Low-Level Topics

Low-level topics use DDS and are suitable for high-frequency state, sensor data, and joint control. C++ applications publish and subscribe through the ChannelPublisher and ChannelSubscriber templates.

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Warning

Publishing rt/joint_ctrl directly participates in low-level joint control, and commands take effect only while the robot is in Custom mode. Call B1LocoClient::ChangeMode(RobotMode::kCustom) first, then verify the joint count, joint indices, and control frequency. Start with subscribe-only examples when debugging state topics.

Initialization

#include <booster/robot/channel/channel_factory.hpp>

booster::robot::ChannelFactory::Instance()->Init(0, "<network_ip>");

C++ Subscription Example

#include <chrono>
#include <iostream>
#include <thread>

#include <booster/idl/b1/LowState.h>
#include <booster/robot/b1/b1_api_const.hpp>
#include <booster/robot/channel/channel_factory.hpp>
#include <booster/robot/channel/channel_subscriber.hpp>

int main() {
    booster::robot::ChannelFactory::Instance()->Init(0, "<network_ip>");

    booster::robot::ChannelSubscriber<booster_interface::msg::LowState> sub(
        booster::robot::b1::kTopicLowState,
        [](const void *msg) {
            const auto *state =
                static_cast<const booster_interface::msg::LowState *>(msg);
            std::cout << state->motor_state_parallel().size() << "\n";
        });

    sub.InitChannel();
    std::this_thread::sleep_for(std::chrono::seconds(10));
    sub.CloseChannel();
    return 0;
}

C++ Publishing Example

This example creates a LowCmd frame with zero control weight. For actual control, configure every motor according to the robot model, control mode, and joint layout, then publish continuously at a stable rate.

#include <vector>

#include <booster/idl/b1/LowCmd.h>
#include <booster/idl/b1/MotorCmd.h>
#include <booster/robot/b1/b1_api_const.hpp>
#include <booster/robot/channel/channel_factory.hpp>
#include <booster/robot/channel/channel_publisher.hpp>

int main() {
    booster::robot::ChannelFactory::Instance()->Init(0, "<network_ip>");

    booster::robot::ChannelPublisher<booster_interface::msg::LowCmd> publisher(
        booster::robot::b1::kTopicJointCtrl);
    publisher.InitChannel();

    std::vector<booster_interface::msg::MotorCmd> motors(
        booster::robot::b1::kJointCnt);
    for (auto &motor : motors) {
        motor.mode(0);
        motor.q(0.0F);
        motor.dq(0.0F);
        motor.tau(0.0F);
        motor.kp(0.0F);
        motor.kd(0.0F);
        motor.weight(0.0F);
    }

    booster_interface::msg::LowCmd cmd;
    cmd.cmd_type(booster_interface::msg::PARALLEL);
    cmd.motor_cmd(std::move(motors));
    publisher.Write(&cmd);
    publisher.CloseChannel();
    return 0;
}

Motion-Control Topics

Minimum firmware refers to the robot-side firmware version. Topics without a separate version record use >= v1.7.1.0.

Topic	C++ constant	C++ message type	Minimum firmware
rt/joint_ctrl	b1::kTopicJointCtrl	booster_interface::msg::LowCmd	>= v1.0.0.0
rt/low_state	b1::kTopicLowState	booster_interface::msg::LowState	>= v1.0.0.0
rt/fall_down	b1::kTopicFallDown	booster_interface::msg::FallDownState	>= v1.2.0.2
rt/odometer_state	b1::kTopicOdometerState	booster_interface::msg::Odometer	>= v1.3.1.1
rt/booster_hand_data	b1::kTopicBoosterHandData	booster_interface::msg::HandReplyData	>= v1.7.1.0
rt/booster_hand_touch_data	b1::kTopicHandTouchData	booster_interface::msg::HandTouchData	>= v1.7.1.0
rt/robot_states	b1::kTopicRobotStates	booster_interface::msg::RobotStatesMsg	>= v1.3.1.1
rt/prone_body_control_status	b1::kTopicProneBodyControlStatus	booster_interface::msg::ProneBodyControlStatus	>= v1.7.1.0
rt/robot_replay_traj_id	b1::kTopicRobotReplayTrajID	booster_interface::msg::RobotReplayTrajID	>= v1.7.1.0
rt/trained_traj_status	b1::kTopicTrainedTrajStatus	booster_interface::msg::TrainedTrajStatus	>= v1.8.0.9
rt/robocup_behavior_status	b1::kTopicRobocupBehaviorStatus	booster_interface::msg::RobocupBehaviorStatus	>= v1.7.1.0
rt/kick_ball	b1::kTopicKickReference	booster_interface::msg::Kick	>= v1.7.1.0
rt/button_event	Use the topic string	booster_interface::msg::ButtonEventMsg	>= v1.7.1.0
rt/remote_controller_state	Use the topic string	booster_interface::msg::RemoteControllerState	>= v1.2.0.2

