This is a significant release with a lot of changes, so please read the change summary below carefully.

• changed LED scripting API to allow more than 32 LEDs on a pin
• added support for ProfiLED LEDs
• added u-blox GPS moving baseline u-blox auto-configuration
• fixed handling of GPS antenna positions on EKF GPS switch
• changed default USB IDs to new ArduPilot specific IDs
• fixed bug in handling trim for RC control of camera mounts
• added LGR_OPTIONS bits to control landing gear behaviour on takeoff/landing

• improved mavlink streaming output control to better allocate time to each channel
• fixed send of mavlink PARAM_VALUE on set of a readonly parameter
• fixed mag variance reporting in EKF_STATUS_REPORT mavlink message
• fixed time wrap bug in BMP085 barometer driver
• fixed buffer overflow in ST24 RC input driver
• fixed EKF usage of WMM tables when user has specified a specific declination
• fixed bug in AP_Terrain on-disk format
• added script for offline generation of terrain data
• severel improvements to smbus battery drivers

• fixed a race condition in parameter storage on ChibiOS
• fixed use of zero GNSS timestamp in UAVCAN GPS driver
• improved GCS messages during bootloader flash
• fixed CS pin in bootloader that could corrupt FRAM on some boards
• added GPS yaw to MAVLink GPS_RAW_INT message
• added Hott telemetry support
• added FRSky FPort support
• fixed bug in CAN clock and queue handling on H7 based boards
• added support for BRD_ALT_CONFIG for alternative hardware configs on several boards
• added new boards CUAV-Nora, CUAV-X7, MatekH743, R9Pilot, mRoNexus
• improved reporting of internal errors to GCS

• fixed recursion bug in tonealarm player
• fixed flaperon SERVO_AUTO_TRIM behaviour
• added option to compensate forward throttle for battery voltage
• added compensation in VTOL gains for pressure altitude
• switched to new more flexible compass ordering system
• fixed forcing of safety off on IOMCU reset
• increased maximum compass scale factor to 1.4
• added RTL_CLIMB_MIN parameter for initial climb in RTL
• fixed disable of throttle nudge during a RC failsafe
• added support for a wider range of DLVR airspeed sensors

• fixed RC input processing for out of range RC channels
• added THR_FAILSAFE=2 option for flying BVLOS with only GCS failsafes enabled
• fixed reordering of compasses on boot based on compass priorities
• fixed use of minimum accuracy for GPS data in EKF2 and EKF3, fixing an issue with RTK GPS modules that report overly optimistic accuracy values
• fixed handling of RC_OPTION bit for disabling receiver failsafe handling
• fixed LOITER_TO_ALT with terrain altitude target
• fixed an issue with swapping UAVCAN compasses and calibration

• fixed use of VTOL quadplane missions (where the plane flies as a multi-rotor for auto waypoints)
• fixed legacy parsing of some lightware i2c lidars when beyond max range
• fixed RTL_AUTOLAND with MIS_RESTART=1
• enable more compasses on low flash boards
• HAL erase storage fix for flash storage boards
• prevent jump to circle mode in TAKEOFF if flying for less than 10s
• fixed handling of out of range on LightwareI2C Lidar
• fixed init of HoTT telemetry
• added support for mRo Pixracer Pro, Holybro Pix32v5
• added arming check for terrain data healthy if needed

• increased monitor thread size to 768
• fixed IMU fast sampling on F35Lightning board

The key changes to existing behaviour to watch out for in this update
are:

USB IDs

ArduPilot has now switched to it’s own USB IDs for all boards. For most users this won’t cause any change, except they may notice the drop down list of devices in MissionPlanner will have the ArduPilot flight controllers labelled more usefully as “ArduPilot” instead of
just “STM32”. If you hit issues on windows please try reinstalling the
device drivers from this URL:
https://firmware.ardupilot.org/Tools/MissionPlanner/driver.msi 3

Terrain

A bug fix in the format ArduPilot uses to store terrain data means
that your flight controller will need to re-download the terrain data onto the sdcard via your GCS. If you fly without a GCS and you use terrain data then please re-download the terrain data you need by setting up a mission when you have internet access and allowing your
flight controller to request terrain data from your GCS.

Pressure Altitude Compensation

This release adds in the missing hook for the VTOL motor controller on a quadplane to compensate the VTOL gains using your pressure
altitude. For most people this will not have a noticible effect, but some users that have tuned their aircraft for high locations may notice a tuning change.

Compass Ordering

The new compass ordering system in this release gives a lot more flexibility and should preseve existing configurations and calibrations. If you hit issues then please have a look at the new compass ordering user interface in recent beta releases of MissionPlanner.

THR_FAILSAFE=2

For people flying before visual range (with appropriate
authorisations) there is a new option which allows for safer
operation. By setting THR_FAILSAFE=2 you can setup the R/C failsafe so that R/C input will stop being used when one of the receiver failsafe conditions is met, while not triggering any failsafe actions. This is a significant improvement over setting THR_FAILSAFE=0 as it prevents the receiver inputs being used for stick mixing and other inputs that would be inappropriate when in receiver failsafe.