Description

This repository contains a simple ROS2 publisher and subscriber to find the time difference of GPS measurements in the Dataset file. It further contains unit tests to evaluate the correctness of the two ROS nodes.

Credits for dataset file : https://github.com/Lavkushwaha/GPS-Data-Prediction-ML-RNN

Requirements

Install Screen

sudo apt-get install screen

Python Dependencies

pip3 install -r requirements.txt

Running

Clone and Build

Clone and build the repository

git clone https://github.com/s-m-asjad/ROS2_Time_Diff.git
cd ROS2_Time_Diff
colcon build
source install/setup.bash

Running the Publisher and Subscriber

To run both two ROS nodes (Publisher and Subscriber)

ros2 launch time_diff time_diff.launch.py "file_path:=<Absolute File Path>.csv"         # This is a Required argument.

To run only publisher (publishes to topic /data)

 ros2 run time_diff data_publisher --ros-args --param file:=<absolute path to file>.csv 
 # Not a Required argument, will use Dataset.csv in the workspace if value is not provided

To run only subscriber (subscribes to /data and publishes to /diff when more than one message has been subscribed)

ros2 run time_diff data_subscriber

Running Unit Tests

To run unit tests

colcon test

The results of the tests are saved to log file under log/latest_test/time_diff

Code Overview

data_publisher.py

• Checks if data file exists

• Checks data file is not empty

• Asks parsing.py to parse the data

• publishes data to topic /data since it is a ROS node

• Shuts down when end of file is reached

parsing.py

• Checks if the required columns exist
• Evaluates if the data types and values are correct / within bounds
• returns parsed values to data_publisher.py in the format required by Gps.msg

data_subscriber.py

• Receives data from topic /data
• If there is no previously received message then waits for the next message
• Evaluates if the messages received are in sequence -> Calculates the time difference (this happens NOT for the header.stamp but for the time variable containing the time from csv file)
• publishes the difference to topic /diff

test_parsing.py

• Tests for correct and incorrect values/failing cases for parsing.py

test_subscriber.py

• Tests if subscriber is calculating the difference correctly
• Tests if subscriber is subscribed to the correct topic (and does not listen to any other topic)
• Tests if subscruber is publishing the difference to the correct topic

test_publisher.py

• Tests if publisher is publishing data correctly (in the correct format and their respective fileds in the message)
• Tests if publisher is publishing on the correct topic
• Tests if publisher stops publishing once end of file is reached
• Tests if publisher is publishing at the correct rate `