Standard Messages

HORUS provides 75+ typed message types covering every common robotics domain. All are importable from horus and binary-compatible with Rust for cross-language topics.

from horus import CmdVel, Imu, LaserScan, Pose2D, Odometry

Which Message Do I Need?

I need to...	Use	Category
Send velocity commands to motors	`CmdVel`, `Twist`	Control
Read IMU data (accel + gyro)	`Imu`	Sensor
Read LiDAR scans	`LaserScan`	Sensor
Publish robot position	`Odometry`, `Pose2D`, `Pose3D`	Sensor, Geometry
Send camera images	`Image`	Image API
Send point clouds	`PointCloud`	PointCloud API
Report ML detections	`Detection`, `Detection3D`	Perception
Send navigation goals	`NavGoal`, `NavPath`	Navigation
Report system health	`DiagnosticReport`, `NodeHeartbeat`	Diagnostics
Send force/torque data	`WrenchStamped`, `ForceCommand`	Force
Send joystick/keyboard input	`JoystickInput`, `KeyboardInput`	Input
Send audio data	`AudioFrame`	ML
Send dynamic/untyped data	Python dicts (GenericMessage, 4KB)	Topic API

Message Categories

Category	Types	Page
Sensor	Imu, LaserScan, Odometry, NavSatFix, BatteryState, RangeSensor, Temperature, MagneticField	Sensor Messages
Control	CmdVel, MotorCommand, ServoCommand, PidConfig, DifferentialDriveCommand, JointCommand	Control Messages
Geometry	Pose2D, Pose3D, Twist, Vector3, Point3, Quaternion, TransformStamped, Accel	Geometry Messages
Navigation	NavGoal, NavPath, Waypoint, OccupancyGrid, CostMap, VelocityObstacle	Navigation Messages
Perception	Detection, Detection3D, BoundingBox2D/3D, SegmentationMask, TrackedObject, Landmark	Perception Messages
Diagnostics	Heartbeat, DiagnosticReport, EmergencyStop, SafetyStatus, NodeHeartbeat	Diagnostics Messages
Vision	CompressedImage, CameraInfo, StereoInfo, RegionOfInterest	Vision Messages
Force & Haptics	WrenchStamped, ForceCommand, ContactInfo, HapticFeedback, TactileArray	Force Messages
Input	JoystickInput, KeyboardInput	Input Messages
Clock	Clock, TimeReference	Clock Messages
ML	AudioFrame	ML Messages
Tensor	Tensor descriptors	Tensor Messages

Import

All standard messages are available from the top-level horus module:

import horus

# Direct attribute access
cmd = horus.CmdVel(linear=1.0, angular=0.5)
imu = horus.Imu(accel_x=0.0, accel_y=0.0, accel_z=9.81)

# Or import specific types
from horus import CmdVel, Imu, LaserScan, Pose2D, Odometry

Custom Messages

Need a type that doesn't exist? Use Python dicts for prototyping:

node.send("motor_status", {
    "rpm": 1500.0,
    "current_amps": 2.3,
    "temperature_c": 45.0,
})

For production cross-language use, define message types in Rust with message! and they become available in Python automatically. See Custom Messages.

Typed vs Generic Performance

Transport	Latency	Cross-Language
Typed messages (`horus.CmdVel`)	~1.7μs	Yes
Python dicts (GenericMessage)	~6-50μs	No
`Image` zero-copy (DLPack)	~1.1μs	Yes

Rule: Use typed messages for control loops and cross-language topics. Use dicts for Python-only prototyping.