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Arduino boards

In this tutorial, we'll show you how to connect Arduino to Leo Rover.

What is Arduino?​

Before we get started, let's say a few words about what Arduino actually is.

Arduino is an open-source electronic platform that allows users to easily access advanced technologies interacting with the physical world.

What do I need Arduino for?​

You might wonder what the point of having Arduino inside Leo Rover is. After all, isn't the robot already equipped with a Raspberry Pi micro-computer?

Well, the simplicity of Arduino makes it more convenient for typical hardware projects. Arduino has analog capabilities that the Raspberry Pi lacks by default. Its flexibility allows you to work with almost any type of sensor.

Arduino speeds up the creation of simple projects that don't require advanced software and a good Internet connection.

Let's not forget that behind the name "Arduino" hide many boards, so if you want to learn how to choose the best one for your project, look here. For our projects, we mostly use Arduino DUE.

What to expect?​

Having finished the tutorial you'll know how to connect Arduino to the Leo Rover and use its potential to further improve your projects and make the development process of future projects a little bit faster.

Arduino on Leo Rover

Prerequisites​

📄Connect via remote desktop
Learn how to remotely access your Leo Rover's desktop environment using RDP and popular remote desktop clients.
📄Connect to a local network and the Internet
Learn how to connect your Leo Rover to a local network and the internet to download files and forward internet to your computer.

List of components​

  • Any Arduino ( or any other compatible board)
  • Any way of connecting the board to the rover
  • USB cable

Mechanical integration​

We have created mechanical interfaces for Arduino DUE, which you can get here:

📄Integrations' adapters
Access a variety of Leo Rover adapter designs for easy integrations with various sensors and components.

You'll need to press in ten M3, threaded heat-set inserts into the base part. This allows you to use M3x6 Allen screws to hold the Arduino securely. The cover is held by 4 screws of the same size.

Since Arduino Due has the largest footprint out of all the Arduino boards it should be pretty easy to adapt the provided Arduino DUE adapter models to fit other boards inside. All you need to do is use 3D CAD program like Autodesk Fusion to change the way mounting holes for the board are positioned.

Wiring and electronics connection​

For most intents and purposes the only connection you need to provide is an USB connection between the board and the USB port at the top of the rover. However, you may want to provide the microcontroller, and the sensors that you are using, with external power source. For such cases powerbox addon might be a good choice.

00188 MEB cover for Leo Rover
Powerbox
The Powerbox module significantly enhances Leo Rover's capabilities by providing versatile power options and enabling continuous operation through battery hot-swaps and external power access.

Software integration​

There are several ways to integrate Arduino into the rover. From this tutorial, you'll learn about two of them so that you can decide which one works best for you.

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This way saves you from having to dive into the rover's insides. It works; however, it does not allow you to communicate between the rover's onboard computer and Arduino - this, in turn, makes it harder to use the data harvested by any sensors connected to the Arduino.

First, install Arduino IDE using any of those provided tutorials:

Then, you need to set up Arduino IDE (we're using Arduino DUE which needs a special configuration in Arduino IDE).

To do so, do as follows: while in IDE, go to: Tools -> Board -> Boards Manager

Type DUE in the search bar and install the latest version of Arduino SAM Boards (32-bits ARM Cortex-M3).

The next step is to take care of the board specific setup:

  • Connect the board to a USB port in your computer (use the port closer to the barrel jack socket)
  • Go to: Tools -> Board -> Arduino ARM (32-bits) Boards and choose Arduino Due (Programming Port)
  • Go to: Tools -> Port and choose the port Arduino is connected to

Checking setup​

The easiest way to check if the board is working, is to use pre-created example codes. One of them is the blink sketch provided in the Arduino IDE examples.

Go to: File -> Examples -> 01.Basics and choose the Blink sketch

You should see something similar to this:

Now, you'll have to verify the code and send it to the board. First, make sure the correct board and ports are chosen as shown below:

Now you can verify(1) and upload(2) the code.

After a few seconds, you should see two things:

  • the following statement:
  • and Arduino's built-in LED blinking

Setting up the Rosserial communication​

First step is to download the rosserial library.

Go to: Tools -> Manage Libraries

Type rosserial in the search bar and download Rosserial Arduino Library

The board that we are using - Arduino Due - needs one additional step in order to properly work with rosserial.

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Skip this step if you are using another board.

Find ArduinoHardware.h. The proper path to find the folder is as follows:

/Arduino/libraries/Rosserial_Arduino_Library/src

Modify line 73 to state:

#if defined(USBCON) and !(defined(USE_USBCON)) and !(defined(_SAM3XA_))

Examples​

From this point forward, most of our instructions will be rephrased instructions made by wiki.ros.org. You can check this site for more detailed instructions.

