ArduCopter Release Notes:
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ArduCopter 3.1 14-Dec-2013
Changes from 3.1-rc8
1) Pixhawk improvements:
    a) switch to use MPU6k as main accel/gyro
    b) auto loading of IO-board firmware on startup
2) RTL fixes:
    a) initialise waypoint leash length (first RTL stop would be more aggressive than 2nd)
    b) reduce projected stopping distance for higher speed stops
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ArduCopter 3.1-rc8 9-Dec-2013
Changes from 3.1-rc7
1) add Y6 motor mapping with all top props CW, bottom pros CCW (set FRAME = 10)
2) Safety Changes:
    a) ignore yaw input during radio failsafe (previously the copter could return home spinning if yaw was full over at time of failsafe)
    b) Reduce GPSGLITCH_RADIUS to 2m (was 5m) to catch glitches faster
3) Bug fixes:
    a) Optical flow SPI bus rates
    b) TradHeli main rotor ramp up speed fix
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ArduCopter 3.1-rc7 22-Nov-2013
Changes from 3.1-rc6
1) MOT_SPIN_ARMED default to 70
2) Smoother inertial nav response to missed GPS messages
3) Safety related changes
    a) radio and battery failsafe disarm copter if landed in Loiter or AltHold (previously they would RTL)
    b) Pre-Arm check failure warning output to ground station every 30 seconds until they pass
    c) INS and inertial nav errors logged to dataflash's PM message
    d) pre-arm check for ACRO_BAL_ROLL, ACRO_BAL_PITCH
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ArduCopter 3.1-rc6 16-Nov-2013
Improvements over 3.1-rc5
1) Heli improvements:
    a) support for direct drive tails (uses TAIL_TYPE and TAIL_SPEED parameters)
    b) smooth main rotor ramp-up for those without external govenor (RSC_RAMP_TIME)
    c) internal estimate of rotor speed configurable with RSC_RUNUP_TIME parameter to ensure rotor at top speed before starting missions
    d) LAND_COL_MIN collective position used when landed (reduces chance copter will push too hard into the ground when landing or before starting missions)
    e) reduced collective while in stabilize mode (STAB_COL_MIN, STAB_COL_MAX) for more precise throttle control
    f) external gyro parameter range changed from 1000~2000 to 0~1000 (more consistent with other parameters)
    g) dynamic flight detector switches on/off leaky-i term depending on copter speed
2) SingleCopter airframe support (contribution from Bill King)
3) Drift mode replaces TOY
4) MPU6k SPI bus speed decreased to 500khz after 4 errors
5) Safety related changes:
    a) crash detector cuts motors if copter upside down for more than 2 seconds
    b) INS (accel and gyro) health check in pre-arm checks
    c) ARMING_CHECK allows turning on/off individual checks for baro, GPS, compass, parameters, board voltage, radio
    d) detect Ublox GPS running at less than 5hz and resend configuration
    e) GPSGlitch acceptable radius reduced to 5m (stricter detection of glitches)
    f) range check roll, pitch input to ensure crazy radio values don't get through to stabilize controller
    g) GPS failsafe options to trigger AltHold instead of LAND or to trigger LAND even if in flight mode that does not require GPS
    h) Battery failsafe option to trigger RTL instead of LAND
    i) MOT_SPIN_ARMED set to zero by default
6) Bug fixes:
    a) missing throttle controller initialisation would mean Stabilize mode's throttle could be non-tilt-compensated
    b) inertial nav baro and gps delay compensation fix (contribution from Neurocopter)
    c) GPS failsafe was invoking LAND mode which still used GPS for horizontal control
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ArduCopter 3.1-rc5 22-Oct-2013
Improvements over 3.1-rc4
1) Pixhawk USB reliability improvements
2) AutoTune changes:
    a) enabled by default
    b) status output to GCS
    c) use 2 pos switch only
3) ch7/ch8 LAND
4) Tricopter stability patch improvements [thanks to texlan]
5) safety improvements:
    a) slower speed up of motors after arming
    b) pre-arm check that copter is moving less than 50cm/s if arming in Loiter or fence enabled
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ArduCopter 3.1-rc4 13-Oct-2013
Improvements over 3.1-rc3
1) Performance improvements to resolve APM alt hold issues for Octacopters:
     a) SPI bus speed increased from 500khz to 8Mhz
     b) Telemetry buffer increased to 512bytes
     c) broke up medium and slow loops into individual scheduled tasks and increased priority of alt hold tasks
2) Bug fix for Pixhawk USB connection
3) GPS Glitch improvements:
       a) added GPS glitch check to arming check
       b) parameters for vehicle max acceleration (GPSGLITCH_ACCEL) and always-ok radius (GPSGLICH_RADIUS)
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ArduCopter 3.1-rc3 09-Oct-2013
Improvements over 3.1-rc2
1) GPS Glitch protection - gps positions are compared with the previous gps position.  Position accepted if within 10m or copter could have reached the position with max accel of 10m/s/s.
