ROS support for the RoDI educational robot

RoDI is an open hardware and software, wireless, low cost and easy to use educational robot designed and built by Gary Servin. The name RoDI is an acronym of “Robot Didáctico Inalámbrico”, which in Spanish means wireless didactic robot.

The robot has a custom PCB based on the ATMEGA328p microcontroller that has a bunch of sensors (ultrasonic, infrared, light), actuators (motors, led, RGB led), a rechargeable battery over micro USB and a ESP8266 WiFi module to interact with the ATMEGA over a wireless connection.


The Arduino UNO board has the same ATMEGA328p microcontroller so the Arduino IDE and libraries can be used to program the robot’s firmware.

But since the goal is to be use RoDI as an educational tool for kids, its default’s firmware (rodi-web developed by Martin Abente) is a small daemon that accepts HTTP requests, to control the robot using a very simple API.

Because the robot can be controlled over HTTP, it’s very easy to develop clients for RoDI. For example there is a Python client library (rodi-py),  Android (rodroid) and IOS (RoDios) client apps and even a plugin for the Turtleblocks visual programming tool (rodi-plugin-turtlebots) so the robot can be controlled using visual building blocks. The robot can even be controlled using commands like curl and wget so the entry level is really low!

I’m learning about the Robot Operating System (ROS) in my free time, so I thought that an easy first project would be to add ROS support for RoDI. One way to do this is to use the rosserial_arduino package, and in fact Gary already has a custom RoDI firmware that does exactly this. The firmware subscribes to a cmd_vel topic and receives Twist messages to move the robot, and publish the sonar data as Range messages into a ultrasound topic.

But a disadvantage of this approach is that the default rodi-web firmware has to be replaced in order to control the robot from ROS. So I wrote the rodi_robot package that also subscribes to the cmd_vel topic and publishes the sonar data to a ultrasound topic, but does a translation between ROS messages and HTTP requests to use the rodi-web API directly. That way, RoDI is supported by ROS without the need to replace its default firmware.

I hope this package can be useful for people wanting to learn ROS using a (not simulated) robot, since its low cost makes RoDI very affordable.

Happy hacking!

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