MPU9250 Calibration using Python and a Raspberry Pi Computer

Calibration procedure for the MPU9250's accelerometer, gyroscope, and magnetometer using Python and a Raspberry Pi Computer.

Full tutorials at the following links:

• Calibration of an Inertial Measurement Unit (IMU) with Raspberry Pi - Part I
• Gyroscope and Accelerometer Calibration with Raspberry Pi
• Calibration of a Magnetometer with Raspberry Pi

- Wiring Diagram -

Power is supplied to the MPU9250 via the 3.3V/GND pins on the Raspberry Pi computer. The MPU9250 board communicates with the RPi over its Inter-Integrated Circuit (I²C) pins, labeled SDA/SCL on both the RPi and MPU9265 boards. On the RPi, SDA is located on hardware pin 3, and SCL is located on hardware pin 5.

- Python Library Installs and IMU Tests -

Install the following Python packages onto the Raspberry Pi:

pi@raspberrypi~ $ sudo pip3 install scipy matplotlib numpy
pi@raspberrypi~ $ sudo apt-get install libatlas-base-dev

Upon successful of the library installs above, download the mpu9250_i2c.py (the main backend for reading the MPU9250) from the repository along with the imu_test.py code.

• Run the imu_test.py

Verify that the 9 variables are being outputted similar to the screenshot below:

- Calibration Outline -

The calibration procedure uses a uniform cube to calibrate each sensor on the IMU (accel, gyro, mag). There are different procedures involved in calibrating each sensor, which can be broken down as follows:

• Gyroscope: calibrate under steady conditions
• Accelerometer: calibrate under graviation for each axis
• Magnetometer: calibrate under 360 degree rotation for each axis

Keeping in mind the coordinate reference for the MPU9250:

- Full Calibration and Real-Time Output -

The plot below is an example output of the following script:

• mpu9250_full_calibration.py

- Gyroscope Calibration Output -

The plot below is an example output of the following script:

• gyroscope_calibration.py

- Accelerometer Calibration Output -

The plot below is an example output of the following script:

• accel_calibration.py

- Displacement Approximated from Accelerometer Double Integration -

The plot below is an example output of the following script:

• accel_integration.py

- Magnetometer Hard Iron Offset -

The plot below is an example output of the following script:

• mag_hard_calibration.py