BMI088 IMU library

A Python library for the Bosch BMI088 IMU over I2C, with built-in AHRS sensor fusion and ready-to-use helpers for robotics development.

Installation

From PyPI:

pip install imu-bmi088

From source:

pip install -e .

Quick start

from bmi088 import BMI088

with BMI088(i2c_bus=1) as imu:
    acc  = imu.read_accelerometer()        # ndarray (3,) in g
    gyro = imu.read_gyroscope()            # ndarray (3,) in rad/s
    quat = imu.get_quat(dt=0.01)           # ndarray (4,) (w, x, y, z)
    roll, pitch, yaw = imu.get_euler(dt=0.01, degrees=True)

Features

• Raw accelerometer / gyroscope / temperature reads
• Orientation fusion via Madgwick, Mahony, EKF, or Tilt (selectable)
• Output as quaternion, ZYX Euler angles, or 3×3 rotation matrix
• Gyroscope bias auto-calibration; accelerometer offset/scale calibration
• Gravity-compensated linear acceleration
• Tilt (roll/pitch) directly from accelerometer
• Free-fall detection
• Background-thread streamer for low-latency control loops
• Context-manager support (with BMI088(...) as imu:)

Configuration

from bmi088 import BMI088, AccRange, AccBandwidth, GyroRange, GyroBandwidth

imu = BMI088(
    i2c_bus=1,
    acc_range=AccRange.RANGE_6G,
    acc_bandwidth=AccBandwidth.BANDWIDTH_100,
    gyro_range=GyroRange.RANGE_500_DPS,
    gyro_bandwidth=GyroBandwidth.BANDWIDTH_100,
    filter_type="madgwick",   # "madgwick" | "mahony" | "ekf" | "tilt"
)

Reading raw data

acc  = imu.read_accelerometer(m_per_s2=False)   # default: g
gyro = imu.read_gyroscope(deg_per_s=False)      # default: rad/s
temp = imu.read_temperature()                   # °C

Returned arrays are NumPy ndarray of shape (3,) and are indexable like tuples (acc[0], acc[1], acc[2]).

Orientation

dt is the time step in seconds since the previous update.

quat   = imu.get_quat(dt)                       # (w, x, y, z)
euler  = imu.get_euler(dt, degrees=True)        # (roll, pitch, yaw)
matrix = imu.get_rotation_matrix(dt)            # 3x3 body-to-world
imu.reset_orientation()                         # reset fused quaternion to identity

For a quick gravity-only estimate (no gyro, no yaw):

roll, pitch = imu.get_tilt(degrees=True)

Calibration

Gyroscope bias — keep the sensor still and call:

bias = imu.calibrate_gyro(samples=200)          # rad/s, stored on the instance

Bias is subtracted automatically on every read_gyroscope().

To apply pre-computed values:

imu.set_gyro_bias([bx, by, bz])                 # rad/s
imu.set_acc_calibration(offset=[ox, oy, oz],    # g
                        scale=[sx, sy, sz])

Calibrated accelerometer reading is (raw_g - offset) * scale.

Robotics derivatives

gravity_body = imu.get_gravity(dt)              # gravity unit vector in body frame
linear_acc   = imu.read_linear_acceleration(dt, m_per_s2=True)  # gravity-removed
falling      = imu.is_free_fall(threshold_g=0.3)

Background streamer

Poll the IMU in a daemon thread and read the latest cached sample without blocking your control loop:

from bmi088 import BMI088, BMI088Streamer

with BMI088(i2c_bus=1) as imu, BMI088Streamer(imu, rate_hz=200) as stream:
    while running:
        acc  = stream.acceleration              # latest sample, thread-safe
        gyro = stream.gyroscope
        quat = stream.quaternion
        ...

Do not call read methods directly on the BMI088 instance while the streamer is running.

Quaternion utilities

Pure-math helpers (no hardware needed). All quaternions use scalar-first convention q = (w, x, y, z).

from bmi088 import (
    quat_to_euler,
    quat_to_matrix,
    quat_normalize,
    quat_conjugate,
    rotate_vector,
)

Examples

See the exemples/ directory:

• accelerometer.py — raw acceleration
• gyroscope.py — raw angular velocity
• quaternion.py — fused orientation as a quaternion
• orientation.py — fused orientation as Euler angles
• linear_acceleration.py — gyro calibration + gravity-compensated acceleration + free-fall detection
• streamer.py — background-thread streaming

API reference

BMI088

• read_accelerometer(m_per_s2=False) — calibrated acceleration, g or m/s²
• read_gyroscope(deg_per_s=False) — bias-corrected angular velocity, rad/s or deg/s
• read_temperature() — temperature in °C
• get_quat(dt, acc=None, gyro=None) — update and return fused quaternion
• get_euler(dt, degrees=False) — roll, pitch, yaw
• get_rotation_matrix(dt) — 3×3 body-to-world matrix
• get_tilt(degrees=False) — roll, pitch from accelerometer alone
• get_gravity(dt) — gravity unit vector in body frame
• read_linear_acceleration(dt, m_per_s2=False) — gravity-compensated acceleration
• is_free_fall(threshold_g=0.3) — free-fall detector
• calibrate_gyro(samples=200, delay=0.005) — estimate and store gyro bias
• set_gyro_bias(bias) — apply external gyro bias
• set_acc_calibration(offset, scale) — apply external accelerometer calibration
• reset_orientation() — reset fused quaternion to identity
• close() / __exit__ — release the I2C bus

BMI088Streamer

• start() / stop(timeout=1.0) — manage the polling thread
• acceleration — latest acceleration (g)
• gyroscope — latest angular velocity (rad/s)
• quaternion — latest fused quaternion (if enabled)
• timestamp — time.monotonic() of the latest sample