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Hello everybody,

I would like to get some help from you. I want to use a Dynamixel servo but I do not want to have many different files just for listening the positions and setting new goals, so I created the following Python node:

#!/usr/bin/env python

import rospy
from math import fabs
from dynamixel_msgs.msg import JointState
from std_msgs.msg import Float64

goal_pos = 0;
pub = rospy.Publisher('/tilt_controller/command', Float64)

def transform_callback(data):
    global goal_pos
    rospy.loginfo(rospy.get_name() + ': Current motor angle {0}'.format(data.current_pos))

    # If the motor has reached its limit, publish a new command.
    if fabs(goal_pos-data.current_pos) < 0.01:
        if goal_pos == 0:
            goal_pos = 3.141592
            goal_pos = 0

        str = "Time: {0} Moving motor to {1}" .format(rospy.get_time(), goal_pos)

def dxl_control():
    rospy.init_node('dxl_control', anonymous=True)
    rospy.Subscriber('/tilt_controller/state', JointState, transform_callback).
    # Initial movement.

if __name__ == '__main__':
    except rospy.ROSInterruptException:

The code is just a union of the simple publisher and listener tutorials adapted to my application. As I do not have too much experiences programming with ROS (neither Python) I would like to know what do you think about having the publisher and the goal_pos as global variables and also the publisher and the listener in the same node and file.

The plan is that transform_callback will also publish a tf message. Is it ok as it is or would you do it in separate files and nodes?

Thank you!

Originally posted by Javier V. Gómez on ROS Answers with karma: 1305 on 2013-12-05

Post score: 5


1 Answer 1


Rosanswers logo

After some experience with ROS, and with no other answers, I can say this is perfectly OK and common among ROS nodes.

Originally posted by Javier V. Gómez with karma: 1305 on 2015-06-26

This answer was ACCEPTED on the original site

Post score: 13

Original comments

Comment by jester on 2020-07-23:
is it possible to give rospy.spin a rate?

Comment by Hugo on 2021-03-02:
@jester, yes, it is! Take a look at this answer: https://answers.ros.org/question/62327/how-to-create-a-combining-subscriber-and-publisher-node-in-python/


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