Raspberry Pi: A Tiny Computerfor Big Projects

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<D.YoE In 2011 at World Maker Faire, many makers got

their first chance to see a little board that we hadjust begun hearing whispers about on the

Internet. No bigger than a deck of cards, theRaspberry Pi is a fully-functional, Linux-poweredcomputer - with the added bonus of including a setof general purpose 1/0 pins that can be accessedeasily from the command line or with the help of acouple of simple scripting languages. TheRaspberry Pi launched in March 2012, and soonmakers across the globe started pumping out excit­ing projects using the device.

The Raspberry Pi FoundationThe Raspberry Pi was created by the RaspberryPi Foundation with the goal of developing a small,low-cost computer that would be a useful platformfor teaching kids how to get started with computerprogramming. The organization has designed twoboards: the lower cost and less functional Model Aand the currently available Model B board.

The Raspberry PI Foundation is a registeredcharity from Cambridgeshire, UK. It has set up dis­tribution deals with multiple electronics suppliersaround the world to help distribute the boards.

The Hardware

The Raspberry Pi Model B has a 700-MHz ARMprocessor with 512 Mb of RAM and a dedicated GPU

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unit capable of delivering full 1080P HD video. TwoUSB ports provide access for a keyboard andmouse, along with other USB accessories. HDMIvideo out allows you to have HD (high definition)video , but analog video is also supported with a com­posite RCA plug. Audio can also be sent over theHDMI, but an audio out jack is present as well.Onboard Ethernet gives your Pi and projects accessto the Internet. Storage is solved with an SD cardslot ratherthan using a full bulky hard drive . 17 GPIOpins round out the hardware. All this can be yoursfor the low low price of just $35. This price point ishelping fuel the demand for the boards.

The Model A is similar but with less RAM, oneUSB port, and no onboard Ethernet. This helpsdrop the price down to $25 and reduces the amountof power that is required to run the device by half .At the time of the writing of this article, the ModelA boards are not yet available for sale .

One criticism of the board is its lack of analoginputs. These would allow for easy access to manydifferent types of sensors. This has largely beensolved with the use of an extra external chip thatcan read analog sensors and then transmit the databack over a serial interface to the Raspberry PI.

The Software

The Raspberry Pi is designed to run a Linux oper­ating system (although some users have shoe­horned other operating systems on board). Thestandard OS is called Raspbian and is based onDebian Wheezy. Variations on this OS have been

The Raspberry Pi Model B

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The plO helps lidy up your Raspberry Pi by allowing you to use micro SO cards.

created to help users with specificdesired operations for their device.

The Raspbmcdistribution allows youto use your Pi as a media center with

your HD television . Once everything isconnected and configured, users caneasily stream videos , music, and pic­tures across their network, right to their

TV. Many commercial systems give youthis functionality , but often at double theprice and with fewer options and con­figurability.

Occidentaliswas created as the hard­ware hacker distribution. Occidentalisgives greater access to the GPIO pinsand enables common serial protocolslike 12C on them. New updates haveincluded such things as servo librariesand greater support for sensor mod­ules. The Python scripting languagecomes pre-installed, allowing users toquickly get up and running writing theirown apps to interact with the on-boardhardware and any device connected tothe GPIO pins.

Toppings for your PiWith the popularity of the new system, itwasn't long before many creators beganreleasing accessories to help users withtheir Pi needs. Maker extraordinaireLimor Fried (named 2012 Entrepreneurof the year by Entrepreneur magazine)of Adafruit Industries began selling smallscreens, keyboards, WiFi modules, andmany other useful items along with theirown custom creations. The Pi Cobbleris a breakout board that allows the userto easily be able to connect their Pi to abreadboard for prototyping newprojects.

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For those wanting a little more I/O power from theirRaspberry Pis (or just don't want to rewrite all of their Arduinocode), the Wyolum open hardware group created theAlaMode Arduino compatible shield. The AlaMode shield ispin-compatible with a standard Arduino and is capable ofaccepting any of the numerous shields that have been cre­ated for the Arduino.

