astro_hardware_interface

ROS 2 ros2_control hardware interface for the Astro differential-drive mobile robot. Handles serial communication with a Teensy microcontroller and exposes velocity command and position/velocity state interfaces for both wheels.

---

Prerequisites

• ROS 2 Humble
• colcon build tool
• libserial-dev

sudo apt install libserial-dev

Install ROS 2 dependencies:

sudo apt install \
  ros-humble-ros2-control \
  ros-humble-ros2-controllers \
  ros-humble-controller-manager \
  ros-humble-robot-state-publisher \
  ros-humble-joint-state-broadcaster \
  ros-humble-diff-drive-controller \
  ros-humble-rviz2

---

Clone & Build

# Create workspace (skip if you already have one)
mkdir -p ~/astro_hw_ws/src
cd ~/astro_hw_ws/src

# Clone the repository
git clone <repository-url> astro_hardware_interface

# Install remaining ROS dependencies
cd ~/astro_hw_ws
rosdep install --from-paths src --ignore-src -r -y

# Build
colcon build --packages-select astro_hardware_interface

# Source the workspace
source install/setup.bash

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Hardware Setup

• Connect the Teensy to the PC via USB. The default serial device is /dev/ttyACM0 at 115200 baud.
• To use a different port, edit description/ros2_control/astro.ros2_control.xacro.
• Grant serial port access if needed:

sudo usermod -aG dialout $USER
# Log out and back in for the change to take effect

---

Usage

Visualize the robot model (no hardware required)

ros2 launch astro_hardware_interface view_robot.launch.py

Full bringup (hardware + controllers + RViz)

ros2 launch astro_hardware_interface astro_hardware.launch.py

This starts:

• ros2_control_node with the Astro hardware interface
• robot_state_publisher
• joint_state_broadcaster
• astro_diff_drive_controller
• RViz

Verify hardware interfaces

ros2 control list_hardware_interfaces

Expected output:

command interfaces
      left_wheel_joint/velocity [available] [claimed]
      right_wheel_joint/velocity [available] [claimed]
state interfaces
      left_wheel_joint/position
      left_wheel_joint/velocity
      right_wheel_joint/position
      right_wheel_joint/velocity

Verify controllers

ros2 control list_controllers

Expected output:

astro_diff_drive_controller[diff_drive_controller/DiffDriveController] active
joint_state_broadcaster[joint_state_broadcaster/JointStateBroadcaster] active

Send velocity commands

ros2 topic pub --rate 30 /astro_diff_drive_controller/cmd_vel_unstamped geometry_msgs/msg/Twist "{
  linear: {x: 0.5, y: 0.0, z: 0.0},
  angular: {x: 0.0, y: 0.0, z: 0.5}
}"

The robot accepts:

• linear.x — forward/backward velocity (m/s), max ±1.0 m/s
• angular.z — rotational velocity (rad/s), max ±1.0 rad/s

---

Package Structure

astro_hardware_interface/
├── hardware/
│   ├── astro_interface.cpp          # Hardware interface implementation
│   └── include/astro_hardware_interface/
│       ├── astro_interface.hpp      # AstroHardware class
│       ├── teensy_comms.hpp         # Serial communication with Teensy
│       └── wheel.hpp                # Wheel state/command data
├── bringup/
│   ├── launch/astro_hardware.launch.py
│   └── config/astro_controllers.yaml
├── description/
│   ├── launch/view_robot.launch.py
│   ├── urdf/                        # Robot URDF/xacro model
│   ├── ros2_control/                # ros2_control hardware config
│   └── rviz/                        # RViz configurations
└── astro_hardware_interface.xml     # pluginlib plugin description

Robot Parameters

Parameter	Value
Wheel separation	0.304 m
Wheel radius	0.036 m
Serial device	/dev/ttyACM0
Baud rate	115200
Control loop rate	30 Hz
Encoder counts/rev	3436