📷 200W USB Camera Introduction and Usage

1. Course Overview

This course will introduce the basic characteristics of the 200W pixel USB HD wide-angle camera equipped on the A1 Pro robot, and demonstrate how to use the ROS 2 driver to start the camera node, use rqt_image_view to view the color image stream in real-time, and read the camera intrinsic parameters /camera_info topic.

🎯 Course Objectives

1. Understand the hardware specifications and operating parameters of the 200W USB camera

2. Master how to start the camera driver and image visualization using usb_cam

3. Master how to view and understand the camera intrinsic topic /camera_info

2. Camera Hardware Introduction

The USB HD camera equipped on A1 Pro features wide dynamic range, high frame rate, and plug-and-play capability:

• Sensor Resolution: Up to 1920×1080 (1080P) / Calibration default output 640×480

• Working Frame Rate: 30 FPS

• Field of View (FOV): Large field of view with no distortion/minor distortion wide-angle lens

• Interface Type: USB 2.0 driver-free UVC standard protocol

• Data Output Format: YUYV / MJPEG

3. Preparation and Driver Startup

3.1 Start USB Camera Driver Node

Open the terminal and run the following command to start the camera driver:

ros2 launch usb_cam camera.launch.py

After the driver starts successfully, it will continuously capture images in the background and publish /image_raw (or /usb_cam/image_raw) and /camera_info topics.

4. Hands-on Demo and Visualization

4.1 Use rqt_image_view to View Real-time Images

Run the following in a new terminal:

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ros2 run rqt_image_view rqt_image_view

In the pop-up interface, select the camera's image topic (/usb_cam/image_raw) from the dropdown list on the upper left to view the RGB color image captured by the camera in real-time:

4.2 View Camera Intrinsic Topic (/usb_cam/camera_info)

Execute in the terminal:

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ros2 topic echo /usb_cam/camera_info --once

5. Core Source Code and Parameter Analysis

5.1 Launch File

Path:

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$HOME/yahboomcar_ros2_ws/software/library_ws/src/usb_cam/launch/camera.launch.py

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def generate_launch_description():
    camera_node = Node(
        package='usb_cam',
        executable='usb_cam_node_exe',
        name='usb_cam',
        output='screen',
        parameters=[
            {'video_device': '/dev/video0'},
            {'image_width': 640},
            {'image_height': 480},
            {'framerate': 30.0},
            {'pixel_format': 'yuyv2rgb'},
            {'io_method': 'mmap'},
            {'camera_frame_id': 'camera_link'},
        ],
    )
    return LaunchDescription([camera_node])

5.2 Core Parameter Description