How To Utilize the Arduino Software Serial Library

This demo will walk you through how to set up a Software Serial connection using Arduino's SoftwareSerial library.

Required Hardware

• Sphero RVR+/RVR

• Arduino Uno

• 5V FTDI Cable (like this one)

• USB 2.0 Cable Type A/B

• Jumper wires

Instructions

If you want your Arduino program to print some output while also talking to RVR+/RVR, you may find that using the Arduino's built-in hardware for serial communication gives you messy results:

Getting NORDIC main application version...

ç:.....ìÿç8....ˇ...?.ˇ..ˇ.Eÿç8....ˇ...?ˇ..ˇ..EÿVersion: 7.1.422

This is where Arduino's SoftwareSerial library comes in. The SoftwareSerial library can configure other digital pins on your Arduino so that they can be used for serial communication.

Using the SoftwareSerial Library

A complete example of using the SoftwareSerial library can be found in software_serial_demo.ino. This tutorial will walk you through the lines of code that set up and use this library.

#include <SoftwareSerial.h>

The first thing you have to do to use any library is include it!

SoftwareSerial serial(2, 3);

You'll need to declare an instance of SoftwareSerial to use in your code. In this declaration, we're using pin 2 as the RX pin and pin 3 as the TX pin. This will be important to note for when we're hooking everything up.

serial.begin(115200);

Inside the setup() function of your Arduino file, be sure to include this line to begin the serial connection. 115200 is the baud rate RVR+/RVR uses for serial communication.

That's all there is to it! Now you can use your Software Serial connection to print output from your program, like this:

serial.println("Getting NORDIC main application version...");

Setting Up a Serial Port Terminal Application

Now that your code is all set up, you'll need a way to actually see the output that you're printing. For this we use a serial port terminal application. It's up to you which application you use, but we used CoolTerm. There are two main things you'll need to do to get the terminal set up to print your output.

First, you'll need to make sure the application is reading from the correct USB port. You can usually figure this out with trial and error (because it won't work if it's not reading from the right port!)
Second, make sure the baudrate matches the one you used in your serial.begin() call. For us, that's 115200.

That should be all you need to do! If things don't seem to be working later, try playing around with the different options (like the USB port).

Bringing It All Together

The last thing to do is connect all your hardware! Once you've flashed your program to the Arduino, disconnect it from your computer. Next we want to get the 5V FTDI Cable hooked up to your Arduino. You'll need to connect jumper wires to the RX and TX pins of the FTDI cable. Then, hook them up to the Arduino as follows:

• connect the RX pin to pin 3 (the TX pin) on the Arduino

• connect the TX pin to pin 2 (the RX pin) on the Arduino

That's it! Now you can plug the USB side of the cable in to your computer.

Next, use your A/B USB cable to connect the Arduino to the RVR+/RVR (don't turn the RVR+/RVR on just yet!). Move over to your terminal application and tell it to start reading from the serial port (in CoolTerm this is the Connect button). Finally, it's time to turn on your RVR+/RVR and see what happens! If you used the provided software_serial_demo.ino file, you should see something like this:

Getting NORDIC main application version...

Version: 7.1.422

Go Further

Now head over the Arduino SDK to continue making your own code, or check out our two sample projects: WeatherBot and PartyBot