IMU

When you have created two breakout boards for the ADXL345 accelerometer and the ITG3200 gyroscope and you have those two nice sensors what you can do? Simple: create an implementation of an Attitude sensor fusion which runs with those chips!

So, I started documenting myself and reading lot of stuff on IMUs (inertial measurement units - composed by an accelerometer and a gyroscope) and MARG sensor (an IMU which also has a magnetometer to sense heading).

One really good article you should read to get started with IMUs is A Guide To using IMU (Accelerometer and Gyroscope Devices) in Embedded Applications available on http://www.starlino.com/ . Also from the same website there is a nice implementation of the theory from the IMU guide: you can find it on Arduino code for simplified Kalman filter. Using a 5DOF IMU.

So, I took the algorithm above and converted it to be used with the ADXL345 and the ITG3200. I came out with two implementations both with parts in Arduino and Processing code (see the attachments to this page below).

IMPORTANT: If you use the IMU Digital Combo Board from Sparkfun you will need to change the address of the Gyroscope from 0x69 in my code to 0x68.

The first implementation simply reads the raw accelerometer and gyroscope values on the Arduino while the Processing code (running on the PC) will compute the sensor fusion algorithm, produce the orientation vector and siplay a nicely oriented cube.

In other implementation all the sensor fusion logic is implemented in Arduino code so it will run embedded in the microcontroller. Looks like Arduino can coupe with that without any problems! So, once the orientation is computed is all sent to the PC where the Processing application will display incoming data and the oriented cube.

You can see a demonstration in the following video:

All the code is available in the attachments below. You can see the circuit in the picture below. Note that these are custom made breakout boards, your pin configurations will vary depending on the schematics of your breakout board. If you have questions just leave a comment below.

The processing programs need to be executed on the Processing IDE, available for download from http://processing.org/
Remember to adjust the serial port configuration in the Processing code to match your connection to the Arduino in your system. Here I use /dev/ttyUSB9, if you are under windows you'll probably have to use something like COM3 or something like that. See in the Arduino IDE under Tools->Serial Port to get the exact value you have to use.