X13-Core

Codebase for the the X13 version of the ROV

Software Versions Ubuntu 18 Raspbian Buster ROS Melodic

Hardware Raspberry Pi 4

Getting ROS to work with Python 3

Previous X repos have ROS working both with Python 2 and 3. This behavior is determined by the shebang (e.g. #!/usr/bin/python) at the top of relevant ROS scripts. These should be set to #!/path/to/python3 going forward.

If you already have ROS Kinetic installed, I would highly recommend wiping it with sudo apt remove ros-* and removing any dependencies installed with it with sudo apt autoremove. This works if Kinetic was installed with apt in the first place.

If Kinetic was compiled from source, simply delete the catkin_ws folder (or whatever you named it) and any sources in your .bashrc if you added them.

Table of Contents

• Install/Upgrade
  1. Existing Melodic Install
  2. Fresh Install
  3. Compile from Source
• Troubleshooting

ROS Melodic Already Installed

This assumes Melodic was installed with apt and not compiled from source. If it was compiled from source, delete the install directory, and follow these instructions.

1. Install Python 3 ROS dependencies with pip3

   Make sure pip3 is installed in the first place with sudo apt install python3-pip.

   Run sudo pip3 install -U rosdep rosinstall_generator vcstool rosinstall. Note the use of pip3.

   Optional: Remove Python 2 versions of above tools with sudo apt remove python-ros* python-wstool

2. Set the environment variable ROS_PYTHON_VERSION to 3

   Run export ROS_PYTHON_VERSION=3.

3. Update dependencies

   Run sudo rosdep init to find where the dependency list file is.

   Delete that file.

   Run sudo rosdep init again.

   Run rosdep update.

You should now have everything ready to go. Simply add the source line to your .bashrc file to make life easier for every time you open a terminal window.

Fresh Install

1. Follow the standard instructions up to but NOT including 1.4 (i.e Install Step)

2. Set the environment variable ROS_PYTHON_VERSION to 3

   Run export ROS_PYTHON_VERSION=3.

   I'm not sure how necessary it is at this stage, but it is required down the line anyway.

3. Install ROS Melodic

   Full: sudo apt install ros-melodic-desktop-full (Recommended by Ivan because this was tested)

   Regular: sudo apt install ros-melodic-desktop (Recommended on ROS Wiki, but should work just the same)

   Base: sudo apt install ros-melodic-ros-base (Why?)

4. Install Python 3 dependencies

   Run sudo pip3 install -U rosdep rosinstall_generator vcstool rosinstall. Note the use of pip3.

5. Init/Update ROS dependencies

   Run sudo rosdep init

   Run rosdep update

Everything should be set up now. Remember to source your install of ROS.

Compile from Source

Oh dear, what are you doing here? These are only meant for those working with Ubuntu versions other than 18.04. When I compiled from source, I was using Ubuntu 19.04, so bear that in mind. If you have nothing else going on your Ubuntu install, I would highly recommend wiping it and getting 18.04 instead. If you're crazy like me, welcome.

1. Install Python 3 dependencies

   Run sudo pip3 install -U rosdep rosinstall_generator vcstool rosinstall. Note the use of pip3.

2. Set the environment variable ROS_PYTHON_VERSION to 3

   Run export ROS_PYTHON_VERSION=3.

3. Init/Update ROS dependencies

   Run sudo rosdep init

   Run rosdep update

4. Create a catkin workspace

   Make a directory somewhere (e.g. mkdir ~/some_name_like_ROS_install)

   Go into it cd ~/some_name_like_ROS_install

   Make a src directory mkdir src

5. Fetch relevant files

   Again, this is following step-by-step of what I did, so I'm only covering Full Desktop install, but the process should be the same for other versions

   Run rosinstall_generator desktop_full --rosdistro melodic --deps --tar > melodic-desktop-full.rosinstall

   Run vcs import src < melodic-desktop-full.rosinstall

6. Resolve dependencies

   There is a trick to this step. You're essentially tricking rosdep into thinking you're on 18.04.

   Run rosdep install --from-paths src --ignore-src --rosdistro melodic -y --os=ubuntu:bionic

   Very important to add --os=ubuntu:bionic.

7. Build it

   Run ./src/catkin/bin/catkin_make_isolated --install -DCMAKE_BUILD_TYPE=Release

After what seems like an eternity (about 30 minutes for me), you should have a working install of ROS Melodic compiled. All that is left is to add the setup.bash script to your .bashrc file for an easy life.

Troubleshooting

• Something went wrong during installation

  This should only be an issue if you're compiling from source or attempting to install with apt on anything other than Ubuntu 18.04. For the former, I have no answer. For the latter, I recommend installing 18.04 or following Compile from Source instructions.

• catkin_make fails 70-90% way through a workspace

  If this was ported from X12, some files still contain python shebangs. Try changing them to python3 ones. Another issue might be is that you need to build nodes in /ros before /surface/ros

In all cases, especially if you have had previous ROS installs on your machine, make sure rosdep init's file is up-to-date with Python 3 dependencies. Meaning run rosdep init to find the file and delete it. Run that command again and run rosdep update. You may need to use sudo with the init stage.

Updated: 9/29/21