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Home > IoT & Hardware > Robotics > Learning Javascript Robotics
Learning Javascript Robotics
Learning Javascript Robotics

Learning Javascript Robotics: Design, build, and program your own remarkable robots with JavaScript and open source hardware

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Profile Icon Kassandra Perch
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€8.99 €19.99
Full star icon Full star icon Full star icon Full star icon Half star icon 4.3 (6 Ratings)
eBook Nov 2015 160 pages 1st Edition
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Profile Icon Kassandra Perch
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€8.99 €19.99
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eBook Nov 2015 160 pages 1st Edition
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Learning Javascript Robotics

Chapter 2. Working with Johnny-Five

In this chapter, we'll begin working with Johnny-Five to build our own robotics projects. We'll cover what makes Johnny-Five a great library for starting with robotics, and we will build our first robot. We'll learn how we can manipulate this robot in real time from the command line—a feat not easily replicated on other platforms! By the end of this chapter, you'll have an open understanding of the software involved, which will serve as a great foundation for more complicated hardware builds.

This chapter will cover the following topics:

  • How a Johnny-Five program works
  • Understanding events in Johnny-Five
  • Wiring an LED and making it blink
  • Using Read-Eval-Print-Loop (REPL)

What you'll need for this chapter

All you'll need for this chapter is your microcontroller (the examples here still use an Arduino Uno) and a small handful of LEDs—we'll be wiring only one LED, but you may want a couple of spares, in case one burns out.

How a Johnny-Five program works

In this section, we'll take a look at the internals of a Johnny-Five program in more detail, so we can start building more complex applications.

Objects, functions, and events

Johnny-Five programs work using an event-based structure, and there are three concepts to keep in mind: objects, functions, and events.

Objects tend to programmatically represent our physical electronic components and are usually constructed using the new keyword. A few examples of objects in Johnny-Five include the five object, which represents the Johnny-Five library, the Board object, which represents our microcontroller; and the LED object, which will programmatically represent our LED:

var led = new five.Led(11);

Functions are available for the objects we create and usually represent the actions that our robots can do. For instance, the LED object has an on() and off() function that turns the LED on and off:

led.on();
led.off();
led.blink();
led.stop();

Events are fired on objects...

Understanding events in Johnny-Five

The events in Johnny-Five are a very important concept—this is also a new concept, especially if you are used to low-level language programming. It's very similar to the idea of interrupts, but definitely strays away from the traditional robotics programming paradigm of an event loop. While you can create timers and loops in Johnny-Five, it highly encourages an event-based programming approach, which can need some practice.

Why events?

A question that gets asked a lot is, "Why event-based? Why not loop-based and interrupt-based as in previous methods?".

A lot of this has to do with the way robots work and the way we think about how we program robots. When you think about what you want a robot to do, you're less likely to think "Every X seconds, I want to check for A and start task B..." and you are more likely to think "When Y happens, I want to start event C...".

The event-based system in Johnny-Five works really...

Wiring up an external LED

For our first hardware project, we're going to wire an LED to the Arduino. An LED, or a Light Emitting Diode, is a component that lights up when electric current is passed through it. They come in many colors and sizes and are one of the most easy-to-use and versatile components in hobbyist robotics.

Setting up the hardware

First, take an LED. We'll determine the positive and negative leads of the LED—for this component, it's straightforward: the positive lead is longer than the negative lead.

Setting up the hardware

Determining the positive and negative ends of an LED

To wire the LED to an Arduino, place the positive lead on pin 11 and the negative lead on the pin marked GND, just like in the following diagram:

Setting up the hardware

Wiring up our LED

You can also use a breadboard if you wish to—it will look like the following:

Setting up the hardware

Wiring an LED with a breadboard

Now that we've wired up the LED, we're going to make it blink as we did in the last chapter. The script looks very familiar...

