FC Communication Error

Discussion in 'Cinestar 8' started by Scott Mouat, Mar 11, 2015.

  1. Scott Mouat

    Scott Mouat New Member

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    Hi Guys,

    This is our first post here, sadly due to a tech issue and crash. Would love to get some possible ideas as to why this happened. details below.

    Cinestar 8, mikrokopter Bl Ctrl V3.5, Fl Ctrl 2.5, Navi Ctrl 2.0, Movi M10, Nikon D750 17 - 35 lens

    FC Communication Failure.

    Yesterday we crashed. In the morning we had had two good flights with no problems to speak of. In the afternoon we returned to get some more still shots. The Weather was clear, wind 15 - 20km/hr.

    As you will see from the GPX file the flight started well. When GPS hold was applied Matilda (thats what we call our cinestar 8) circled, as she does some times but sorted herself fairly quickly. GPS hold was disengaged and Alt hold applied then things went wrong. the pilot tried to engage Carefree to bring her back but no response, As you will see from the GPX file (entry 126 on grid view) Carefree is applied and then the stick inputs freeze. From that point on the pilot has no control. A few seconds later the FC error appears. Control was never regained and she drifted inland till her battery died.

    This morning we reconnected Matilda and found she had no errors and (according to Mikrokopter tool) appears to be in a perfect bill of health. So what happened?

    I have read that a user in the USA had FC issues and intermittent control due possibly to a rabbit ear receiver issue but our issue seems to be related to the Care Free switch.

    This is a concern as we have been unable to find the cause and obviously want to ensure this does not happen again. Our other question is this. Why did the GPS failsafe not take over when we lost control. Should she not have returned home?


    The other question is why did she only record a 2 minute flight when she flew for well over this length of time?
     

    Attached Files:

  2. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Scott:
    It sounds like you may be confusing "Carefree" with "Come Home?"
    I've not had a chance to look at the GPX file, but I'll look at it later on this evening. If you do see "Carefree" in the GPX file, the copter will not return to the takeoff point -- all that Carefree does is allow you to give right-hand stick input to the copter and have those inputs corrected for which way boom #1 is pointing.

    Come Home, on the other hand, really does do that. It will bring the copter back to the takeoff point.

    The FC error itself might have been caused by a fault in the I2C bus wiring that runs between the FC, the Navigation Control board, and the GPS. It is odd to see that happen as a transient fault, though. Certainly, when it happens, it is likely to put garbage data onto the I2C bus -- and the Navigation Control board might no longer be able to make sense of what to write to the GPX file. The other possibility is that there is actually a fault on the FC board, so I would not fly again with that FC board until you can resolve the issue.

    Out of curiosity, and this has nothing to do with the possible causes, did Matilda descend slowly to the ground or crash hard?

    Andy
     
  3. Scott Mouat

    Scott Mouat New Member

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    Thanks Andy,

    I've had a look at the log again and i can see no record of the pilot hitting the come home button, just the carefree button. Shortly after the carefree button was applied ability to communicate with Matilda ended and a few seconds later we got the FC communication error. From that point on we could not communicate. Having said that entry 117 on grid view in the speech column indicates 'GPS home'. Communication failed at the same point we had an FC SPI Error. At that same time it looks like 'carefree' was switched from on to off.

    If the drone is in Carefree mode when you lose FC communication should she then return home?

    In answer to your curiosity question, neither the pilot nor i saw the impact (we were running to try and keep sight of her, i may have been jumping a fence or wiping sweat out of my eyes at the time) but i suspect, from the mess the gimbal and legs were in, it was not slow...

    Thanks again
    S
     
  4. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Hi Scott: Carefree Mode and Come Home are completely disjunct, I'm afraid. So the answer to your question is no -- turning Carefree on and it being on when the Serial Peripheral Bus (SPI) error happened does not imply that the copter would do anything.

    However, when that SPI bus error occurred I'm afraid that Matilda's fate was that she would not be Waltzing for a while. :)

    Sorry to hear that the gimbal and legs took the brunt of the "landing." Not good...

    But at least you're not alone on this forum -- several of us have had the gimbal center-punch Mother Earth....
    Andy
     
  5. Scott Mouat

    Scott Mouat New Member

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    Thanks Andy, I guess my biggest concern to come from this is the issue of safe operating. I know MK are working on a redundancy system and I'm not sure i would now be happy flying without that. As far as i'm aware the MK double quadro board has redundancy for a single motor fail and you can attach 2 x Flight controls, and 2 x navi controls. My concern flying the rig we have at present is that there are components within it that have no failsafe. At the end of the day the gimbal can be fixed and the drone can be fixed but what happens if she comes down on buildings or vehicles or people? Plus trying to run across farmland at 40Km/hr to keep up with a drone sucks. I guess the cows had a laugh at least.

    Thanks again
    Best
    S
     
  6. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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