ROS writes subscribers and publishers in python (using custom MSG files stored in other packages)

This paper records the use of python Write messages that use custom messages ros Some problems with subscribers and publishers .

​ Make a statement , The code of this article is intercepted from your own project , Not suitable for direct use , Only suitable as a reference template

1、 The first is how to create msg File and compile

The file structure is as shown in the figure ：

catkin_ws
├── build
├── devel
└── src
├── robot_msgs
│ ├── CMakeLists.txt
│ ├── msg
│ │ └── Controldata.msg
│ └── package.xml
└── tcp_ros
└── script
└── test.py

catkin_ws There are two in the workspace package, One is only used to store messages ( You can add more messages by yourself ), One for storing code .

Controldata.msg The message file is as follows ：

uint32 cmd
float32 param1
float32 param2

stay robot_msgs In the bag CMakerList.txt：

cmake_minimum_required(VERSION 2.8.3)
project(robot_msgs)
# Add dependency here message_generation Used to generate messages
find_package(catkin REQUIRED COMPONENTS
message_generation
std_msgs
geometry_msgs
)
# Add message file here Controldata.msg
add_message_files(
DIRECTORY msg
FILES
Controldata.msg
)
generate_messages(DEPENDENCIES std_msgs geometry_msgs)
# Message generation package is added here message_runtime
catkin_package(CATKIN_DEPENDS message_runtime std_msgs geometry_msgs)

stay robot_msgs In the bag package.xml Add the following ：

<build_depend>message_generation</build_depend>
<run_depend>message_runtime</run_depend>

stay tcp_ros In the bag CMakerList：

find_package(catkin REQUIRED COMPONENTS # lookup robot_msgs package
roscpp
rospy
std_msgs
robot_msgs
)
catkin_package( # contain robot_msgs package
INCLUDE_DIRS include
LIBRARIES tjurobot
CATKIN_DEPENDS roscpp rospy std_msgs robot_msgs message_runtime
DEPENDS system_lib
)

2、python Write the publisher node

• Publisher program ： The key is how to python There are other... Imported in the node package Of msg file ！！

  #!/usr/bin/env python
  # license removed for brevity
  import rospy
  from robot_msgs.msg import Controldata # Translated into ： from robot_msgs In the bag msg Import a folder named Controldata Of msg file ！
  def talker():
  pub = rospy.Publisher('chatter', Controldata, queue_size=10) # Set the publishing topic to be named “chatter”, The message type is Controldata.msg, The maximum message queue capacity is 10 The object of the frame pub
  rospy.init_node('talker', anonymous=True) # The initialization name is “talker” The node of 
  rate = rospy.Rate(10) # 10hz 
  while not rospy.is_shutdown():
  send_msg = Controldata() # Initialize a message structure ： Directly with this msg File name as a function 
  send_msg.cmd =0X15 # to send_msg Parameter assignment in the structure （ That is the msg Parameters in the file ）
  send_msg.param1 = 123
  send_msg.param2 = 0
  pub.publish(send_msg) # call pub Object's publish Function publishing topic 
  rate.sleep() # During the cycle, you can use just the right sleep time to maintain the desired rate , Applicable to topics that need to be published constantly 
  if __name__ == '__main__':
  try:
  talker()
  except rospy.ROSInterruptException:
  pass
  

3、python Write the subscriber node

• Subscriber program ： The key is how to use topic data in callback function

  #!/usr/bin/env python
  import rospy
  from robot_msgs.msg import Controldata
  def callback_fuc(data): # The data Is equivalent to the publisher's send_msg Structure 
  rospy.loginfo("I heard %d,%d,%d", data.cmd,data.param1,data.param2)
  def listener():
  rospy.init_node('listener', anonymous=True) # The initialization name is “listener” Subscriber node for ：anonymous=True A unique name will be generated for the node to avoid duplicate node names 
  rospy.Subscriber("chatter", Controldata, callback_fuc) # Set subscriber properties ： Subscribed topic name “chatter”, The topic corresponds to msg Message file name , Callback function name 
  rospy.spin() # There must be , Otherwise, we can't receive , But it will be equivalent to an endless loop, and the program will get stuck here 
  if __name__ == '__main__':
  listener()
  

  About how to solve rospy.spin() For the problem that the post program is stuck and cannot be executed, please refer to this blog ：

(94 Bar message ) solve rospy.spin() Cycle all the time , Unable to execute remaining programs _DLUT_ Xiaodingdang's blog -CSDN Blog _rospy.spin