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Raspberry Pi

Onderstaande tekst kwam ik tegen in CQ AMATEUR van maart 2013. Een leuk project om mee te experimenteren. Zowel met XBMC, Linux en hamsoftware voor digimodes.


BY MATT STULTZ,* KB3TAN

Raspberry Pi: A Tiny Computer for Big Projects

In 2011 at World Maker Faire, many makers got their first chance to see a little board that we had just begun hearing whispers about on the Internet. No bigger than a deck of cards, the Raspberry Pi is a fully-functional, Linux-powered computer- with the added bonus of including a set of general purpose I/O pins that can be accessed easily from the command line or with the help of a couple of simple scripting languages. The Raspberry Pi launched in March 2012, and soon makers across the globe started pumping out exciting projects using the device.

The Raspberry Pi Foundation

The Raspberry Pi was created by the Raspberry Pi Foundation with the goal of developing a small, low-cost computer that would be a useful platform for teaching kids how to get started with computer programming. The organization has designed two boards: the lower cost and less functional Model A and the currently available Model B board.

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

The Hardware

The Raspberry Pi Model B has a 700-MHz ARM processor with 512 Mb of RAM and a dedicated GPU unit capable of delivering full 1080P HD video. Two USB ports provide access for a keyboard and mouse, along with other USB accessories. HDMI video 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 the HDMI, but an audio out jack is present as well. Onboard Ethernet gives your Pi and projects access to the Internet. Storage is solved with an SD card slot rather than using a full bulky hard drive. 17 GPIO pins round out the hardware. All this can be yours for the low low price of just $35. This price point is helping fuel the demand for the boards. [fusion_builder_container hundred_percent=”yes” overflow=”visible”][fusion_builder_row][fusion_builder_column type=”1_1″ background_position=”left top” background_color=”” border_size=”” border_color=”” border_style=”solid” spacing=”yes” background_image=”” background_repeat=”no-repeat” padding=”” margin_top=”0px” margin_bottom=”0px” class=”” id=”” animation_type=”” animation_speed=”0.3″ animation_direction=”left” hide_on_mobile=”no” center_content=”no” min_height=”none”]

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

One criticism of the board is its lack of analog inputs. These would allow for easy access to many different types of sensors. This has largely been solved with the use of an extra external chip that can read analog sensors and then transmit the data back 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). The standard OS is called Raspbian and is based on Debian Wheezy. Variations on this OS have been created to help users with specific desired operations for their device.

The Raspbmc distribution allows you to use your Pi as a media center with your HD television. Once everything is connected and configured, users can easily stream videos, music, and pictures across their network, right to their TV. Many commercial systems give you this functionality, but often at double the price and with fewer options and configurability.

Occidentalis was created as the hardware hacker distribution. Occidentalis gives greater access to the GPIO pins and enables common serial protocols like I2C on them. New updates have included such things as servo libraries and greater support for sensor modules. The Python scripting language comes pre-installed, allowing users to quickly get up and running writing their own apps to interact with the on-board hardware and any device connected to the GPIO pins.

Toppings for your Pi

With the popularity of the new system, it wasn’t long before many creators began releasing accessories to help users with their Pi needs. Maker extraordinaire Limor Fried (named 2012 Entrepreneur of the year by Entrepreneur magazine) of Adafruit Industries began selling small screens, keyboards, WiFi modules, and many other useful items along with their own custom creations. The Pi Cobbler is a breakout board that allows the user to easily be able to connect their Pi to a breadboard for prototyping new projects.

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

One downside to the design of the Pi that bothered me initially was how much the SD card stuck out of the side of the board. Of course I was not the only one who disliked this and Rick Winscot decided to turn to Kickstarter.com to help him fix the problem. Rick ran a successful campaign to build a micro SD card adapter that would allow you to plug a memory card into your Pi without having it stick out of the device <http://kck.st/OsmYH7>. I received my boards after backing the project and couldn’t be happier with them. They do exactly what they are supposed to and the build quality is excellent.

Bushels of Apps

In December of 2012 the Raspberry Pi foundation launched the “Pi Store,” an online venue for developers to give away or sell their applications for the Pi. Unlike some systems though, the Raspberry Pi does not require that you download your apps from the store. Apps may be downloaded from many sources around the internet and still be loaded onto the 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 help teach children programming, the games section has a large number of options. The Dev Tools section helps you get started 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 interesting possibilities. The store contains apps that turn your Pi into a voice over IP system or a full-featured router for your digital network. One of the more fun options that I discovered in the app store is a system that turns your Raspberry Pi into a controller to operate your modified RC car and could possibly be the beginning of a robotics project.