ROS-Like Topics

These topics use common ROS message structures while still using the SDK DDS channel:

Topic	C++ constant	C++ message type	Minimum firmware
rt/tf	b1::kTopicTF	tf2_msgs::msg::TFMessage	>= v1.1.0.6
rt/odom	b1::kTopicRosOdometer	nav_msgs::msg::Odometry	>= v1.7.1.0
rt/imu/data	b1::kTopicRosImu	sensor_msgs::msg::Imu	>= v1.7.1.0
rt/joint_states	b1::kTopicRosJointStates	sensor_msgs::msg::JointState	>= v1.7.1.0

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Note

rt/tf currently supports ROS 2 subscription only. TFMessage describes the wire schema; the current SDK release package does not expose a public C++ IDL header for this type.

AI and LUI Topics

Topic	C++ constant	C++ message type	Minimum firmware
rt/ai_subtitle	kTopicAiSubtitle	booster_interface::msg::Subtitle	>= v1.3.1.1
rt/lui_asr_chunk	kTopicLuiAsrChunk	booster_interface::msg::AsrChunk	>= v1.5.0.9

Joint Indices

Joint-index constants are defined in include/booster/robot/b1/b1_api_const.hpp:

Layout	Joint count	C++ enum
Default layout	kJointCnt = 23	JointIndex
K1 layout	kJointCntK1 = 22	JointIndexK1
T1_7DofArm 7-DoF arm layout	kJointCnt7DofArm = 29	JointIndexWith7DofArm

const auto head_yaw =
    static_cast<int>(booster::robot::b1::JointIndex::kHeadYaw);
const auto right_wrist_yaw =
    static_cast<int>(
        booster::robot::b1::JointIndexWith7DofArm::kRightWristYaw);

Bundled Examples

example/low_level contains low-level publishing, low-level subscription, odometry, battery-state, and hand-data C++ examples. See C++ Example Index for build instructions and executable names.

Public Topic Constants and Enum Members

The following tables describe every application-facing topic constant in b1_api_const.hpp. Topic names are protocol contracts; use the kTopic* constants instead of constructing similar strings in application code.

Constant	Topic	Business meaning
kTopicJointCtrl	rt/joint_ctrl	Low-level joint commands; active only in Custom mode. Verify the layout and publish rate first.
kTopicLowState	rt/low_state	Motor, joint-feedback, and low-level sensor state.
kTopicFallDown	rt/fall_down	Fall detection and recovery state.
kTopicOdometerState	rt/odometer_state	Planar odometry consumed by the motion controller.
kTopicBoosterHandData	rt/booster_hand_data	Actuator feedback from an installed Booster hand; requires compatible hardware.
kTopicHandTouchData	rt/booster_hand_touch_data	Touch-sensor data from a compatible hand; availability is hardware-dependent.
kTopicRobotStates	rt/robot_states	Current RobotMode, BodyControl, and Action states.
kTopicProneBodyControlStatus	rt/prone_body_control_status	Prone-body and visual-kick status; non-inactive states depend on T1 body controllers.
kTopicRobotReplayTrajID	rt/robot_replay_traj_id	ID of the upper-body trajectory being replayed; recording/replay is normally enabled on K1/T1.
kTopicTrainedTrajStatus	rt/trained_traj_status	Built-in or custom trained-trajectory execution state for action highlighting; T1 normally reports idle.
kTopicRobocupBehaviorStatus	rt/robocup_behavior_status	Robocup soccer behavior state for K1/T1; soccer mode is disabled on T2.
kTopicKickReference	rt/kick_ball	Ball-position/kick reference for visual kick; T2 has no visual-kick controller.

Constant	Topic	Business meaning
kTopicTF	rt/tf	Robot transform tree; the current release is consumed through ROS 2.
kTopicRosOdometer	rt/odom	ROS nav_msgs/Odometry-compatible odometry; requires the ROS bridge.
kTopicRosImu	rt/imu/data	ROS sensor_msgs/Imu-compatible IMU data; requires the ROS bridge.
kTopicRosJointStates	rt/joint_states	ROS sensor_msgs/JointState-compatible joint state; requires the ROS bridge.

