ROS 2 create node - publisher / subscriber

紀錄ROS 2 ardent 版本下

如何建立workspace 及自定義msg type 並建立publisher 及 subscriber 程式

因為目前ROS 2 ardent 不支援catkin ，所以很多步驟還是得手動進行

如果沒將 source /opt/ros/ardent/setup.bash 放到bashrc，記得先進行一次source

https://github.com/ros2/ros2/wiki/Rosidl-Tutorial

在Windows 10建立ROS 2 node的方式跟Linux 一樣

package.xml 及cmake file 幾乎不用改 (只要改include path . link path )

使用VS2015 x64 Native Tools Command Prompt 設置ROS 2 環境變數後，進到workspace 輸入ament build

程式碼可以到以下github 查看部分sample

https://github.com/ros2/examples

建立worksapce 及package

mkdir -p ~/ros2_ws/src cd ~/ros2_ws/src mkdir -p karl_demo/src

建立一個自定義的msg file  (ROS data format)，ROS 2 可以在build 時自動gen 出idl file (DDS data format)，再連鎖gen 出header 檔案開發用

注意msg 檔名要大寫開頭

cd ~/ros2_ws/src/karl_demo mkdir msg cd msg vim Custom.msg

資料結構先定為一個uint32 的data

Custom.msg

uint32 data

建立cmake file 及package.xml 寫入所需的內容

並用ament gen 出 header

cd ~/ros2_ws/src/karl_demo vim CMakeLists.txt vim package.xml cd ~/ros2_ws ament build ls install/include/karl_demo/msg/ #custom__functions.h #custom.h #custom.hpp #custom__rosidl_typesupport_introspection_c.h #custom__rosidl_typesupport_introspection_cpp.hpp #custom__rosidl_typesupport_opensplice_c.h #custom__rosidl_typesupport_opensplice_cpp.hpp #custom__struct.h #custom__struct.hpp #custom__traits.hpp #custom__type_support.h #dds_opensplice #dds_opensplice_c #rosidl_generator_c__visibility_control.h #rosidl_typesupport_introspection_c__visibility_control.h #rosidl_typesupport_opensplice_cpp__visibility_control.h #rosidl_typesupport_opensplice_c__visibility_control.h

CMakeLists.txt

cmake_minimum_required(VERSION 3.5) project(karl_demo) # Default to C++14 if(NOT CMAKE_CXX_STANDARD)   set(CMAKE_CXX_STANDARD 14) endif() if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")   add_compile_options(-Wall -Wextra -Wpedantic) endif() find_package(ament_cmake REQUIRED) find_package(rclcpp REQUIRED) find_package(rosidl_default_generators REQUIRED) rosidl_generate_interfaces(${PROJECT_NAME}   "msg/Custom.msg" ) ament_export_dependencies(rosidl_default_runtime) ament_package()

package.xml

<?xml version="1.0"?> <?xml-model href="http://download.ros.org/schema/package_format3.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?> <package format="3">   <name>karl_demo</name>   <version>0.0.3</version>   <description>     C++ nodes which were previously in the ros2/examples repository but are now just used for demo purposes.   </description>   <maintainer email="william@osrfoundation.org">William Woodall</maintainer>   <license>Apache License 2.0</license>   <buildtool_depend>ament_cmake</buildtool_depend>   <buildtool_depend>rosidl_default_generators</buildtool_depend>   <build_depend>rclcpp</build_depend>   <exec_depend>rclcpp</exec_depend>   <exec_depend>rosidl_default_runtime</exec_depend>   <member_of_group>rosidl_interface_packages</member_of_group>   <export>     <build_type>ament_cmake</build_type>   </export> </package>

接著先建立一個publisher 程式

並修改CMakeLists.txt

cd ~/ros2_ws/src/karl_demo/src vim talker.cpp

talker.cpp

#include <iostream> #include <memory> #include <string> #include "rclcpp/rclcpp.hpp" #include "karl_demo/msg/custom.hpp" int main(int argc, char * argv[]) {   rclcpp::init(argc, argv);   auto node = rclcpp::Node::make_shared("talker");//node name = talker   rmw_qos_profile_t custom_qos_profile = rmw_qos_profile_default;   custom_qos_profile.depth = 7;   auto chatter_pub = node->create_publisher<karl_demo::msg::Custom>("chatter", custom_qos_profile);//topic name = chatter   rclcpp::WallRate loop_rate(2);   auto msg = karl_demo::msg::Custom();   auto i = 1;   while (rclcpp::ok()) {     msg.data = i;     std::cout << "Publishing: '" << msg.data << "'" << std::endl;     chatter_pub->publish(msg);     rclcpp::spin_some(node);     loop_rate.sleep();     i++;   }   return 0; }

修改cmake file 並回到workspace build

cd ~/ros2_ws/src/karl_demo vim CMakeLists.txt cd ~/ros2_ws ament build

CMakeLists.txt

cmake_minimum_required(VERSION 3.5) project(karl_demo) # Default to C++14 if(NOT CMAKE_CXX_STANDARD)   set(CMAKE_CXX_STANDARD 14) endif() if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")   add_compile_options(-Wall -Wextra -Wpedantic) endif() find_package(ament_cmake REQUIRED) find_package(rclcpp REQUIRED) find_package(rosidl_default_generators REQUIRED) rosidl_generate_interfaces(${PROJECT_NAME}   "msg/Custom.msg" ) ament_export_dependencies(rosidl_default_runtime) ######### find_package(karl_demo REQUIRED) include_directories(include /home/karlkwchen/ros2_overlay_ws/install/include) add_executable(talker src/talker.cpp) ament_target_dependencies(talker rclcpp karl_demo) install(TARGETS talker DESTINATION lib/${PROJECT_NAME}) ament_package()

執行talker

source ~/ros2_ws/install/local_setup.bash ros2 run karl_demo talker #Publishing: '1' #Publishing: '2' #Publishing: '3' #Publishing: '4' #Publishing: '5' #Publishing: '6' #Publishing: '7' #Publishing: '8'

再開一個terminal，可以先用ros2 指令測試接收topic

注意topic 要加斜線

source ~/ros2_ws/install/local_setup.bash ros2 topic echo /chatter karl_demo/Custom #data: 2 # #data: 3 # #data: 4 # #data: 5 # #data: 6 # #data: 7 # #data: 8

如果要換成Opensplice 傳輸，先設變數再去啟動程式即可

export RMW_IMPLEMENTATION=rmw_opensplice_cpp

目前確定Opensplice 及 FastRTPS 在ROS 2b3 arch下可以互通

建立subscriber，範例如下

回去修改cmake 再重新ament build 即可

#include <iostream> #include "rclcpp/rclcpp.hpp" #include "karl_demo/msg/custom.hpp" void callback(const karl_demo::msg::Custom::SharedPtr msg) {     printf("I heard [%d]\n", msg->data); } int main(int argc, char **argv) {     rclcpp::init(argc, argv);     auto node = rclcpp::Node::make_shared("listener");     auto chatter_sub = node->create_subscription<karl_demo::msg::Custom>("chatter", callback);     rclcpp::spin(node);     rclcpp::shutdown();     return 0; }