What is MotorBridge?

v0.1.3 Rust Core Python Binding MotorBridge is a unified motor control stack with pluggable vendor drivers and a C ABI for cross-language integration.

The Problem We Solve

Every motor vendor has a different protocol:

Vendor	Protocol	CAN Format	Control Modes
Damiao (达妙)	DM-J4310/4340	CAN 2.0	MIT, POS_VEL, VEL, FORCE_POS
RobStride	RobStride MIT	CAN 2.0	MIT, Position, Velocity
MyActuator	RMD	CAN 2.0	Current, Position, Velocity
HighTorque	HT Native	CAN 2.0	MIT, POS_VEL, VEL, FORCE_POS
Hexfellow	Hexfellow MIT	CAN-FD	MIT, POS_VEL, FORCE_POS

Without MotorBridge, you need to:

Learn 5+ different protocols
Maintain separate codebases per vendor
Rewrite control logic when switching motors
Build your own debugging tools

MotorBridge Architecture

┌─────────────────────────────────────────────────────────────────────┐
│                          Your Application                            │
│                     (Python / Future: C++, ROS2)                     │
├─────────────────────────────────────────────────────────────────────┤
│                                                                      │
│    ┌─────────────────────────────────────────────────────────────┐  │
│    │                    Language Bindings                         │  │
│    │  ┌──────────────┐  ┌──────────────┐  ┌──────────────┐      │  │
│    │  │   Python     │  │   C++ (WIP)  │  │  ROS2 (WIP)  │      │  │
│    │  │   Binding    │  │   Binding    │  │   Node       │      │  │
│    │  └──────────────┘  └──────────────┘  └──────────────┘      │  │
│    └─────────────────────────────────────────────────────────────┘  │
│                                │                                     │
│                                ▼                                     │
│    ┌─────────────────────────────────────────────────────────────┐  │
│    │                       C ABI (FFI)                            │  │
│    │              libmotor_abi.so / .dylib / .dll                 │  │
│    │                                                              │  │
│    │  • motor_controller_new_socketcan()                         │  │
│    │  • motor_controller_add_damiao_motor()                      │  │
│    │  • motor_handle_send_mit()                                  │  │
│    │  • motor_handle_get_state()                                 │  │
│    └─────────────────────────────────────────────────────────────┘  │
│                                │                                     │
│                                ▼                                     │
│    ┌─────────────────────────────────────────────────────────────┐  │
│    │                     Rust Core                                │  │
│    │                                                              │  │
│    │  ┌─────────────┐ ┌─────────────┐ ┌─────────────┐           │  │
│    │  │ motor_core  │ │ motor_abi   │ │ motor_cli   │           │  │
│    │  │ (abstractions)│ (FFI layer) │ │ (CLI tools) │           │  │
│    │  └─────────────┘ └─────────────┘ └─────────────┘           │  │
│    │                                                              │  │
│    │  ┌───────────────────────────────────────────────────────┐ │  │
│    │  │                   Vendor Drivers                       │ │  │
│    │  │  ┌────────┐ ┌────────┐ ┌────────┐ ┌────────┐ ┌────────┐│ │  │
│    │  │  │ Damiao │ │RobStride│ │MyActuat.│ │HighTorq.│ │Hexfellow││  │
│    │  │  │        │ │        │ │        │ │        │ │        ││ │  │
│    │  │  └────────┘ └────────┘ └────────┘ └────────┘ └────────┘│ │  │
│    │  └───────────────────────────────────────────────────────┘ │  │
│    └─────────────────────────────────────────────────────────────┘  │
│                                │                                     │
│                                ▼                                     │
│    ┌─────────────────────────────────────────────────────────────┐  │
│    │                     Transport Layer                          │  │
│    │                                                              │  │
│    │  ┌────────────┐  ┌────────────┐  ┌────────────┐            │  │
│    │  │ SocketCAN  │  │ SocketCAN-FD│  │  DM Serial │            │  │
│    │  │ (CAN 2.0)  │  │  (CAN-FD)  │  │   Bridge   │            │  │
│    │  └────────────┘  └────────────┘  └────────────┘            │  │
│    └─────────────────────────────────────────────────────────────┘  │
│                                                                      │
└─────────────────────────────────────────────────────────────────────┘

