Which Raspberry Pi should you buy?

Since the release of the Raspberry Pi in 2012 the credit card-sized Linux computer has sold close to four million units.

During that time a whole ecosystem of products have grown up around the Pi, each aimed at subtly different users.

But which Pi should you get? Here's our guide to which flavour of Pi is best for you.

Raspberry Pi A+

Who's it for?

Budget-conscious hardware hackers or robot builders looking for a compact board that won't suck a battery dry in double-quick time.

What is it?

The A+ drives down the cost of the Pi to just $20. It's smaller size - 65mm-long versus the 85mm B+ -  is suited to being packed inside robots. Not only is it slight, it also consumes significantly less power than the model B - making it a good choice for battery-powered ventures, such as orbital camera rigs, that can't be tethered to a power cable.

What makes the A+ a decent choice for controlling external hardware, be it steppers motors on a 3D printer or robotic arms are its 40 general purpose input-output (GPIO) pins, the communications channels the Pi uses to swap messages with hardware. The B+ also offers the same number of pins.

On the Raspberry Pi blog one user expressed excitement at being able to use the board as a '"wifi to GPIO gateway" to monitor and control other pieces of hardware for less than $30'.

The lack of ports relative to the B+ is less of an issue for roboticists, who don't want wires streaming behind their quadcopter.

However, if you're looking to use the Pi as a desktop computer or media streamer, while the A+ will work acceptably, the B+ would be probably be the better choice, as outlined in the next slide.

The Specs

Chip: Broadcom BCM2835 SoC

Core: architecture ARM11

CPU: 700 MHz Low Power ARM1176JZFS Applications Processor

GPU: Dual Core VideoCore IV Multimedia Co-Processor. Provides Open GL ES 2.0, hardware-accelerated OpenVG, and 1080p30 H.264 high-profile decode. Capable of 1Gpixel/s, 1.5Gtexel/s or 24GFLOPs with texture filtering and DMA infrastructure.

Memory: 256MB SDRAM

Dimensions: 65mm x 56mm / 2.5" x 2.25"

Power: Micro USB socket 5V, 2A

No Ethernet

Audio Output: 3.5mm jack, HDMI

USB: 1 x USB 2.0 Connector

GPIO: Connector 40-pin 2.54 mm (100 mil) expansion header: 2x20 strip. Providing 27 GPIO pins as well as +3.3 V, +5 V and GND supply lines

Video Output: HDMI and Composite

Sound: L/R Stereo (via 3.5mm 4 Pole Cable)

Memory: 256MB Ram

Operating System: Uses microSD card slot to load OS. A range of Linux-based OSes are available to download, including NOOBS, Raspbian, Pidora, OpenELEC, RaspBMC. Also available is RiscOS, a non-Linux distro.

Digital interfaces: 2 onboard ribbon slots for Camera and Display

Raspberry Pi Foundation

By Nick Heath

Nick Heath is a computer science student and was formerly a journalist at TechRepublic and ZDNet.