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message_generation功能包是用于生成C++或Python能使用的代码。

message_runtime则是提供运行时的支持。

消息类型与C++或者Python的数据类型对应关系如下表：

自定义消息

在功能包中新建一个文件夹，名字为msg，这很重要，若非特别想要，尽量不要修改这个文件夹的名字。
在msg文件夹其中新建一个名为topic_msg.msg消息类型文件。
然后在这个消息文件写入以下测试内容:

0安装环境

1-1 安装ros

https://www.cnblogs.com/gooutlook/p/16363452.html

1-2 安装串口

1	`sudo apt-get` `install ros-noetic-serial`

1	`noetic是板本号`

1创建环境工程

1创建catkin_ros工程文件环境

1	`mkdir -p catkin_ros/src`

在catkin_ros路径下编译

1	`catkin_make`

自动生成

#将新的工作空间加入到环境变量中

1	`source devel/setup.bash`

2 创建项目工程

环境工程catkin_ros/src下创建工程imu_gps_publish

方法1 程序创建imu_gps_publish包

（没有工程前提下，程序自动创建基本依赖的等）

1	`#创建一个名为'imu_gps_publish'的新程序包，这个程序包依赖于std_msgs、roscpp和rospy：`

1	`catkin_create_pkg imu_gps_publish roscpp rospy std_msgs message_generation message_runtime`

此时整个工作空间的文件架构如下：

catkin_ros   #工作空间
        build
        devle
        src
            imu_gps_publish
                include
                src
                CMakeLists.txt
                package.xml
      CMakeLists.txt

　其中CMakeLists.txt和package.xml在自动阶段加入roscpp等基本库引用

方法2 已有程序直接导入已有的工程

将现有工程拷贝过来，但是要修改名字和一些路径

拷贝CMakeLists.txt package.xml src代码 msg自定义消息等

2 创建自定消息

2-1创建消息文件

在项目包里面创建msg文件夹

创建自定义消息topic_msg.msg

bool bool_msg
int8 int8_msg
uint8 uint8_msg
int16 int16_msg
uint16 uint16_msg
int32 int32_msg
uint32 uint32_msg
int64 int64_msg
uint64 uint64_msg
float32 float32_msg
float64 float64_msg
string string_msg
time time_msg
duration duration_msg

2-2 创建编辑package.xml　

<?xml version="1.0"?>
<package format="2">
  <name>imu_gps_publish</name>
  <version>0.0.0</version>
  <description>The imu_gps_publish package</description>
 
  <!-- One maintainer tag required, multiple allowed, one person per tag -->
  <!-- Example:  -->
  <!-- <maintainer email="jane.doe@example.com">Jane Doe</maintainer> -->
  <maintainer email="dongdong@todo.todo">dongdong</maintainer>
 
 
  <!-- One license tag required, multiple allowed, one license per tag -->
  <!-- Commonly used license strings: -->
  <!--   BSD, MIT, Boost Software License, GPLv2, GPLv3, LGPLv2.1, LGPLv3 -->
  <license>TODO</license>
 
  <buildtool_depend>catkin</buildtool_depend>
  <build_depend>message_generation</build_depend>
  <build_depend>roscpp</build_depend>
  <build_depend>rospy</build_depend>
  <build_depend>std_msgs</build_depend>
  <build_export_depend>roscpp</build_export_depend>
  <build_export_depend>rospy</build_export_depend>
  <build_export_depend>std_msgs</build_export_depend>
  <exec_depend>message_runtime</exec_depend>
  <exec_depend>roscpp</exec_depend>
  <exec_depend>rospy</exec_depend>
  <exec_depend>std_msgs</exec_depend>
 
 
  <!-- The export tag contains other, unspecified, tags -->
  <export>
    <!-- Other tools can request additional information be placed here -->
 
  </export>
</package>

修改

1项目名字imu_gps_publish和文件夹一样

<name>imu_gps_publish</name>
<version>0.0.0</version>
<description>The imu_gps_publish package</description>

2如果你是在已有的功能包中想要自定义消息，则在package.xml文件中添加功能包依赖：

1 2	`<build_depend>message_generation</build_depend>` `<run_depend>message_runtime</run_depend>`

2-3创建编辑CMakeLists.txt

cmake_minimum_required(VERSION 3.0.2)
project(imu_gps_publish)
 
## Compile as C++11, supported in ROS Kinetic and newer
# add_compile_options(-std=c++11)
 
 
find_package(catkin REQUIRED COMPONENTS
  message_generation
  message_runtime
  roscpp
  rospy
  std_msgs
)
 
add_message_files(
  FILES
  topic_msg.msg
)
 
generate_messages(
  DEPENDENCIES
  std_msgs
)
 
catkin_package(
#  INCLUDE_DIRS include
#  LIBRARIES my_topic002
#  CATKIN_DEPENDS message_generation message_runtime roscpp rospy std_msgs
#  DEPENDS system_lib
)
 
