moonspacedancer's profile - activity

the last few times I have done anything w ROS while doing beginning tutorials, I just say 'roscore' and it seems to all run fine, but now im watching a video and it seems like he's saying I need to do the setup.bash steps every time I want to use ros. 1. is it necessary to do the setup.bash steps every time? 2.if so, why have I been able to use turtlesim and other things just running roscore?

edit: I went into .bashrc and added source ~/catkin_ws/devel/setup.bash thinking that was what I was missing but then realized the one I was thinking of was already there, called 'source /opt/ros/kinetic/setup.bash'

1. is that the one I need to run every time or should I also add the catkin setup to run every time as well?
2. also, do I still now need to roscd everytime to enter the workspace?

hey I have another question but this comes first, how can I paste some xml code here to format my question? I've tried the 101010 thing but it still deletes a big chunk of the code within < / node > tags

~beginner decrypting the workings of ROS~ hmm.. how to phrase this.. well, partly, I'm wondering

1. if I need to also be in my catkin workspace before roslaunching...
2. what is the difference between the catkin and roslaunch?
3. I understand that the catkin is like a framework/build system basically for package management??
4. So now that I'm learning about nodes, I'm wondering, how is the node different from a catkin built package?
5. How are roslaunch and associated tools, different from catkin?

Hey guys, I am all in all pretty new to computer science in general and learning ROS now. came across some tutorials on tf after completing the beginner tutorials. I want to use rososc but that's another story since it is not updated for kinetic and catkin and I'm still trying to work out how to make that work for me... anyway,

-explain what tf is used for as if I am a 5 year old. -why would I use it in developing robots? -what type of applications is it useful for?

I am taking this edx course on robotics using ROS and our first project is "writing a node that subscribes to a topic and publishes to another. Your code will subscribe to a topic called 'two_ints', on which a custom message containing two integers can be broadcast. Make sure to familiarize yourself with the message format of this topic:

int16 a
int16 b

. Those two integers are to be added and the result published to topic 'sum' as an Int16 from std_msgs. "

ok this is what I have so far from stringing other examples I have seen together and guessing... very lost now though about how to connect these and also what the 'callback' thing does or if I need to define that..

#!/usr/bin/env python  
import rospy

from std_msgs.msg import Int16
from project1_solution.msg import TwoInts

def listener():
 rospy.init_node('project1_solution', anonymous=True)
 rospy.Subscriber("two_ints", TwoInts, callback)
 rospy.spin()

while not rospy.is_shutdown():
  msg = TwoInts()
  solution = msg.a + msg.b


def talker():
 pub = rospy.Publisher('Sum', Int16, queue_size=10)
 rospy.init_node('project1_solution', anonymous=True)
 rate = rospy.Rate(0.5) #.5hz



 while not rospy.is_shutdown():
  msg = Int16()

  pub.publish(msg)
  rate.sleep()

thank you, any tips or help would be great!

@jayess I believe it starts up when I roslaunch urdf_tutorial display.launch model:=chatbot.urdf

rviz urdf joint state publisher issue I am making my first actual urdf beyond just using the ones from tutorials. there

@jayess, I have completed 1-20 plus beginning tf tutorials and some urdf tutorials now. also reading 'gentle introductio

writing a publisher and subscriber and unsure how to finish it I am taking this edx course on robotics using ROS and our

let's say I want to download ros-kinetic-ros-tutorials through

sudo apt-get install ros-<distro>-ros-tutorials

where do I need to be cd'd into at that time or does it matter? I am currently in catkin_ws/devel, is that going to be fine?

also, in general, when installing packages, does the same answer apply?

simple Q about where to install packages let's say I want to download ros-kinetic-ros-tutorials through sudo apt-get in

simple Q about where to install packages let's say I want to download ros-kinetic-ros-tutorials through sudo apt-get in

@jayess it does solve the problem for me to switch to Mozilla as I state in the answer I accepted. thank you for your he

 <launch>
  <!-- Turtlesim Node-->

      <node pkg="turtlesim" type="turtlesim_node" name="sim"/>
      <node pkg="turtlesim" type="turtle_teleop_key" name="teleop" output="screen"/>


        <param name="turtle" type="string" value="turtle1" />
      </node>

        <param name="turtle" type="string" value="turtle2" /> 
      </node>

    </launch>

What is wrong with this launch file? and I don't mean the spacing, I have reformatted it a bunch and already know xml formatting has to be spaced right and all that. it's got to be the code itself, which is directly from http://wiki.ros.org/tf/Tutorials/Writ... tf tutorial and I'm surprised I only saw one unanswered question about this issue, but I assume it's because the others know how to make xml syntax correct and just moved on.

@tfoote oh wow. now that is very interesting. I can't see what else to consider there since it only shows me the full te