Although the name might trick you into thinking that it is something that you can eat, a Raspberry Pi is actually a computer. However, it is not an everyday computer. It has quite a few important characteristics that make it very special:
- It is very small. Marketed as “the credit card size computer”, the Raspberry Pi really does not take up much space. It fits in your palm and you can carry it around in your pocket. The small dimensions (85.6 x 56 x 21 mm) make it very easy to embed into all kinds of small size systems in which it can act as the brain (or the heart, if you will). The use of it in “intelligent” robots is a good example of this.
- It is very power efficient, draining surprisingly low amounts of current, even when its CPU and peripherals are stressed to the max. Operating at 5V DC, model A uses a maximum of 300 mA (1.5 W) and model B drains a maximum of 700 mA (3.5 W), but the real-life power usage in practice is probably only around half of the maximum ratings. Aside from the obvious environment friendly aspect, the low power consumption also means that it can be left running 24/7 virtually forever without causing a noticeable change in the electricity bill. This makes the Raspberry Pi very suitable to be used for hosting server applications (web servers, ftp servers, mail servers, database servers, etc.) that run all the time. In fact the very article that you are reading right now is supplied to your browser by an Apache2 web server hosted on a Raspberry Pi model B. Because of the amazingly low power requirements, it can be utilized with success in independent systems which run on batteries. For example, you can use 4 AA rechargeable cells (4x 1.2V = 4.8V) to power a Raspberry Pi but it will become unstable as the batteries are worn out and the voltage of the cells drops. With the help of voltage regulators and voltage converters (it needs stable 5V) it can also be used with normal AA batteries, bigger 12V batteries (car batteries for example) and so on. Yet another aspect that makes it very suitable for being incorporated into small robots and similar systems.
- Affordability. The Raspberry Pi is probably one of the cheapest (if not the cheapest) general-purpose computer that you can buy. With a factory price of only 25$ for model A and only 35$ for model B, almost anybody can afford to have a Raspberry Pi computer. In fact, the low price was one of the most important considerations during the design process. The Raspberry Pi Foundation originally intended it to be an affordable computer that children all around the globe can buy and use to learn about computers, especially to develop software. They really have accomplished that goal and we owe them some sincere thanks for giving us this amazing piece of machine at such low prices. They could have sold them at much higher prices, but The Raspberry Pi Foundation chose to give this gift to humanity instead of trying to get rich through it. The Raspberry Pi, however, has outgrown its original purpose. The community around it has grown fast, has embraced it and has used it in amazingly creative ways to create very useful projects.
- General purpose. In spite of its small size, its low power consumption, its low price, its ARM architecture, the Raspberry Pi is not a specialized computer like a smart phone or a tablet. It is a real computer that can be used for pretty much everything that “normal” desktop or laptop computers are used for. Well, to be honest, this is not 100% true, but almost. The only limitation which poses obstacles in front of it being used for really everything are its low resources (low frequency processor and small relatively small amount of memory) and its ARM architecture which is not supported by every operating system and by any piece of software. The main operating system that runs on a Raspberry Pi is Linux. The recommended distribution is the Raspbian, which is version of Debian Linux customized for the Raspberry Pi. Arch Linux and RISC OS are also officially supported and people have even had some limited success with running Windows on it. Still, the users of Raspberry Pi are mostly restricted to running Linux on it and software that was designed to work on Linux, but that is usually not a problem today, when Linux has become quite user friendly but still keeps the cleanness, security and efficiency of older versions. It offer a great variety of highly reliable applications, all free, which you can use to accomplish pretty much everything.