2) Bug fix for pixhawk SPI bus contention that could lead to corrupted accelerometer values on pixhawk resolved
3) Auto Tuning (compile time option only add "#define AUTOTUNE ENABLED" to APM_Config.h and set CH7_Opt or CH8_Opt parameter to 17)
4) CPU Performance improvement when reading from MPU6k for APM
5) SUPER_SIMPLE parameter changed to a bit map to allow some flight modes to use super simpler while others use regular simple (MP release to allow easier selection will go out with AC3.1 official release)
6) Safety changes:
    a) safety button must be pushed before arming on pixhawk
    b) RGB LED (aka toshiba led) changed so that disarmed flashes, armed is either blue (if no gps lock) or green (if gps lock)
    c) sensor health bitmask sent to groundstations
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ArduCopter 3.1-rc2 18-Sep-2013
Improvements over 3.1-rc1
1) bug fix for MOT_SPIN_ARMED to allow it to be higher than 127
2) PX4/pixhawk auto-detect internal/external compass so COMPASS_ORIENT should be set to ORIENTATION_NONE if using GPS+compass module
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ArduCopter 3.1-rc1 9-Sep-2013
Improvements over 3.0.1
1) Support for Pixhawks board
2) Arm, Disarm, Land and Takeoff in Loiter and AltHold
3) Improved Acro
    a) ACRO_RP_P, ACRO_YAW_P parameters added to control speed of rotation
    b) ACRO_BAL_ROLL, ACRO_BAL_PITCH controls speed at which copter returns to level
    c) ACRO_TRAINER can be set to 0:disable trainer, 1:auto leveling when sticks released, 2:auto leveling and lean angle limited to ANGLE_MAX
    d) Ch7 & Ch8 switch to set ACRO_TRAINER options in-flight
4) SPORT mode - equivalent of earth frame Acro with support for simple mode
5) Sonar ground tracking improvements and bug fixes that reduce reaction to bad sonar data
6) Safety improvements
    a) motors always spin when armed (speed can be controlled with MOT_SPIN_ARMED, set to 0 to disable)
    b) vehicle's maximum lean angle can be reduced (or increased) with the ANGLE_MAX parameter
    c) arming check that GPS hdop is > 2.0 (disable by setting GPS_HDOP parameter to 900)
    d) slow take-off in AUTO, LOITER, ALTHOLD to reduce chance of motor/esc burn-out on large copters
7) Bug fixes:
    a) Optical flow sensor initialisation fix
    b) altitude control fix for Loiter_turns mission command (i.e. mission version of CIRCLE mode)
    c) DO_SET_ROI fix (do not use "ROI")
8) Distribute Loiter & Navigation calcs over 4 cycles to reduce impact on a single 100hz loop
9) RCMAP_ parameters allow remapping input channels 1 ~ 4
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ArduCopter 3.0.1-rc2 / 3.0.1 11-Jul-2013
Improvements over 3.0.1-rc1
1) Rate Roll, Pitch and Yaw I fix when we hit motor limits
2) pre-arm check changes:
    a) double flash arming light when pre-arm checks fail
    b) relax mag field checks to 35% min, 165% max of expected field
3) loiter and auto changes:
      a) reduced Loiter speed to 5 m/s
      b) reduced WP_ACCEL to 1 m/s/s (was 2.5 m/s/s)
      c) rounding error fix in loiter controller
      d) bug fix to stopping point calculation for RTL and loiter during missions
4) Stability Patch fix which was freezing Rate Taw I term and allowing uncommanded Yaw
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ArduCopter 3.0.1-rc1 26-Jun-2013
Improvements over 3.0.0
1) bug fix to Fence checking position after GPS lock was lost
2) bug fix to LAND so that it does not attempt to maintain horizontal position without GPS lock
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ArduCopter 3.0.0 / 3.0.0-rc6 16-Jun-2013
Improvements over 3.0.0-rc5
1) bug fix to Circle mode's start position (was moving to last loiter target)
2) WP_ACCEL parameter added to allow user to adjust acceleration during missions
3) loiter acceleration set to half of LOIT_SPEED parameter value (was hard-coded)
4) reduce AltHold P to 1.0 (was 2.0)
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ArduCopter 3.0.0-rc5 04-Jun-2013
Improvements over 3.0.0-rc4
