Feetech Motors - LeRobot

LeRobot provides comprehensive support for Feetech servo motors through the FeetechMotorsBus class. Feetech motors are affordable smart servos commonly used in robotics projects, offering position control, velocity feedback, and temperature monitoring.

Overview

Feetech motors communicate via a serial protocol similar to Dynamixel, supporting both Protocol 0 and Protocol 1. LeRobot handles motor communication, calibration, and control through a unified interface. Supported Features:

Position, velocity, and torque control
Real-time position and velocity feedback
Temperature monitoring
Motor calibration and homing
Synchronized read/write for multi-motor control
Drive mode configuration (forward/inverted)

Supported Models

LeRobot supports various Feetech motor series including:

SCS series (SCS15, SCS215, etc.)
STS series (STS3215, STS3032, etc.)
SMS series

Refer to the model tables in the source code for complete compatibility: /home/daytona/workspace/source/src/lerobot/motors/feetech/tables.py

Installation

Hardware Requirements

Feetech servo motors
USB-to-TTL adapter or Feetech serial interface board
Power supply (voltage depends on motor model, typically 6-12V)

Software Dependencies

Install the SCServo SDK:

pip install scservo-sdk

Or install LeRobot with motor support:

pip install lerobot[motors]

Configuration

Motor Configuration

Define your motors in a configuration dictionary:

from lerobot.motors.feetech import FeetechMotorsBus
from lerobot.motors.motors_bus import Motor

# Define motors
motors = {
    "shoulder": Motor(
        id=1,
        model="sts3215",
        # Optional: initial_id if motor needs ID change
    ),
    "elbow": Motor(
        id=2,
        model="sts3215",
    ),
    "wrist": Motor(
        id=3,
        model="sts3215",
    ),
}

# Create motor bus
port = "/dev/ttyUSB0"  # Linux
# port = "COM3"  # Windows
# port = "/dev/cu.usbserial-*"  # macOS

motor_bus = FeetechMotorsBus(
    port=port,
    motors=motors,
    protocol_version=0,  # Use 0 or 1 depending on your motors
)

Protocol Versions

Protocol 0: Older Feetech motors (SCS series)
Protocol 1: Newer Feetech motors (STS series, SMS series)

Check your motor’s documentation to determine which protocol to use. Note that Protocol 1 motors do not support broadcast ping, so motor discovery is slower.

Basic Usage

Connecting to Motors

# Connect and verify motors are present
motor_bus.connect()
print(f"Connected: {motor_bus.is_connected}")

# Configure motors with optimal settings
motor_bus.configure_motors(
    return_delay_time=0,      # Minimize response delay (2µs)
    maximum_acceleration=254,  # Maximum acceleration
    acceleration=254          # Current acceleration
)

From /home/daytona/workspace/source/src/lerobot/motors/feetech/feetech.py:221

Reading Motor State

# Read single motor position
position = motor_bus.read("Present_Position", "shoulder")
print(f"Shoulder position: {position}°")

# Read velocity
velocity = motor_bus.read("Present_Velocity", "shoulder")
print(f"Shoulder velocity: {velocity}°/s")

# Read temperature
temp = motor_bus.read("Present_Temperature", "shoulder")
print(f"Shoulder temperature: {temp}°C")

# Synchronized read from multiple motors
positions = motor_bus.sync_read("Present_Position", ["shoulder", "elbow", "wrist"])
print(f"All positions: {positions}")

Writing Motor Commands

# Write single motor position
motor_bus.write("Goal_Position", "shoulder", 45.0)  # Move to 45 degrees

# Write velocity (if motor supports velocity mode)
motor_bus.write("Goal_Velocity", "shoulder", 100.0)  # 100°/s

# Synchronized write to multiple motors
goal_positions = {
    "shoulder": 45.0,
    "elbow": -30.0,
    "wrist": 90.0,
}
motor_bus.sync_write("Goal_Position", goal_positions)

Torque Control

# Enable torque on specific motors
motor_bus.enable_torque(["shoulder", "elbow"])

# Disable torque (motors will be back-drivable)
motor_bus.disable_torque(["shoulder", "elbow"])

# Enable/disable all motors
motor_bus.enable_torque()  # All motors
motor_bus.disable_torque()  # All motors

Disconnecting

motor_bus.disconnect()