###########
## Build ##
###########
 
 
include_directories(
# include
  ${catkin_INCLUDE_DIRS}
)
 
 
#add_executable(publisher_topic002 src/publisher_topic002.cpp)
#target_link_libraries(publisher_topic002 ${catkin_LIBRARIES})
#add_dependencies(publisher_topic002 ${PROJECT_NAME}_generate_messages_cpp) 
 
#add_executable(subscriber_topic002 src/subscriber_topic002.cpp)
#target_link_libraries(subscriber_topic002 ${catkin_LIBRARIES})
#add_dependencies(subscriber_topic002 ${PROJECT_NAME}_generate_messages_cpp) 

其中

1修改项目名字和文件夹一样

1 2	`cmake_minimum_required(VERSION 3.0.2)` `project(imu_gps_publish)`

2 修改自定义的消息

3其他说明（自动生成的时候加入的，这里直接贴了出来给查看）

CMakeLists.txt要修改4-5个地方，根据实际场景修改即可：

3-1首先调用find_package查找依赖的功能包，必须要有的是roscpp、rospy、message_generation、message_runtime，而在消息文件中嵌套了其他的消息，则需要依赖其他的功能包。

find_package(catkin REQUIRED COMPONENTS
  message_generation
  message_runtime
  roscpp
  rospy
  std_msgs
)

3-2添加消息文件，指定.msg文件。

add_message_files(
  FILES
  topic_msg.msg
)

3-3指定生成消息文件时的依赖项，其实如果消息文件中有依赖的话，就需要在这里设置，此处假设我依赖了std_msgs（当然我是没有依赖的），就要配置如下：

generate_messages(
  DEPENDENCIES
  std_msgs
)

3-4 catkin_package声明相关的依赖，一般来通过catkin_create_pkg命令选择了依赖的话，这里是不需要设置的，不过我也给出来我的配置：

catkin_package(
#  INCLUDE_DIRS include
#  LIBRARIES my_topic002
#  CATKIN_DEPENDS message_generation message_runtime roscpp rospy std_msgs
#  DEPENDS system_lib
)

3-5编写编译规则，生成的可执行文件名字、源码、链接库、依赖等内容。

消息阶段用不到

add_executable(publisher_topic002 src/publisher_topic002.cpp)
target_link_libraries(publisher_topic002 ${catkin_LIBRARIES})
add_dependencies(publisher_topic002 ${PROJECT_NAME}_generate_messages_cpp) 
 
add_executable(subscriber_topic002 src/subscriber_topic002.cpp)
target_link_libraries(subscriber_topic002 ${catkin_LIBRARIES})
add_dependencies(subscriber_topic002 ${PROJECT_NAME}_generate_messages_cpp) 

编译消息

在catkin_ros文件路径下编译

1	`catkin_make`

可以看到生成的自定义消息文件地址

在devel的include文件夹中

3对消息的引用

3-1发布器

imu_gps_publish/src下创建publisher_topic002.cpp

#include <cstdlib>
#include <iostream>
#include <string>
#include <cstring>
 
//0 导入ros依赖
#include "ros/ros.h"
 
//0 导入消息 工程名字/消息名字
#include "imu_gps_publish/topic_msg.h"
#include "std_msgs/String.h"
 
int main(int argc, char **argv)
{
 
    // 0-1 ROS节点初始化
    ros::init(argc, argv, "publisher_topic002");
    // 0-2 创建节点句柄
    ros::NodeHandle n;
 
 
    // 1 创建发布器
    // 1-1创建一个Publisher，发布名为my_topic_msg，消息类型为imu_gps_publish::topic_msg，队列长度100
    ros::Publisher pub_topic = n.advertise<my_topic002::topic_msg>("my_topic_msg",100);
    // 1-2设置循环的频率
    ros::Rate loop_rate(1);
 
    while (ros::ok())
    {
        // 2 创建消息
        // 2-0 创建消息
        my_topic002::topic_msg msg;
        // 2-1 消息初始化
        msg.bool_msg = true;
        msg.string_msg = "hello world!";
        msg.float32_msg = 6.66;
        msg.float64_msg = 666.666;
        msg.int8_msg = -66;
        msg.int16_msg = -666;
        msg.int32_msg = -6666;
        msg.int64_msg = -66666;
        msg.uint8_msg = 66;
        msg.uint16_msg = 666;
        msg.uint32_msg = 6666;
        msg.uint64_msg = 66666;
        msg.time_msg = ros::Time::now();
 
        // 3 发布消息
        pub_topic.publish(msg);
 