1) bug fix to LAND flight mode in which it could try to fly to mission's next waypoint location
2) bug fix to Circle mode to allow counter-clockwise rotation
3) bug fix to heading change in Loiter, RTL, Missions when pilot's throttle is zero
4) bug fix for mission sticking at take-off command when pilot's throttle is zero
5) bug fix for parameters not saving when new value is same as default value
6) reduce pre-arm board min voltage check to 4.3V (was 4.5V)
7) remove throttle controller's ability to limit lean angle in loiter, rtl, auto
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ArduCopter 3.0.0-rc4 02-Jun-2013
Improvements over 3.0.0-rc3
1) loiter improvements:
     i) repositioning enhanced with feed forward
     ii) use tan to convert desired accel to lean angle
2) stability patch improvements for high powered copters or those with roll-pitch rate gains set too high
3) auto mode vertical speed fix (it was not reaching the desired speeds)
4) alt hold smoothed by filtering feed forward input
5) circle mode fix to initial position and smoother initialisation
6) RTL returns to initial yaw heading before descending
7) safe features:
    i) check for gps lock when entering failsafe
    ii) pre-arm check for mag field lenght
    iii) pre-arm check for board voltage between 4.5v ~ 5.8V
    iv) beep twice during arming
    v) GPS failsafe enabled by default (will LAND if loses GPS in Loiter, AUTO, Guided modes)
    vi) bug fix for alt-hold mode spinning motors before pilot has raised throttle
8) bug fixes:
    i) fixed position mode so it responding to pilot input
    ii) baro cli test
    iii) moved cli motor test to test sub menu and minor change to throttle output
    iv) guided mode yaw control fix
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ArduCopter 3.0.0-rc3 22-May-2013
Improvements over 3.0.0-rc2
1) bug fix for dataflash erasing unnecessarily
2) smoother transition to waypoints, loiter:
    intermediate point's speed initialised from copter's current speed
3) Ch8 auxiliary function switch (same features as Ch7)
4) safety checks:
    Warning to GCS of reason for pre-arm check failure
    ARMING_CHECK parameter added to allow disabling pre-arm checks
    Added compass health and offset check to pre-arm check
    compassmot procedure displays interference as percentage of total mag field
5) WPNAV dataflash message combined into NTUN message
6) allow TriCopters to use ESC calibration
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ArduCopter 3.0.0-rc2 13-May-2013
Improvements over 3.0.0-rc1:
1) smoother transition to waypoints, loiter:
    reduced loiter max acceleration to smooth waypoints
    bug fix to uninitialised roll/pitch when entering RTL, AUTO, LOITER
2) fast waypoints - copter does not stop at waypoints unless delay is specified
3) WPNAV_LOIT_SPEED added to allow faster/slower loiter repositioning
4) removed speed limits on auto missions
5) enhance LAND mission command takes lat/lon coordinates
6) bug fix for RTL not pointing home sometimes
7) centrifugal correction disabled when copter is disarmed to stop HUD moving
8) centrifugal correction disabled when sat count less than 6 (AHRS_GPS_MINSATS)
9) compass calibration reliability improvements when run from mission planner
10) bug fix to allow compassmot to be run from mission planner terminal screen
11) add support for H-quad frame
12) add COMPASS_ORIENT parameter to support external compass in any orientation
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ArduCopter 3.0.0-rc1 01-May-2013
Improvements over 2.9.1b:
1) Inertial navigation for X & Y axis (Randy/Leonard/Jonathan)
2) 3D waypoint navigation library (Leonard/Randy)
    WPNAV_SPEED, WPNAV_SPEED_UP, WPNAV_SPEED_DN control target speeds during missions and RTL
    WP_YAW_BEHAVIOR to allow disabling yaw during missions and RTL
3) PX4 support (some features still not available) (Tridge/Pat/PX4Dev Team)
4) Safety improvements:
    Tin-can shaped fence (set FENCE_ENABLED to 1 and copter will RTL if alt > 150m or horizontal distance from home > 300m) (Randy/Tridge/Leonard)
