smahajan07/beginner_tutorials

A basic ROS package created by following the steps as per ROS Wiki Tutorials and some modifications

Beginner Tutorials

Overview

This respository is an adapted version of the basic ROS tutorials for publishing and subscribing to a topic and displaying the contents of the message received, creating a service to edit a string and publishing it, logging output, creating a launch file and taking in arguments, using the TF library in ROS, writing Unit Tests and recording and playing from a ROS bag. These are some commonly used features of ROS and even though a lot of resources are available online, it can sometimes still be tricky. Please refer to the official ROS tutorials for more details. They are a good source for all ROS beginner and even intermediate level users.

Dependencies

• Ubuntu Xenial (16.04)
• ROS Kinetic

Build Instructions

• If you already have a catkin workspace then:

cd <catkin workspace>
cd src
git clone https://github.com/smahajan07/beginner_tutorials.git
cd ..
catkin_make
source devel/setup.bash

• If you do not have a catkin workspace, you can create one by following:

mkdir -p ~/catkin_ws/src
cd ~/catkin_ws/
catkin_make
source devel/setup.bash
cd src/
git clone https://github.com/smahajan07/beginner_tutorials.git
cd ..
catkin_make

Rostest

Before you proceed to run it, check whether it passes the unit tests:

cd <your catkin workspace>
source devel/setup.bash
catkin_make run_tests

This should end with an output like

[ROSTEST]-----------------------------------------------------------------------

[beginner_tutorials.rosunit-testTalker/checkTF][passed]
[beginner_tutorials.rosunit-testTalker/checkCustomMsgServer][passed]

SUMMARY
 * RESULT: SUCCESS
 * TESTS: 2
 * ERRORS: 0
 * FAILURES: 0

Run Instructions (Using Launch File)

cd <your catkin workspace>
source devel/setup.bash
# Option 1: Run with default message 
roslaunch beginner_tutorials allNodes.launch

# Option 2: Run with your custom message and publishing frequency
roslaunch beginner_tutorials allNodes.launch pubRate:=5 inpStr:=carpe_diem
# Note: pubRate:=<frequency of your choice> 
# inpStr:=<string_of_your_choice> // But currently it takes a single word or words connected with an underscore (_) 

• It will raise a fatal error if you enter a negative value or zero for frequency
• It will warn you that frequency is high if you enter a value more than 10
• To kill the terminal please press CTRL+C (twice, because additional output window is opened as well)

Inspect TF frames

If your nodes are still running , then you can directly follow these steps ELSE please launch the nodes using the previous instructions. Open a new terminal and run:

rosrun tf tf_echo world talk

[Optional] If you wish to view them using view frames tool you can either check out the provided as results/frames.pdf OR you can run this command from the terminal and it will save the diagram in the directory from where the command was run. Again, make sure your nodes are running.

rosrun tf view_frames

Rosbags

• Inspect

Along with the package a sample ROS bag was provided results/automatic.bag. If you wish to look at the topics in the rosbag and find out more details about it:

cd <your catkin workspace>
source devel/setup.bash
cd src/beginner_tutorials/results
rosbag info automatic.bag

• Play

You can play the above mentioned rosbag by running the following in two different terminals:

roscore

and

rosbag  play automatic.bag

• Record

If you wish to record the data in a rosbag you can run the rosbags command separately in a new terminal OR you can make use of the option provided in the launch file. You just need to set the record argument to true by running:

cd <your catkin workspace>
source devel/setup.bash
roslaunch beginner_tutorials allNodes.launch record:=true

This will save a rosbag in your results directory of the package, by the name automatic.bag.

Run Instructions (Calling the service from the terminal)

1. Terminal 1

roscore

2. Start the server

cd <your catkin workspace>
source devel/setup.bash
rosrun beginner_tutorials customMsgServer

3. Call the service

cd <your catkin workspace>
source devel/setup.bash
rosservice call /custom_message_service go_terps
# Usage: rosservice call /custom_message_service <word/string of your choice-connected with _>

Run Instructions (Vanilla way)

Open four terminals and follow the steps:

1. Terminal 1

roscore

2. Terminal 2

cd <your catkin workspace>
source devel/setup.bash
# Option 1: Run with default message 
roslaunch beginner_tutorials talker

# Option 2: Run with your custom message and publishing frequency
roslaunch beginner_tutorials talker carpe_diem 5
# Usage: roslaunch beginner_tutorials talker <string_of_your_choice> <frequency of your choice>
# For <string_of_your_choice> currently it takes a single word or words connected with an underscore (_)

3. Terminal 3

cd <your catkin workspace>
source devel/setup.bash
rosrun beginner_tutorials customMsgServer
rosrun beginner_tutorials listener

4. Terminal 4

cd <your catkin workspace>
source devel/setup.bash
rosrun beginner_tutorials listener