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rosserial MBED Setup

Introduction

MBED is a platform and operating system for devices based on 32-bit ARM Cortex-M microcontrollers. It is a great tool for quickly and easily programming hardware. Using the rosserial_mbed package, you can use ROS directly with your MBED enabled board. rosserial provides a ROS communication protocol that works over your MBED's UART. It allows your MBED to be a full fledged ROS node which can directly publish and subscribe to ROS messages, publish TF transforms, and get the ROS system time.

In order to use the rosserial libraries in your own code, you must first put

• #include <ros.h>

prior to including any other header files, e.g.

• #include <std_msgs/String.h>

otherwise the compiler will not be able to locate them.

Using the official online compiler

melodic noetic   Show EOL distros: 

Using the offline compiler

Install gcc4mbed

You need to install gcc4mbed by following the "Quick start" instructions on the Readme.

Let's assume that you've installed gcc4mbed to ~/gcc4mbed.

Cloning the rosserial repo

Clone the rosserial repo on your ros workspace src directory, e.g.: ~/catkin_ws/src/

Generating the ros_lib library

Go to the root of your workspace and execute:

• $ catkin_make

And then:

• source devel/setup.bash

Now you are able to generate the ros_lib library, needed to compile every project using rosserial_mbed:

• rosrun rosserial_mbed make_libraries.py ~/ros/lib

where the last parameter is the output path for the generated ros_lib directory to reside in. You should modify it according to your directory structure.

Exporting path variables

Now, move to your mbed project's directory and set the environment variables for the gcc4mbed and the ros-lib paths: Example:

• $ export GCC4MBED_DIR=~/gcc4mbed

  $ export ROS_LIB_DIR=~/ros/lib/ros_lib

Make sure to point to the ros_lib directory, which is inside the directory specified in the above rosrun. It is important that you DON'T put trailing slashes (especially for the ROS_LIB_DIR). If you do, you might end up getting a "missing header" error when compiling your project.

You can export these two variables in your .bashrc or modify your MBED project's makefile with the desired path for both variables (we are going to cover that later on in this tutorial).

Compiling and deploying an mbed project

Once you've finished all the above tasks you must be able to compile and deploy your mbed project into the board:

We are going to base this part of the tutorial on the 'Blink' project that came with the rosserial_mbed repo you've downloaded earlier, you can find it in the following relative path:

• rosserial/rosserial_mbed/src/examples/Blink/

There you should find a typical source for an mbed project: a C++ source file (Blink.cpp) and a makefile file, which you can use as a base for other projects by modifying the things according to your needs.

Then, from your makefile path directory do:

• $ make

This will generate a compiled binary file, and now you're able to copy it into your mbed device for testing. Or, simply run:

• $ make deploy

to do the compilation and deployment in one step.