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Raspberry Pi B y GE OF F G R A H A M The Raspberry Pi is an internet phenomenon. It is a small, single board computer costing just $35 and it caused a sensation when it was first released, selling more than a million units in the first 12 months. So what is the Raspberry Pi and what’s all the fuss about? F OR ANYONE WHO has been living under a rock and has not heard of the Raspberry Pi, a short description is in order. It is a small computer on a credit card-sized PCB which packs a lot of punch. It has two USB ports, HDMI video output with up to 1920 x 1200 resolution, composite video, stereo audio, Ethernet and a number of general purpose input/output pins. 24  Silicon Chip It runs Linux and it boots up into a graphical Windowslike environment where you can run a web browser, word processing and so on. It sounds like a cheap PC and it is. But there’s a lot more to it than that . . . In the beginning The Raspberry Pi was developed by a number of acasiliconchip.com.au This is what you can expect once you have connected everything to the Raspberry Pi and booted it up. It features a graphical user interface which looks a little like that on a Windows PC or an Apple Mac. You can browse the web, write programs and do word processing. Performance is not bad considering that the Raspberry Pi costs $35 and is the size of a credit card. The top side of the Raspberry Pi board is quite compact, being the same size as a standard credit card. In the centre is the Broadcom BCM2835 ARM processor which runs at 700MHz. This is hidden by the Samsung memory chip which is mounted on top of the Broadcom ARM chip, a technique known as “package on package” technology (see panel). demics in the Computer Laboratory of the University of Cambridge (UK). They were concerned about the declining skill levels of students entering the Computer Science courses. In the 1990s, most prospective students had gained a basic knowledge of programming from playing with the hobby computers that flourished in the 1980s. But by the late 2000s, the typical incoming student might have done a little web design but not much more. Their idea was to resurrect the heydays of the 80s and 90s by making available a cheap computer that could be used by students at home and in the classroom to learn the basics of programming. Thus the Raspberry Pi was born, with the initial aim of building just 1000 units for new undergraduates at the University of Cambridge. Overall development took six years and during this time the expectations for the device increased enormously. From the beginning, the Raspberry Pi was surrounded by a lot of hype. Even before it was available for sale, the first 10 boards were put up for auction on eBay and sold for about 70 times their retail price. This and other events ensured that there was plenty of media and internet coverage before the official launch in February 2012. When the Raspberry Pi was eventually released, this promotion paid off handsomely. Eager buyers rushed to enter their orders and the ensuing chaos brought the distributors’ websites to their knees. When their systems recovered, the whole production run of 10,000 units sold out within hours. Just three weeks later, orders had reached 200,000 units – this despite the fact that the estimated delivery delay at that time was measured in months. For most of the past 12 months the Raspberry Pi has been out of stock at various times and by the time that you read this, over a million will have been sold. Designing the Raspberry Pi When the University of Cambridge dons set out to design the Raspberry Pi, they had a couple of aims; it had to be cheap and it had to meet the technical expectations of today’s tech-savvy younger generation. Raspberry Pi Resource Sites Official Raspberry Pi website: www.raspberrypi.org/ The official Raspberry Pi discussion forum: http://www.raspberrypi.org/phpBB3 The Raspberry Pi Store (download software, including games): http://store.raspberrypi.com/projects RS Components Sales Website: http://australia.rs-online.com/web/generalDisplay.html?id=raspberrypi Element 14 Sales Website: http://www.element14.com/community/groups/raspberry-pi Why “Raspberry Pi”? It seems that the name is not particularly significant but is simply based on a “friendly fruit” and an abbreviation for Python, the recommended programming language for the device. News items for the Raspberry Pi: http://www.geek.com/articles/tagged/raspberry-pi/ Some things that users have done with their Raspberry Pi: http://www.treehugger.com/slideshows/gadgets/20-awesome-projectsraspberry-pi-microcomputers/ XBMC – A very capable Media Player that runs on the Raspberry Pi: http://xbmc.org/ Turn your Raspberry Pi into a network storage manager: http://www.howtogeek.com/139433 siliconchip.com.au May 2013  25 HDMI OUTPUT BROADCOM BCM2835 ARM PROCESSOR AND RAM MICRO USB POWER SOCKET (5V DC, 1A) SD CARD SOCKET (BACK OF BOARD) ETHERNET SOCKET CSI CONNECTOR (CAMERA) DSI DISPLAY CONNECTOR 2 x USB 2.0 AUDIO OUTPUT COMPOSITE VIDEO GPIO HEADERS The layout of the connectors on the Raspberry Pi board. It’s almost the same size as a credit card. They did this by adopting mass production techniques and mobile telephone technology. For example, the main processor uses a package-on-package technique (see the panel) pioneered by the mobile