ROS for Arduino Robot

Control your Arduino Robot with ROS

Introduction

The Arduino robot is the first Arduino on wheels, see: https://www.arduino.cc/en/guide/robot

The Arduino Robot. Copyright: arduino.cc

Unfortunately this robot is retired now, but if you might still have one, it is be fun to use it with ROS:-)

http://wiki.ros.org/noetic

The Robot

The robot consists of two boards. To control it from ROS, the original firmware for the motor board will work. For the control board a rosserial_arduino client should run for publishing and subscribing of ROS topics. The USB connector from the control board forms the serial interface and it can, for instance, be connected to a single board computer carried by the robot.

Unfortunately, the standard Robot Control library uses too much resources to leave enough free memory space to run a rosserial_arduino client. A stripped down version of the Robot Control library can be found here: https://github.com/MartinStokroos/Robot_Control_Lite

ROS lib for Arduino

The ROS library for Arduino can be installed via the Arduino IDE library manager, or the library can be generated with a Python script from the ros-noetic-rosserial-arduino package. Modify ros.h by adding support for the Atmega32u4 MCU.

Add under namespace ros:

```
#elif defined(__AVR_ATmega32U4__)

  typedef NodeHandle_<ArduinoHardware, 5, 3, 150, 150> NodeHandle;

```

The NodeHandle arguments are: number of publishers, number of subscribers, input buffer size, output buffer size. Always keep an eye on the available free memory after compiling the sketch for the robot ( use <80% for stable operation ).

The Sketch

• Robot_Control_ROS.ino

Currently supported topics	publisher/subscriber	message type	function
cmd_vel	sub	twist	Linear and radial velocity as raw PWM values (float)
msg_compass	pub	Int16	Compass heading 0...360 degrees (int16)
msg_irarray	pub	Adc	5 element array of uint16 for IR sensors

This work is under development...

Testing

Start the serial node (using direct USB cable connection to a Linux system):

rosrun rosserial_python serial_node.py /dev/ttyACM0

Check for available topics:

rostopic list

Check the data rate:

rostopic hz /msg_compass

Echo the compass heading:

rostopic echo msg_compass

Plot IR array sensor response:

rqt_plot msg_irarray

Drive the motors straight forward:

rostopic pub -r 1 /cmd_vel geometry_msgs/Twist "linear: x: 75.0 y: 0.0 z: 0.0 angular: x: 0.0 y: 0.0 z: 0.0"