JointIndex (the default 23-joint T1 layout):

Member	Value	Meaning
kHeadYaw	0	Head yaw.
kHeadPitch	1	Head pitch.
kLeftShoulderPitch / kLeftShoulderRoll	2 / 3	Left shoulder pitch / roll.
kLeftElbowPitch / kLeftElbowYaw	4 / 5	Left elbow pitch / yaw.
kRightShoulderPitch / kRightShoulderRoll	6 / 7	Right shoulder pitch / roll.
kRightElbowPitch / kRightElbowYaw	8 / 9	Right elbow pitch / yaw.
kWaist	10	Waist yaw.
kLeftHipPitch / kLeftHipRoll / kLeftHipYaw	11 / 12 / 13	Left hip pitch / roll / yaw.
kLeftKneePitch	14	Left knee pitch.
kCrankUpLeft / kCrankDownLeft	15 / 16	Left upper / lower crank.
kRightHipPitch / kRightHipRoll / kRightHipYaw	17 / 18 / 19	Right hip pitch / roll / yaw.
kRightKneePitch	20	Right knee pitch.
kCrankUpRight / kCrankDownRight	21 / 22	Right upper / lower crank.

JointIndexK1 (the 22-joint K1 layout):

Member	Value	Meaning
kHeadYaw / kHeadPitch	0 / 1	Head yaw / pitch.
kLeftShoulderPitch / kLeftShoulderRoll	2 / 3	Left shoulder pitch / roll.
kLeftElbowPitch / kLeftElbowYaw	4 / 5	Left elbow pitch / yaw.
kRightShoulderPitch / kRightShoulderRoll	6 / 7	Right shoulder pitch / roll.
kRightElbowPitch / kRightElbowYaw	8 / 9	Right elbow pitch / yaw.
kLeftHipPitch / kLeftHipRoll / kLeftHipYaw	10 / 11 / 12	Left hip pitch / roll / yaw.
kLeftKneePitch	13	Left knee pitch.
kCrankUpLeft / kCrankDownLeft	14 / 15	Left upper / lower crank.
kRightHipPitch / kRightHipRoll / kRightHipYaw	16 / 17 / 18	Right hip pitch / roll / yaw.
kRightKneePitch	19	Right knee pitch.
kCrankUpRight / kCrankDownRight	20 / 21	Right upper / lower crank.

JointIndexWith7DofArm (the 29-joint T1_7DofArm layout):

Member	Value	Meaning
kHeadYaw / kHeadPitch	0 / 1	Head yaw / pitch.
kLeftShoulderPitch / kLeftShoulderRoll	2 / 3	Left shoulder pitch / roll.
kLeftElbowPitch / kLeftElbowYaw	4 / 5	Left elbow pitch / yaw.
kLeftWristPitch / kLeftWristYaw / kLeftHandRoll	6 / 7 / 8	Left wrist pitch / yaw / hand roll.
kRightShoulderPitch / kRightShoulderRoll	9 / 10	Right shoulder pitch / roll.
kRightElbowPitch / kRightElbowYaw	11 / 12	Right elbow pitch / yaw.
kRightWristPitch / kRightWristYaw / kRightHandRoll	13 / 14 / 15	Right wrist pitch / yaw / hand roll.
kWaist	16	Waist yaw.
kLeftHipPitch / kLeftHipRoll / kLeftHipYaw	17 / 18 / 19	Left hip pitch / roll / yaw.
kLeftKneePitch	20	Left knee pitch.
kCrankUpLeft / kCrankDownLeft	21 / 22	Left upper / lower crank.
kRightHipPitch / kRightHipRoll / kRightHipYaw	23 / 24 / 25	Right hip pitch / roll / yaw.
kRightKneePitch	26	Right knee pitch.
kCrankUpRight / kCrankDownRight	27 / 28	Right upper / lower crank.

Hand and remote-controller enums:

Enum member	Value	Meaning
HandIndex::kLeftHand / kRightHand	0 / 1	Left / right hand index used by hand and gripper APIs.
BoosterHandType::kInspireHand	0	Inspire dexterous hand without touch feedback.
BoosterHandType::kInspireTouchHand	2	Inspire dexterous hand with touch sensing.
BoosterHandType::kRevoHand	3	Revo dexterous hand.
BoosterHandType::kUnknown	-1	Unknown or unavailable hand type.
HandAction::kHandOpen	0	Open the hand or start the selected hand action.
HandAction::kHandClose	1	Close the hand or stop the selected action; individual APIs may restrict manual stopping.
RemoteControllerEvent::NONE	0	No event.
RemoteControllerEvent::AXIS	0x600	Analog-axis motion.
RemoteControllerEvent::HAT	0x602	Directional-hat position change.
RemoteControllerEvent::BUTTON_DOWN	0x603	Button pressed.
RemoteControllerEvent::BUTTON_UP	0x604	Button released.
RemoteControllerEvent::REMOVE	0x606	Controller device removed.