Troubleshooting & FAQ¶

I2C Permission Denied¶

Error: Failed to open I2C device: /dev/i2c-1 (Permission denied) Cause: The user running the binary does not have access to the hardware I2C bus. Solution: Add your user to the i2c group:

sudo usermod -aG i2c $USER

Then log out and log back in.

BNO055 Clock Stretching (I2C Lockups on Raspberry Pi)¶

Error: [Warning] Temporary communication dropout appears frequently. Cause: The Broadcom I2C hardware on Raspberry Pi has a known bug handling the BNO055’s clock stretching, causing the kernel driver to timeout. Solution:

Lower the I2C baudrate. Edit /boot/firmware/config.txt (or /boot/config.txt) and set:
```
dtparam=i2c_arm=on,i2c_arm_baudrate=10000
```
(The BNO055 supports up to 400kHz, but 10kHz to 50kHz is significantly more stable on the Raspberry Pi).
Reboot the Pi.

Hardware Lockups or Unresponsive Sensor¶

Error: [Error] I2C read failed continuously or no data is being published, even after Auto-Recovery kicks in. Cause: The BNO055 internal microcontroller occasionally crashes or permanently locks the I2C/UART bus when exposed to severe voltage spikes or EM interference. Solution:

You can force a complete software hardware-reset without rebooting your computer by calling the ~/reset service:
```
ros2 service call /bno055_publisher_node/reset std_srvs/srv/Trigger
```
This invokes the SYS_TRIGGER register, power cycles the internal logic, and restores your previous operating mode.

Sensor Calibration is Lost on Reboot¶

Error: The heading (Yaw) drifts immediately after power-on. Cause: The BNO055 does not have internal non-volatile memory for calibration profiles. It loses its calibration every time it loses power. Solution: Use the provided calibrate_imu example to generate a bno055_calib.bin file, then load it in your code immediately after begin():

imu.loadCalibrationFile("bno055_calib.bin");

Why isn’t the Magnetometer working indoors?¶

Error: Calibration status for Mag is always 0 or 1, and heading is highly erratic. Cause: Indoor environments with heavy metal structures, motors, and power lines cause severe magnetic distortion. Solution: Do not use NDOF mode indoors. Switch to IMUPlus mode:

imu.begin(bno055lib::OpMode::IMUPlus);

IMUPlus mode ignores the magnetometer and provides a relative heading using only the high-precision gyroscope and accelerometer.

ROS 2 Specific Troubleshooting¶

Intra-Process Zero-Copy Communication is not taking effect¶

Error: High CPU/Memory overhead still present; pointers are not being passed directly. Cause: For ROS 2 to optimize message passing via zero-copy, the publishing node and the subscribing node must:

Be loaded into the same component container (single process).
Utilize std::unique_ptr and std::move() for publishing (which bno055_publisher_node does by default).
Both have use_intra_process_comms option enabled. Solution: When creating your pipeline, compose the BNO055 component and your subscriber component inside a single container executable (using rclcpp_components) and set use_intra_process_comms to True in the launch parameters.

Lifecycle Node fails to publish data immediately¶

Error: The lifecycle node starts up, but ros2 topic echo /imu/data outputs nothing. Cause: ROS 2 Lifecycle Nodes start in the Unconfigured state. They do not start the timer or open hardware connections until transitioned. Solution: Trigger the state transitions using the ROS 2 lifecycle CLI:

ros2 lifecycle set /bno055_lifecycle_publisher_node configure
ros2 lifecycle set /bno055_lifecycle_publisher_node activate

You can verify the current node state with:

ros2 lifecycle get /bno055_lifecycle_publisher_node