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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RC10 has something changed again in the GPS department I guess as I flew it today and it was very erratic compared to rc9. RC9 was almost ideal, this RC10 flight today was nothing like it.

with rc9 I did not have anymore HDOP 0 or 99.99 issues - with RC10 I had 99.99 stuck HDOP on first GPS unit for 3 power-ups consequently, plus during flight drone was wondering from location to location way more aggressively than with rc9. may be it was a solar storm today, who knows, but I kinda doubt it as with rc9 on same field I always had RTL to return within 50cm from the take off point, and today RTL did a wild hunt for landing spot with a 20m arch going left and right at aggressive angle, so I had to drop drone down to the grass which I did not have to do once since  rc5.

so it was a bit unexpected. Did you by any chance reverted GPS code from RC9 into old from RC8 as Rc8 used to behave like that.  

here is log file. Both GPS units were from 20 to 19 sats with good link from what I can see, overall vehicle attitude was horrible compared to hw RC9 behaved, it was constantly jerking from one position to another, so, I bet something was altered.

If there is a plan how to make it work better I think it has to be a priority now, as it was close to unusable today and for no obvious reason.

here is a link to log file.



Glad you are happy with 3.2.1! Do you know or appreciate why you are so happy with 3.2.1? It's because of this exhaustive process of beta testing. Lets refresh our memories. Work on 3.2 beta began with the first release candidate on May 9, 2014 (actually work began long before that with the dev release), followed by a series of 14 release candidates until its "stable" release sometime in November, 2014. A few quick enhancements and bug fixes were tested and released by February, 2015. So that's May-2014 to February-2015 (10 months) to give you the "stable" release you are so happy with.

Now lets talk about the current beta cycle; The first beta release candidate was presented for beta testing in April of this year and is currently on RC10. By all accounts it's quite good (at least for me).

Patience is the key here. If you don't want to follow the 279 page thread that's OK, but don't complain about how long the process takes to bring you a "stable" product you can use with any degree of confidence.

I agree that these threads can get extremely long. But if they were only filled with on topic discussion they would be much shorter.

Enjoy 3.2.1 while you wait.


Nathaniel ~KD2DEY

GPS quality out on the west coast has been very unreliable over the last week. Some times I get 15 sats in 30 seconds other days this week no lock after 30 minutes. All this with no change in firmware.

Others on RCgroups have given similar reports.

I would suggest you try it a few more times and see if some days are better than others.
Unless Randy sees something else in the log i sent i think issue is with code switching between 2 gps signals non stop and making drones final position unstable.

K Index indicates all is quiet


I just reviewed the commits and as far as I can see we haven't made any changes to the GPS code between -rc9 and -rc10.  Just in case anyone wants to check (now or for future reference) the list of commits can be seen here and the changes in -rc10 are all the things after the "Copter: version to AC3.3-rc9" commit.  The first part of the description describes the area of the code change and there's no "GPS:" changes.

I've looked at the logs and, like you, I also see the constant changing back and forth between GPSs (see "U" field in GPS and GPS2 messages) which we know leads to ugly shifts in position although I don't directly see the impact of these shifts on the EKF innovations or vehicle lean angles.  Still, to be honest, it's the first time I've really looked for them.  I suspect you're right that this is the cause.

So a couple of suggestions/comments:

  • Try disabling one of the GPSs (GPS_TYPE2 = 0)
  • Try disabling some of the satellite types (i.e. set GPS_GNSS_MODE to "3" to enable only GPS and SBAS).  I've updated the param descriptions so bitmasks should appear in the mission planner's Advanced Config page for this parameter eventually.
  • Try using u-center to increase the GPS's Baud rate.  This is very speculative and not evidence-based but I've heard from Michael Du Breuil that when we have a lot of satellites the 38400 baud rate is not enough to get all the satellite info from the GPS to the flight controller.  I know this sounds scary and important so let me follow up with Michael.  From what I see in your logs all the GPS messages are arriving at regular 200ms intervals as they should.

Thanks for this information, i will try to experiment with ucenter.
As of disabling second GPS it is not a real solution and i still believe firmly proper design requires full redundancy of all critical navigational systems and current code tries to implement it, it only needs some additional finesse to be crafted to smooth up transitions.


Yes, totally agree that disabling the 2nd GPS is not the ideal solution.  It's on the to-do list to fix for AC3.4 so I'm sure we will sort it out in the coming months.

So, yes, this "Calibrate Level" button on the MP is (indirectly) adjusting the AHRS_TRIM_X and AHRS_TRIM_Y parameters.  This is a good way to adjust the trim without having to do the whole accel calibration again.  As many have guessed, it's not the same as the old 1-D calibration procedure we had way back in the old days.

The wiki really doesn't explain this so we will add that.

I've updated the image here and added a new section here.

Hey Randy,

I thought on boot, the autopilot was setting the gps's baud rate back to 38400, regardless of what was already set via uCenter.  Is that not accurate? I'm very likely mistaken, but don't know how to read the code well enough to verify on my own.



Could you try testing with the latest Tower beta app?  There's a new version out today and I just gave it a try and it seemed ok.

By the way this latest Tower beta also includes the live EKF viewer (Vibe viewer will come in about a week).  The EKF viewer widget can be enabled by going to Settings, User Interface, Widget Preferences and then click the EKF Status checkbox.  All UI look-and-feel type feedback should go to the Tower guys (Search page for "Send Feedback").

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