Well it was only a matter of time, had my first two real crashes happen the past two days. The first one was my fault, I had just finished putting the Cinestar 8 back together after packing it up and flying with it. Went up for my first test flight and one of the motors turned upon takeoff and sent her into a spiral. Tried my best to control it but ended up bringing her down for a crash landing into a tree, it flipped and landed flat, upside down on the batteries. I will never forget to check boom tightness again, that is for sure. Took her back out yesterday and had a successful flight with two 5s 5000mAh batteries. Swapped those out for the 4s 8000mAh batteries that took most of the fall the previous day. I could tell something wasn't right as the copter was making strange noises coming out of the buzzer that I had never heard, almost like radio interference. You can hear in the video below, the gimbal also making a constant beeping noise, this isn't the issue though. If you listen closely, its more of an intermittent buzzing sound. Anyways, it wouldn't let me take her up at first. Almost as it was in "safe" mode. I was a little confused and started flipping transmitter switches to make sure I had them all in the right place. Flipped one of the flaps and she took off....the video can tell the rest. It started behaving erratically, I attempted to calm her but she wasn't having it so I dumped it into the beach as a safety precaution. No physical damage other than sand in the motors. Really lucked out. Looks like my KML file is corrupted as I can't view it. I've got the logs attached below from all three flights yesterday. Any input would be greatly appreciated, I'm not exactly sure what Im looking for. The crash file is 15053002. Thank you! Alex
Alex, I checked the GPX files and except the I2C errors, everything looks OK. If I2C bus breaks down, there's no way to control the copter. I2C errors is not only related with BL controllers; but also with PDB. If the board got cracked internally from previous damage; it's possible that the I2C bus error could occur because of that. Just a guess. If you inspect your copter closely, probably you will see that all BL controllers are working fine. What I would recommend you is to change the PDB to avoid I2C error again which might be the cause.
I reviewed the GPX file, I agree with Ozkan. Spurious I2C errors on startup are an issue with the older V2 BLs, but if you experience on in flight, it's typically a very bad thing. I'd very carefully check the little multi-pin Molex connectors, as well as the connections between the navi board and the FC board. Do this when you're on the ground with the props removed and the motors running. I would not fly it again until you've conclusively found and fixed this problem. It could be worse next time. Landing in that large body of water next to where you were flying could destroy the copter.
Steve and Ozkan are both right -- the I2C bus connects all of the MK boards together: Flight Controller, Navigation Controller, GPS, Power Distribution Board and all ESCs. It's how all the boards talk to each other and how the NC board collects all the data to write out to the GPX file. Sadly, the weakness of bus structures like the I2C is that if one board or one I2C connection goes down and junk data gets put on the I2C bus, then it drags everything down and can easily cause a crash. That said, if you are getting valid-looking GPX data, then the bus data traffic did not get completely trashed -- thus pointing to an intermittent fault -- each data packet injected on to the I2C bus has a simple checksum to ensure that the packet is valid -- if the checksum doesn't add up, then an I2C error is deemed to have happened. So there's something intermittently bad if you see I2C errors clocking up but you still have a valid GPX file. I've not had a chance to look at the GPX files yet...(you all know the frenzy of packing before leaving on a trip! ) Andy.
Hey guys, thank you for taking a look at all this, I really appreciate it. Sounds like I have some careful scoping to do, will report back with what I find. Cheers
Alex just for your info that sound you hear at the 30 secs mark into your video is the I2C error. http://gallery3.mikrokopter.de/var/albums/MKBilder/Beepcode_I2C_Error.WAV?m=1411130828 If you dont know what the error sounds are please learn them they can be found here http://wiki.mikrokopter.de/en/ErrorCodes at the BOTTOM of the page. Good luck with your investigation