MPU6050 Attitude Estimator

Overview

This project implements register-level MPU6050 bring-up, calibration, sensor data acquisition, and roll/pitch attitude estimation.

The repository currently covers two versions of the same project:

• An Arduino Nano Every version used for initial bring-up, calibration, validation, and attitude-estimation development
• An STM32 version used to port the same pipeline to a more industry-standard embedded platform, now running on a FreeRTOS task-based architecture with improved timing control and a cleaner path toward higher-rate sampling

Rather than relying on third-party MPU6050 libraries, all sensor communication, configuration, calibration, and attitude estimation are implemented from scratch using direct I2C register access and the MPU6050 datasheet.

Current capabilities include:

• Register-level MPU6050 configuration
• Accelerometer calibration
• Gyroscope calibration
• Raw sensor data acquisition
• Physical unit conversion
• Roll and pitch estimation
• Gyroscope attitude integration
• Complementary filtering
• Fixed-rate sampling and timing control
• FreeRTOS task-based architecture (STM32)
• Modular software organization

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Project Status

Active development.

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Hardware

Arduino Version

• Arduino Nano Every
• MPU6050 IMU Module
• Breadboard
• Jumper Wires

STM32 Version

• STM32 Development Board
• MPU6050 IMU Module
• Breadboard
• Jumper Wires

Wiring

MPU6050	Arduino Nano Every	STM32 Version
VCC	3.3V	3.3V
GND	GND	GND
SDA	SDA	I2C SDA
SCL	SCL	I2C SCL

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Features

Accelerometer

The accelerometer is configured for a ±2 g measurement range.

During startup, the system:

1. Collects 500 stationary samples.
2. Computes average offsets for each axis.
3. Accounts for gravity on the Z-axis.
4. Stores calibration biases.
5. Converts readings into g and m/s².

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Gyroscope

The gyroscope is configured for a ±250 °/s measurement range.

During startup, the system:

1. Collects 500 stationary samples.
2. Computes average bias values.
3. Stores the offsets.
4. Converts readings into degrees per second.

Values close to zero while stationary indicate successful calibration.

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Attitude Estimation

Roll and pitch are estimated from accelerometer measurements using trigonometric relationships.

A gyroscope attitude estimate is maintained by integrating angular velocity over time.

A complementary filter combines both estimates:

Filtered Angle = α × Gyroscope Estimate + (1 - α) × Accelerometer Estimate

This provides:

• Short-term stability from the gyroscope
• Long-term drift correction from the accelerometer

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Sensor Configuration

Accelerometer

Setting	Value
Full Scale Range	±2 g
Sensitivity	16384 LSB/g

Gyroscope

Setting	Value
Full Scale Range	±250 °/s
Sensitivity	131 LSB/(°/s)

Filtering

Register	Value
DLPF_CFG	3
Sample Rate Divider	9
Effective Sample Rate	100 Hz

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Telemetry Output

The current firmware outputs one compact CSV telemetry line per sample over the serial/UART interface. This format is intended for logging, plotting, and host-side parsing.

CSV Format

time_MS,accel.roll,accel.pitch,gyro.roll,gyro.pitch,filtered.roll,filtered.pitch

Each field represents:

1. time_MS — loop timestamp in milliseconds
2. accel.roll — roll estimate from the accelerometer
3. accel.pitch — pitch estimate from the accelerometer
4. gyro.roll — roll estimate from gyroscope integration only
5. gyro.pitch — pitch estimate from gyroscope integration only
6. filtered.roll — complementary-filtered roll estimate
7. filtered.pitch — complementary-filtered pitch estimate

Example Output

1250,0.842,-1.316,0.905,-1.271,0.904,-1.272
1260,0.851,-1.308,0.914,-1.262,0.913,-1.263
1270,0.847,-1.311,0.923,-1.254,0.921,-1.255

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Building and Running

Arduino Version

1. Open the Arduino/ project in PlatformIO.
2. Build and upload the firmware to the Arduino Nano Every.
3. Open the serial monitor to view the telemetry stream.

STM32 Version

1. Open the STM32_Nucleo_F446RE/ project in your STM32 development environment.
2. Build and flash the firmware to the STM32 board.
3. Open the configured serial/UART output to view the telemetry stream.

The STM32 firmware runs on FreeRTOS, with sensor acquisition, attitude estimation, and telemetry output implemented as separate tasks.

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Repository Layout

Arduino/
  docs/
    architecture.md
    attitude_estimation.md
    calibration.md
    roadmap.md
    testing.md

  include/
    Attitude.h
    Calibration.h
    MPU6050.h

  src/
    Attitude.cpp
    Calibration.cpp
    main.cpp
    MPU6050.cpp

  .gitignore
  platformio.ini

STM32_Nucleo_F446RE/
  Core/
    Inc/
      attitude.h
      calibration.h
      main.h
      mpu6050.h
      stm32f4xx_hal_conf.h
      stm32f4xx_it.h

    Src/
      attitude.c
      calibration.c
      main.c
      mpu6050.c
      stm32f4xx_hal_msp.c
      stm32f4xx_it.c
      syscalls.c
      sysmem.c
      system_stm32f4xx.c

.gitignore
README.md

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Lessons Learned

This project provided practical experience with:

• Reading technical datasheets
• Register-level embedded programming
• I2C communication
• Sensor calibration techniques
• Noise reduction and filtering
• Converting raw digital measurements into physical units
• Debugging embedded hardware and software systems
• Organizing embedded software into reusable modules

It also served as a foundation for future projects involving sensor fusion, attitude estimation, STM32-based embedded development, and real-time control software.

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Future Work

Immediate

• Improved attitude initialization
• Real-time roll and pitch visualization
• Data logging

Near-term

• Higher-rate sampling and performance optimization
• STM32 refinement and cleanup

Long-term

• Quaternion attitude representation
• Madgwick or Mahony sensor fusion
• Kalman filtering
• 3D orientation tracking
• Motor control integration

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References

MPU6050 Product Specification:
https://invensense.tdk.com/wp-content/uploads/2015/02/MPU-6000-Datasheet1.pdf

MPU6050 Register Map:
https://invensense.tdk.com/wp-content/uploads/2015/02/MPU-6000-Register-Map1.pdf

Arduino Wire Library Documentation:
https://www.arduino.cc/reference/en/language/functions/communication/wire/