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SO basically what I am trying to do is load multiple parameters from one yaml file and distribute them to multiple nodes. I have provided the code below. Basically instead of launch parameters I want to load them all through a single yaml. Any help would be greatly apprecaited.

`import os import yaml from ament_index_python.packages import get_package_share_directory from launch import LaunchDescription from launch.actions import IncludeLaunchDescription, ExecuteProcess, GroupAction from launch.launch_description_sources import PythonLaunchDescriptionSource from launch_ros.actions import Node, PushRosNamespace from launch.substitutions import LaunchConfiguration

def generate_launch_description(): # Load parameters from yaml file launch_params_path = os.path.join(get_package_share_directory('ros2_bringup'), 'config', 'parms.yaml') with open(launch_params_path, 'r') as file: launch_params = yaml.safe_load(file)['jetson_1']['ros__parameters']

# namespace = launch_params.get('namespace', '')
# camera_type = launch_params.get('camera_type', '')
# serial = launch_params.get('serial', '')
# sonar = launch_params.get('sonar', '')
# cam_topic = launch_params.get('cam_topic', '')
# frequency = launch_params.get('frequency', '')

# Paths to other files
microstrain_launch_file = os.path.join(get_package_share_directory('microstrain_inertial_examples'),
                                       'launch', 'cv7_launch.py')
microstrain_params_file = os.path.join(get_package_share_directory('microstrain_inertial_examples'),
                                       'config', 'cv7', 'cv7.yml')
empty_params_file = os.path.join(get_package_share_directory('microstrain_inertial_driver'),
                                 'config', 'empty.yml')
sonar_config_file = os.path.join(get_package_share_directory('imagenex831l_ros2'), 'cfg', 'sonar.yaml')

cam_driver_launch_file = os.path.join(get_package_share_directory('spinnaker_camera_driver'),
                                      'launch', 'driver_node.launch.py')
gui_launch_file = os.path.join(get_package_share_directory('custom_guyi'),
                               'launch', 'gui.launch.py')

# Nodes and actions
included_cam_launch = GroupAction(
    actions=[
        PushRosNamespace(namespace),
        IncludeLaunchDescription(
            PythonLaunchDescriptionSource(cam_driver_launch_file),
            launch_arguments={'camera_type': camera_type, 'serial': serial, 'frame_rate': frequency}.items()
        )
    ]
)

ping1d_node = Node(
    package='ms5837_bar_ros',
    executable='bar30_node',
    namespace=namespace,
    output="screen"
)

base_to_range = Node(
    package='tf2_ros',
    executable='static_transform_publisher',
    output='screen',
    namespace=namespace,
    arguments=['0.0', '0.0', '0.0', '0', '0.0', '0.0', 'base_link', 'bar30_link']
)

included_imu_launch = GroupAction(
    actions=[
        PushRosNamespace(namespace),
        IncludeLaunchDescription(
            PythonLaunchDescriptionSource(microstrain_launch_file),
            launch_arguments={'namespace': namespace}.items()
        )
    ]
)

included_sonar_launch = GroupAction(
    actions=[
        PushRosNamespace(namespace),
        IncludeLaunchDescription(
            PythonLaunchDescriptionSource(os.path.join(get_package_share_directory('imagenex831l_ros2'),
                                                       'launch', 'sonar.launch.py')),
            launch_arguments={'sonar': sonar, 'device': namespace, 'config': sonar_config_file}.items()
        )
    ]
)

included_screen_launch = GroupAction(
    actions=[
        PushRosNamespace(namespace),
        IncludeLaunchDescription(
            PythonLaunchDescriptionSource(gui_launch_file),
            launch_arguments={'cam_topic': cam_topic, 'device': namespace}.items(),
        )
    ]
)

debayer_node = Node(
    package='ros2_bringup',
    executable='debayer.py',
    name='debayer',
    namespace=namespace,
    output='screen',
    parameters=[{'cam_topic': cam_topic, 'device': namespace}]
)

nodes = [
    included_cam_launch,
    ping1d_node,
    base_to_range,
    included_imu_launch,
    included_sonar_launch,
    included_screen_launch,
    debayer_node
]

# Topics to record
topics = [
    '/jetson_1/image/compressed',
    '/jetson_1/bar30/depth',
    '/jetson_1/bar30/pressure',
    '/jetson_1/bar30/temperature',
    '/jetson_1/imagenex831l/range',
    '/jetson_1/imu/data',
    '/jetson_1/ekf/status',
    '/jetson_1/imagenex831l/range_raw'
]

return LaunchDescription(
    nodes + [
        ExecuteProcess(
            cmd=['ros2', 'bag', 'record'] + topics,
            output='screen'
        )
    ]
)

`

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1 Answer 1

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You can define the parameters for multiple nodes within one parameter file like such:

from launch import LaunchDescription
from launch_ros.actions import Node
from ament_index_python.packages import get_package_share_directory
import os

def generate_launch_description():
    pkg_share = get_package_share_directory('package_where_your_config_is')
    ld = LaunchDescription()
    talker_node = Node(
        package="demo_nodes_cpp",
        executable="talker",
        name="talker_node",
        parameters=[os.path.join(pkg_share, 'config', config.yaml')] 
    )
    listener_node = Node(
        package="demo_nodes_py",
        executable="listener",
        name="listener_node",
        parameters=[os.path.join(pkg_share, 'config', config.yaml')] 
    )
    ld.add_action(talker_node)
    ld.add_action(listener_node)
    return ld

where the config.yaml then is:

/talker_node:
  ros__parameters:
    talker_parameter_1: 1.0
    talker_parameter_2: 2.0
/listener_node:
  ros__parameters:
    listener_parameter_1: 1.0
    listener_parameter_2: 2.0

You must only know what the node names or set them like I did in the minimal example. It parses only the parameters that follow the name of the node, since it's parsed in a struct-like fashion.

Concerning namespaces, you can

namespace_variable = LaunchConfiguration('namespace_launchArgument')
declare_namespace_cmd = DeclareLaunchArgument(
name='namespace_launchArgument',
default_value='foonamespace',
description='Namespace for all Nodes.')
ld.add_action(declare_namespace_cmd)

and hand over the namespace to any Node by adding it as another argument, e.g.:

talker_node = Node(
        package="demo_nodes_cpp",
        executable="talker",
        name="talker_node",
        namespace=namespace_variable ,
        parameters=[os.path.join(pkg_share, 'config', config.yaml')] 
    )

The beauty of this is that LaunchArguments can be passed to "child"-launch-files, see ROS2 Docs on the topic

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