Using the Read-Eval-Print-Loop (REPL)

The Read, Eval, Print Loop, or REPL, is a concept relative to many scripting languages, but it is new to libraries, and definitely new to robotics. Think about how you alter the state in a typical Arduino program: you modify the source code, re-load it onto the board, and wait for it to run.

However, due to the way Johnny-Five works, we can modify the state of our robot code while the code is running. This is because we use Firmata—the board is just a thin client that reacts to instructions from our node program, so if we let our Node programs send different instructions, we can change how our robot works in real time.

The way to do this in a Johnny-Five program is by injecting components into the REPL, which allows us to use them.

Making components available to the REPL

We're going to modify our script from the previous section in order to manipulate our LED. To do this, we're going to use the this.repl.inject() function. The this keyword...

What you'll need for this chapter

All you'll need for this chapter is your microcontroller (the examples here still use an Arduino Uno) and a small handful of LEDs—we'll be wiring only one LED, but you may want a couple of spares, in case one burns out.

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Description

There has been a rapid rise in the use of JavaScript in recent times in a variety of applications, and JavaScript robotics has seen a rise in popularity too. Johnny-Five is a framework that gives NodeBots a consistent API and platform across several hardware systems. This book walks you through basic robotics projects including the physical hardware builds and the JavaScript code for them. You'll delve into the concepts of Johnny-Five and JS robotics. You'll learn about various components such as Digital GPIO pins, PWM output pins, Sensors, servos, and motors to be used with Johnny-Five along with some advanced components such as I2C, and SPI. You will learn to connect your Johnny-Five robots to internet services and other NodeBots to form networks. By the end of this book, you will have explored the benefits of the Johnny-Five framework and the many devices it unlocks.

What you will learn

  • Familiarise yourself with JohnnyFive Read, Eval, and Print Loop (REPL) to modify and debug robotics code in real time
  • Build robots with basic output devices to create projects that light up, make noise, and more
  • Create projects with complex output devices, and employ the JohnnyFive API to simplify the use of components that require complex interfaces, such as I2C
  • Make use of sensors and input devices to allow your robotics projects to survey the world around them and accept input from users
  • Use the Sensor and Motor objects to make it much easier to move your robotics projects
  • Learn about the Animation API that will allow you to program complex movements using timing and key frames
  • Bring in other devices to your JohnnyFive projects, such as USB devices and remotes
  • Connect your JohnnyFive projects to external APIs and create your own Internet of Things!

Product Details

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Publication date, Length, Edition, Language, ISBN-13
Publication date : Nov 25, 2015
Length: 160 pages
Edition : 1st
Language : English
ISBN-13 : 9781785880872
Vendor :
Netscape
Category :
IoT & Hardware
Languages :
JavaScript
Concepts :
Robotics
Tools :
ROS

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Product Details

Publication date : Nov 25, 2015
Length: 160 pages
Edition : 1st
Language : English
ISBN-13 : 9781785880872
Vendor :
Netscape
Category :
IoT & Hardware
Languages :
JavaScript
Concepts :
Robotics
Tools :
ROS

