View source for Drone compass calibration

back to [[Drone control]]

== Calibration setup ==

Once the controller is mounted on the drone, it is time to calibrate the compass.

Upload the calibration firmware to the Teensy (using the Arduino GUI)

Run the calibration app - in the bin directory for Linux, or here for other platforms https://www.pjrc.com/store/prop_shield.html 

=== Compass calibration app ===

If on Linux go to 

 cd mobotware/drone_ctrl/trunk/CalibrateSensors
 ./MotionCal

[[File:compass-calibrate-app.png | 400px]]

Calibration app - with a fair set of values.
Runs directly on Ubuntu 18.04, for Ubuntu 20.04 see below

==== Ubuntu 20.04 ====

The calibration app is rather old, so it asks for libpng12.so.0.

I managed to install it through package nsight-systems

 sudo apt install nsight-systems
 cd /usr/lib/x86_64-linux-gnu
 sudo ln -s ../nsight-systems/Host-x86_64/libpng12.so.0

Another option is to get the source code, but the Makefile asks for wxwidgets/3.0.2.gtk2-opengl/bin/wx-config, which I couldn't find.

== Arduino code for compas calibration ==

In arduino open the calibration firmware in mobotware/drone_ctrl/trunk/CalibrateSensors

Run the arduino version, where you have installed the Teensyduino and open the CalibrateSensors.ino

In my case
 
 cd mobotware/drone_ctrl/trunk/CalibrateSensors
 /home/chr/Downloads/arduino-1.8.13/arduino 

* Select board Teensy3.5
* Compile
* upload (to /dev/ttyACM0 or the port to which the Teensy is connected)

[[File:arduino-compass-calibrate.png | 400px]]

Arduino with sensor calibration code. Sending raw data to app and receive the calibration data when send is pressed on the calibration app.

== Rotate drone and save result ==

In the Calibration app, clear the buffer when you are ready to rotate the drome in all directions.

* press 'clear'

Rotate the drone in all directions, until you get a sphere or an ellipsoid as in the figure above.

I got a 'Fit error' of 2.3% and gaps of just 1.1% - seems to be OK, in the above figure it is even lower.

When it looks good, upload to the Teensy by "Send Cal"

* press 'send Cal'

And the reply should be a green tick-mark as shown.

It is then saved in the Teensy flash (addresses below the first 512 bytes, that is not used by the drone firmware).

== Reload drone control firmware ==

Go back to the drone_ctrl directory and reload

 cd mobotware/drone_ctrl/trunk/drone_ctrl
 make
 make upload

The new compas calibration should be in effect.