Motor Calibration

Overview

Calibration establishes the mapping between motor positions and robot joint angles. LeRobot uses three calibration parameters per motor:

Homing Offset: Position offset from motor zero to robot zero
Range Min: Minimum allowed position (in motor units)
Range Max: Maximum allowed position (in motor units)

From /home/daytona/workspace/source/src/lerobot/motors/feetech/feetech.py:251

Automatic Calibration

LeRobot provides helper methods for calibration:

from lerobot.motors.motors_bus import MotorCalibration

# Step 1: Record range of motion
print("Move each joint through its full range...")
mins, maxes = motor_bus.record_ranges_of_motion(
    motors=["shoulder", "elbow", "wrist"],
    display_values=True  # Show live positions
)
# Press Enter when done moving joints

print(f"Recorded ranges:")
for motor in mins:
    print(f"  {motor}: {mins[motor]:.1f}° to {maxes[motor]:.1f}°")

# Step 2: Move motors to zero position
print("Manually move each joint to its zero position (robot home pose)...")
input("Press Enter when ready")

# Read current positions as homing offsets
zero_positions = motor_bus.sync_read("Present_Position", ["shoulder", "elbow", "wrist"])

# Step 3: Create calibration
calibration = {}
for motor in motors:
    motor_id = motors[motor].id
    homing_offset = motor_bus._get_half_turn_homings({motor: zero_positions[motor]})[motor]
    
    calibration[motor] = MotorCalibration(
        id=motor_id,
        drive_mode=0,
        homing_offset=int(homing_offset),
        range_min=int(mins[motor]),
        range_max=int(maxes[motor]),
    )

# Step 4: Write calibration to motors
motor_bus.write_calibration(calibration)
print("Calibration complete!")

# Step 5: Verify calibration
if motor_bus.is_calibrated:
    print("✓ Motors are properly calibrated")
else:
    print("✗ Calibration verification failed")

Manual Calibration

You can also create calibration data manually:

from lerobot.motors.motors_bus import MotorCalibration

calibration = {
    "shoulder": MotorCalibration(
        id=1,
        drive_mode=0,
        homing_offset=2048,  # Half-turn offset for zero position
        range_min=1024,      # Minimum safe position
        range_max=3072,      # Maximum safe position
    ),
    # ... other motors
}

motor_bus.write_calibration(calibration)

Reading Calibration

# Read current calibration from motors
current_cal = motor_bus.read_calibration()

for motor, cal in current_cal.items():
    print(f"{motor}:")
    print(f"  Homing Offset: {cal.homing_offset}")
    print(f"  Range: {cal.range_min} to {cal.range_max}")

Advanced Usage

Operating Modes

Feetech motors support multiple operating modes (from /home/daytona/workspace/source/src/lerobot/motors/feetech/feetech.py:44):

from lerobot.motors.feetech.feetech import OperatingMode

# Position servo mode (default)
motor_bus.write("Operating_Mode", "shoulder", OperatingMode.POSITION.value)

# Velocity mode (constant speed)
motor_bus.write("Operating_Mode", "shoulder", OperatingMode.VELOCITY.value)

# PWM mode (open-loop)
motor_bus.write("Operating_Mode", "shoulder", OperatingMode.PWM.value)

# Step servo mode
motor_bus.write("Operating_Mode", "shoulder", OperatingMode.STEP.value)

Drive Mode (Direction Inversion)

Invert motor direction if needed:

from lerobot.motors.feetech.feetech import DriveMode

# Normal direction
motor_bus.write("Drive_Mode", "shoulder", DriveMode.NON_INVERTED.value)

# Inverted direction
motor_bus.write("Drive_Mode", "shoulder", DriveMode.INVERTED.value)

Baudrate Configuration

# Change motor baudrate (requires motor restart)
motor_bus.write("Baudrate", "shoulder", 1_000_000)  # 1 Mbps

# After changing baudrate, reconnect with new rate
motor_bus.disconnect()
motor_bus.set_baudrate(1_000_000)
motor_bus.connect()