One downside to the design of the Pi that bothered meinitially was how much the SO card stuck out of the side ofthe board. Of course I was not the only one who disliked thisand Rick Winscot decided to turn to Kickstarter.com to helphim fix the problem. Rick ran a successful campaign to builda micro SO card adapter that would allow you to plug a mem­ory card into your Pi without having it stick out of the device<http://kck.sVOsmYH7>. I received my boards after backingthe project and couldn 't be happier with them. They doexactly what they are supposed to and the build qualityis excellent.

Bushels of AppsIn December of 2012 the Raspberry Pi foundation launchedthe "Pi Store," an online venue for developers to give awayor sell their applications for the Pi. Unlike some systemsthough, the Raspberry Pi does not require that you downloadyour apps from the store. Apps may be downloaded frommany sources around the internet and still be loaded ontothe Raspberry Pi.

The Raspberry Pi Foundation separated the store into dif­ferent categories, so the apps could be listed by their func­tion. The Raspberry Pi being a system developed to helpteach children programming, the games section has a largenumber of options. The Dev Tools section helps you getstarted developing apps for the Raspberry Pi.The Media sec­tion contains downloads of MagPi, a digital magazine dedi­cated to the Raspberry Pi.

The Apps section contains some of the more interestingpossibilities . The store contains apps that turn your Pi into avoice over IP system or a full-featured router for your digitalnetwork. One of the more fun options that I discovered in theapp store is a system that turns your Raspberry Pi into a con-

troller to operate your modified RC car and could possibly bethe beginning of a robotics project.

Since the Raspberry Pi runs Linux, many applications thathave been designed to run on other Linux hardware will workwith the Pi. Many of those that currently do not run nativelyare being worked on to make them compatible .

A Slice of Pi With Your Ham

Never being ones to not embrace a new technology, hamshave already begun availing themselves with the tools that

The Assembled piGate (photo by Jatinderjit Singh)

Parts of the piGate going into its case. (Photo by Jatinderjit Singh)

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the Raspberry Pi brings to them. The size, low power usage,and access to both conventional I/O and the GPIO pins, lendthemselves to the types of projects in which hams have atendency to get involved.

AMSAT-UK has written about the work that Dave Johnsonhas been doing using the Raspberry Pi to help him with satel­lite tracking. Dave installed GPredictto help him track upcom­ing satellite passes in his area. The Raspberry Pi, with itsGPIO, could easily expand this project to allow not only theprediction of the location of the next AMSAT pass, but couldalso allow for the automatic rotation of an antenna during thepass to help the user get more time on the contacts and lesstime fiddling with their antenna.

The amateur radio multi-tool, FLDIGI, has been success­tully used on the Raspberry Pi by multiple hams. With its lowpower consumption and small footprint, this could easily be agood option for emergency services work when combined withNBEMS (the Narrow Band Emergency Messaging System).

Pi In The SkyI am a big fan of amateur radio high altitude balloon launch­es. This is a great way to have fun solving interesting prob­lems while also putting many of our ham radio skills to work.When I first saw the Raspberry Pi, I thought "Hey let's putthat in a balloon payload." There is more than enough horse­power there to run an APRS tracker, SSTV, and other exper­iments on board. In the past we have relied on independentsystems in our payloads to handle all of these functions . Thisincreases the redundancy and helps prevent a single cata­strophic failure bringing down all of our systems, it alsoincreases weight and complexity, as we have to indepen­dently power and verify each system separately.

www.cq-amateur-radio.com

Of course, if you wait too long on a great idea like this, some­one is bound to beat you to it and a team from England hassuccessfully sent its Pi up into the upper atmosphere. You canread more details about the flight in the "Raspberry Pi in TheSky" article featured in the Winter 2013 issue of CO VHF.

