Rust API Reference¶

The moteus Rust library is split into two crates. Full auto-generated documentation is available on docs.rs.

This page provides a curated summary of the key types and their roles.

moteus crate¶

BlockingController: Synchronous controller with auto-discovered transport. Simplest API for single-threaded use. Provides set_position(), set_stop() and other blocking methods that send a command and return a QueryResult.
AsyncController: Async controller for use with async/.await. Supports both wrapped-blocking and true async (tokio feature) transports. Same method set as BlockingController, but all methods return futures.
Controller: Low-level frame builder. Produces Command values without any transport — use for custom transports or embedded systems. Provides make_position_command(), make_stop(), parse_query(), etc.

Command: A routed moteus message combining destination/source/prefix with serialized multiplex protocol data. Produced by Controller::make_*() methods. Convert to a wire-level CanFdFrame via into_frame().
command::PositionCommand: Position mode parameters: position, velocity, feedforward torque, torque limits, PID scales, acceleration/velocity limits, and more. Uses a builder pattern — chain .position(), .velocity(), .maximum_torque(), etc.
command::StopCommand: Stop command that clears faults and sets the controller to stopped mode.
command::CurrentCommand: Direct current (d/q axis) control command.
command::VFOCCommand: Voltage FOC (field-oriented control) command.
command::StayWithinCommand: Stay-within bounds command — the controller maintains position within specified limits.
command::ZeroVelocityCommand: Zero velocity mode command — the controller actively holds zero velocity.
query::QueryFormat: Specifies which registers to query and at what resolution. Customize to request additional telemetry fields beyond the defaults (mode, position, velocity, torque).
query::QueryResult: Parsed response containing mode, position, velocity, torque, voltage, temperature, fault code, and other telemetry fields.

Transport: Manages communication channels to moteus controllers. Provides cycle() (batch send/receive), write() (fire-and-forget), read() (receive unsolicited), and flush_read(), matching the Python API.
TransportOptions: Configuration for transport auto-discovery. Set preferred interfaces, timeouts, and other options.
TransportOps: Trait for blocking transport implementations. Implement this to create custom transport backends.
AsyncTransport (requires tokio feature): Async transport wrapper for true non-blocking I/O with tokio.
AsyncTransportOptions (requires tokio feature): Configuration for async transport creation.
AsyncTransportOps (requires tokio feature): Trait for async transport implementations.

transport::fdcanusb::Fdcanusb: fdcanusb serial (CDC) transport. Auto-detected when an fdcanusb device is connected via USB.
transport::socketcan::SocketCan: Linux SocketCAN transport. Uses the kernel CAN interface (e.g., can0).
transport::async_fdcanusb::AsyncFdcanusb (requires tokio feature): Async fdcanusb transport using tokio-serial.
transport::async_socketcan::AsyncSocketCan (requires tokio feature): Async SocketCAN transport using tokio.

DiagnosticStream: Blocking diagnostic protocol stream for reading and writing configuration values, firmware info, and other diagnostic commands.
AsyncDiagnosticStream (requires tokio feature): Async variant of the diagnostic stream.
move_to(): Free function for coordinated multi-servo moves. Moves multiple servos to target positions simultaneously, waiting for all to arrive.
async_move_to() (requires tokio feature): Async variant of coordinated multi-servo moves.
Error: Error enum with variants: Io, Timeout, NoResponse, Fault, InvalidResponse, NotConnected, DeviceNotFound, Protocol. Implements std::error::Error and From<std::io::Error>.

get_singleton_transport(): Returns a shared global transport instance. Creates the transport on first call using auto-discovery.
create_default_transport(): Creates a new transport with default auto-discovery settings.
register(): Register a custom transport factory for auto-discovery. Allows third-party transport backends to participate in automatic transport selection.
DeviceAddress: Address a device by CAN ID, UUID, or both. UUID-based addressing enables automatic ID resolution on the bus.

This crate is no_std compatible (with optional std feature) and provides the wire protocol types:

CanFdFrame: Raw CAN-FD frame with arbitration_id, data, size, brs, and fdcan fields. Contains no routing information — routing is handled by Command in the moteus crate.
Register: Enum of all moteus register addresses (mode, position, velocity, torque, voltage, temperature, fault, encoder registers, etc.).
Resolution: Register value resolution: Ignore, Int8, Int16, Int32, Float. Controls the precision and wire size of register values.
Mode: Controller operating mode enum: Stopped, Fault, Position, ZeroVelocity, StayWithin, Current, etc.
HomeState: Homing state enum: Relative, Rotor, Output.
Scaling: Register scaling helpers for encoding/decoding fixed-point values to/from wire format.
command::*: Command structs and serialization for all command types. Each command type has a corresponding format struct that controls which fields are sent and at what resolution.
query::*: Query format and result types with deserialization. QueryFormat controls which registers are requested; QueryResult holds the parsed response.
calculate_arbitration_id(): Compute a CAN arbitration ID from source, destination, prefix, and reply flag.
parse_arbitration_id(): Parse source, destination, prefix, and reply flag from a CAN arbitration ID.

tokio: Enables true async transports using tokio. Adds AsyncFdcanusb, AsyncSocketCan, AsyncTransport, AsyncDiagnosticStream, and async_move_to().
clap: Enables add_transport_args() for CLI argument parsing with clap.

For usage examples and tutorials, see the Rust Client integration guide.