Backstop Media - Make: JavaScript Robotics: Building NodeBots with Johnny-Five, Raspberry Pi, Arduino, and BeagleBone

by Backstop Media and Rick Waldron

Copyright 2015 Backstop Media, LLC. All rights reserved.

Printed in Canada.

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• April 2015: First Edition

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978-1-4571-8695-0

[TI]

By Rick Waldron

I love programming and I also love making things. When I discovered Chris Williams node-serialport module (for Node.js), I remember thinking, Now I can program the things that I make. So I did! I contributed an Arduino sketch that printed a photoresistor sensor value to the open serial port and a small JavaScript handler program that listened for data and printed a graph to the terminal. Months later, I started contributing to Cam Pedersens duino project, until Julian Gaultier approached me with his JavaScript implementation of the Firmata protocol. From there, we set out to build a collection of high-level component classes with one goal: to make it easy and fun to control hardware with JavaScript. This book will show you what we built and how to use it to program the things that you make.

While the physical challenges of engineering a hardware project remain the same as they would for a project programmed in any other language, this book is going to show you how to think about that hardware in terms of objects that maintain state and provide control behaviors in the form of intuitively designed interfaces.

So, how would you verbally describe adding an LED to a project and then turning it on? You might say, Connect the LED to ground and pin 9, then turn it on. Using the Johnny-Five framework, that would be written as:

What about connecting a servo and then setting its horn to a specific angle in degrees? Attach the servo to pin 10 and position its horn to 110. Heres what that looks like:

These examples both illustrate an output, but what about input? Consider how Arduino sketches work: they generally rely on a program loop and often introduce some form of delay when reading and processing input. This means that your Arduino sketch is blocked whenever it is waiting for input. When writing programs in JavaScript, the process is never blocked; instead, your handlers wait for data to arrive and process it asynchronously:

These are trivial examples, but they illustrate the patterns that you will see repeated consistently throughout this book. Each project will show you how to construct it in the physical sense, then construct it in the abstract programming sense, and the latter will align with the former.

With these concepts, you will build and program:

• Walkers, typers, swimmers, and rovers (Chapters )
• A dancing hexapod ()
• Voice-activated relay control ()
• An indoor sundial ()
• Holiday, mood, or anytime lighting (Chapters )
• A security and notification system ()
• Sonar-based artificial intelligence ()
• A delta bot ()
• Musical shoes ()

For me, the most exciting part about this book is the authors themselves. This group is an excellent representation of NodeBots community members that have stood out since the very beginning. They are more than just writers or engineers: they are teachers, communicators, leaders, and (in my opinion) heroes. It would be an understatement to say that I couldnt have done it without them.

Enough talk, more rock. These projects do not have to be done in any specific order, so take a look at the Table of Contents, find a project that sounds like fun, and start building!