    GCS failsafe (set FS_GCS_ENABLED to 1 and if you are using a tablet to fly your copter it will RTL and return control to the radio 3 seconds after losing telemetry) (Randy)
    pre-arm checks to ensure accelerometer and radio calibration has been performed before arming (Randy)
5) motor interference compensation for compass (Jonathan/Randy)
6) Circle mode improvements:
    set CIRCLE_RADIUS to zero to do panorama shots in circle mode (copter does not move in a circle but instead slowly rotates)
    CIRCLE_RATE parameter allows controlling direction and speed of rotation in CIRCLE mode and LOITER_TURNS (can also be adjusted in flight from CH6 knob)
7) SONAR_GAIN parameter add to allow reducing the response to objects sensed by sonar (Randy)
8) support for trapezoidal quads (aka V shaped or FPV quads) (Leonard/Craig)
9) performance improvements to dataflash logging (Tridge)
10) bug-fix to analog read which could cause bad sonar reads when using voltage or current monitor (Tridge)
11) bug-fix to motors going to minimum when throttle is low while switching into Loiter, AUTO, RTL, ALT_HOLD (Jason/Randy)
12) bug-fix for auto disarm sometimes disarming shortly after arming (Jason/SirAlex)
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ArduCopter 2.9.1b 30-Feb-2013
Improvements over 2.9.1:
1) reduce INS_MPU6K_FILTER to 20hz
2) reduce InertialNav Z-axis time constant to 5 (was 7)
3) increased max InertialNav accel correction to 3 m/s (was 1m/s)
4) bug fix for alt_hold being passed as int16_t to get_throttle_althold_with_slew
5) bug fix for throttle after acro flip (was being kept at min throttle if pilot switched out of ACRO mode while inverted)
6) reduce yaw_rate P default to 0.20 (was 0.25)
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ArduCopter 2.9.1 & 2.9.1-rc2 01-Feb-2013
Improvements over 2.9.1-rc1:
1) small corretion to use of THR_MID to scale lower end of manual throttle between THR_MIN and 500 instead of 0 and 500
2) bug fix for longitude scaling being incorrectly calculated using Next Waypoint instead of home which could lead to scaling being 1
3) ESC calibration change to set update rate to ESCs to 50hz to allow simonk ESC to be calibrated
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ArduCopter 2.9.1-rc1 31-Jan-2013
Improvements over 2.9:
1) THR_MID parameter added to allow users to adjust the manual throttle so that vehicle hovers at about mid stick
2) bug fix for autotrim - roll axis was backwards
3) bug fix to set sonar_alt_health to zero when sonar is disabled
4) capture level roll and pitch trims as part of accel calibration
5) bug fix to ppm encoder false positives
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ArduCopter 2.9 & 2.9-rc5 14-Jan-2013
Improvements over 2.9-rc4:
1) add constraint to loiter commanded roll and pitch angles
2) relax altitude requirement for take-off command to complete
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ArduCopter 2.9-rc4 12-Jan-2013
Improvements over 2.9-rc3:
1) Smoother transition between manual and auto flight modes (Leonard)
2) bug fix for LAND not actually landing when initiated from failsafe (Randy/Craig)
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ArduCopter 2.9-rc3 11-Jan-2013
Improvements over 2.9-rc2:
1) alt hold with sonar improvements - now on by default (Leonard/Randy)
2) performance and memory useage improvements (Tridge/Randy)
3) increase APM1 baro pressure read from 5hz to 8.3hz to improve alt hold (Randy)
4) bug fix: altitude error reported to GCS (Randy)
5) limit inertial nav's max accel offset correction to 100cm/s/s to speed up recovery after hard impacts (Randy)_
6) moved rate controllers to run after ins read (Tridge/Randy)
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ArduCopter 2.9-rc2 31-Dec-2012
Improvements over 2.9-rc1:
1) increased throttle rate gains from 1.0 to 6.0
2) APM1 fix so it works with inertial nav (5hz update rate of baro was beyond the tolerance set in the inav library)
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ArduCopter 2.9-rc1 23-Dec-2012
Improvements over 2.8.1:
1) altitude hold improvements:
    a)inertial navigation for vertical axis [Randy/Jonathan/Leonard/Jason]
    b)accel based throttle controller [Leonard/Randy]
    c)accelerometer calibration routine updated to use gauss-newton method [Randy/Tridge/Rolfe Schmidt]
    d)parameters to control climb rate:
        AUTO_VELZ_MIN, AUTO_VELZ_MAX - allows you to control the maximum climb and descent rates of the autopilot (in cm/s)
        PILOT_VELZ_MAX - allows you to control the maximum climb/descent rate when in alt hold or loiter (in cm/s)
2) landing improvements [Leonard/Randy]
    LAND_SPEED - allows you to set the landing speed in cm/s
3) camera related improvements:
    a) AP_Relay enabled for APM2 and integrated with AP_Camera [Sandro Benigno]
    b) camera trigger with channel 7 switch or DO_DIGICAM_CONTROL mission command [Randy]
    c) allow yaw override by pilot or with CONDITIONAL_YAW command during missions [Randy]
        YAW_OVR_BEHAVE - Controls when autopilot takes back normal control of yaw after pilot overrides (0=after next wp, 1=never)
4) trad heli improvements [Rob]
    a) code tested and brought back into the fold (2.8.1 was never released for trad helis)
    b) enabled rate controller (previously only used angle controllers)
    c) fix to rotor speed controllers - now operates by switching off channel 8
    d) allow wider collective pitch range in acro and alt hold modes vs stabilize mode
    e) removed angle boost function because it created more problems than it solved
    f) bug fix to allow collective pitch to use the entire range of servos
5) mediatek gps driver improvements [Craig]
    a) added support for 1.9 firmware
    b) bug fix to start-up routine so sbas can be enabled
6) failsafe improvements (both throttle and battery) [Randy/Craig/John Arne Birkeland]
    a) RTL will not trigger if your throttle is zero - reduces risk of accidentally invoking RTL if you switch off your receiver before disarming
    b) failsafe triggered in unlikely case of a PPM encoder failure
    c) bug fix to resolve motors momentarily reducing to zero after failsafe is triggered
7) mpu6k filtering made configurable and default changed to 42hz for copters [Leonard/Tridge]
8) support ppm sum for transmitters with as few as 5 channels [Randy/John Arne Birkeland]
9) acro trainer - copter will return to be generally upright if you release the sticks in acro mode [Leonard]
    ACRO_BAL_ROLL, ACRO_BAL_PITCH - controls rate at which roll returns to level
    ACRO_TRAINER - 1 to enable the auto-bring-upright feature
10) other changes and bug fixes:
    a) allow >45 degrees when in stabilize mode by adding lines like below to APM_Config (compile time option only) [Jason]
        #define MAX_INPUT_ROLL_ANGLE 6000     // 60 degrees
        #define MAX_INPUT_PITCH_ANGLE 6000    // 60 degrees
    b) bug fix to stop RTL from ever climbing to an unreasonable height (i.e. >80m) [Jason]
    c) event and state logging [Jason]
    d) allow cli to be used over telemetry link [Tridge]
    e) bug fix to allow compass accumulate to run when we have spare cpu cycles [Randy]
    f) bug fix so do_set_servo command works [Randy]
    g) bug fix to PID controller's so they don't calculate crazy D term on the first call [Tridge]
    h) bug fix to initialise navigation parameter to resolve twitch when entering some navigation modes [Jason]
    i) performance improvement to copter leds - use DigitalFastWrite and DigitalFastRead instead of native arduino functions  [Randy]
    j) removed unused stab_d from roll and pitch controller [Jason]
    k) bug fix for guided mode not reaching target altitude if it reaches horizontal target first [Randy]
    l) code clean-up, parameter documentation improvements [Randy/Jason/Rob/others]

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ArduCopter 2.8.1 22-Oct-2012
Improvements over 2.8:
- 430 bytes of RAM freed up to resolve APM1 level issue and reduce chance of memory corruption on both APM1 and APM2

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)
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