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Table of Contents

10 Chapters
1. Getting Started with JS Robotics Chevron down icon Chevron up icon
1. Getting Started with JS Robotics
Understanding JS Robotics, NodeBots, and Johnny-Five
Setting up your development environment
Hello, World! – Blinking an onboard LED
Summary
2. Working with Johnny-Five Chevron down icon Chevron up icon
2. Working with Johnny-Five
What you'll need for this chapter
How a Johnny-Five program works
Understanding events in Johnny-Five
Wiring up an external LED
Using the Read-Eval-Print-Loop (REPL)
Summary
3. Using Digital and PWM Output Pins Chevron down icon Chevron up icon
3. Using Digital and PWM Output Pins
What you'll need for this chapter
How GPIO pins work
Multiple pins with several LEDs
Using PWM pins with the Piezo element
Summary
4. Using Specialized Output Devices Chevron down icon Chevron up icon
4. Using Specialized Output Devices
What you'll need for this chapter
Outputs that require multiple pins
Checking compatibility with Johnny-Five
Obtaining documentation, wiring diagrams, and so on
Project – character LCD display
Summary
5. Using Input Devices and Sensors Chevron down icon Chevron up icon
5. Using Input Devices and Sensors
What you'll need for this chapter
How analog input pins work
Johnny-Five sensor events
Using basic inputs – buttons and potentiometers
Using sensors – Light and Temperature
Summary
6. Moving Your Bot Chevron down icon Chevron up icon
6. Moving Your Bot
What you'll need for this chapter
The different kinds of servos and motors
Special concerns when using motors and servos
Wiring up servos and motors
Creating a project with a motor and using the REPL
Creating a project with a servo and a sensor
Summary
7. Advanced Movement with the Animation Library Chevron down icon Chevron up icon
7. Advanced Movement with the Animation Library
What you'll need for this chapter
What is the Animation API?
Looking at the Animation API
Writing Servo Animations
Animation events
Summary
8. Advanced Components – SPI, I2C, and Other Devices Chevron down icon Chevron up icon
8. Advanced Components – SPI, I2C, and Other Devices
What you'll need for this chapter
Why do we need the I2C and SPI protocols?
Exploring SPI (Serial Peripheral Interface) devices
Exploring I2C devices
External Devices
Summary
9. Connecting NodeBots to the World, and Where to Go Next Chevron down icon Chevron up icon
9. Connecting NodeBots to the World, and Where to Go Next
What you'll need for this chapter
Connecting NodeBots to the Web
Johnny-Five and the wide world of microcontrollers
Other JS libraries and platforms
Where to go from here
Index Chevron down icon Chevron up icon
Index

Customer reviews

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Full star icon Full star icon Full star icon Full star icon Half star icon 4.3
(6 Ratings)
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1 star 16.7%
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Andrew Connell Dec 18, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
I'm a seasoned JavaScript developer and aspiring hardware guy for my own personal projects. Having heard Kassandra on a podcast episode or two, I wanted to pick this book up. I found it very easy to grok and pickup the concepts. I am more of a Raspberry Pi guy and all the projects used the Arduino Uno - my only "complaint" that it should have been more visible in the marketing / cover - however I walked away placing an order for the Uno, something I've wanted to learn! All the projects were super simple to understand and implement... as a tech author I know how much work goes into this, but hoping for something that goes even deeper for her next work!
Amazon Verified review Amazon
Rick Waldron Nov 30, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
This book is a great way to "break in" to JavaScript Robotics with Johnny-Five. Each chapter walks you through the basics and then illustrates how to build something with with what you've learned—which is a great strategy!
Amazon Verified review Amazon
Roberto M. Pensotti Apr 19, 2017
Full star icon Full star icon Full star icon Full star icon Full star icon 5
If you want to learn programming for robots, or micro controllers in general, this is the book.JavaScript on NodeJS is the best language for this type of application.Well illustrated, well documented..Excellent!
Amazon Verified review Amazon
K Feb 11, 2016
Full star icon Full star icon Full star icon Full star icon Full star icon 5
This book assumes quite a bit less of your robotics experience than it does of your experience with JavaScript. It focuses a great deal on the excellent Johnny Five library for Raspberry Pi and Arduino. It helps you to learn the basics of motor control as well as sensor information through GPIO. If you already have JavaScript experience, this is definitely the best foray into extending your ability into the world of robotics.
Amazon Verified review Amazon
Grayson Nov 30, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
The animation chapter alone makes this a great book. Great introduction to nodebots and generally working with electronics + javascript. Presented in an approachable manner with clear explanations.
Amazon Verified review Amazon

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About the author

Profile icon Kassandra Perch
Kassandra Perch
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Kassandra Perch is an open web developer and supporter. She began as a frontend developer and moved to server-side with the advent of Node.js and was especially enthralled by the advance of the NodeBots community. She travels the world speaking at conferences about NodeBots and the fantastic community around them.
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