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Maintenance & Support

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Connection and Serial Port

What should I do if /dev/ttyUSB0 or /dev/ttyUSB1 cannot be found?

First confirm that the USB cable, UC-01, and robotic arm power supply are working normally, and then run the following commands to check the device:

ls -l /dev/ttyUSB*
lsusb
sudo dmesg | grep ttyUSB

If the device exists but does not have permission, run:

sudo chmod 777 /dev/ttyUSB*

If the serial port is occupied by brltty, you can try uninstalling it:

sudo apt remove brltty

What should I do if the Serial Port connection fails?

  • Check whether the USB cable is loose. Replace the USB cable or USB port if necessary.
  • Confirm that the Leader and Follower port numbers are configured correctly.
  • Confirm that the robotic arm power is on and the servo communication cable is connected reliably.
  • Confirm that the baud rate in the program is 1000000.
  • If a serial-related exception occurs in the ROS2 driver, run sudo apt install --reinstall python3-serial.

What should I do if the Follower robotic arm does not follow the Leader?

  • Check whether LEADER_PORT_NAME and FOLLOWER_PORT_NAME are swapped.
  • Confirm that both robotic arms are recognized by the system as serial port devices.
  • Check whether the servo IDs match the example program.
  • Check whether the power supply is stable to avoid a servo reset caused by insufficient voltage.

Where can I find drivers and configuration tools?

Calibration, Cameras and ACT

What if calibration is missing or joint names do not match?

Check that the device type, plugin version and robot.id match those used during calibration. The released ACT example and other LeRobot integrations may use different joint names, units and calibration files. Do not simply replace device type names or copy calibration files from another integration. Start with Versions and Compatibility, then check the corresponding procedure.

What if a camera will not open, views are swapped or model movements are unstable?

Stop the real arm first, then check camera device paths, access by other programs and input names. The ACT example requires up for the overhead view and front for the front view. Resolution, camera placement, lighting and objects must also match. Follow the example checklist and retain records of failed trials.

Routine Checks and Maintenance

  • Before each run, check the base mounting, fasteners, cable wear and joint clearances. Stop and inspect any loose parts or unusual sounds.
  • Disconnect power before changing wiring or replacing structural parts, then follow Assembly Preparation and Checks.
  • Hardware zero, factory parameters and LeRobot calibration are different operations. Do not reset all parameters to resolve an ordinary connection issue. When needed, follow the corresponding procedure in the Robot Arm Configuration Tool Guide.
  • After replacing a servo, structural parts or software versions, recheck communication, direction and calibration before testing small movements.

Python SDK

What scenarios is the Python SDK suitable for?

The Python SDK is suitable for quick verification, teaching demonstrations, and basic teleoperation. It is easy to configure and usually only requires installing pyserial and fashionstar-uart-sdk, then confirming the two serial port devices.

What should I do if the control frequency is low?

  • Confirm that serial port communication is normal and that there are no frequent reconnects or errors.
  • Reduce high-load background programs.
  • Use a stable USB port where possible, and replace the USB cable if necessary.
  • Confirm that the servo power supplies for Leader and Follower are stable.

ROS2 / MoveIt / Gazebo

What should I do if ROS2 compilation fails?

Confirm that ROS2 Humble and MoveIt2 are installed, and compile in the correct directory:

source /opt/ros/humble/setup.bash
cd ~/Star-Arm-102/ROS2_HUMBLE
colcon build
source install/setup.bash

If MoveIt2 dependencies are missing, run:

sudo apt install ros-humble-moveit*

What should I do if the RViz2 interface flickers?

Try disabling Qt auto scaling and then restart RViz2:

export QT_AUTO_SCREEN_SCALE_FACTOR=0

What should I do if Gazebo cannot start or remains abnormal after closing?

First close other running ROS2 and Gazebo nodes. If Gazebo has residual processes, run:

killall -9 gazebo gzserver gzclient ros2

Then restart the Gazebo and MoveIt2 launch commands.

Will the real robotic arm move after starting the driver?

Yes. After the real robotic arm driver starts, the arm moves to the zero position. Before running the command, confirm that there are no people, tools, cables, or other obstacles around the robotic arm.

Teaching and Trajectories

How do I enter teaching mode?

In teaching mode, the joints need to be unlocked:

ros2 run robo_driver driver --ros-args -p lock:='disable'

Then record the trajectory through ros2_bag_recorder:

ros2 run ros2_bag_recorder bag_recorder --ros-args -p dataset:=star/record-test

What should I do if the recording path already exists?

You can delete the old path or use a new dataset path:

rm -rf star/record-test
ros2 run ros2_bag_recorder bag_recorder --ros-args -p dataset:=star/record-test2

Drawings and Models

Where can I download drawings and 3D printing models?

Why are some resources updated faster on GitHub or MakerWorld?

The GitHub repository maintains source code, hardware resources, and the README. MakerWorld is used to publish 3D printing models. The Wiki periodically synchronizes key content, but if you need the latest source files, check the corresponding source site first.

Getting Support

If the issue still cannot be resolved, prepare the following information before submitting an Issue:

  • Control method used: web tool, Python SDK, ROS2 or LeRobot, with the relevant repository commit or plugin versions.
  • Operating system version, Python version, and ROS2 version.
  • The serial port device list and run command.
  • Complete error message or terminal log.
  • Whether you are using Star Arm 102-LD, HD, FL, or a Leader + Follower combination.
  • For camera or model issues, include camera names, scene photographs, model version, reproduction steps, and expected and actual results.

Submission entry: Star-Arm-102 Issues