ROS学习手记 - 7 创建ROS msg & srv
至此,我们初步学习了ROS的基本工具,接下来一步步理解ROS的各个工作部件的创建和工作原理。
本文的详细文档:http://wenku.baidu.com/view/623f41b3376baf1ffd4fad7a
Creating a ROS msg and srv
This tutorial covers how to create and build msg and srv files as well as therosmsg, rossrv and roscp commandline tools.
1. msg & srv 文件介绍
msg 文件 就是用来让不同语言能产生message的一个指导性文本文件。
srv file describes a service. It is composed of two parts: a request and a response.
2. msg & srv 文件存储位置:
<workspace>/packagename/msg/
&
<workspace>/packagename/srv/
==== msg file 说明 ==== 3. msgfile 的格式和生成 生成: $ cd ~/catkin_ws/src/beginner_tutorials $ mkdir msg $ echo "int64 num" > msg/Num.msg 格式: string first_name string last_name uint8 age uint32 score 4. msgfile 添加到package.xml的dependency中 <build_depend>message_generation</build_depend> <run_depend>message_runtime</run_depend> 5. 对CMakeLists.txt文件的修改: 5.1 添加message_generation dependency到CMakeLists.txt中: message_generation before the closing parenthesis find_package(catkin REQUIRED COMPONENTS roscpp rospy std_msgs message_generation // add ’message_generation’ ) 5.2 export the message runtime dependency. catkin_package( ... CATKIN_DEPENDS message_runtime ... ...) 5.3 添加msg文件 add_message_files( FILES Num.msg ) 添加了.msg文件在CMake里,我们保证在你添加其他.msg文件时,CMake知道何时它需要reconfigure重新配置项目。 5.4 确保generate_messages 函数被调用 generate_messages( DEPENDENCIES std_msgs ) 6. rosmsg 工具的使用 make sure that ROS can see it using the rosmsg show command. Usage: $ rosmsg show [message type] Example: $ rosmsg show beginner_tutorials/Num $ rosmsg show Num =================== |
=== srv file 说明 === 1. srv的路径和生成 $ roscd beginner_tutorials $ mkdir srv Instead of creating a new srv definition by hand, we will copy an existing one from another package. For that, roscp is a useful commandline tool for copying files from one package to another. 使用roscp工具从一个package拷贝文件到另一个。 Usage: $ roscp [package_name] [file_to_copy_path] [copy_path] Now we can copy a service from the rospy_tutorials package: $ roscp rospy_tutorials AddTwoInts.srv srv/AddTwoInts.srv 2. 保证package.xml里有dependency配置(可能独立修改了srv,确保一下) <build_depend>message_generation</build_depend> <run_depend>message_runtime</run_depend> 3.1 add the message_generation dependency to generate messages in CMakeLists.txt: # Do not just add this line to your CMakeLists.txt, modify the existing line find_package(catkin REQUIRED COMPONENTS roscpp rospy std_msgs message_generation ) 3.2 添加 srvice 文件 add_service_files( FILES AddTwoInts.srv ) 3.3 确保generate_messages 函数被调用 generate_messages( DEPENDENCIES std_msgs ) 4. 使用rossrv工具 添加以后,确保ROS can see it using the rossrv show command. Usage: $ rossrv show <service type> Example: $ rossrv show beginner_tutorials/AddTwoInts You will see: int64 a int64 b --- int64 sum Similar to rosmsg, you can find service files like this without specifying package name: $ rossrv show AddTwoInts [beginner_tutorials/AddTwoInts]: int64 a int64 b --- int64 sum [rospy_tutorials/AddTwoInts]: int64 a int64 b --- int64 sum |
无论是修改了msg还是srv,都需要做的步骤:
CMakeLists.txt文件的修改
1.
find_package(catkin REQUIRED COMPONENTS
roscpp
rospy
std_msgs
message_generation // add ’message_generation’
)
2. add any packages you depend on which contain .msg files that your messages use (in this case std_msgs), such that it looks like this:
generate_messages(
DEPENDENCIES
std_msgs
)
终于到了catkin_make出手的时候:
Now that we have made some new messages we need to make our package again:
# In your catkin workspace (by default:~/catkin_ws$)
$ cd ../..
$ catkin_make
$ cd -
至此,我们就编译完成了一套ROS 的 msg & srv
Any .msg file in the msg directory will generate code for use in all supportedlanguages.
The C++ message header file will be generated in ~/catkin_ws/devel/include/beginner_tutorials/.
The Python script will be created in ~/catkin_ws/devel/lib/python2.7/dist-packages/beginner_tutorials/msg.
The lisp file appears in ~/catkin_ws/devel/share/common-lisp/ros/beginner_tutorials/msg/.
The full specification for the message format is available at theMessage Description Language page.
Getting Help
We've seen quite a few ROS tools already. It can be difficult to keeptrack of what arguments each command requires. Luckily, most ROS tools providetheir own help.
Try:
$ rosmsg -h
You should see a list of different rosmsg subcommands.
Commands:
rosmsgshow Show message description
rosmsgusers Find files that use message
rosmsgmd5 Display message md5sum
rosmsgpackage List messages in a package
rosmsgpackages List packages that contain messages
You can also get help for subcommands
$ rosmsg show -h
- This shows the arguments that are needed for rosmsg show:
· Usage: rosmsg show[options] <message type>
·
· Options:
· -h, --help show this help message and exit
-r, --raw show raw message text, including comments
Review
Lets just list some of the commands we've used so far:
- rospack = ros+pack(age) : provides information related to ROS packages
- roscd = ros+cd : changes directory to a ROS package or stack
- rosls = ros+ls : lists files in a ROS package
- roscp = ros+cp : copies files from/to a ROS package
- rosmsg = ros+msg : provides information related to ROS message definitions
- rossrv = ros+srv : provides information related to ROS service definitions
- catkin_make : makes (compiles) a ROS package
- rosmake = ros+make : makes (compiles) a ROS package (if you're not using a catkin workspace)
Next Tutorial
Now that you've made a new ROS msg and srv, let's look at writing a simplepublisher and subscriber(python)(c++).
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