Project Structure

rust_dm/
├── motor_core/           # Core abstractions (CanBus, MotorDevice)
├── motor_abi/            # C ABI / FFI layer (cdylib + staticlib)
├── motor_vendors/        # Vendor-specific protocol implementations
│   ├── damiao/          # 达妙 motor protocol
│   ├── robstride/       # RobStride motor protocol
│   ├── myactuator/      # MyActuator RMD protocol
│   ├── hightorque/      # HighTorque native protocol
│   └── hexfellow/       # Hexfellow MIT protocol (CAN-FD)
├── bindings/
│   └── python/          # Python binding (ctypes-based)
├── motor_cli/           # Command-line utilities
├── integrations/
│   └── ws_gateway/      # WebSocket gateway for remote control
└── tools/
    └── factory_calib_ui/ # Factory calibration web UI

Why “Python Binding” Not “SDK”?

What is a Binding?

A binding is a thin wrapper that exposes a native library to another language via FFI (Foreign Function Interface).

┌─────────────────────────────────────────────────┐
│  Python Code                                    │
│  motor.send_mit(pos, vel, kp, kd, tau)          │
└───────────────────────┬─────────────────────────┘
                        │ ctypes call
                        ▼
┌─────────────────────────────────────────────────┐
│  C ABI (libmotor_abi.so)                        │
│  motor_handle_send_mit(ptr, pos, vel, kp, kd, tau)│
└───────────────────────┬─────────────────────────┘
                        │ native call
                        ▼
┌─────────────────────────────────────────────────┐
│  Rust Core                                      │
│  DamiaoMotor::send_mit_target(...)             │
└─────────────────────────────────────────────────┘

Key characteristics:

Logic lives in Rust, not Python
Python is a 1:1 mapping to C ABI functions
No duplicate implementation
Minimal overhead (direct FFI calls)

How the ABI Works

The motor_abi crate compiles to a shared library:

# motor_abi/Cargo.toml
[lib]
crate-type = ["cdylib", "staticlib"]  # Dynamic + Static library

Python loads it via ctypes:

# abi.py
lib = ctypes.CDLL("libmotor_abi.so")

# Bind function signature
lib.motor_handle_send_mit.argtypes = [c_void_p, c_float, c_float, 
                                       c_float, c_float, c_float]
lib.motor_handle_send_mit.restype = c_int32

# Call it
lib.motor_handle_send_mit(motor_ptr, 0.5, 0.0, 30.0, 1.0, 0.0)

This is zero-copy for primitive types - floats and ints pass directly between Python and Rust.

SDK vs Binding Comparison

Aspect	SDK	Binding (MotorBridge)
Logic location	In the SDK itself	In Rust core
Language	Pure Python	Rust + Python wrapper
Performance	Python overhead	Near-native speed
Memory safety	Python GC	Rust ownership
Other languages	N/A	Same ABI for C++, etc.
Deployment	Pure Python	Need native library

MotorBridge is a Binding because:

The “SDK” is the Rust core (motor_core + vendor drivers)
Python is just one interface to that core
Future: C++, ROS2 nodes will use the same ABI

Why Rust for the Core?

Requirement	Rust Advantage
Real-time control	No garbage collection pauses
Memory safety	No buffer overflows, use-after-free
Deterministic timing	Predictable execution for control loops
Zero-cost abstractions	High-level code, low-level performance
Cross-platform	Linux, macOS, Windows support
CAN integration	Native SocketCAN bindings

Core Components

Controller

Manages CAN interface and motor lifecycle:

from motorbridge import Controller

# SocketCAN (most common)
with Controller("can0") as ctrl:
    # ctrl manages the CAN socket
    # ctrl tracks all registered motors
    # ctrl handles cleanup on exit
    pass

# CAN-FD (for Hexfellow)
ctrl = Controller.from_socketcanfd("can0")

# DM Serial Bridge (达妙专用)
ctrl = Controller.from_dm_serial("/dev/ttyACM0", 921600)

Each Controller is bound to one vendor. You cannot mix Damiao and RobStride motors in the same Controller instance.