In the first tutorial, you can see how to get data from Arduino to the rover`s mind.

Arduino Code (hello world - simple publisher)​

You can get to the sample code by following the path shown below:

Upload the code to Arduino. Make sure to use the correct PORT and BOARD in Arduino.

Then, start a new terminal window and launch rosserial node, that will start communication between Arduino and the rover's onboard computer.

rosrun rosserial_python serial_node.py port:=/dev/ttyACM0 __name:=my_node
warning

Remember to set the port argument, to the same port you saw in Arduino IDE.

__name argument can be set to whatever you like your node to be called

Start another terminal window and check the list of running nodes (you should see your node there):

rosnode list

You can get more information about your node - eg. what topics it is listening/publishing to. As you can see, /Arduino_COM_node is publishing to /chatter topic

rosnode info /node_name
info

After /, you need to provide the correct name of your node. You can start typing the name, and fill the line with Tab key (double tap).

You can also see list of all active topics by typing:

rostopic list

You should see one called chatter that was created by Arduino after you've created the node you've named.

Now to see data published to our topic, type in the terminal:

rostopic echo /chatter
info

If everything went according to our plan, by running this command you should be able to see the Arduino sending “Hello World” message to this topic.

Ctrl+C lets you stop the program running in the terminal.

Arduino as publisher and subscriber​

In this example, we will show you our real live use case of Arduino with Leo Rover.

Description​

Our task was to check whether there is a correlation between soil quality and motor current in Leo Rover pulling a plow. Therefore we have designed a lowered plow, capable of gathering pulling force data and drove Leo Rover through soil of different quality, while gathering the data. And in the end, we could analyze gathered data.

The Plow is connected to the rest of the rover with a strain gauge beam. Pulling force can be observed as tiny changes in voltage, that get amplified with an amplifier. Arduino is used to gather the data and send it to the computer.

note

It's obvious that you will not be able to follow this guide with a plow, so you can replace it with a potentiometer or any other analog sensor. Here are the instruction, how to connect it, so it works with the rest of the tutorial:

  • Connect your sensor to A0 pin on Arduino,
  • Use 2 LEDs connected to respectively digital pin 10 and digital pin 11 (remember to use resistors) to test the subscriber part of the code.

Code​

#include <Arduino.h>
#include <ros.h>
#include <std_msgs/Bool.h>
#include <std_msgs/Float32.h>

ros::NodeHandle  nh;

std_msgs::Float32 tension_msg;
std_msgs::Bool plow_state;

void plow_control_callback( const std_msgs::Bool& msg){

  if(msg.data == true){         //plow up
    digitalWrite(10, HIGH);
    digitalWrite(11, LOW);
  }
  else if (msg.data == false)    //plow down
  {
    digitalWrite(10, LOW);
    digitalWrite(11, HIGH);
    }
}

//setup a publisher
ros::Publisher pub_tension("tension", &tension_msg);
//setup a subscriber, make Arduino react to a message with plow_control_callback function
ros::Subscriber<std_msgs::Bool> plow_control ("plow_control", &plow_control_callback );

void setup()
{
  //actuator pins setup
  pinMode(10, OUTPUT);
  pinMode(11, OUTPUT);

  //rosserial communication setup
  nh.initNode();
  nh.subscribe(plow_control);    //make arduino listen to messages sent to a plow_control top-ic
  nh.advertise(pub_tension);     //give arduino the ability to send messages to pub_tension topic
}
void loop()
{
  //get data and publish it
  tension_msg.data = analogRead(A0);
  pub_tension.publish(&tension_msg);
  nh.spinOnce();
  delay(1);
}

Running and visualizing​

With the code imported to Arduino and all the necessary wires connected, you can start the Arduino node. To do so, open new terminal and type:

rosrun rosserial_python serial_node.py _port:=/dev/ttyACM0 __name:=Arduino_node

In another terminal run:

rqt_plot /tension/data

You`ll see a graph following the changes in sensor output.

Sending either True or False to plow_control topic controls the plow position for us (either lowered or raised) for you it can control any binary device e.g. turn the LEDs on and off. You can send those messages by typing in the terminal:

rostopic pub /plow_control std_msgs/Bool  „data: false”

or:

rostopic pub /plow_control std_msgs/Bool  „data: true”

For instructions related to data recording refer to this site. And If you want to make recordings easier to use, you can change .bag files to .csv files by following this tutorial.

What next?​

If you want to Learn more about working with ROS (e.g. make arduino node start on Leo Rover startup) check this tutorial.

You can also find other ideas and tutorials here:

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Now, everything should work, if not, contact us at contact@fictionlab.pl. We'll be happy to answer your questions and help you.