Arducopter 2.8.1 is now in the mission planner and in the downloads area! Remember to do your MP configuration again after loading this code, since it erases your EEPROM and sets it to the new defaults. 

Note: Issues with APM1 user's level feature not working are now resolved.  If you installed 2.8 we highly recommend you upgrade to 2.8.1 as 430 extra bytes of RAM have been freed up which reduces the chance of memory corruption (although we haven't seen any cases of this on the APM2 at least) .

Note #2: this release has not gone out for Traditional Helicopters until they can be tested fully.  Flip and Toy mode have also not been fully tested.

Improvements over 2.7.3:

  • Improved ACRO mode (Leonard Hall)
  • Improved stability patch to reduce "climb-on-yaw" problem (Leonard, Rob Lefebvre, Randy)
  • Rate controller targets moved to body frames (yaw control now works properly when copter is inverted) (Leonard/Randy)
  • Less bouncy Stabilize yaw control (Leonard)
  • OpticalFlow sensor support for APM2.5 (Randy)
  • DMP works again by adding "#define DMP_ENABLED ENABLED" to APM_Config.h You can also log DMP vs DCM to the dataflash by adding "#define SECONDARY_DMP_ENABLED ENABLED" (Randy)
  • Watch dog added to shutdown motors if main loop feezes for 2 seconds (Randy)
  • Thrust curve added to linearize pwm->thrust. Removes deadzone found above 90% throttle in most ESC/motors (Randy)
  • More timing improvements (main loop is now tied to MPU6000s interrupt) (Randy)
  • GPS NMEA bug fix (Alexey Kozin)
  • Logging improvements (log I terms, dump all settings at head of dataflash log) (Jason)


Bug Fixes / Parameter changes:

  • fixed skipping of last waypoint (Jason)
  • resolved twitching when no GPS attached (Tridge)
  • fixed loss of altitude if alt hold is engaged before first GPS lock (Randy/Jason)
  • moved Roll-Pitch I terms from Stabilize controllers to Rate controllers
  • TILT_COMPENSATION param tuned for TradHeli (Rob)

Code Cleanup:

  • HAL changes for platform portability (Pat Hickey)
  • Removed INSTANT_PWM (Randy)

As per usual PIDs are optimised for the 3DR/jDrones quad with 850 motors and 10" props. If you're using more powerful motors/props and are seeing bad flight behaviour in stabilize, start by turning down Rate Roll P in 25% steps.

Please note that on this release we've moved the Roll and Pitch I terms from the Stabilize controller to the Rate controller. There's some evidence that says this can lead to flips on take-off if you move the roll or pitch sticks around as you take-off so we recommend you leave these sticks in the middle until you're in the air.

Please feel free to report issues you find in the discussion below and/or add them to the issues list.

Thanks and enjoy!

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    If you're in stabilize mode you shouldn't see any difference between 2.8.1 and 2.9.  It's only once you enter alt hold or loiter mode that the new throttle will be used.

    Sorry, what's inaccurate re the accelerometer set-up video?


I did lots of things at one time. My quad is just restored. But it is already dark.  I will wait and see what is happening on 2.9-rc1, may be rc2 on next weekend.

 I will follow your instruction on your video. I did not think that accelerometer setup needs so accurate orientation and hold some time to reduce unnecessary movement.

Anyway, I am so excited about this new version.

Appreciate for hard working dev. team and yourself. 

Does it have to be stationary when leaning or is just holding it 90 degrees tipped enough?


     stable is important.  It will take a number of accelerometer readings but if you're holding it in your hand while doing this, it's likely it will be moving a bit.  It may work well enough but I always lean it up against something while doing this calibration.

Hi Joe, thanks for the info :-) when you say lean the copter ? how much are you having to lean it over?

"how much are you having to lean it"

'Til the engine runs rough - sorry, inside joke among the pilots here.

and here was me thinking it was until the props cut you (only joking)

Will using levels, plumb bob's etc. increase the effectiveness of this calibration?


    It's probably clear from the video below but absolutely no need to use plumb bobs.  It won't help because the algorithm just takes 6 orientations and tries to find the accel offsets and scaling doesn't know (or care) whether they're exactly vertical, or horizontal or whatever.  In fact, in the accel calibration process, the MP prompts you to do it in a particular order but even the order doesn't matter.  The most important thing is try not to move the copter around as you push the MP button.

Here's a video demo of how to do the accelerometer calibration.  You should try and keep it stable but it actually doesn't matter if it's perfectly level, or perfectly on it's left side etc.

Hope this help me avoid the copter drift 5km/h on the side as soon it takes off... this is making it impossible to even try inflight calibration of accellerometers


     There is a slight change to how the auto trim works.  There's now a "save trim" as well as "auto trim" method.

     "Auto Trim" - This method is unchanged from 2.8.1.  It's invoked by holding the throttle down and rudder right for 10 ~ 15 seconds.  You then have 25 seconds in which you should fly and try to maintain a stable hover.  The average roll and pitch values over that time period are saved as to the AHRS_TRIM_X, Y parameters and used from then as an adjustment to your attitude which should mean it flies level.

     "Save Trim" - you must set this up on the arduCopter Config screen's CH7 Opt field.  Then you fly and use your radio trims to get your copter level.  Then land and flick the CH7 switch once, remove your radio's trim and fly again.  It should fly level.  Essentially what you're doing here is transferring your radio's trims to your APM.

I've already started updating the wiki with this change and others ahead of the official 2.9 release.



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