Copter-3.3 beta testing

Warning #1: an issue has been found with Tower's Pause button which can cause the vehicle to fly to an old position if the vehicle has not sent a position update to Tower in some time.

Warning #2: Copter-3.3.2 fixes a bug found in Copter-3.3.1's desired climb rate initialisation which could lead to a sudden momentary drop when switching from Stabilize or Acro to AltHold, Loiter or PosHold.

Warning #3: Copter-3.3.2 fixes an issue found in Copter-3.3.1 which could lead to hard landings in RTL or AUTO if the WPNAV_SPEED_DN was set too high (i.e. >400 or 4m/s) and/or the WPNAV_ACCEL_Z was set too low (i.e. <100 or 1m/s/s).

Warning #4: a bug was found in Copter-3.3 which could cause a sudden crash if you abort a Take-off initiated from a ground station.  Video description is here.  The bug is fixed in Copter-3.3.1 so we recommend upgrading.

Note #1: AC3.3-rc8 corrected a long standing bug in the HDOP reporting.  HDOP values will appear about 40% lower than previously but this does not actually mean the GPS position is better than before.
Note #2: if upgrading from AC3.2.1 the vehicle's accelerometer calibration needs to be done again.
Note #3: set SERIAL2_PROTOCOL to "3" and reboot the board to enable FrSky telemetry like in previous versions.
Note #4: the wiki will be updated over the next few weeks to explain how to use the new features

Copter-3.3.1 is available through the mission planner.  The full list of changes vs AC3.2.1 can be see in the ReleaseNotes and below are the most recent changes since AC3.3.

Sadly this version (and all future versions) will not run on the APM2.x boards due to CPU speed, flash and RAM restrictions.

Changes from 3.3:

1) Bug fix to prevent potential crash if Follow-Me is used after an aborted takeoff

2) compiler upgraded to 4.9.3 (runs slightly faster than 4.7.2 which was used previously)

Changes from 3.3-rc11:

1) EKF recovers from pre-arm "Compass variance" failure if compasses are consistent

Changes from 3.3-rc10:

1) PreArm "Need 3D Fix" message replaced with detailed reason from EKF

Changes from 3.3-rc9
1) EKF improvements:
    a) simpler optical flow takeoff check
2) Bug Fixes/Minor enhancements:
    a) fix INS3_USE parameter eeprom location
    b) fix SToRM32 serial protocol driver to work with recent versions
    c) increase motor pwm->thrust conversion (aka MOT_THST_EXPO) to 0.65 (was 0.50)
    d) Firmware version sent to GCS in AUTOPILOT_VERSION message
3) Safety:
    a) pre-arm check of compass variance if arming in Loiter, PosHold, Guided
    b) always check GPS before arming in Loiter (previously could be disabled if ARMING_CHECK=0)
    c) sanity check locations received from GCS for follow-me, do-set-home, do-set-ROI
    d) fix optical flow failsafe (was not always triggering LAND when optical flow failed)
    e) failsafe RTL vs LAND decision based on hardcoded 5m from home check (previously used WPNAV_RADIUS parameter)

Thanks for your testing!

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                  • I'm game to try the failsafe with the buzzer disconnected. I'll report back soon. However: why would the problem arise with 3.3rc7?

            • Developer

              Slight update - I checked another log from a user in Japan who also had an MPU6k failure, and his log also seems related to the battery voltage.  I don't think this changes the advice (RMA the board) but the correlation with the main battery voltage and mpu6k failures may be there but we just haven't noticed it before.

              Thanks again for the log.

              • Hi Randy,

                Thanks a lot to you and Leonard for your analysis. I'll get in touch with 3DR support.


            • Developer


              Leonard and I had a look at the logs and it shows a very unusual problem, not something that we've ever seen before.  It seems that once the battery voltage drops to about 10.3V the MPU6k's Z-axis accelerometer develops a 3m/s bias.  This bias comes and goes very quickly but it messes up the inertial navigation height estimate which causes the vehicle to climb.

              Eventually the battery completely dies and the vehicle comes crashing down because it simply doesn't have the power to remain flying.  That's not unusual but the sudden bias developing on just one IMU is very odd.

              I'd guess this is a variation of the MPU6k issue that 3DR had due to a manufacturing fault.  It looks similar although the bias is much smaller than we normally saw (often we saw 10G of bias developing).  I think this this vehicle was purchased between June 2014 ~ Feb 2015 you could ask for an RMA from 3DR.


          • Thanks Randy - I will post the logs later today. I figured the same: low battery, rapid descent. The gain in altitude at failsafe remains a mystery, though. The logs will tell.

  • Hello,

    Normally my copter flies well but after installing 3.3rc7 it started to give bad ahrs error (hud started to move randomly) and an unusual tone (like simonk fw esc's first start tone). Sorry i dont have logs because of cant fly it and didnt minded take a disarmed logs. I reverted back to 3.2.1 and it started to give baro, mag errors and osd started to say high vspeed even copter is disarmed and staying on the ground. I take a risk and tried to fly. It flies but sometimes it force to descend itself, random wobbles, and yaw drifts. Lastly i tried to autotune, yaw drift starts badly and forced itself to descend even full throttle. I switched off autotune and started to wobble badly. At last it landed a position that i cant reach to take copter. Rearmed and it flies again normally. I dont understand whats happening inside really.

    Here is my log

    Shared with Dropbox
    • Developer


      So this is an AC3.2.1 log (as you've said) so I only had a quick look at it.  The GPS quality is very bad with HDOP never below 3.97 and number of satellites never above 8.  It detects a number of glitches during the flight.

      If some new equipment has been installed on the vehicle or the GPS has been moved that could point towards the cause.

  • OK, guys, best my novice investigation skills can tell, something has changed recently for tricopters. I'm fairly certain I flew 3.3RC5, but I know I have flown 3.3RC3 or RC4, because I have used the new autotune mode, one axis at a time, and things worked alright, if that gives you some historical reference.

    ANYWAY, in AC3.3RC7, the firmware doesn't seem to take RC7_REV into account, meaning that the tricopter goes into a death spiral as soon as it leaves the ground. I've tried it with RC7_REV = 1 (Normal) and RC7_REV = -1 (Reversed) and there was no change in behavior. It even spins the same direction (to the right, or clockwise when viewed from above). Confirmed that this does NOT happen with AC3.2.1, but not sure when it showed up in AC3.3 (like I said, I have flown versions of AC3.3 without issue, I believe that this is new with 3.3RC7, but maybe I missed RC5, not sure). Log attached below, if that's helpful. They are labeled as they were set, one with Normal servo direction on RC7_REV, and one with Reversed servo direction. Shared via DropBox due to size limitations. Let me know if this is the wrong format or doesn't work.

    Tricopter is currently unflyable. Help me Obi-Wan, you're my only hope.

    • Also, how do you get to that page on the wiki for Tricopters? Other than following the direct link, obviously. I had no idea there was a Tricopter page.
      • Developer


        It's been added to the left side menu of the copter wiki now just below Traditional Heli.

        Indeed, we changed the parameter and didn't tell anyone so no wonder you couldn't find it.

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