rosserial for VEX V5

This package contains everything needed to run rosserial on the VEX V5 Robot Brain, on the PROS 3.x.x tooling.

Requirements

• Software:
  1. Linux (Only tested on Ubuntu 18.04LTS) (possible on windows with a Linux virtual machine, provided there is USB support)
  2. ROS installed on Linux (Only tested on ROS Melodic) - installation guide.
  3. PROS installed on Linux - installation guide
• Hardware:
  1. VEX essentials:
  • V5 Robot Brain
  • V5 Robot Battery
  • MicroUSB cable

Setup

This setup requires knowledge of entering commands into a Linux terminal.

Note: it is possible to follow along with this guide without understanding basic ROS constructs (such as workspaces, projects, rosrun, roslaunch, and catkin_make). However, in order to work with ROS beyond the examples in this project, you will need to learn about the ROS framework itself. See the ROS documentation, getting-started, and tutorials pages for more information.

ROS Workspace

This workspace is used to generate a PROS project, and then help the Robot Brain interact with ROS using that generated project.

Notice the first source command below. This includes ROS commands into the terminal (such as catkin_make), so it will come first in most of the terminal commands in this setup process. Make sure you replace melodic with your corresponding ROS version name, if it

is not melodic (e.g. kinetic). Open up a terminal, and enter:

source /opt/ros/melodic/setup.bash
mkdir -p ~/ros-vex-workspace/src; cd ~/ros-vex-workspace/src
git clone https://github.com/ros-drivers/rosserial.git
cd ..; catkin_make; catkin_make install

PROS Project

1. Generate a PROS project. A PROS project has the code that runs on the Robot Brain. The project can exist anywhere (it should NOT need to be inside the ROS workspace). Also see the getting-started documentation if you need help.

cd ~
prosv5 conductor new-project example-project-name

2. Download the newest ros_lib zip file template from it's repository. Then fetch and apply the template to your project by following below.

cd example-project-name
prosv5 conductor fetch ~/Downloads/[email protected]
prosv5 conductor apply [email protected]

Examples

These examples are made to run out-of-the-box, and they made to be proof-of-concepts of what ROS can provide. ROS allows standardized messages to be sent to and from the Brain and an outside computer, which allows for all kinds of ideas and projects to be organized with messages!

To understand what is going on with the example code, look at the tutorials for the sister project, Rosserial Arduino.

Set up the physical download connection by plugging in the microUSB into the Robot Brain and into the computer.

Hello World Example

To run the hello world example, make sure that the hellow_world() method in the main.cpp file is not commented.

After doing that, run the following commands.

source ~/ros-vex-workspace/install/setup.bash
cd ~/example-project-name
prosv5 mu --execute #this will make, upload, and execute the program to the brain
roslaunch rosserial_vex_v5 hello_world.launch #run this so that the computer can talk to the brain

Sensors Example

To run the sensors example, make sure that the main.cpp file looks like this:

  //hello_world();
  sensors();
  //odometry();

Note: you might also want to change the code in the example-project-name/include/ros_lib/rosserial_vex_v5/examples/sensors.hpp file.

After doing that, run the following commands.

source ~/ros-vex-workspace/install/setup.bash
cd ~/example-project-name
prosv5 mu --execute #this will make, upload, and execute the program to the brain
roslaunch rosserial_vex_v5 hello_world.launch #run this so that the computer can talk to the brain

Odometry Example

To run the odometry example, make sure that the main.cpp file looks like this:

  //hello_world();
  //sensors();
  odometry();

Note: you might also want to change the code in the example-project-name/include/ros_lib/rosserial_vex_v5/examples/odometry.hpp file.

After doing that, run the following commands.

source ~/ros-vex-workspace/install/setup.bash
cd ~/example-project-name
prosv5 mu --execute #this will make, upload, and execute the program to the brain
roslaunch rosserial_vex_v5 odometry.launch #run this so that the computer can talk to the brain

There is a video that shows what this should look like.

Generating Custom Messages

To design you own ROS messages, it is necessary to add the msgs directory to this project, add the message_generation dependency, and make several modifications to this project's CMakeLists.txt. This infrastructure is removed from this project by default, because there are many useful built-in message types that are used commonly across ROS packages anyway.

See documentation and source of sister packages, such as rosserial_arduino, for more information about generating custom messages.

Platforms

This has been developed and tested on ROS melodic, but it should work on many earier/later versions as well.

Speed

Over microUSB, any message can stream at 100hz. Higher speeds (e.g. 500hz) are unstable right now.

Troubleshooting

If any part of the launching or downloading process fails, try unplugging the V5 Brain and replugging it in after 20 seconds. It is possible that the ports being used (user vs. system) got switched around, and need to reset.

This project is similar to Rosserial Arduino in usage, so refer to these tutorials for even more information.