- A well-specified single-board computer for engineers, makers and experimentalists of all ages
- Several operating systems are available
- Includes a good range of educational application software
- Continues the tradition of the UK's pioneering Acorn computers
- Requires various additional items before it's ready to run
- The NOOBS memory card must be the February 2015 (or later) release
- The Raspberry Pi must be programmed with a chosen operating system before it's ready for use
- Default overscan allowance results in an unused border on many monitors
- Quick Start Guide is basic, and considerable digging is required to find vital information elsewhere
The latest version of the Raspberry Pi single-board computer, the Raspberry Pi 2, was launched on 2 February. Otherwise similar to its predecessor, and in fact backwards-compatible, the Pi 2 beefs up the computing power by moving to an ARM Cortex-A7 quad-core processor (a Broadcom BCM2836 SoC) running at 900MHz and 1GB of on-board RAM. The original Raspberry Pi had an ARM Cortex-A6 single-core processor running at 700MHz with 512MB of RAM and was beginning to be criticised for lack of power. The new configuration addresses that power issue and apparently benchmarks 6 times quicker than the previous model. Software for the Raspberry Pi is almost exclusively open source and includes a choice of Linux-based operating systems.
Literally the size of a credit card in footprint (86mm by 56mm), the Raspberry Pi 2 features an RJ-45 Ethernet connector (10/100 Mbps), four USB 2.0 ports, two 15-way ribbon connectors (CSI and DSI) for the add-on camera and a touch display, an HDMI connector for the display, a 3.5mm A/V jack for audio and composite video, a MicroSD card slot, a MicroUSB connector for power (5V at 2A) and a 40-pin DIL for GPIO.
The original Raspberry Pi created quite a stir on its initial launch and eventually became available in 5 models; the A, B, A+, B+ and the Compute Module, with the Model B+ as the most highly specified. Despite the hardware upgrades, the $35 price (or £24.90 ex. VAT from Radio Spares in the UK) has not changed for the Raspberry Pi 2 Model B.
Billed as the $35 computer (because the component purchase and manufacturing are negotiated in USD), the Raspberry Pi 2 is certainly a low-cost computer, retailing at around £30 (inc. VAT) in the UK. The price from RS is 24.90 (ex. VAT, £29.88 inc. VAT), but that's not in a ready-to-run state: in addition to the Pi 2 computer board, you'll at least need an HDMI-compatible display (a TV can be used), an HDMI cable, a USB keyboard and mouse, a MicroSD memory card and possibly a 5V power supply with a MicroUSB connector. So you might spend another £120 (inc. VAT) or so for a working system. And there is an entire support ecosystem built up around cases and other accessories such as cameras, wi-fi adapters and USB hub cards.
If you decide you must have a slice of Pi and buy a NOOBS SD card as well, with a choice of operating systems preinstalled, make sure you get an up-to-date copy of NOOBS. As this reviewer discovered, the version from last year is not compatible with the Pi 2, although the new version is backwards compatible with the original Pi.
The following operating systems are included on the NOOBS card: Raspian (the recommended Debian-based OS); the lightweight Arch Linux distro; OpenELEC, which turns the Pi into a Linux-based media centre; the Fedora-based Pidora; RISC OS, a Reduced Instruction Set Computing operating system designed by the same Acorn Computers team that created the original ARM processor; RaspBMC a Raspian version of XBMC (now Kodi) which is another popular media centre application; and Raspian boot to Scratch, which is Raspian configured to boot directly to Scratch (more on this below).
Alternatively, rather than buy a NOOBS card with the above software ready to install, all of the software is available for download, using an existing desktop or laptop, from the downloads page of the raspberrypi.org website, either as a NOOBS image or, for most of the options, as individual downloads. A Snappy Ubuntu core is also available. Downloads can then be copied across to a MicroSD card for use with the Pi.
The Raspberry Pi, with its use of the ARM processors and ability to run RISC OS, offers not just the opportunity to learn about programming and get close to the hardware, but also a direct connection to the history of personal computing in the UK.
Raspberry Pi's use of the ARM processor core and emphasis on open source is clearly far from the mainstream 'Wintel' culture, although even Microsoft is getting in on the act with the announcement of a free Windows 10 for the Raspberry Pi. However, this will be a command-line-driven version for Internet of Things (IoT) development, rather than anything that supports a desktop GUI.