APRS on The RunWhile our team has been off running around Ohio chasingballoons , we have run into a problem from time to time of notbeing able to get our APRS traffic out to a digipeater or aniGate. This has led to confusion as to whether the payloadshave been working or where individual team members are inthe search party. The discussion has often come up aboutstocking some of the chase vehicles with more robust APRSgear to help digipeat our signals out or possibly just sendthem straight to the Internet. When I ran across an article athackaday.com on building a portable iGate using theRaspberry Pi, I knew a solution might have been found.

Jatinderjit Singh (aka Sunny) is the creator of the piGateproject. Sunny combined a Raspberry Pi with an HT, a USBWi-Fi adapter, and a USB sound card to create his iGate.He packaged the entire thing nicely in an enclosure for avery professional look. Sunny uses the multiman packageto decode the transmissions that are coming in and thenwrote his own Python script to handle capturing that dataand transmitting it back to the APRS servers. His website<http: //www.ultratechie.com/> offers a great writeup andphotos of his build and the many user comments led me tobelieve that this is not the last Raspberry Pi iGate projectthat we will see.

The more digipeaters and iGates that are setup across theworld, the more robust the APRS system will become. The

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My Raspberry Pi in a laser cut case <http://www.thingiverse.com/thing:24461>

cost of this project and the power savings over running a nor­mal computer for this task makes the piGate a lot more fea­sible for many of us to finally get some APRS equipment run­ning in our homes. I hope to soon be running one myself!

A Growing CommunityRecently, MAKE magazine hosted its first InternationalRaspberry Pi meetup - during which people from all over theworld met at some of their local hackerspaces or tech-cen­tered organizations and showed off their Raspberry Pi pro­jects to the world over web cams and a Google Hangout. Mylocal meet up, held in one of AS220's studios, was fortunateenough to have both of the authors of MAKE's new GettingStarted with Raspberry Pi book in-house to talk about theirbook and give us a demo of some of what is possible withthe Raspberry Pi.

Shawn Wallace and Matt Richardson have written a greatprimer that covers so much more than just the Raspberry Pi.If you are looking to get started with the Raspberry Pi, thisbook will save you a lot of time hunting for information on theInternet. Beyond just getting started, though, the bookcovers the basics of programming in Python and movesyou on to being able to create small video games, hardwareinterfacing , and accessing the web all programmatically onthe Pi.

Another section of the book covers the Scratch program­ming environment that is also included in many distributionsof the Raspberry Pi operating systems. Scratch is a language

specifically designed to help teach children the basics of pro­gramming . Developed by MIT, Scratch combines drag anddrop programming with concepts like variables and loopsused by higher level languages. Scratch is growing in popu­larity with many schools across the nation now beginningto teach it to their students . The Raspberry Pi gives thema low cost programming environment that doesn't conflictwith other family members ' needs to use their home's regu­lar computers.

One of Shawn's demos during the night was showing offone of his first projects that he created on the Raspberry Pi.Using a free programming environment called Pure Data,Shawn created a synthesizer. His synth was capable of beinghooked up to a MIDI keyboard or other inputs and creatingmusic with programmable effects. This could easily be incor­porated into an existing instrument enclosure or strappedonto the side of a case and take the place of a bulky laptopor desktop computer.

Other participants were showing off their Raspberry Pi pro­jects and discussing the ideas they had for moving forwardwith the platform. I was showing my Raspberry Pi in a lasercut case that I had created from open source plans designedby Adafruit. All in all, the night was a great success and helpedlink those interested in getting started with the platform withpeople who had already begun to get their feet wet with it.Be sure to keep an eye out for more meet ups in the futureas we continue to grow the user base.

If you would like to find more about the Raspberry Pi besure to check out the links 73, Matt, KB3TAN

The official Raspberry Pi site: http://www.raspberrypi.org/Adafruil's Raspberry Pi learning site: hUp://learn .adafruit.com/category /raspberry-piHackaday 's Raspberry Pi projects: http://hackaday.com/category/raspberry-pi-2/Getting Started with Raspberry Pi: http://oreil.ly /Stgvhv

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