ROS 2 Bridge to ROS

demo 如何讓ROS 及ROS 2 互通，至於動機是甚麼呢，因為還有很多功能或者用戶還是在ROS

注意需要先安裝ROS 及ROS 2

https://github.com/ros2/ros1_bridge

下載安裝官方的ros1_bridge package

文件顯示從source code 自己build 需要系統有4 GB 的RAM

sudo apt-get update sudo apt-get install ros-ardent-ros1-bridge # if you use beta 3 version , use below instead # sudo apt-get install ros-r2b3-ros1-bridge

先開一個terminal 啟動roscore 

再開第二個terminal 啟動bridge，讓他連到roscore

export ROS_MASTER_URI=http://localhost:11311 ros2 run ros1_bridge dynamic_bridge     #created 2to1 bridge for topic '/chatter' with ROS 2 type 'std_msgs/String' and ROS 1 type '' #[INFO] [ros1_bridge]: Passing message from ROS 2 ROS2_T to ROS 1 ROS1_T (showing msg only once per type) (ros2_callback() at /tmp/binarydeb/ros-r2b3-ros1-bridge-0.0.3/include/ros1_bridge/factory.hpp:144) #removed 2to1 bridge for topic '/chatter'

再開兩個terminal 分別啟動ROS 及ROS 2 的node，就可以測試連通性了

ros2 run demo_nodes_cpp talker #Publishing: 'Hello World: 1' #Publishing: 'Hello World: 2' #Publishing: 'Hello World: 3' #Publishing: 'Hello World: 4' #Publishing: 'Hello World: 5' #Publishing: 'Hello World: 6' #Publishing: 'Hello World: 7' #Publishing: 'Hello World: 8' #Publishing: 'Hello World: 9' #Publishing: 'Hello World: 10' #Publishing: 'Hello World: 11' #Publishing: 'Hello World: 12' #Publishing: 'Hello World: 13' #Publishing: 'Hello World: 14' #Publishing: 'Hello World: 15'         rosrun roscpp_tutorials listener #[ INFO] [1513059523.468086510]: I heard: [Hello World: 3] #[ INFO] [1513059523.967160215]: I heard: [Hello World: 4] #[ INFO] [1513059524.467541429]: I heard: [Hello World: 5] #[ INFO] [1513059524.967622988]: I heard: [Hello World: 6] #[ INFO] [1513059525.467242192]: I heard: [Hello World: 7] #[ INFO] [1513059525.967151196]: I heard: [Hello World: 8] #[ INFO] [1513059526.467345780]: I heard: [Hello World: 9] #[ INFO] [1513059526.967592714]: I heard: [Hello World: 10] #[ INFO] [1513059527.467160224]: I heard: [Hello World: 11] #[ INFO] [1513059527.967049629]: I heard: [Hello World: 12] #[ INFO] [1513059528.467056936]: I heard: [Hello World: 13] #[ INFO] [1513059528.967666693]: I heard: [Hello World: 14] #[ INFO] [1513059529.467657316]: I heard: [Hello World: 15]

如果自己建立msg type，ROS 2 提供的ros1_bridge package 無法支援( 需要從source code 重新build ，目前還沒嘗試)

但也可以選擇自己寫一個bridge

其實原理就是一支程式同時使用ROS 及ROS 2 的API 來建構，如果只是要轉換自己的msg 不難(官方的ros1_bridge 用良好的架構處理多種的msg 轉換)

難的地方反而是在link library !? (一開始想抄官方的cmake 寫，但因為他的模組化還需要時間消化修改才能用，最後是直接寫cmake 語法較簡單)

底下的source code，示範將ROS 的msg 轉丟到ROS 2 上( ROS 2 sub 可以收到ROS pub 的topic )

處理方式是在callback function 內將ROS 的msg sample copy 塞到ROS 2 的msg sample

此處的package name 在ROS 及ROS 2 剛好都叫 beginner_tutorials ，可以不一樣

bridge.cpp

#include <iostream> #include <memory>   #ifdef __clang__ # pragma clang diagnostic push # pragma clang diagnostic ignored "-Wunused-parameter" #endif #include "ros/ros.h" //your custom msg header in ROS #include "beginner_tutorials/Daq.h" #ifdef __clang__ # pragma clang diagnostic pop #endif   #include "rclcpp/rclcpp.hpp" //your custom msg header in ROS 2 #include "beginner_tutorials/msg/daq.hpp"   rclcpp::Publisher<beginner_tutorials::msg::Daq>::SharedPtr pub;   void callback(const beginner_tutorials::Daq::ConstPtr & ros1_msg) {   std::cout << "I heard: [" << ros1_msg->length << "]" << std::endl;     auto ros2_msg = std::make_shared<beginner_tutorials::msg::Daq>();   ros2_msg->length = ros1_msg->length;   for(int i=0;i<ros1_msg->length;i++)     ros2_msg->data.push_back(ros1_msg->data[i]);   pub->publish(ros2_msg); }   int main(int argc, char * argv[]) {   // ROS 2 node and publisher   rclcpp::init(argc, argv);   auto node = rclcpp::Node::make_shared("bridger2");   pub = node->create_publisher<beginner_tutorials::msg::Daq>("test");     // ROS 1 node and subscriber   ros::init(argc, argv, "bridger1");   ros::NodeHandle n;   ros::Subscriber sub = n.subscribe("test", 10, callback);     ros::spin();     return 0; }

建置步驟

我是用ROS 2的ament 建置，所以檔案要放到ROS 2 的workspace 內

流程請參考 ROS 2 ardent create node - publisher / subscriber

需要先gen 出ROS 2 的msg header file

修改cmake file，再底下加入如下內容

CMakeLists.txt

include_directories(include /opt/ros/kinetic/include)   add_executable(bridge src/bridge.cpp) target_link_libraries(bridge /opt/ros/kinetic/lib/libroscpp.so) target_link_libraries(bridge /opt/ros/kinetic/lib/librosconsole.so) target_link_libraries(bridge /opt/ros/kinetic/lib/libroscpp_serialization.so) ament_target_dependencies(bridge rclcpp beginner_tutorials )   install(TARGETS bridge DESTINATION lib/${PROJECT_NAME})

要做到以下三件事情

• include ROS header
• link ROS library
• include ROS msg header ( 程式碼的這行#include "beginner_tutorials/Daq.h" )
  • 因為我將Daq.h 放到ROS 2 的workspace 所以不用寫到cmake file 內了

cd ~/ros2_ws ament build

啟動步驟跟用官方的一樣