Zit Seng's Blog

A Singaporean's technology and lifestyle blog

What Is The Raspberry Pi

_DSC4299The Raspberry Pi, a low cost credit card sized single board computer, has been around for over two years. Many people are familiar with it, but many more aren’t. Earlier this week I had a meeting with some people about using the Raspberry Pi in a project, and they were quite amazed at what the Raspberry Pi can do.

I’ve been writing about the Raspberry Pi a few times, and I have wanted to move on with some how-to tutorials. But perhaps there’s still some room to introduce the Raspberry Pi to people and share about what it can do.

What is the Raspberry Pi? It’s a computer, minified into a single board that’s about the area of a credit card. We’re talking about a real computer here. It’s not some fancy gadget built to serve a single dedicated purpose. The Raspberry Pi uses an ARM CPU, so you may have trouble putting Windows in it, but it will run Linux just fine. If you can put Linux in it, you can certainly do plenty of things with it just like you’d expect to do on a desktop computer.

You can use the Raspberry Pi as if it were a desktop computer. But it’s more fun when you use it to build appliances like, say, media servers, TV set top boxes, interfaces to sensors for environment monitoring, controls for home automation, etc. I’ll go into that a little later.

What makes the Raspberry Pi so exciting? Well, apart from small and cheap, let’s look at the hardware:

  • Powered from microUSB, the Raspberry Pi draws only about 3.5 W of power (700 mA).  It certainly won’t make an impact on your electricity consumption.
  • The computer, or System-on-Chip (SoC), comprises a 700 MHz ARM11 type CPU, 250 MHz GPU, and 512 MB of RAM.
  • It has a bunch of useful interfaces already built-in: 2x USB, Ethernet, HDMI, RCA composite and 3.5mm audio jack.
  • SD card slot for storage.
  • GPIO pins, used for General Purpose Input and Output, so you can interface with a bunch of other things. Good for a gadget project. Includes an UART, I2C bus and SPI bus.
  • Connector for a camera module.

(The above describes the Model B. There’s also a Model A that has just one USB port, no Ethernet, and just 256 MB RAM.)

There are many things you can do with the Raspberry Pi. They can basically be broken down into two broad categories.

  • The easiest thing to do is to use the Raspberry Pi like it’s just an ordinary Linux computer, albeit one that’s less powerful than your typical desktop or notebook computer. Apart from really using it as a desktop computer replacement, popular applications including using the Raspberry Pi as a TV set top box, media streaming player, or a digital signage display.
  • The other category are things that involve some level of hardware interfacing, usually via the Raspberry Pi’s 26-pin header. The GPIO pins, UART, I2C and SPI connections are there. The serial links can be used for communication with other smart devices, while the low-level GPIO can connect to sensor inputs, or used as output to control relays that in turn control other stuffs.

The haze sensor I’ve built falls in the second category. It’s still pretty straight-forward, nothing really fancy there.

At work, we have a simple display that shows the time (and a few other things), which we built as an alternative to going with more expensive NTP-synchronised matrix LED clock displays. This is something even simpler to build, because the application on the display is really just a fullscreen web browser with all its controls hidden. This would be an example of a project in the first category. It’s just a computer. However, we are working on adding sensors, one of them being a 1-wire temperature probe that would connect to the I2C bus of the Raspberry Pi.

I want to elaborate more on this display with a fullscreen web browser concept. You see, this is a very powerful model that can be used to build many applications. The applications just live in a web browser. If you can do something on the web now, you can do it with the Raspberry Pi that’s been turned into a fullscreen web browser. Your application development is simply web development, and you don’t have to know anything (almost) about the Raspberry Pi, or even Linux.

What’s coming up in the future of the Raspberry Pi? Some people have been clamouring for more power, something with the Raspberry Pi makers don’t seem very keen to develop. Other Raspberry Pi kind of hardware have begun to sprout out, including the most recently announced HummingBoard.

For me, one thing that I’ve been a little upset with the Raspberry Pi is about the price. Oh, it is cheap. It’s just that the board launched in early 2012 at US$35, and today it still costs US$35. You know all computer stuffs are supposed to drop in price over time. The Raspberry Pi Model B did get a small upgrade from 256 MB RAM to 512 MB RAM towards the end of 2012, but other than that, the hardware has remained the same. You’d think the price ought to have come down somewhat.

However, despite the price still holding at US$35, the Raspberry Pi remains extremely affordable and perhaps still the cheapest single board computer of its kind.

I’m going to try out XBMC soon. It’s an open source alternative to the Windows Media Centre for HTPC, or basically a funky media player. There’s a build just for the Raspberry Pi. Stay tuned!

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