Software Setup

LeRobot Installation

LeRobot is the only software package you need for the SO-101. It handles servo communication, calibration, teleop, and data recording.

Create a virtual environment

python -m venv ~/.venvs/so101
source ~/.venvs/so101/bin/activate   # Windows: .venvs\so101\Scripts\activate

Install LeRobot

pip install lerobot

Verify installation

python -c "import lerobot; print(lerobot.__version__)"

Install from source (optional — for latest features)

git clone https://github.com/huggingface/lerobot.git
cd lerobot
pip install -e ".[so101]"

SO-101 Robot Configuration

LeRobot includes a built-in SO-101 robot config. You specify the USB port for the follower arm (and leader arm if using two-arm teleop).

Find your USB port

# Linux / macOS
ls /dev/ttyUSB*    # typical: /dev/ttyUSB0, /dev/ttyUSB1
ls /dev/tty.usbserial*   # macOS alternative

# Windows — check Device Manager → Ports → COMx

SO-101 config YAML

LeRobot uses an inline config on the command line or a YAML file. For a single-arm setup:

# ~/.lerobot/robots/so101_follower.yaml
robot_type: so101
port: /dev/ttyUSB0   # update to your port
cameras:
  wrist_cam:
    type: opencv
    index_or_path: 0
    fps: 30
    width: 640
    height: 480

Two-arm (leader–follower) config

# ~/.lerobot/robots/so101_bimanual.yaml
robot_type: so101
port: /dev/ttyUSB1      # follower arm
leader_arms:
  main:
    type: so101
    port: /dev/ttyUSB0   # leader arm
cameras:
  top_cam:
    type: opencv
    index_or_path: 0
    fps: 30
    width: 640
    height: 480

Test connection

python -m lerobot.scripts.control_robot \
  --robot.type=so101 \
  --robot.port=/dev/ttyUSB0 \
  --control.type=none   # just connects and reads state

You should see joint position readings printed. If you get a port error, check Troubleshooting.

Servo Calibration

Unlike CAN-bus arms that use absolute encoders, the Feetech STS3215 servos need calibration to define their zero positions. LeRobot handles this automatically.

Run calibration

python -m lerobot.scripts.control_robot \
  --robot.type=so101 \
  --robot.port=/dev/ttyUSB0 \
  --control.type=calibrate

The script will prompt you to move the arm to specific positions (home, min, max for each joint) and press Enter at each position. It saves calibration data to ~/.cache/huggingface/lerobot/calibration/so101/.

Calibration positions

LeRobot will ask you to position each joint at three poses:

• Home position: arm fully extended, end-effector pointing forward
• Zero torque position: arm hanging naturally under gravity
• 90-degree reference: each joint at its midpoint

Verify calibration

python -m lerobot.scripts.control_robot \
  --robot.type=so101 \
  --robot.port=/dev/ttyUSB0 \
  --control.type=teleoperate   # move arm by hand to verify joint readout

Move the arm manually (compliance mode). Joint positions should read near zero at home and increase/decrease smoothly as you move each joint.

Leader–Follower Teleoperation

The SO-101 is designed for leader–follower teleoperation: one arm (leader) captures your hand movements, and the second arm (follower) mirrors them in real time. This produces the highest quality training demonstrations.

Start leader–follower teleop

python -m lerobot.scripts.control_robot \
  --robot.type=so101 \
  --robot.port=/dev/ttyUSB1 \
  --robot.leader_arms.main.type=so101 \
  --robot.leader_arms.main.port=/dev/ttyUSB0 \
  --control.type=teleoperate

Single-arm keyboard teleop (no second arm)

If you only have one arm, use keyboard control mode:

python -m lerobot.scripts.control_robot \
  --robot.type=so101 \
  --robot.port=/dev/ttyUSB0 \
  --control.type=teleoperate \
  --control.teleop_keys=true

Compliance / gravity compensation mode

Put the leader arm into low-torque mode so you can move it freely with your hand:

python -c "
from lerobot.common.robot_devices.robots.so101 import SO101Robot
robot = SO101Robot(port='/dev/ttyUSB0')
robot.connect()
robot.set_compliance_mode(True)   # arm moves freely under hand guidance
"

Python API Quickstart

You can control the SO-101 directly via the LeRobot robot API without the CLI scripts.

Basic joint control

from lerobot.common.robot_devices.robots.so101 import SO101Robot
import torch

robot = SO101Robot(port="/dev/ttyUSB0")
robot.connect()

# Read current joint positions (6 DOF)
obs = robot.capture_observation()
print("Joint positions:", obs["observation.state"])

# Send joint position command (in degrees, normalized to [-1, 1] range)
action = torch.zeros(6)   # all joints to zero position
robot.send_action(action)

robot.disconnect()

Gravity compensation (backdrivable mode)

from lerobot.common.robot_devices.robots.so101 import SO101Robot

robot = SO101Robot(port="/dev/ttyUSB0")
robot.connect()

# Enable backdrive — arm can be moved freely by hand
robot.set_compliance_mode(True)

import time
for _ in range(100):
    obs = robot.capture_observation()
    print(obs["observation.state"])   # prints live joint positions as you move arm
    time.sleep(0.02)

robot.disconnect()

Reading servo status

from lerobot.common.robot_devices.motors.feetech import FeetechMotorsBus

bus = FeetechMotorsBus(port="/dev/ttyUSB0",
                       motors={"joint1": (1, "sts3215"),
                               "joint2": (2, "sts3215"),
                               "joint3": (3, "sts3215"),
                               "joint4": (4, "sts3215"),
                               "joint5": (5, "sts3215"),
                               "gripper": (6, "sts3215")})
bus.connect()
positions = bus.read("Present_Position", ["joint1", "joint2", "joint3"])
print("Positions:", positions)
bus.disconnect()

Top 3 Common Issues

# Check if the device is listed
ls /dev/ttyUSB*   # Linux
ls /dev/tty.usbserial*   # macOS

# Linux: add yourself to the dialout group (requires logout)
sudo usermod -aG dialout $USER

# Windows: install CP2102 or CH340 USB driver,
# then check Device Manager for COM port number

# 1. Verify 5V power supply is connected and LED on servo board is on
# 2. Check all servo daisy-chain cables are fully seated
# 3. Try scanning for servos directly:
python -c "
from lerobot.common.robot_devices.motors.feetech import FeetechMotorsBus
bus = FeetechMotorsBus('/dev/ttyUSB0', motors={})
bus.connect()
ids = bus.find_motor_ids()
print('Found motor IDs:', ids)
bus.disconnect()
"

# Check calibration file location
ls ~/.cache/huggingface/lerobot/calibration/so101/

# Re-run calibration if the file is missing
python -m lerobot.scripts.control_robot \
  --robot.type=so101 \
  --robot.port=/dev/ttyUSB0 \
  --control.type=calibrate

# Pass explicit calibration path if needed
python -m lerobot.scripts.control_robot \
  --robot.type=so101 \
  --robot.port=/dev/ttyUSB0 \
  --robot.calibration_dir=/path/to/calibration \
  --control.type=teleoperate

Still stuck? Ask on the SO-101 Forum or check the LeRobot GitHub issues.