Hello, World! – Blinking an onboard LED

Now that we have our development environment set up, we can begin writing the JavaScript to use with our Arduino board. We'll start by blinking an LED that is already built into the Arduino microcontroller.

Writing the Johnny-Five script

In your favorite IDE, create a new hello-world.js file in your project directory. Then, copy and paste, or write, the following code:

var five = require("johnny-five");
var board = new five.Board();

board.on("ready", function() {
  var led = new five.Led(13);
  led.blink(500);
});

We'll go over more of what this script does in Chapter 2, Working with Johnny-Five, but the basic overview is this: we require this script in the Johnny-Five module and use it to create a new board object. When this board is ready, we will create an LED object at pin 13 (this pin is wired to the onboard LED on an Arduino Uno board). We then program this LED to blink every half second.

Running the script

In order to run the script, go to your terminal, and in your project folder, run the following:

node hello-world.js

You should see an output that looks like the following:

You should see an LED blink on your Arduino Uno. The following figure shows where the LED is on the board:

If all is well and the LED is blinking, congratulations! You're ready to start building robots and applications with Arduino and Johnny-Five!

Tip

If there is a problem, many troubleshooting issues can be solved by checking the Johnny-Five website (www.johnny-five.io).