Feetech Servo SDK for TypeScript

A TypeScript SDK for controlling Feetech servo motors using Web Serial API. This library provides a modern, type-safe interface for interacting with STS, SMS, and SCS series servo motors in web browsers.

Features

• 🌐 Web Serial API Integration - Direct browser-to-servo communication
• 📦 TypeScript Support - Full type definitions and IntelliSense
• 🔄 Synchronous Operations - Control multiple servos simultaneously
• 🛡️ Error Handling - Comprehensive error detection and reporting
• 🚀 Modern API - Promise-based async/await interface
• 📱 Cross-Platform - Works on any browser supporting Web Serial API

Browser Compatibility

This SDK requires Web Serial API support:

• Chrome 89+
• Edge 89+
• Opera 75+

Installation

npm install @feetech/servo-sdk

Quick Start

import { FeetechServo } from '@feetech/servo-sdk';

// Create servo instance
const servo = new FeetechServo({ baudRate: 1000000 });

// Connect to servo
await servo.connect();

// Ping servo
const result = await servo.ping(1);
console.log(`Found servo: ID=${result.id}, Model=${result.modelNumber}`);

// Enable torque
await servo.enableTorque(1);

// Move servo to center position
await servo.writePosition(1, 512, 200); // position: 512, speed: 200

// Read current position
const position = await servo.readPosition(1);
console.log(`Current position: ${position}`);

// Disconnect
await servo.disconnect();

API Documentation

Connection Management

// Connect to servo
await servo.connect();

// Check connection status
const isConnected = servo.getConnectionStatus();

// Disconnect
await servo.disconnect();

Basic Operations

// Ping servo
const pingResult = await servo.ping(servoId);

// Scan for servos
const foundServos = await servo.scan(0, 20); // Scan IDs 0-20

// Read/Write position
const position = await servo.readPosition(servoId);
await servo.writePosition(servoId, targetPosition, speed);

// Position control in degrees
await servo.setPositionInDegrees(servoId, 150); // 0-300 degrees
const degrees = await servo.getPositionInDegrees(servoId);

// Torque control
await servo.enableTorque(servoId);
await servo.disableTorque(servoId);

// Read complete status
const status = await servo.readStatus(servoId);

Synchronous Control

// Sync write positions
await servo.syncWritePosition([
  { id: 1, position: 512 },
  { id: 2, position: 768 },
  { id: 3, position: 256 }
]);

// Sync read positions
const positions = await servo.syncReadPosition([1, 2, 3]);
positions.forEach((pos, id) => {
  console.log(`Servo ${id}: ${pos}`);
});

Advanced Operations

// Change servo ID
await servo.setID(currentId, newId);

// Set baud rate
await servo.setBaudRate(servoId, 1000000);

// Factory reset
await servo.factoryReset(servoId);

// Reboot servo
await servo.reboot(servoId);

// Direct register access
const value = await servo.readByte(servoId, address);
await servo.writeByte(servoId, address, value);

Group Operations

// Create sync write group
const syncWrite = servo.createSyncWrite(ControlTable.GOAL_POSITION_L, 2);
syncWrite.addParam(1, new Uint8Array([0x00, 0x02])); // Position 512
syncWrite.addParam(2, new Uint8Array([0x00, 0x03])); // Position 768
await syncWrite.txPacket();

// Create sync read group
const syncRead = servo.createSyncRead(ControlTable.PRESENT_POSITION_L, 2);
syncRead.addParam(1);
syncRead.addParam(2);
await syncRead.txRxPacket();

const data1 = syncRead.getData(1);
const data2 = syncRead.getData(2);

Helper Functions

import { helpers } from '@feetech/servo-sdk';

// Check Web Serial support
if (helpers.isWebSerialSupported()) {
  // Web Serial is available
}

// Convert between degrees and position values
const position = helpers.degreesToPosition(150); // 150° → position value
const degrees = helpers.positionToDegrees(512);  // position → degrees

// Convert RPM to speed value
const speed = helpers.rpmToSpeed(60); // 60 RPM → speed value
const rpm = helpers.speedToRpm(512);  // speed → RPM

// Clamp values to valid ranges
const safePosition = helpers.clampPosition(2000); // Returns 1023
const safeSpeed = helpers.clampSpeed(-100);       // Returns 0

Error Handling

import { ServoError, ErrorCode } from '@feetech/servo-sdk';

try {
  await servo.connect();
} catch (error) {
  if (error instanceof ServoError) {
    switch (error.code) {
      case ErrorCode.CONNECTION_FAILED:
        console.error('Failed to connect to servo');
        break;
      case ErrorCode.TIMEOUT:
        console.error('Operation timed out');
        break;
      case ErrorCode.CHECKSUM_ERROR:
        console.error('Communication error');
        break;
    }
  }
}

Examples

Check the examples directory for complete working examples:

1. Basic Control - Simple position and torque control
2. Servo Scanner - Scan and identify connected servos
3. Sync Control - Control multiple servos simultaneously
4. Advanced Settings - Change IDs, baud rates, and factory reset

To run examples:

cd examples
npm install
npm run dev

Then open http://localhost:3000 in your browser.

Development

Setup

# Install dependencies
npm install

# Install example dependencies
cd examples && npm install && cd ..

Development Workflow

When developing the SDK and testing with examples:

1. Start SDK build in watch mode (in the root directory):

   npm run dev

   This watches for changes in src/ and automatically rebuilds to dist/

2. In a separate terminal, run the example (in the examples directory):

   cd examples && npm run dev

3. Both processes must run simultaneously for live updates:

   • SDK changes in src/ → automatically built to dist/
   • Example imports from dist/ → sees updates immediately

Alternative: One-time build

# Build once and run example
npm run build && cd examples && npm run dev

Other Commands

# Run tests
npm run test

# Lint code
npm run lint

# Format code
npm run format

# Build for production
npm run build

Protocol Information

This SDK implements the Feetech servo protocol, compatible with:

• STS Series (Serial Bus Servo)
• SMS Series (Serial Bus Servo)
• SCS Series (Serial Bus Servo)

Default communication parameters:

• Baud Rate: 1,000,000 bps
• Data Bits: 8
• Stop Bits: 1
• Parity: None

License

MIT License - see LICENSE file for details

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Support

For issues and feature requests, please use the GitHub issues page.