        // 4按照循环频率延时
        loop_rate.sleep();
    }
 
    return 0;
}

修改

1自定义消息路径和名字工程包名字imu_gps_publish+自定义的消息名字topic_msg

包含头文件

1 2	`//0 导入消息工程名字/消息名字` `#include "imu_gps_publish/topic_msg.h"`

2 所有关于自定义消息的引用名字　　

1	`imu_gps_publish::topic_msg`

3-2接收节点

创建subscriber_topic002.cpp

#include <cstdlib>
#include <iostream>
#include <string>
#include <cstring>
 
//0 导入ros依赖
#include <ros/ros.h>
 
//0 导入消息 工程名字/消息名字
#include "imu_gps_publish/topic_msg.h"
#include <std_msgs/String.h>
 
 
// 接收到订阅的消息后，会进入消息回调函数
void test_topic_cb(const imu_gps_publish::topic_msg::ConstPtr & msg)
{
    // 将接收到的消息打印出来
    ROS_INFO("------------------ msg ---------------------");
    ROS_INFO("bool_msg:    [%d]", msg->bool_msg);
    ROS_INFO("string_msg:  [%s]", msg->string_msg.c_str());
    ROS_INFO("float32_msg: [%f]", msg->float32_msg);
    ROS_INFO("float64_msg: [%f]", msg->float64_msg);
    ROS_INFO("int8_msg:    [%d]", msg->int8_msg);
    ROS_INFO("int16_msg:   [%d]", msg->int16_msg);
    ROS_INFO("int32_msg:   [%d]", msg->int32_msg);
    ROS_INFO("int64_msg:   [%ld]", msg->int64_msg);
    ROS_INFO("uint8_msg:   [%d]", msg->uint8_msg);
    ROS_INFO("uint16_msg:  [%d]", msg->uint16_msg);
    ROS_INFO("uint32_msg:  [%d]", msg->uint32_msg);
    ROS_INFO("uint64_msg:  [%ld]", msg->uint64_msg);
    ROS_INFO("time_msg:    [%d.%d]", msg->time_msg.sec, msg->time_msg.nsec);
}
 
 
int main(int argc, char **argv)
{
    // 初始化ROS节点
    ros::init(argc, argv, "subscriber_topic002");
 
    // 创建节点句柄
    ros::NodeHandle n;
 
    // 创建一个Subscriber，订阅名为my_topic_msg的消息，注册回调函数test_topic_cb
    ros::Subscriber sub_topic = n.subscribe<imu_gps_publish::topic_msg>("my_topic_msg", 100, test_topic_cb);
 
    // 循环等待回调函数
    ros::spin();
 
    return 0;
}

修改

1自定义消息路径和名字工程包名字imu_gps_publish+自定义的消息名字topic_msg

1 2	`//0 导入消息工程名字/消息名字` `#include "imu_gps_publish/topic_msg.h"`

2 所有关于自定义消息的引用名字　　

imu_gps_publish::topic_msg

3-3 修改CMakeLists.txt编译节点

添加发射和接受节点的生成

add_executable(publisher_topic002 src/publisher_topic002.cpp)
target_link_libraries(publisher_topic002 ${catkin_LIBRARIES})
add_dependencies(publisher_topic002 ${PROJECT_NAME}_generate_messages_cpp) 
 
add_executable(subscriber_topic002 src/subscriber_topic002.cpp)
target_link_libraries(subscriber_topic002 ${catkin_LIBRARIES})
add_dependencies(subscriber_topic002 ${PROJECT_NAME}_generate_messages_cpp) 

完整的

cmake_minimum_required(VERSION 3.0.2)
project(imu_gps_publish)
 
## Compile as C++11, supported in ROS Kinetic and newer
# add_compile_options(-std=c++11)
 
 
find_package(catkin REQUIRED COMPONENTS
  message_generation
  message_runtime
  roscpp
  rospy
  std_msgs
)
 
add_message_files(
  FILES
  topic_msg.msg
)
 
generate_messages(
  DEPENDENCIES
  std_msgs
)
 
catkin_package(
#  INCLUDE_DIRS include
#  LIBRARIES my_topic002
#  CATKIN_DEPENDS message_generation message_runtime roscpp rospy std_msgs
#  DEPENDS system_lib
)
 
###########
## Build ##
###########
 
 
include_directories(
# include
  ${catkin_INCLUDE_DIRS}
)
 
 
add_executable(publisher_topic002 src/publisher_topic002.cpp)
target_link_libraries(publisher_topic002 ${catkin_LIBRARIES})
add_dependencies(publisher_topic002 ${PROJECT_NAME}_generate_messages_cpp) 
 
add_executable(subscriber_topic002 src/subscriber_topic002.cpp)
target_link_libraries(subscriber_topic002 ${catkin_LIBRARIES})
add_dependencies(subscriber_topic002 ${PROJECT_NAME}_generate_messages_cpp) 