9-axis-IMU

This repository is an implementation of an inertial measurement unit created for private purposes.

Overview

1. Hardware
2. Extern librarys
3. Current state of project
4. Known issues
5. Future projects

Hardware

The Discovery kit STM32F3DISCOVERY was used for the implementation. Following parts are used for the implementation:

1. The microcontroller STM32F303VC
2. The 3 axis digital gyroscope I3G4250D
3. The eCompass module LSM303AGR with a 3 axis digital accelerometer and a 3 axis digital magnetometer

The sensor I3G4250D is connected with the microcontroller via SPI and LSM303AGR is connected via I2C.

Extern librarys

The software was developt with the STM32CubeIDE. Some parts of the main.c and the main.h file are auto generated. The HAL-Library was used for GPIO-Pins, SPI-Communication, I2C-Communication, USB-Communication, Timers, Interrupts, etc. It's files are not included in this repository. Furthermore the library USB_DEVICE from ST was used to create a virtual USB COM port. The USB_DEVICE files are also not included in this repository.

Current state of project

• Library for I3G250D was created based on the HAL-library. The sensor data registers are read with DMA via SPI. After the communication finished a interrupt get called. In the interrupt the angular rate get calculated and low-pass-filtered. The functions can be used with a external interrupt from the data-ready-pin of the sensor.
• Library for LSM303AGR was also created with the HAL-library. The sensor data registers are read with DMA via I2C. After finished communication, sensor value get calculated in interrupt and low-pass filtered. The functions can be used with a external interrupt from the data-ready-pins of the sensor.
• Calculation of pitch, roll and yaw angle based on acceleration, magnetometer and gyroscope data. Sensor fusion of the angles are calculated with a extended Kalman filter. Gyroscope is used for predict current state and the accelerometer and the magnetometer are used to update the estimation.
• send inertial measurement unit data as String or as float values via USB to display it on a computer.

Known issues

• a pitch angle of 90 Degres will result in NaN for all three angles

Future projects

• This project is finished, everything is implemented. Maybe I'll cleanup some parts of the code in the future.