- Easy hardware interaction. The Raspberry Pi has a set of general purpose input-output (GPIO) pins which make it very easy to connect it to custom hardware (LEDs, motors, input buttons, sensors, etc.). The P1 GPIO header present on both models contains 17 programmable pins (usable both as input and output, some even in PWM mode) but has a slightly different layout on the two models. Model B also contains a second GPIO header, the P5 header, which supplies an additional 4 programmable GPIO pins. It’s important to emphasize that the presence of the GPIO ports is one of the things that makes the Raspberry Pi stand out from the line of usual computers (which don’t offer this). It’s what makes it so easy to use it in creative hardware projects. The original intent was to use the Python programming language for communication through the GPIO port (hence the name Pi), but in practice many languages can be used today to access the GPIO pins (Python, C/C++, Java, bash script, etc.).
In order to find out exactly what can be done with a Raspberry Pi, let’s examine the hardware specifications:
- The CPU is based on the ARM v6 architecture and it runs at 700 MHz, although it can easily be overclocked to achieve frequencies of of to 1 GHz. No hacking is needed to achieve this, overclocking is supported by the system. The processor chip is a Broadcom BCM2835 SoC, which was chosen because of the great performance/price ratio that it delivers but also for the low power consumption.
- The Broadcom BCM2835 also incorporates a high power GPU, which can be used without problems to play BluRay quality videos and its fast 3D core even allows many games to run nicely on the Raspberry Pi.
- The amount of operating memory (RAM) originally available on the Raspberry Pi was 128 MB for model A and 256 MB for model B, but the newest revisions have doubled the amount to 256 MB for model A and 512 MB for model B, making it possible to run applications which require larger amounts of memory.
- The Raspberry Pi has no incorporated storage device. Obviously, hard disks, optical (CD/DVD/etc) readers/writers cannot even be imagined with a device of this size, price and power rating. The storage solution chosen for the Raspberry Pi is the highly popular and widely available SD card. But it does not contain one by default, it just has an SD card slot, you need to buy your own memory card to use with it.
- A wide spectrum of input/output connectors are available on the Raspberry Pi, making it possible to connect to virtually everything. First of all, it is powered through a micro-USB port and has no on/off button. Plug it in and it’s on, pull the plug and it’s off. It’s that simple! It is recommended to use a micro-USB power supply for it which can supply at least 1A of current at 5V (especially for model B or if you have many peripherals connected to it). The most popular connector on it is perhaps the USB port, two of which exist on model B and only one on model A. Obviously, you can use powered or non-powered USB hubs to connected more USB devices to it. This is the most straightforward way to connect a keyboard, mouse or webcam to the Pi. The other difference between model A and model B is that the latter has an Ethernet connector too, which, unfortunately causes the major difference in the power consumption. Model A can still be connected to a local network or to the Internet by utilizing a USB WiFi dongle. Other exciting connectors on the Raspberry Pi include a HDMI port, for connecting it to modern TVs and other display devices, a standard 3.5 mm audio jack and RCA video connector for communication with older devices or or attaching a microphone, for example.
It is obvious by now that when you buy a Raspberry Pi, you only get the little computer itself, no SD card, no cables (not even a power cord), not to mention no case, just the device itself. You’ll have to buy everything else that you need to use with it separately. This is more than understandable at the price it has and it was planned like this because depending on what it is used for, different accessories will be required, so there’s no point in supplying default accessories, which would only push the price up unnecessarily.
All in all, the Raspberry Pi is a great tool for people to turn their creativity into real-life hardware and software projects and also a great gadget. It is produced in the UK (amazingly not in China) by Sony and it is currently available for buying through Element14/Farnell and their re-sellers from many countries. When it was originally released, in the first part of 2012, there was a restriction which allowed one person to buy only one Raspberry Pi (a restriction lifted since), because of the huge demand for it. The initial lot was sold in a matter of minutes on the first day and the pre-orders registered in the first day covered about 6 months of production into the future. The first released model was the higher priced model B (factory price: 35$) and because of the huge demand it was impossible to release model A until the beginning of 2013.
The community around Raspberry Pi has grown very fast, with lots of friendly and helping members and has produced unimaginably vast and useful projects based on the Pi. You can find many resources on the official web site of The Raspberry Pi Foundation and you can discuss your projects in the official forum.