Topics & services

Index of the ROS topics and services that bar_ros2 publishes, subscribes, or serves. Use this page to find "who publishes X" or "what topic carries Y".

Topics

Always-on (any bringup)

Topic	Type	QoS	Publisher	Notes
/lite/joint_states	sensor_msgs/JointState	RELIABLE depth 10	joint_state_broadcaster (remapped at bringup)	Position/velocity/effort in joint frame (post-calibration). Owner-prefixed — there is no global /joint_states. 50 Hz real, 200 Hz sim.
/imu/data	sensor_msgs/Imu	RELIABLE	IMU driver	Subscribed by RemotePolicyController and bar_policy.
/robot_description	std_msgs/String	RELIABLE TRANSIENT_LOCAL depth 1	robot_state_publisher	URDF XML. Latched — subscribers can join any time.
/tf, /tf_static	tf2_msgs/TFMessage	RELIABLE	robot_state_publisher	Kinematic chain from /lite/joint_states.
/clock	rosgraph_msgs/Clock	RELIABLE	mujoco_sim (sim only)	Sim-time on the MuJoCo path. Every other node consumes when use_sim_time:=true.

Bringup-dependent

Topic	Type	QoS	Publisher	When present
/control_mode	bar_msgs/ControlMode	RELIABLE depth 10	mode_manager	When enable_mode_manager:=true (default for real.launch.py / mujoco.launch.py). 50 Hz.
/safety_status	bar_msgs/SafetyStatus	RELIABLE TRANSIENT_LOCAL depth 1	every hardware plugin	Per-bus (bar_robstride/can0, bar_robstride/can1 for Lite). Published only on change.
/standby_controller/state	bar_msgs/StandbyState	RELIABLE TRANSIENT_LOCAL depth 1	bar/StandbyController (when active)	Carries is_finished — the gate for START_* intents.
/joy	sensor_msgs/Joy	SENSOR_DATA	joy_node	When enable_gamepad:=true (default). The launch hard-fails on missing /dev/input/js*.

Active-controller-dependent

Topic	Type	QoS	Direction	When
/remote_policy_controller/command	bar_msgs/MITCommand	RELIABLE depth 4	subscribed by RemotePolicyController	When RemotePolicyController is active. Published by bar_policy/remote_policy_runner (or its pianist_policy.PianoPolicyRunner subclass).
/piano/key_state	pianist_msgs/PianoKeyState	RELIABLE KEEP_LAST(1)	sim: pianist_policy/piano_state_bridge; real: pianist_policy/midi_keyboard_driver	Piano runs. Measured key state.
/piano/target_keys	pianist_msgs/PianoKeyState	RELIABLE KEEP_LAST(1)	pianist_policy/PianoPolicyRunner._tick	Piano runs. Song's goal frame, re-published every tick for bag-based metrics.
/forward_mit_controller/commands	std_msgs/Float64MultiArray	RELIABLE depth 10	subscribed by upstream forward_command_controller/MultiInterfaceForwardCommandController	Used by mit_slider_gui.

/parameter_events and friends

Every node (controllers, mode_manager, plugins) publishes the standard ROS infrastructure topics:

• /parameter_events, /rosout
• ~/get_parameters, ~/set_parameters, etc. (per node)

These are conventional ROS — not specific to bar_ros2. Mentioned here so ros2 topic list output isn't confusing.

Services

mode_manager FSM-transition services

std_srvs/Trigger services. Same intents as the gamepad — for use on keyboardless lab boxes or scripted tests.

Service	Effect
/bar/mode/damp	→ DAMPING from any state
/bar/mode/load	DAMPING → STANDBY
/bar/mode/start_remote	STANDBY → REMOTE (gated on is_finished)
/bar/mode/start_locomotion	STANDBY → LOCOMOTION (gated on is_finished)
/bar/mode/quit	exit (only from ZERO_TORQUE or DAMPING)

controller_manager-side (under /controller_manager)

Standard controller_manager services. Useful ones:

Service	Type	Purpose
/controller_manager/list_controllers	controller_manager_msgs/ListControllers	What's loaded, active state per controller
/controller_manager/list_hardware_components	controller_manager_msgs/ListHardwareComponents	Which <ros2_control> blocks are active
/controller_manager/load_controller	controller_manager_msgs/LoadController	Backing for ros2 control load_controller
/controller_manager/switch_controller	controller_manager_msgs/SwitchController	Backing for ros2 control switch_controllers
/controller_manager/configure_controller	controller_manager_msgs/ConfigureController	Force on_configure

mode_manager is a client of /controller_manager/switch_controller (async, STRICT). You can call it directly from ros2 control for operator-driven debug — see How-to → Switch without the FSM.

Per-node services (parameter handling)

Every node hosts the standard rclcpp parameter services:

• ~/get_parameters, ~/set_parameters, ~/list_parameters, etc.

rqt_reconfigure is a generic frontend for these.

QoS reference

Used in the tables above:

QoS profile	Reliability	Durability	History	When
RELIABLE (default)	RELIABLE	VOLATILE	KEEP_LAST 10	Most topics
SENSOR_DATA	BEST_EFFORT	VOLATILE	KEEP_LAST 5	High-rate sensors — IMU, joy
TRANSIENT_LOCAL	RELIABLE	TRANSIENT_LOCAL	KEEP_LAST 1	Latched — late subscribers see the most-recent value (URDF, SafetyStatus, StandbyState)

If a publisher's QoS doesn't match a subscriber's, ROS may silently drop messages. The TRANSIENT_LOCAL combo is the most common mismatch source — subscribers must also request TRANSIENT_LOCAL durability to receive the latched value.

Inspecting at runtime

From a sourced workspace env (cd bar_ws && pixi shell):

# What's published right now?
ros2 topic list

# Who's publishing X?
ros2 topic info /control_mode --verbose

# What's the QoS?
ros2 topic info /safety_status --verbose

# Recent rate
ros2 topic hz /lite/joint_states

# What service does X expose?
ros2 service list | grep mode_manager
ros2 service info /controller_manager/switch_controller

See also

• Reference → Messages — full field schemas for the custom bar_msgs types.
• Reference → Quick reference — common ros2 topic echo / ros2 topic hz invocations.
• Concepts → Safety pipeline — what triggers a /safety_status publish.