You'll need the Raspberry Pi that you set up in Chapter 1, Setting Up Your Development Environment, a breadboard, and a Pi Cobbler for easier pin access. You can get a Pi Cobbler (also sometimes called a Pi Wedge) from Adafruit, SparkFun, or Amazon. A Pi Cobbler also comes in the kits recommended in Chapter 1, Setting Up Your Development Environment.

The following diagram shows two different Raspberry Pi Cobblers, both from Adafruit. The one on the right has the ribbon cable attached:

We'll talk about how to set up the cobbler later in this chapter. You'll also need an LED, some jumper or breadboard wires, and a 330-ohm resistor.

I find the best way to organize your Raspberry Pi is to put each project in its own folder. In the source code that accompanies this book, I've done just that. But let's walk through how to set up your own project folders. First, you'll want to create the folder itself. For the project in this chapter, which we'll call led-blink, you'll want to run the following:

cd ~
mkdir led-blink

Make sure that you're running this in your SSH session to the Raspberry Pi, and not on your desktop.

Now that our project folder is ready for dependencies, we'll start exploring the Johnny-Five and Raspi-IO documentation that'll help us create the projects in this book.

There are two main sources of documentation that we'll be using for the projects in this book:

• The Johnny-Five website: http://johnny-five.io/
• The Raspi-IO GitHub README and wiki: https://github.com/nebrius/raspi-io

The following screenshot shows the Raspi-IO README on GitHub:

We will be using the Johnny-Five documentation at johnny-five.io to look up API calls and other information about the Johnny-Five library, and the Raspi-IO...

Now that we've gone through the documentation and figured out what goes where, we can start assembling our Raspberry Pi project. You'll need your Raspberry Pi, Pi Cobbler, two breadboard wires, an LED (doesn't matter what color), and a 300-ohm resistor.

In order to make sure the cobbler is seated correctly, you'll want to make sure that the ribbon cable points outward from the Raspberry Pi when placed on the GPIO pins, and that the little tab on the side of the connector faces the right way in the cobbler itself (this is usually ensured by a plastic wall around the pins that the ribbon cable plugs into; make sure that you check that it's lined...

In order to make the LED blink, we'll need to install the code on the Raspberry Pi, and then run it!

If you wrote your code on your desktop and need to transfer it to your Raspberry Pi, there are a couple of ways to go about it: you can use rsync on an macOS X or Linux machine:

rsync ./blink-led.js 
pi@raspberrypi.local:~/<project folder>/

Replace <project folder> with the folder you want to transfer into (for example, the book folder would be hands-on-robotics-with-javascript/ch2/blink-led).

Congratulations! You've made a Johnny-Five bot! In this chapter, you've learned how to wire up an LED, navigate the documentation for Johnny-Five and Raspi-IO, and run your code on the Raspberry Pi!

1. Look in the Johnny-Five documentation, under the LED heading in the section on the API. Look for the strobe function. What does the first argument do? What would happen if you passed 500 as that first argument?
2. What is the second argument in the LED.strobe() function? How would this come in handy for applications waiting for the LED to be off?
3. Does the Johnny-Five LED object emit any events? Why, or why not?
4. Using the Raspi-IO documentation, what does the Raspberry Pi pin P1-29 translate to in terms of GPIO #?
5. Using the Johnny-Five documentation, name a function that is an alias for the LED.strobe() function.
6. What happens before the board's ready event fires in a Johnny-Five application?