Initial work of so3 nonlinear complementary filter
I missed to add build command
Fixed few minor bug
I do not know why roll angle is not correct. But system looks okay
Roll pitch yaw should be verified again
To use freeIMU processing visualization tool, I have implemented float number transmission over uart (default /dev/ttyS2, 115200)
But this not tested yet. I should.
Test flight has been performed with nonlinear SO(3) attitude estimator.
Here are few observations:
 - When the system initialized, roll angle is initially reversed.
   As filter converged, it becomes normal.
 - I put a negative sign on roll, yaw. It should naturally has right
   sign, but I do not know why for now. Let me investigate again.
 - Gain : I do not know what gain is good for quadrotor flight.
   Let me take a look Ardupilot gain in the later.

Anyway, you can fly with this attitude estimator.
Merge remote-tracking branch 'upstream/master'
 - Mikrokopter BLCTRL seems to be updated
 - HMC5883L calibration problem has been corrected.
    (This is because of RAM mis allocation?)
    See https://groups.google.com/forum/?fromgroups#!topic/px4users/yTYJiDBBKfo
 - Fixed wing control updated
    https://groups.google.com/forum/?fromgroups#!topic/px4users/s7owpvZN8UI
 - GPIO module has been removed.
 - STM32 DRV updated
I finished to implement nonlinear complementary filter on the SO(3).
The previous problem was roll,pitch and yaw angle from quaternion.
Now it is fixed. 1-2-3 Euler representation is used.
Also accelerometer sign change has been applied.
I finished to implement nonlinear complementary filter on the SO(3).
The previous problem was roll,pitch and yaw angle from quaternion.
Now it is fixed. 1-2-3 Euler representation is used.
Also accelerometer sign change has been applied.
Merge branch 'master' of https://github.com/limhyon/Firmware
Visualization code has been added.
GPL Licensed code has been removed
Fix syncing issue with receiver on startup.
Merge pull request #296 from sjwilks/hott-init-fix

Fix HoTT syncing issue with receiver on startup.
HOTFIX: Added start / stop syntax to GPIO led command
Merge pull request #287 from DrTon/sdlog2

sdlog2 - new APM compatible logger
Add detailed documentation for SO3 gains tuning.
USB nsh has been removed.
Merge pull request #284 from limhyon/master

Nonlinear complementary SO(3) filter has been implemented.
Removed big RAM consumer (inactive filter)