phone industry, in which two chips are stacked on top of each other. Another example is the PCB where lasers are used to bore holes in the PCB for the vias (instead of a drill). Overall, the PCB is about the size of a credit card and is covered on both sides of the board with components (many microscopic). There’s definitely no assemble-yourself-kits or hand-soldering here; it’s only sold in assembled form. The main processor is a Broadcom BCM2835 which is an ARM processor running at 700MHz and designed for multimedia applications. It includes most of what is needed in a computer so it is called a system-on-a-chip (SoC). This includes a graphics processor (capable of Blu-ray quality playback), digital video output, audio system, memory controller and some general purpose I/O used for the SD This is an example of what you will see as the Raspberry Pi boots up. The total boot time is under a minute. card interface and other duties. Stacked on top of this is a 512MB memory chip (256MB on the cheaper Model A). The only other significant chip on the board provides the two USB ports and an ethernet interface. Other than a few voltage regulators and a logic buffer, that’s it; a complete computer based on two chips. The resulting Raspberry Pi is well equipped. It has a HDMI interface for a monitor, two USB ports (generally one is used for the keyboard and the other for a mouse), a 10/100 Ethernet socket and 17 general-purpose I/O pins which you can use for a serial port, I2C interface etc. An RCA composite video output socket and a 3.5mm audio What Is Package On Package? The Raspberry Pi uses a package on package technique to conserve board space and reduce costs. This technology was initially developed for the mobile phone market and in the Raspberry Pi’s case, this means that the memory chip is stacked on top of the processor chip. Both packages use a ball grid array (BGA) to connect the chip to the PCB but in the case of the memory chip (which is on top), the BGA connects to the carrier for the processor chip below. This makes sense as most of the memory interconnects will go to the processor chip – see http://upload.wikimedia.org/wikipedia/ commons/0/08/ASIC_%2B_Memory_PoP_Schematic.JPG The main advantage of package on package technology is the small size of the final assembly and the elimination of the copper tracks to connect the memory to the processor. Other useful characteristics include faster signal propagation and reduced noise and crosstalk. The main disadvantage (for us mere mortals) is that for all practical purposes these can only be assembled and soldered by robots. 26  Silicon Chip The underside of the Raspberry Pi board is also covered with components, some of which are microscopic. That’s why the Raspberry Pi is sold fully-assembled – only robots can practically assemble such a board. jack socket are provided for people who do not want to use the HDMI digital video/audio output. All the software for the unit is stored on an SD card. Getting it running The Raspberry Pi comes with only a single sheet of paper entitled “Quick Start Guide”. So to get it going you will need a number of additional components. Power for the unit is supplied via a micro USB connector (this is for power only) so you will need a plugpack/ charger with one of these connectors. These are readily available as they are used by many smart phones, book siliconchip.com.au The Raspian OS is stored on an SD card which is inserted into a socket on the back of the board. readers etc. If you already have a phone charger with a micro USB plug, you’re in business. You will also need a monitor (up to 1920 x 1200 resolution) with an HDMI input. If your monitor has a DVI socket, you can use it with an HDMI to DVI adaptor cable. Alternatively, if your monitor has a VGA socket, you will need an HDMI to VGA adapter cable. Both of these are readily available where computer accessories are sold or via the internet. You will also need a USB keyboard and a USB mouse. Finally, an SD card (or Micro SD card with an adaptor) with a minimum capacity of 2GB (4GB or more is recommended) is needed for the operating system and applications. To get started, you first have to download the Linux operating system from the Raspberry Pi website and install it onto your SD card (using a larger personal computer). There are a number of operating system variants to choose from but it’s usually best to use the official version called “Raspbian”. This version is well-supported and has a graphical interface similar to other operating systems in use today. Once you have plugged everything in and applied power, the Raspberry Pi will chug through loading Linux until you are at the graphical user screen. The whole boot up process takes about a minute. Now what? The Linux/Raspbian interface is a lot like the Microsoft or Apple graphical user interface that most of us are Raspian lets you install and run all sorts of applications on the Raspberry Pi, including GIMP (an image editing program). Don’t expect it to operate at lightning speed though. used to. You use the mouse to point at icons, menus and windows and click to run or select. The windows on the screen can be resized and dragged around or minimised. It is amazing to consider that all this is being generated by the tiny Raspberry Pi. You can run a web browser or a word processor and use the thing like a tiny personal computer. It is not the fastest computer on the block but considering that the whole computer is on a credit-card-sized PCB, it’s not bad. Once you move beyond the superficial, the complexities of Linux will become more obvious. For people who are familiar with Linux, this will be well-known territory but for the rest of us, it can initially be a little confusing when you try to do something like install an application or configure a network. This is where some people who have bought the Rasp- Australia’s Lowest Priced DSOs Shop On-Line at emona.com.au Now you’ve got no excuse ... update your old analogue scopes! Whether you’re a hobbyist, TAFE/University, workshop or service technician, the Rigol DS-1000E guarantee Australia’s best price. 