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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According to Nikolay Arsov the communication problem is with the APM/Mission planner code. As Craig mentioned the racer was developed with the PX4 stack and works great. I don't think that any solution exists at this point and I don't think APM and QGC dance without lots of sore toes. You can use PX4 stack for now although IMHO QGC is a bit tough to get use to after using Mission Planner. QGC is much easier to use than it was a few months ago, the set up screen is actually pretty cool.

It's APM side firmware and I didn't have any luck loading APM with QGC. If you want to fly just use PX4 and QGC, a little bit of a learning curve from MP but works great. The racer is a very well built and designed little controller, I think you'll like it.

Cheers R

The APM stack uses a different approach than the PX4 stack. With APM you have a HAL [hardware abstraction layer] which is where the "drivers" for sensors and other things go. This allows the kernel at the end to talk with the HAL [the middle] and all the sensors and what not to finally talk with the clever bits that takes all that info and tell the motors to do things. [very simplified but you get the idea]. The PX4 stack is more of a RTOS and has all that HAL stuff in the kernel.Lorenz and team ethz.ch developed the Racer so it is their flight stack that now works with the Racer. The APM devs still need to get a working HAL for the Racer to talk with the rest of the APM stack. Once that is done it won't really matter which stack you choose. But it is still best to use PX4 with QGC and APM with Mission Planner.

We going to sort out the loading of pixracer with Copter-3.3.3 via mission planner (and other GCSs) this week.  It should be possible to load master (also known as "latest") already by using beta mission planner and pressing Alt-Q from the Install Firmware screen.  That's using bleeding edge Copter though so we're going to sort out the load of Copter-3.3.3 very soon.  Sorry for the delay on that!

A small correction, the APM stack has been working with pixracer for months.  In fact, I believe it flew first on APM.  The issue is just that we've been slow to get the code available through the mission planner (which we will sort out very soon).

The QGC vs Mission Planner thing is interesting because some developers (with support from Intel) have been improving QGC's support for APM.  I haven't tried it myself but I hear good things.

I want to mention, so my logs and info don't get lost in the chatter...
I did successfully load APM, and fly with it. 

It's just that the compass settings sometimes get lost/erased if I hook it up to the computer. 

And, I get gyro and accel prearm warnings most of the time. 

I'm wondering if this is possibly issues because it is in development, or if these things should be working, and I should look in  to an RMA?

Edited to mention, I have the same issues in MP and QGC with the config not saving (it goes through the steps, but then keeps saying I need to calibrate the compass).  No problem installing the developer version of the software.

We think the pixracer should work.  I don't believe there are any known issues in the software.

I know there was a change to the board's design (before it was mass produced) to move which (SPI?) bus the eeprom was on which could be related to the issues saving parameters.  Or it could be unrelated... for example if the compass was not being reliably detected at startup then it could also lead to the "Compass not calibrated" pre-arm check appearing.


The motors rework has taken a little longer than expected which is why Copter-3.4 hasn't begun beta testing yet.  There's also another important decision that needs to be made which is do we include any/all of these features in Copter-3.4 or push them off to 3.5?

  • Terrain following
  • Precision landing
  • AP_Arming consolidation with Plane/Rover (this will produce better pre-arm check reporting to the ground station allowing it to display a single full list of all checks that are currently failing)

I'd say each one of these features will consume about 1 extra week of dev.

I'd like to push out Copter-3.3.3 as the official version in the next day or so.  Has anyone given it a fly and can confirm that it seems ok or not?

We will do a special build so pixracer will be officially supported using Copter-3.3.3 at the same time.

take the week + to get it right. Pushing out new versions for the sake of pushing out new versions is never a good thing. Take the time to write it correctly. 99% of us can wait a few weeks before a new version. I personally would rather wait a few months and get a well written code base then to have these things churned out week after week and having to deal with any issues that arrive with them. I'd go so far as saying a new version every 6 months is almost too much too fast.

That's not to say bug fixes could not be released on a fast ring, but I'd much rather see new "versions" released on a much slower and defined "slow ring" :)


One answer is the desired yaw can be dragged around by the actual yaw if it strays more than about 10 degrees.  There's some argument about whether that's too small an error to lead to the dragging but.. in any case, that's why you're seeing the desired yaw drifting.

I had a chat with Leonard and we think it's primarily a tuning issue.  If we can get the control better then the desired vs actual will stay closer together and the dragging will stop.

It looks like the tail servo is oscillating (see blue line below).  Leonard suggests reducing the RATE_YAW_P and RATE_YAW_I by 50% and keep doing that until the oscillations go away. RATE_YAW_P is already low at 0.08 but try even lower like 0.05.  RATE_YAW_I is currently 0.015 so maybe try 0.01.

He also suggests keeping STB_YAW_P low (it's 4.5, don't raise it).

By the way, Leonard's done some work on the TriCopter "stability patch" for Copter-3.4.  It has a number of improvements including reduced throttle-vs-yaw coupling and better prioritisation when it hits the upper throttle limits meaning you should get better maximum vertical acceleration.

We have a bit of a shortage of TriCopter pilots so I hope you can help us test when the Copter-3.4 beta becomes available.

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