Foxy Simple Publisher and Subscriber 20210322

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Context

  • Quick overview for the April 20, 2021 Oregon IEEE RAS Burger Build. See the reference below for details.
  • Find in eepp_ws/src/cpp_pubsub

References

Publish and Subscribe

Prereqs

Steps

Create Workspace and Package - An Overlay

 $ mkdir -p explore_images_ws/src

 $ cd explore_images_ws/src/

 $ ros2 pkg create --build-type ament_cmake cpp_pubsub
   going to create a new package
   package name: cpp_pubsub
   destination directory: /home/eepp/explore_images_ws/src
   package format: 3
   version: 0.0.0
   description: TODO: Package description
   maintainer: ['eepp <eepp@todo.todo>']
   licenses: ['TODO: License declaration']
   build type: ament_cmake
   dependencies: []
   creating folder ./cpp_pubsub
   creating ./cpp_pubsub/package.xml
   creating source and include folder
   creating folder ./cpp_pubsub/src
   creating folder ./cpp_pubsub/include/cpp_pubsub
   creating ./cpp_pubsub/CMakeLists.txt

Copy in the Package Files

This is a shortcut - see references for details.

Source Files

 $ cd ~/eepp_ws/src/cpp_pubsub/src

 $ ls
     publisher_member_function.cpp  subscriber_member_function.cpp

Package and Make Files

 $ cd ~/eepp_ws/src/cpp_pubsub

 $ ls
       CMakeLists.txt  include  package.xml  src

Customizations 

 <description>Minimal publisher/subscriber from Foxy tutorials</description>
 <maintainer email="eepp@zdome.net">eepp</maintainer>
 <license>Apache License 2.0</license>

note 

 <depend>rclcpp</depend>
 <depend>std_msgs</depend>

Important cusomizations 

 add_executable(talker src/publisher_member_function.cpp)
 ament_target_dependencies(talker rclcpp std_msgs)

 add_executable(listener src/subscriber_member_function.cpp)
 ament_target_dependencies(listener rclcpp std_msgs)

 install(TARGETS
   talker
   listener
   DESTINATION lib/${PROJECT_NAME})

Build

 $ cd ~/eepp_ws

 $  colcon build --packages-select cpp_pubsub
     Starting >>> cpp_pubsub
     Finished <<< cpp_pubsub [1.41s]                  

     Summary: 1 package finished [1.62s]

 $ ls install/cpp_pubsub/lib/cpp_pubsub/
     listener  talker

or 

 $ colcon build --symlink-install --parallel-workers 1

Put the following empty file into a project direcoty to bypass build.

CATKIN_IGNORE

Execute

TERMINAL 1 

 $ source ~/eepp_ws/install/setup.bash 

 $ ros2 run cpp_pubsub talker
     [INFO] [1616611188.838432139] [minimal_publisher]: Publishing: 'Hello, world! 0'
     [INFO] [1616611189.338379860] [minimal_publisher]: Publishing: 'Hello, world! 1'
     [INFO] [1616611189.838355264] [minimal_publisher]: Pub
     ...
     ...

TERMINAL 2 

 $ source ~/eepp_ws/install/setup.bash 

 $ ros2 run cpp_pubsub listener
     [INFO] [1616611370.928743717] [minimal_subscriber]: I heard: 'Hello, world! 52'
     [INFO] [1616611371.428557842] [minimal_subscriber]: I heard: 'Hello, world! 53'
     [INFO] [1616611371.928473827] [minimal_subscriber]: I heard: 'Hello, world! 54'
     [INFO] [1616611372.428607106] [minimal_subscriber]: I heard: 'Hello, world! 55'
     [INFO] [1616611372.928570767] [minimal_subscriber]: I heard: 'Hello, world! 56'
     [INFO] [1616611373.428502002] [minimal_subscriber]: I heard: 'Hello, world! 57'
     [INFO] [1616611373.928500708] [minimal_subscriber]: I heard: 'Hello, world! 58'
     [INFO] [1616611374.428463893] [minimal_subscriber]: I heard: 'Hello, world! 59'
     [INFO] [1616611374.928503750] [minimal_subscriber]: I heard: 'Hello, world! 60'
     ...
     ...

Notes and Logs

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