery failsafe since it was set to RTL maybe it was trying to RTL  So I disabled the RTL in battery failsafe and it flew fine with no incidence.  I flew it today and it did the same thing, this time when it started beeping I immediately dropped the throttle and got it on the ground but when it touched down the motor increased and it would not immediately disarm.

Here's the video of the second crash landing, you can here the beeping start about 25 seconds into the video:


The battery was at 15.45 volts and the battery failsafe is disabled.  It also had a flashing yellow LED.  How can I trouble shoot this to determine the cause of this?  How do you download the logs?   I'd share what firmware I'm using but I don't even know how to do that?

Any help would e greatly appreciated.

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  • I realize everyone has a different preference on how they setup failsafe. I prefer to not use it and rely on telemetry to tell me the status of my machine rather than have it lurch into the air while I'm flying in a tight space ie under trees, or a bridge, or heaven forbid (as my wife would say) inside the house. Temporary heavy load can send an autopilot into failsafe and I found it was usually at the most inconvenient time. I'm several years into no automatic failsafe and haven't had an issue (knock on wood) with DJI or 3DR products.

    • Agreed on that. Battery failsafe is a no no. My only exception is radio failsafe. You really need to understand and set that up in case you lose radio contact.
      • I agree 100%. I've seen a few pilots get lost with no video downlink turn off the controller to get the drone to come home. Me, I prefer a fail safe switch however my issue is when fly out of control range which on my Taranis is about 3200 ft out, not up.
  • Here's my log file from the last flight.  Not sure how to interpret the logs yet.  Would someone mind taking a look at this to see if I had a power/battery issue?


    • That's not a log. At least not one I can analyse. You need to provide the .bin or .log file.

      Your issue definitely sounds like an attempt to RTL on a failsafe. The default RTL height is 25m - which is quite high, so looks like a flyaway.

      I too had a similar situation. Failsafe was triggered by EKF which was caused by a faulty compass. Without logs its impossible to say what yours was though, could be anything - all failsafes trigger the same beeps :)

      @vas I too tried to fly after the failsafe was triggered, I too experienced a flyaway, it was caused by a faulty 3DR compass, but it was my error that I didn't know enough to investigate the original problem and thus save myself some considerable expense. These are far from being plug and play right now - but that's the fun of it IMO.

      Proving that it was the compass was another story involving modifying the firmware - but at least now everybody gets the benefit of my experience which is part of the point of open source software :)

      • Is this the right file?

        2015-05-31 15-24-25.bin

        • Can anyone read this log file?  Does it reveal what happened?

          • Hi, have had a look at the log file. Battery failsafe was triggered but the quad did not switch modes and was still in loiter and was until the end of the flight there is no evidense of the quad responding to you change into Alt Hold. Your GPS lock was consistent and showed no sign of any issues however your HDOP is sitting slightly high at 2.3 and you only have 7 satellites. In regards to the battery the voltage seems to fluctuate which is inconsistent with my own logs from my own copter in which the voltage seems to drop off more consistently. However I am new to log analysis and this may just be a difference in our setups etc.  

      • I think it has to be written in BOLD letters on the wiki page to get in and change an option for RTL failsafe to perform it as the current altitude. It also should be set like that by default.

        as with not working/glitching baro and not working compass and not working GPS it tries to get itself to that preset altitude and, well, bye-bye drone.

        • This has been discussed many times before, but RTL at current altitude is NOT a sensible default.  If you're flying at or below head height for whatever reason and it RTLs, your UAV then turns into a people lawnmower.  If you're flying anywhere with a hill, tree or house, you're far more likely to hit it.  The default action of RTL is to climb up out of harms way, then come back home, then land - in an emergency or uncommanded situation such as RTL usually is, it's the safer option.

          However, it could do a better job of maybe of signalling RTL, like lots of beeps or a big red LED, that would probably help a lot of these situations as people would know what it's doing.  

          It should be written in bold on the front of box that if your UAV climbs and stops responding, 99% of the time it's doing a failsafe action and probably doing a better job of flying than you :) (not meant to say anything against your flying skills of course)

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