Jumpstarting the Onion Omega2 An Introduction to a New Low-Cost Internet of Things Computer WOLFRAM DONAT JUMPSTARTING the Onion Omega2 AN INTRODUCTION TO A NEW LOW-COST INTERNET OF THINGS COMPUTER Wolfram Donat Maker Media, Inc. San Francisco Copyright © 2018 Wolfram Donat. All rights reserved. Published by Maker Media, Inc. 1700 Montgomery Street, Suite 240 San Francisco, CA 94111 Maker Media books may be purchased for educational, business, or sales promotional use. Online editions are also available for most titles (safari- booksonline.com). For more information, contact our corporate/institutional sales department: 800-998-9938 or [email protected]. 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You can learn more about the company at the following websites: Maker Media: makermedia.com Maker Faire: makerfaire.com Maker Shed: makershed.com Maker Share: makershare.com CONTENTS Introduction vii 1 Setting Up Everything 1 Graphical Setup 3 Trouble Connecting? 5 Connecting via the Command Line 6 Upgrading Firmware and Installing the Console 7 2 Getting to Know the Console 11 GPIO Tool 12 OLED Control 13 Settings 15 The Terminal App 16 The Editor 16 The Webcam Application 18 Relay and PWM Control 19 OPKG and Python 22 3 The Tweetin’ Onion 25 The Temperature Tweet 25 Install Modules 26 The Twitter Side of Things 27 The Hardware 29 The Code 31 4 The Photovore 35 Parts 36 The Voltage Divider 37 Hardware Setup 39 Software and Code 43 v INTRODUCTION In the proud tradition of computers named after fruit—the Apple, the Raspberry Pi, the Banana Pi, the Pine (okay, maybe not that last one)—comes a new entry into the small, single-board computer (SBC) market: the Onion Omega2. Let’s ignore the fact that an onion is a vegetable, not a fruit, and talk about the Onion Omega2’s origins for a moment. The Onion Omega2 (and its big brother, the Omega2+) are the second offering from a company called, appropriately enough, Onion. The original Omega cost about $18 and ran on a Qual- comm Atheros AR9331 chip. Onion ran a Kickstarter campaign in 2016 to replace the Omega with the Omega2, using a different system on a chip, the MediaTek MT7688. They were ultimately successful, raising well over their goal of $440,000, and the Omega2 shipped late in 2016. A nice feature of the newer ver- sion was the price drop; the new board started at $5, though it was later increased to $7.50. The Omega2+ is only $9. The Omega2 is an SBC geared for the Internet of Things (IoT) market, billed as the “world’s smallest Linux server.” It runs a vari- ant of Linux known as OpenWRT, which is most commonly found on embedded devices like routers. It’s low power and really tiny; at 43mm×26mm×10mm, it’s just a little larger than an Arduino Pro Mini. Don’t let that fool you into thinking it’s not a real computer, however. It’s surprisingly powerful for the size, with its MIPS pro- cessor running at 580MHz. It supports up to 256MB of RAM, and it can support SD card storage. It supports 802.11b/g/n 2.4GHz WiFi and 10/100M Ethernet, as well as a multitude of other pro- tocols like UART, I2S, I2C, and SPI. It operates at 3.3V, but its vii docks and expansion boards come with a convenient onboard voltage regulator, which means you can power it with a variety of power supplies without having to worry about blowing it up. There are just a few differences between the Omega2 and the Omega2+, since they have the same processor. The O2 has 64MB of DDR2 DRAM memory, whereas the O2+ has 128. The O2 has 16MB of onboard flash storage, and the O2+ has 32. Finally, the O2+ has a microSD card slot, which gives you signifi- cantly more room for programs. Given the small difference in price, I suggest you pick up the O2+, but all of the projects in this book will work on either model, so if you’ve already purchased the O2, not to worry. I would like to interject a small observation here. If you really go back and look at those specs, it is insane how far we’ve come when it comes to putting computing power into small packages. My first computer was a Commodore VIC-20, which had a whop- ping 5KB of RAM. That’s less than the size of a standard image thumbnail on the web today, and almost thirteen thousand times smaller than the Omega2’s DRAM package. Quite a few expansion boards and docks are available; you’re going to need at least one right off the bat, as the Onion’s head- ers are at a 2mm pitch instead of the more common 0.1g pitch, which means you can’t just plug it into your breadboard. You’ll have to use either a dock or a breadboard expansion piece, so my suggestion is to purchase the power dock (Figure I-1). It allows you to power the board and whatever add-ons you happen to have using not just a microUSB cable, but also a 2-pin JST-PH connector—the standard connector on many lithium-ion (Li-ion) batteries. None of the expansion boards are very expensive, so it’s worth the time to look around and see what’s available when you’re shopping for your Onion. viii Jumpstarting the Onion Omega2 FIGURE I-1: The power dock Ordinarily this is where I’d walk you through the board and show you what’s on it, but these devices are covered by a metal cover so you can’t really see anything. I can, however, tell you what pins are made available to you when you plug it into a dock. The number of pins depends on the board; the power dock gives you 30 (you lose a power-in pin and a few GPIOs and gain a 5V and a few GNDs), and the breadboard dock gives you all 32. These include the standard 3.3V and GND pins, as well as I2C, Serial, and even Ethernet pins. In this book I’ll be using the Omega2+, the power dock, the relay expansion board, and the OLED expansion board, so if you still have some shopping to do you’ll know what you need.