Motor

Handle to a single physical motor:

# Add a Damiao motor
motor = ctrl.add_damiao_motor(
    motor_id=0x01,      # Command CAN ID
    feedback_id=0x11,   # Feedback CAN ID  
    model="4340P"       # Motor model string
)

# Control commands
motor.send_mit(pos=0.5, vel=0.0, kp=30.0, kd=1.0, tau=0.0)

# Read state
state = motor.get_state()

Mode

Control mode determines how the motor responds:

from motorbridge import Mode

motor.ensure_mode(Mode.MIT, timeout_ms=1000)

Mode	Parameters	Use Case
`MIT`	pos, vel, kp, kd, tau	Full impedance control
`POS_VEL`	pos, vlim	Position with speed limit
`VEL`	vel	Pure velocity control
`FORCE_POS`	pos, vlim, ratio	Force-limited position

MotorState

Real-time feedback structure:

@dataclass
class MotorState:
    can_id: int          # Motor CAN ID
    arbitration_id: int  # CAN arbitration ID
    status_code: int     # Error/status code (0 = OK)
    pos: float           # Position (radians)
    vel: float           # Velocity (rad/s)
    torq: float          # Torque (Nm)
    t_mos: float         # MOSFET temperature (°C)
    t_rotor: float       # Rotor temperature (°C)

Transport Options

Transport	Vendors	Constructor
SocketCAN	All except Hexfellow	`Controller("can0")`
CAN-FD	Hexfellow (required)	`Controller.from_socketcanfd("can0")`
DM Serial	Damiao only	`Controller.from_dm_serial("/dev/ttyACM0", 921600)`

CLI Tools

The project includes command-line utilities:

# Scan for motors
motorbridge-cli scan --vendor all --channel can0

# Enable and test
motorbridge-cli run --vendor damiao --motor-id 0x01 --mode enable

# Dump registers
motorbridge-cli id-dump --motor-id 0x01 --rids 7,8,9,10

Integrations

WebSocket Gateway

Control motors over WebSocket (useful for browser/remote apps):

# Start gateway
cargo run -p ws_gateway

Motor Calibration

Tool for motor calibration routines:

python3 tools/factory_calib_ui/server.py --bind 0.0.0.0 --port 18100

Comparison with Alternatives

Feature	Vendor Libraries	MotorBridge
Multi-vendor	❌ One per vendor	✅ Unified API
Protocol details	❌ Exposed	✅ Abstracted
Type safety	⚠️ Varies	✅ Full type hints
CLI tools	❌ Usually none	✅ Built-in
Real-time safe	⚠️ Python GC	✅ Rust core
Other languages	❌ Python only	✅ C ABI for any language
Documentation	⚠️ Varies	✅ Comprehensive

Quick Start

Install Python Package

pip install motorbridge

Configure CAN Interface

sudo ip link set can0 type can bitrate 1000000
sudo ip link set can0 up

Run Your First Program

from motorbridge import Controller, Mode

with Controller("can0") as ctrl:
    motor = ctrl.add_damiao_motor(0x01, 0x11, "4340P")
    ctrl.enable_all()
    motor.ensure_mode(Mode.MIT, 1000)
    motor.send_mit(0.5, 0.0, 30.0, 1.0, 0.0)
    print("Motor running!")

Get Started

Tutorials

API Reference

Best Practices

Reference

What is MotorBridge?

What is MotorBridge?

The Problem We Solve

MotorBridge Architecture

Project Structure

Why “Python Binding” Not “SDK”?

Why Rust for the Core?

Core Components

Controller

Motor

Mode

MotorState

Transport Options

CLI Tools

Integrations

WebSocket Gateway

Motor Calibration

Comparison with Alternatives

Quick Start

What Can You Build?

Next Steps

Quick Start Guide

API Reference

Tutorials

Best Practices

Get Started

Tutorials

API Reference

Best Practices

Reference

​What is MotorBridge?

​The Problem We Solve

​MotorBridge Architecture

​Project Structure

​Why “Python Binding” Not “SDK”?

​Why Rust for the Core?

​Core Components

​Controller

​Motor

​Mode

​MotorState

​Transport Options

​CLI Tools

​Integrations

​WebSocket Gateway

​Motor Calibration

​Comparison with Alternatives

​Quick Start

​What Can You Build?

​Next Steps

Quick Start Guide

API Reference

Tutorials

Best Practices

What is MotorBridge?

The Problem We Solve

MotorBridge Architecture

Project Structure

Why “Python Binding” Not “SDK”?

Why Rust for the Core?

Core Components

Controller

Motor

Mode

MotorState

Transport Options

CLI Tools

Integrations

WebSocket Gateway

Motor Calibration

Comparison with Alternatives

Quick Start

What Can You Build?

Next Steps