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But as pointed out above, modern versions of Linux have a graphical interface that’s similar to Windows and Mac OS. Once you’ve explored the menus, you will quickly learn where the various application and configuration dialogs (eg, for WiFi set-up) reside. Some set-up configurations may require command line instructions and a quick search using Google will usually turn up the procedure. Getting the Raspberry Pi going on a wired network is straightforward. We simply connected it to our router and the router’s DHCP server then handed out an IP address and the gateway address. After that, we were able to browse the internet but connecting to network shares requires the installation and configuration of additional software (Samba). If you have a compatible wifi adaptor, then you need to double click the WiFi Config icon and enter the network details to get it up and running. Note that the WiFi adaptor may need to be connected via a powered hub, as the Raspberry Pi can only supply a limited amount of power. Programming the Raspberry Pi If you don’t want to do any programming, you could use the Raspberry Pi as a desktop computer for web browsing, spreadsheets and so on. It is rather clunky in this role and as most people already have a desktop computer or laptop, it would not have any particular advantage. The Raspberry Pi is also hampered by its limited memory and the SD card storage – so there is a practical limit in what you can do with it. To get the best from the device you need to learn how to write programs for it and the recommended language for this is Python. This is a sophisticated language that looks a little like Java or C and comes with a huge library of functions to control graphics, the operating system and the hardware. If you don’t like Python you can install compilers for other languages such as Java and C/C++. All these languages are quite powerful and companies 28  Silicon Chip such as Google and Facebook use them to build massive software systems but it is another steep learning curve for those of us who have not been brought up in the Linux/web programming world. There are some easier to use languages such as a limited BASIC but coupled with the Linux operating system, the experience is still a long way from the simple world of the Apple II and Commodore 64 that introduced many kids (now older readers of this magazine) to the world of programming in the 80s. However, if you are prepared to climb the learning curve you will have a potent tool. For example, because of its power, the Raspberry Pi can act as a web server, serving a whole website. The web server could even be used to serve up dynamic data received on its 17 general purpose input/outputs. It could form the core of a multimedia player playing your MP3 collection or displaying your photos. Others have written games for it and used it for dedicated logging or controlling applications like riding high-altitude balloons and directing robots. Summary At a price of just $35 the Raspberry Pi is an easy impulse buy and that must be part of the reason why over a million have been sold. But in many cases, when it is booted up, the complex operating system and programming languages may convert that impulse buy into something that is put aside and forgotten. We advise people not to give up. Learning Linux/Python can be a rewarding experience and a good career move for many. In that case, the Raspberry Pi is an excellent tool for the job. The target audience for this little computer is the technical whiz kid who is at home in the graphics/web world and who expects to go on to university to do a Computer Science degree. If just a few percent of them get it into their hands, it will have done its job. The Raspberry Pi comes in two versions; Model A with 256MB memory (US$25) and, the more popular Model B with Ethernet and 512MB memory (US$35). To these prices you will have to add the cost of freight ($10-20) and accessories such as the power supply, mouse, monitor and keyboard. Where to buy it Australian distributors now have stock and either model can be ordered online from rs-online.com or www.eleSC ment14.com Compatible WiFi Adaptors A list of compatible WiFi adaptors can be found at http://elinux. org/RPi_VerifiedPeripherals#Working_USB_Wi-Fi_Adapters Note that some adaptors may require the installation of additional software to get them working and they may have to be plugged into a powered hub (see text). For a list of other compatible devices, refer to http://elinux.org/ RPi_VerifiedPeripherals siliconchip.com.au