Since the Raspberry Pi runs Linux, many applications that have been designed to run on other Linux hardware will work with the Pi. Many of those that currently do not run natively are being worked on to make them compatible.

A Slice of Pi With Your Ham

Never being ones to not embrace a new technology, hams have already begun availing themselves with the tools that the Raspberry Pi brings to them. The size, low power usage, and access to both conventional I/O and the GPIO pins, lend themselves to the types of projects in which hams have a tendency to get involved.

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

The amateur radio multi-tool, FLDIGI, has been successfully used on the Raspberry Pi by multiple hams. With its low power consumption and small footprint, this could easily be a good option for emergency services work when combined with NBEMS (the Narrow Band Emergency Messaging System).

Pi In The Sky

I 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 put that 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 independent systems in our payloads to handle all of these functions. This increases the redundancy and helps prevent a single catastrophic failure bringing down all of our systems, it also increases weight and complexity, as we have to independently power and verify each system separately.

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 has successfully sent its Pi up into the upper atmosphere. You can read more details about the flight in the “Raspberry Pi in The Sky” article featured in the Winter 2013 issue of CQ VHF.

APRS on The Run

While our team has been off running around Ohio chasing balloons, we have run into a problem from time to time of not being able to get our APRS traffic out to a digipeater or an iGate. This has led to confusion as to whether the payloads have been working or where individual team members are in the search party. The discussion has often come up about stocking some of the chase vehicles with more robust APRS gear to help digipeat our signals out or possibly just send them straight to the Internet. When I ran across an article at hackaday.com on building a portable iGate using the Raspberry Pi, I knew a solution might have been found.

Jatinderjit Singh (aka Sunny) is the creator of the piGate project. Sunny combined a Raspberry Pi with an HT, a USB Wi-Fi adapter, and a USB sound card to create his iGate. He packaged the entire thing nicely in an enclosure for a very professional look. Sunny uses the multimon package to decode the transmissions that are coming in and then wrote his own Python script to handle capturing that data and transmitting it back to the APRS servers. His website <http://www.ultratechie.com/> offers a great writeup and photos of his build and the many user comments led me to believe that this is not the last Raspberry Pi iGate project that we will see.

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

Recently, MAKE magazine hosted its first International Raspberry Pi meetup – during which people from all over the world 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. My local meet up, held in one of AS220’s studios, was fortunate enough to have both of the authors of MAKE’s new Getting Started with Raspberry Pi book in-house to talk about their book and give us a demo of some of what is possible with the Raspberry Pi.

Shawn Wallace and Matt Richardson have written a great primer that covers so much more than just the Raspberry Pi. If you are looking to get started with the Raspberry Pi, this book will save you a lot of time hunting for information on the Internet. Beyond just getting started, though, the book covers the basics of programming in Python and moves you on to being able to create small video games, hardware interfacing, and accessing the web all programmatically on the Pi.

Another section of the book covers the Scratch programming environment that is also included in many distributions of 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 and drop programming with concepts like variables and loops used by higher level languages. Scratch is growing in popularity with many schools across the nation now beginning to teach it to their students. The Raspberry Pi gives them a low cost programming environment that doesn’t conflict with other family members’ needs to use their home’s regular computers.

One of Shawn’s demos during the night was showing off one 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 being hooked up to a MIDI keyboard or other inputs and creating music with programmable effects. This could easily be incorporated into an existing instrument enclosure or strapped onto the side of a case and take the place of a bulky laptop or desktop computer.

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

If you would like to find more about the Raspberry Pi be sure to check out the links

73, Matt, KB3TAN

*3567 West Shore Rd., Warwick, RI 02886 e-mail: <kb3tan@cq-amateur-radio.com>

The official Raspberry Pi site: http://www.raspberrypi.org/

Adafruit’s Raspberry Pi learning site: http://learn.adafruit.com/category/raspberry-pi

Hackaday’s Raspberry Pi projects: http://hackaday.com/category/raspberry-pi-2/

Getting Started with Raspberry Pi: http://oreil.ly/Stgvhv

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