lerobot-find-port

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Command

lerobot-find-port

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Overview

• Lists all available serial ports
• Prompts you to disconnect your robot’s USB cable
• Detects which port disappeared
• Reports the port name for use in configuration

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How It Works

1. Scan: Lists all serial ports before disconnection
2. Wait: Prompts you to unplug the USB cable
3. Compare: Lists ports again and finds the difference
4. Report: Shows the port that disappeared (your robot’s port)

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Usage Example

lerobot-find-port

Finding all available ports for the MotorsBus.
Ports before disconnecting: ['/dev/ttyUSB0', '/dev/ttyUSB1', '/dev/ttyACM0']
Remove the USB cable from your MotorsBus and press Enter when done.
[User unplugs cable and presses Enter]
The port of this MotorsBus is '/dev/ttyUSB0'
Reconnect the USB cable.

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Platform-Specific Behavior

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Linux/macOS

• /dev/ttyUSB0, /dev/ttyUSB1 (USB serial adapters)
• /dev/ttyACM0, /dev/ttyACM1 (USB CDC devices)
• /dev/tty.usbserial-*, /dev/tty.usbmodem-* (macOS)

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Windows

• COM1, COM3, COM4, etc.

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Using the Port in Configuration

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Recording

lerobot-record \
  --robot.type=so100_follower \
  --robot.port=/dev/ttyUSB0 \
  --robot.id=follower \
  --teleop.type=so100_leader \
  --teleop.port=/dev/ttyUSB1 \
  --teleop.id=leader

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Calibration

lerobot-calibrate \
  --robot.type=so100_follower \
  --robot.port=/dev/ttyUSB0 \
  --robot.id=follower

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Setup Motors

lerobot-setup-motors \
  --robot.type=so100_follower \
  --robot.port=/dev/ttyUSB0

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Multiple Devices

1. Find the first device:
   lerobot-find-port
   # Result: /dev/ttyUSB0
   
2. Reconnect first device
3. Connect second device
4. Find the second device:
   lerobot-find-port
   # Result: /dev/ttyUSB1
   

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Troubleshooting

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No Port Difference Detected

Could not detect the port. No difference was found ([])

• Ensure you actually unplugged the USB cable
• Wait a moment after unplugging before pressing Enter
• Try a different USB cable
• Check device is powered on when plugged in
• On Linux, ensure you have permission to access serial ports

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Multiple Ports Disappeared

Could not detect the port. More than one port was found (['/dev/ttyUSB0', '/dev/ttyUSB1'])

• Only one device should be connected initially
• Disconnect other USB serial devices
• Run the script with fewer devices connected

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Permission Denied (Linux)

# Add user to dialout group
sudo usermod -a -G dialout $USER

# Or add to tty group
sudo usermod -a -G tty $USER

# Log out and back in for changes to take effect

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Port Names Change on Reboot (Linux)

1. Find device serial number:
   udevadm info --name=/dev/ttyUSB0 | grep ID_SERIAL
   
2. Create udev rule in /etc/udev/rules.d/99-robot.rules:
   SUBSYSTEM=="tty", ATTRS{serial}="FTDI123456", SYMLINK+="robot_follower"
   
3. Reload udev rules:
   sudo udevadm control --reload-rules
   sudo udevadm trigger
   
4. Use stable name:
   --robot.port=/dev/robot_follower
   

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Alternative Methods

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Manual Port Listing (Linux)

# List all tty devices
ls /dev/tty*

# List with details
ls -l /dev/ttyUSB* /dev/ttyACM*

# Watch devices as you plug/unplug
watch -n 0.5 'ls /dev/ttyUSB* /dev/ttyACM* 2>/dev/null'

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Using dmesg (Linux)

# Plug in device and check kernel messages
dmesg | tail -20

# Look for lines like:
# [12345.678] usb 1-1: FTDI USB Serial Device converter now attached to ttyUSB0

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Device Manager (Windows)

1. Open Device Manager
2. Expand “Ports (COM & LPT)”
3. Unplug device and watch which port disappears
4. Plug back in to confirm

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Programmatic Usage

from lerobot.scripts.lerobot_find_port import find_port

# Interactive detection
find_port()

# Or use the helper function
from lerobot.scripts.lerobot_find_port import find_available_ports

# List all ports
ports = find_available_ports()
print(f"Available ports: {ports}")

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See Also

• lerobot-calibrate - Calibrate robot motors
• lerobot-setup-motors - Configure motor IDs and baudrate
• lerobot-record - Record robot demonstrations
• Robot API - Robot connection and control