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Trying to publish information from subscriber node.

asked 2023-08-08 03:09:57 -0500

Nongtuy gravatar image

updated 2023-08-08 09:15:32 -0500

I'm trying to make system consist of several sections, it must surely have at least 1 node doing 2 roles, both subscriber and publisher. and here it my codes.


First section

#!/usr/bin/env python3

import rospy as R
from std_msgs.msg import Float64

def sender_3():
    x = 0 
    y = float(input("Give us the float num: "))
    pub = R.Publisher("line3", Float64, queue_size=10)
    R.init_node("sender_3", anonymous=True)
    rate = R.Rate(10)
    while not R.is_shutdown() and x < y:
        x += 0.1
        t = x
        print(x)
        pub.publish(t)
        rate.sleep()

if __name__ == "__main__":
    try:
        sender_3()
    except R.ROSInterruptException:
        pass

Second section

#!/usr/bin/env python3
import rospy as R
from std_msgs.msg import Float64, String

def callback(data):
    global r_data
    r_data = data.data
    R.loginfo("sawadee krub i've received as info: %f", data.data)
    global t_o
    t_o = str(r_data)
    R.loginfo("Applied num to chatGPT: %s", t_o)
def receiver_2():
    R.init_node("receiver_2", anonymous=10)
    R.Subscriber("line3", Float64, callback, queue_size=True)
    pub = R.Publisher("translne", String, queue_size=10)
    rate = R.Rate(10)
    while not R.is_shutdown:
        print(t_o)
        pub.publish(t_o)
        rate.sleep()
    R.spin()
#def transporter():
 #   R.init_node("transporter send you", anonymous=10)
  #  pub = R.Publisher("translne", String, queue_size=10)
   # while not R.is_shutdown:
    #    print(receiver_2)
     #   pub.publish(receiver_2)
      #  R.Rate(10)
if __name__ == "__main__":
    receiver_2()

Last section

#!/usr/bin/env python3

import rospy as R
from std_msgs.msg import String

def callback(data):
    R.loginfo("I've received an information: %s", data.data)
def sub_receiver():
    R.init_node("sub_receiver", anonymous=True)
    R.Subscriber("translne", String , callback, queue_size=10)
    R.spin() 

if __name__ == "__main__":
    sub_receiver()

My problem is during the transition between second and last section, it seems like last section didn't receive any information which is translated into String and published to last section, cause there's nothing appears even error. P.S I commented on third section for several previous tries. Edited: Mistakes have been fixed.

Thank you in advance.

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1 Answer

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answered 2023-08-08 07:36:15 -0500

Mike Scheutzow gravatar image

updated 2023-08-08 07:44:25 -0500

Your code is not doing this correctly. Please look at section 2 of http://wiki.ros.org/rospy/Overview/Time for the proper way to construct a while/Rate loop in python.

while not R.is_shutdown:     # <- wrong
    print(t_o)
    pub.publish(t_o)
    R.Rate(10)        # <- wrong
R.spin()    #  <- wrong
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Comments

Oh silly me, I always forget to add () in definition. After I added that it works properly now Thank you Best regard, Tuy

Nongtuy gravatar image Nongtuy  ( 2023-08-08 23:28:41 -0500 )edit

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Asked: 2023-08-08 03:09:57 -0500

Seen: 359 times

Last updated: Aug 08 '23