PID Tuning

# Read current PID values
kp = motor_bus.read("Position_P_Gain", "shoulder")
ki = motor_bus.read("Position_I_Gain", "shoulder")
kd = motor_bus.read("Position_D_Gain", "shoulder")
print(f"Current PID: P={kp}, I={ki}, D={kd}")

# Write new PID values
motor_bus.write("Position_P_Gain", "shoulder", 32)
motor_bus.write("Position_I_Gain", "shoulder", 0)
motor_bus.write("Position_D_Gain", "shoulder", 8)

Speed and Acceleration Limits

# Set maximum velocity
motor_bus.write("Max_Velocity", "shoulder", 500)  # Units depend on motor model

# Set acceleration (Protocol 0 only)
if motor_bus.protocol_version == 0:
    motor_bus.write("Maximum_Acceleration", "shoulder", 254)
    motor_bus.write("Acceleration", "shoulder", 254)

Finding and Auto-Discovering Motors

Find Single Motor

If you don’t know a motor’s ID or baudrate:

from lerobot.motors.feetech import FeetechMotorsBus
from lerobot.motors.motors_bus import Motor

# Define motor with unknown ID
motors = {
    "unknown_motor": Motor(
        model="sts3215",
        # id will be auto-discovered
    ),
}

motor_bus = FeetechMotorsBus(
    port="/dev/ttyUSB0",
    motors=motors,
    protocol_version=0,
)

# This will scan all baudrates and IDs
baudrate, motor_id = motor_bus._find_single_motor("unknown_motor")
print(f"Found motor at baudrate {baudrate}, ID {motor_id}")

# Update motor configuration
motors["unknown_motor"].id = motor_id

From /home/daytona/workspace/source/src/lerobot/motors/feetech/feetech.py:169

Broadcast Ping (Protocol 0 Only)

Discover all motors on the bus:

# Only works with Protocol 0
if motor_bus.protocol_version == 0:
    motor_bus.connect()
    
    # Find all motors (returns dict of id: model_number)
    found_motors = motor_bus.broadcast_ping()
    
    if found_motors:
        print(f"Found {len(found_motors)} motors:")
        for motor_id, model_num in found_motors.items():
            print(f"  ID {motor_id}: Model {model_num}")
    else:
        print("No motors found")

From /home/daytona/workspace/source/src/lerobot/motors/feetech/feetech.py:405

Troubleshooting

Connection Issues

“Motor not found” error:

Check power supply is connected and adequate for your motors
Verify serial port name (ls /dev/ttyUSB* on Linux)
Try different baudrates (common: 1000000, 115200, 57600)
Check wiring: TX->RX, RX->TX (may need level shifter)
Ensure only one motor is connected when using _find_single_motor()

“Some motors use different firmware versions” error:

Update all motors to the same firmware version
Use Feetech’s official software: https://www.feetechrc.com/software

From /home/daytona/workspace/source/src/lerobot/motors/feetech/feetech.py:155 Permission denied on Linux:

sudo chmod 666 /dev/ttyUSB0
# Or add user to dialout group
sudo usermod -a -G dialout $USER
# Log out and back in

Motor Behavior Issues

Motor doesn’t move:

Check torque is enabled: motor_bus.enable_torque("motor_name")
Verify position limits allow movement
Check motor is not overheated (read temperature)
Ensure adequate power supply voltage and current

Erratic movement or jittering:

Reduce acceleration settings
Tune PID parameters
Check for mechanical binding
Verify power supply is stable (no voltage drops)

Position inaccuracy:

Recalibrate motor
Check for mechanical backlash
Tune PID gains
Verify temperature is within normal range

Communication Issues

Slow read/write operations:

Decrease return_delay_time (see configure_motors())
Use synchronized operations (sync_read, sync_write) for multiple motors
Increase baudrate if supported

“Packet timeout” errors:

Check wiring quality
Reduce cable length
Try lower baudrate
Add termination resistors for long cables

Firmware Updates

To update Feetech motor firmware:

Download Feetech’s official software from https://www.feetechrc.com/software
Download latest firmware for your motor model
Connect motor individually to PC
Follow software instructions to flash firmware
Verify new firmware version:

firmware_versions = motor_bus._read_firmware_version([motor_id])
print(f"Firmware version: {firmware_versions[motor_id]}")

Best Practices

Always configure motors after connecting using configure_motors() to minimize delays
Use sync operations for multi-motor control to improve performance
Enable torque only when needed to reduce heat and power consumption
Monitor temperature during extended operation
Calibrate regularly if motors are mechanically adjusted
Set appropriate position limits to prevent mechanical damage
Use retries for critical operations in noisy environments: num_retry=3

Example: Complete Robot Arm Control

import time
from lerobot.motors.feetech import FeetechMotorsBus
from lerobot.motors.motors_bus import Motor

# Define 3-DOF arm
motors = {
    "shoulder": Motor(id=1, model="sts3215"),
    "elbow": Motor(id=2, model="sts3215"),
    "wrist": Motor(id=3, model="sts3215"),
}

motor_bus = FeetechMotorsBus(
    port="/dev/ttyUSB0",
    motors=motors,
    protocol_version=0,
)

try:
    # Connect and configure
    motor_bus.connect()
    motor_bus.configure_motors()
    motor_bus.enable_torque()
    
    # Move to home position
    home_position = {"shoulder": 0.0, "elbow": 0.0, "wrist": 0.0}
    motor_bus.sync_write("Goal_Position", home_position)
    time.sleep(2)
    
    # Move through trajectory
    trajectory = [
        {"shoulder": 45.0, "elbow": -30.0, "wrist": 90.0},
        {"shoulder": -45.0, "elbow": 30.0, "wrist": -90.0},
        {"shoulder": 0.0, "elbow": 0.0, "wrist": 0.0},
    ]
    
    for pose in trajectory:
        motor_bus.sync_write("Goal_Position", pose)
        time.sleep(2)
        
        # Read current state
        positions = motor_bus.sync_read("Present_Position")
        temps = motor_bus.sync_read("Present_Temperature")
        
        print(f"Position: {positions}")
        print(f"Temperature: {temps}")
    
finally:
    # Clean shutdown
    motor_bus.disable_torque()
    motor_bus.disconnect()

References

Source code: /home/daytona/workspace/source/src/lerobot/motors/feetech/feetech.py:1
Control tables: /home/daytona/workspace/source/src/lerobot/motors/feetech/tables.py
Feetech Official Website
SCServo SDK

Robots

Teleoperators

Sensors

Motors

​Overview

​Supported Models

​Installation

​Hardware Requirements

​Software Dependencies

​Configuration

​Motor Configuration

​Protocol Versions

​Basic Usage

​Connecting to Motors

​Reading Motor State

​Writing Motor Commands

​Torque Control

​Disconnecting

​Motor Calibration

​Overview

​Automatic Calibration

​Manual Calibration

​Reading Calibration

​Advanced Usage

​Operating Modes

​Drive Mode (Direction Inversion)

​Baudrate Configuration

​PID Tuning

​Speed and Acceleration Limits

​Finding and Auto-Discovering Motors

​Find Single Motor

​Broadcast Ping (Protocol 0 Only)

​Troubleshooting

​Connection Issues

​Motor Behavior Issues

​Communication Issues

​Firmware Updates

​Best Practices

​Example: Complete Robot Arm Control

​References

Build docs developers (and LLMs) love

Overview

Supported Models

Installation

Hardware Requirements

Software Dependencies

Configuration

Motor Configuration

Protocol Versions

Basic Usage

Connecting to Motors

Reading Motor State

Writing Motor Commands

Torque Control

Disconnecting

Motor Calibration

Overview

Automatic Calibration

Manual Calibration

Reading Calibration

Advanced Usage

Operating Modes

Drive Mode (Direction Inversion)

Baudrate Configuration

PID Tuning

Speed and Acceleration Limits

Finding and Auto-Discovering Motors

Find Single Motor

Broadcast Ping (Protocol 0 Only)

Troubleshooting

Connection Issues

Motor Behavior Issues

Communication Issues

Firmware Updates

Best Practices

Example: Complete Robot Arm Control

References