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Star Arm 102 FAQ

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 command 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 servo reset caused by insufficient voltage.

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: Python SDK, ROS2, or LeRobot.
  • Operating system version, Python version, and ROS2 version.
  • serial port device list and run command.
  • Complete error message or terminal log.
  • Whether you are using Star Arm 102-LD, Star Arm 102-FL, or a Leader + Follower combination.

Submission entry: Star-Arm-102 Issues