Inertial Measurement Unit (IMU)

The hardware_io.imu package provides a small interface for reading linear acceleration and angular velocity from an inertial measurement unit. The included Mpu6050Imu implementation communicates with an MPU-6050 over I2C.

Measurements are returned as immutable Vector3 values in SI units:

• Acceleration: meters per second squared (m/s²)
• Angular velocity: radians per second (rad/s)

The package reports raw sensor measurements. Calibration, filtering, attitude estimation, and application behavior belong in higher-level components.

Hardware Setup

Connect the MPU-6050 to the host’s I2C bus:

Check the voltage requirements of the specific breakout board before wiring it. Enable I2C on Raspberry Pi OS:

sudo raspi-config

Choose Interface Options, enable I2C, and reboot if prompted. Verify that the device is visible:

i2cdetect -y 1

The default MPU-6050 address is 0x68. Boards that expose the AD0 pin can typically use 0x69 when AD0 is high.

Installation

From the project root, install the MPU-6050 feature bundle:

scripts/installers/host_setup.sh --feature mpu6050

This installs i2c-tools, Adafruit Blinka, and the Adafruit CircuitPython MPU-6050 driver. To install only the Python dependencies in an existing environment:

python3 -m pip install adafruit-blinka adafruit-circuitpython-mpu6050

Usage

from hardware_io.imu import Mpu6050Imu


imu = Mpu6050Imu()
imu.start()

try:
    acceleration = imu.get_acceleration_mps2()
    angular_velocity = imu.get_angular_velocity_rad_s()

    print(
        f"acceleration: x={acceleration.x:.3f}, "
        f"y={acceleration.y:.3f}, z={acceleration.z:.3f} m/s²"
    )
    print(
        f"angular velocity: x={angular_velocity.x:.4f}, "
        f"y={angular_velocity.y:.4f}, "
        f"z={angular_velocity.z:.4f} rad/s"
    )
finally:
    imu.stop()

Call start() before reading the sensor and stop() when finished. Repeated calls to start() are safe. Reading before startup or after shutdown raises a RuntimeError.

To use a non-default address:

imu = Mpu6050Imu(address=0x69)

An existing CircuitPython-compatible I2C bus can also be shared:

import board

from hardware_io.imu import Mpu6050Imu


i2c = board.I2C()
imu = Mpu6050Imu(i2c_bus=i2c)

When a bus is supplied by the caller, stop() leaves that bus open. When the driver creates the default bus, stop() releases it.

Interface

Hardware-independent consumers can depend on ImuIf:

from hardware_io.imu import ImuIf


def read_motion(imu: ImuIf) -> None:
    acceleration = imu.get_acceleration_mps2()
    angular_velocity = imu.get_angular_velocity_rad_s()

ImuIf defines:

• start() — initialize the device
• stop() — release owned resources
• is_connected() — report whether initialization succeeded
• get_acceleration_mps2() — return an acceleration Vector3
• get_angular_velocity_rad_s() — return an angular-velocity Vector3

Component Test

Run the live hardware test from the project root:

python3 -m hardware_io.imu.component_test.imu_cli

The CLI prints acceleration and angular velocity every 0.2 seconds. Press Ctrl+C to stop it.

Read one sample and exit:

python3 -m hardware_io.imu.component_test.imu_cli --once

Use a different address or sampling interval:

python3 -m hardware_io.imu.component_test.imu_cli \
    --address 0x69 \
    --interval 0.5

Run the CLI with --help to see all options.

Troubleshooting

• If i2cdetect does not show the sensor, check power, ground, SDA, SCL, the selected I2C bus, and whether I2C is enabled.
• If initialization fails at 0x68, scan the bus and try --address 0x69 if that is the address reported.
• If Python reports a missing MPU-6050 or board module, install the dependencies listed above in the same environment used to run the CLI.
• If access to the I2C device is denied, check the permissions and group ownership of /dev/i2c-* for the host system.