Sample Kalman filtered data from gyro sensor MPU6050 (GY-521) via I2C on a Raspberry Pi

Demonstration of the Sensor Extension Board from https://www.itoffice.eu for Raspberry Pi.

This software prints demo gyro data out in the terminal (stdio/stdout) that in one column shows the effect of the Kalman filter and in another column a complementary filter, compared to no filter in a third column (in reverse order), for as well the roll as the pitch angle.

This C/C++ code is intended to compile and run on a Raspberry Pi. Other hardware than Raspberry Pi might use something different than wiringPiI2C and wiringPi to communicate with the sensor. 'stdio' is a typical Linux library, and microcontrollers might use something entirely different to return visible data.

Regards MPU6050 (GY-521): It has no inbuild magnetometer sensor. Only a I2C master port to communicate with an external that you have to supply extra. A magnetometer is needed to determine the yaw rotation. Consider something like MPU-9250 (https://www.invensense.com/products/motion-tracking/9-axis/mpu-9250/), or extend the MPU-6250 with an HMC5883L.

Copyright (C) 2019 Andreas Chr. Dyhrberg. All rights reserved.

This code is based on the work for the Arduino and Arduino IDE from Kristian Lauszus. With this publication I have ported it to C++ for GCC on Linux on Raspberry Pi, added code, reordered and not at least rewritten it heavily to let it fit to the principles of Clean Code by Robert C. Martin. Credit and thanks to Kristian Lauszus for his initial work.

If you have any suggestions to the code regarding Clean Code, or any other relevant comment, please let me know. (Exceptions to Clean Code are: No lower-camel case, equal signs etc. in columns accross variable lists)

This software may be distributed and modified under the terms of the GNUGeneral Public License version 2 (GPL2) as published by the Free Software Foundation and appearing in the file GPL2.TXT included in the packaging of this file. Please note that GPL2 Section 2[b] requires that all works based on this software must also be made publicly available under the terms of the GPL2 ("Copyleft").

The Kalman filter used is from Kristian Lauszus, TKJ Electronics:

https://github.com/TKJElectronics/KalmanFilter

Note: "The unknown yaw angle ψ represents the rotation from north, but its determination requires the addition of a magnetometer sensor to create an eCompass."

Source for equations and mathematical stuff used:

http://www.freescale.com/files/sensors/doc/app_note/AN3461.pdf

Look at the sample output

https://github.com/itofficeeu/ito-mpu6050-kalman-raspberry/blob/master/ito-mpu6050-kalman_terminal_out_sample.txt