Perhaps the amazing thing about the Raspberry Pi is that the organisation behind it, the Raspberry Pi Foundation, is a registered UK charity. The project to build a low-cost educational computer to teach programming and hardware design became a commercial reality through association with those stalwarts of the UK electronics industry RS Components and Element 14/Premier Farnell, which manufacture and sell the Raspberry computers.
The original Raspberry Pi, despite being a 'me-too' latecomer to the mini-single-board computer market, has been very successful. The project began in 2006, but didn't reach production until 2011. Of the best-known competitors in this market, the Italian Arduino began in 2005, while the US BeagleBoard started as a Texas Instruments project in 2008. Both of these projects are open source in both hardware and software: you can download the schematics and a PCB layout file. The Raspberry Pi uses open-source software, but is only partially open source in hardware.
A 16-language Quick Start Guide booklet is included with the Raspberry Pi 2, but it contains very little information and in any case is printed in a minuscule font. Help and documentation is provided on the Raspberry Pi website, which can either be browsed direct or reached via the 'Help / Raspberry Pi Help' menu selection in Raspian. The documentation is perhaps due for an update since it's not always clear which model is being referred to, and some Pi 2-specific information can be hard to find.
There are options for the display, audio, networking and memory, which users may wish to change from the default settings.
Old analogue TVs and composite input monitors would overscan, extending the display past the edge of the screen to allow for fluctuations in power supply. The Pi display output is set to allow for this by producing an undersized image so that none of the OS controls are lost over the edge of the screen. On a modern monitor this usually means that, by default, there is an unused border around the image. Overscan can be turned off, so that the image fills the screen, through the Advanced options of raspi-config.
By default, the Pi 2's audio is routed through the HDMI connection and will either be heard through the monitor's built-in speakers, or through the headphone jack on the monitor. Alternatively the audio output can be switched to the 3.5mm A/V jack. Connection can be made through a standard camcorder TRRS 4-pole jack to a 3xRCA phono lead, but for the Pi the disposition of the three phonos is non-standard.
The default network connection is through the RJ-45 Ethernet port. Wi-fi connection requires an additional wi-fi dongle plugged in to one of the USB ports.
MicroSD cards are currently available in sizes up to 128GB, but if you need more storage capacity it's possible to connect an external USB hard drive to the Raspberry Pi.
Using the Raspberry Pi 2
If you're a long-term Linux buff, using the Raspberry Pi 2 is a bit like stepping back in time, to when Linux graphical desktops were a lot simpler looking. In some ways this is a good thing as, if you want to concentrate on learning to program, it seems to remove a lot of distractions.
The Raspian desktop is clearly focused on learning about computing, with a wide and clever mix of applications for all levels of ability. The top menu bar carries icons for Mathematica and Wolfram. Wolfram is a knowledge-based language with auto code generation, while Mathematica, which is written in Wolfram, is a mathematical-function-based technical computing environment. These products are not open source, and the Raspberry Pi licence for them is "for non-commercial use". Buying a Raspberry Pi is certainly an affordable way to learn Mathematica and Wolfram: the home edition of Mathematica to run on other platforms costs £190 (ex. VAT).
Mathematica might be a bit scary, but the other programs loaded with Raspian are more immediately accessible. Clicking the Raspberry icon at the left end of the top menu bar reveals a drop-down menu for Programming, Internet, Games, Accessories, Help, Preferences, Run... and Shutdown. The Programming sub-menu offers the aforementioned Mathematica plus Python 2 and Python 3, Scratch, Sonic Pi and Wolfram. Python, in both its variants, is a very widely used programming language with a simple syntax structure.
Scratch is the animation coding IDE for children that features heavily in recent TV adverts from a certain British bank. For those interested in electronic music and digital audio, Sonic Pi is a programmable sound synthesiser. Samples on the Sonic Pi website show some very impressive soundscapes being generated by only a few lines of code.
For browsing there's Web, a stripped-down WebKit 2.4-based browser.
If all that's not enough for you then, as already mentioned, there are at least half a dozen other operating systems to explore, which can be swapped by simply loading them onto separate MicroSD cards. The Raspberry Pi 2 is quite the chameleon: it can be a learning tool, a media centre, a hobby robotics controller, a music synthesiser, the heart of a 3D printer, or even an industrial embedded micro-controller. We recommend you give it a try.