This board supports USB but not doen not support OTG.

    - nuttx in PX4/Firmware (84048890): https://github.com/PX4-NuttX/nuttx/commit/65b87d092a6d5f776ab5f9dbb095d31e45861789
    - nuttx current upstream: https://github.com/PX4-NuttX/nuttx/commit/0ac630e6d0e90480121c74d59a92676f0b951dce
    - Changes: https://github.com/PX4-NuttX/nuttx/compare/65b87d092a6d5f776ab5f9dbb095d31e45861789...0ac630e6d0e90480121c74d59a92676f0b951dce

    0ac630e 2018-04-28 David Sidrane - [BACKPORT] Merged in david_s5/nuttx/master_kinetis_usb_fixes (pull request #634)

 - set BOARD_NUMBER_BRICKS to 0 for boards without analog power bricks

 - px4_add_module now requires MAIN
 - px4_add_library doesn't automatically link

This updates the MAVLink submodule to the current version including the trajectory WIP messages.

Adds support for another MPU9250 or MPU6500 on px4fmu-v4 internal SPI bus. Adds PX4_SPI_BUS_EXT, PX4_SPIDEV_EXT_MPU to board config and spi.c. Call 'mpu9250 -S start' to enable.

- move the analysis parts of the process_logdata_ekf script to
the 'analyse_ekf' function in a new file analyse_logdata_ekf.py
- return a test_results dictionary from analyse_ekf
- still process log loading, preprocessing and results file output in
process_logdata_ekf
- add command line argument to toggle plotting
- add command line argument to use different dictionary to check_level_dict.csv

- move code that is needed for general analysis out of plot scope

With the updated mixer (#9062) it's safe to set maximum thrust to 1 (in
both cases, if MC_AIRMODE is set, or not set).
So I see no reason to limit the maximum thrust.

So that it can be customized better according to personal preferences.

The limitation of 16 chars did not allow to use a better param name.

This matches the maximum rates for the attitude controller.

The meaning of the yaw weight changed with #8003:
- before, the yaw weight decreased with increasing tilt angle error, so
  it was mostly 1
- now, it is constant and depends on the tuning gains (around 0.4 by default)

It means that #8003 reduced the feedforward term, and we get the closer
behavior as before with this change.
It also reduces coupling between different parameters.

memset (http://www.cplusplus.com/reference/cstring/memset/) interprets
the value argument as unsigned char, so passing a float will not work.

The description of IMU_GYRO_CUTOFF was incorrectly saying that it only
affects the driver filtering, but in fact it also set the on-chip filter
to the next higher supported value. This patch fixes that.

And because the IMU_GYRO_CUTOFF and not the IMU_ACCEL_CUTOFF was used for
the on-chip filter, after #9070 which sets the default gyro filter to 80,
we were effectively using a dlpf of 98 Hz.
For this reason this patch changes the on-chip cutoff frequency to 98 as
well, so that the overall default behavior is unchanged.

 - EKF2 airspeed fusion and synthetic sideslip fusion
 - commander eph/epv failsafe thresholds appropirate for FW

    - Changes: https://github.com/PX4-NuttX/nuttx/compare/fe0dc6c41a6bd7d942945459ac960ff2d3e1f4fc...65b87d092a6d5f776ab5f9dbb095d31e45861789

    65b87d0 2018-04-19 Daniel Agar - [PX4 BACKPORT] Merged in dagar/nuttx/pr-stm32f777_typo (pull request #628)

- useful for tuning snapdragon flight

Signed-off-by: Roman <bapstroman@gmail.com>

 * ECL update includes physical constants for https://github.com/PX4/Firmware/pull/9319

Signed-off-by: CarlOlsson <carlolsson.co@gmail.com>

Signed-off-by: CarlOlsson <carlolsson.co@gmail.com>