Your First Bite of Raspberry Pi

I have to give Kyle Rankin all the credit for my Raspberry Pi collection. I never really felt geeky enough to do anything with an Arduino, and for some reason I mentally lumped the RPi into the same world. Boy was I short-sighted! Thankfully Kyle showed me the light, and I managed to snag some of the new 512MB model B units. You'll be hearing about the Raspberry Pi from Kyle as well, but this month, I want to introduce the RPi to those folks who have been hesitant to buy one, thinking they weren't geeky enough. I had to ask a lot of dumb questions when my Raspberry Pis arrived; hopefully, I can save you that embarrassment.

Batteries Not Included

To be honest, "batteries not included" is true, but the Raspberry Pi literally can run with four AA batteries and a tiny little resistor. If your goal is to make a portable project, that might be a viable option for you. Just know the RPi needs five volts of consistent power, and it will suck about 700mAh. If you add USB devices, it will drain the batteries even faster. So while batteries will work, it's likely the Raspberry Pi will fail without warning when the batteries get too low. For that reason, it's recommended to use an AC adapter.

Luckily, the RPi is powered by a micro-USB port, which is the most common power adapter for cell phones and tablets. Chances are you have a dozen potential Raspberry Pi power supplies lying around your house. Like with the battery scenario, however, it's important to find a power supply that can provide at least 700mAh. Remember, when it comes to amperage, more is better, so don't worry about a one- or two-amp power adapter ruining the unit. It will draw only as much as it needs. If the power supply doesn't provide at least 700mAh, however, the Raspberry Pi will not be reliable. Most problems with the RPi tend to be related to a weak or faulty power adapter.

Don't Box Me In

Once you connect power to your RPi, you'll quickly find that it's awkward to handle. I didn't bother talking about a case first, because we all know building a case is not the first thing anyone is going to do. Still, if you want to keep your Pi in good shape, protecting it with some sort of case is important. Thankfully, there are more case options than stars in Hollywood.

Case Option: Buy One

You bought the Raspberry Pi, and it was only $35. It seems only logical to spend an additional $10–$15 on a prebuilt case to house it. There are clear cases, colorful cases, expensive cases and cheap cases. Most of the commercially available cases are plain, square boxes, but the RPi is a little square device, so that makes sense. Buying a case also guarantees a snug fit and proper-fitting connections. If your Pi is going to be handled a lot, a fitted case is a very good idea.

Case Option: Steal from the Nursery

The Raspberry Pi is small, and it really lends itself to a LEGO castle motif. Seriously, when it first came out, there were more LEGO-based RPi cases than anything else. If you have access to the right sort of LEGO blocks, it's surprising how sturdy those little suckers can be when properly built. Plus, if you build a custom case out of LEGO blocks, you can add wings, rockets and LEGO dudes sitting on top. Besides, who wouldn't want to have a desktop computer system that can double as a toy space station?

Case Option: 3-D Printing

If you have a 3-D printer, I can't think of a cooler way to cover your Pi. Templates are available on the Internet, but even without a template, it's possible to make a case as tight-fitting or as ventilated as you want. Now with the different color options available for 3-D printers, the sky is really the limit.

Case Option: Regular Printing

I didn't buy a case. I don't have a 3-D printer. And, my kids no longer have LEGO blocks lying around for me to steal. For me, I wanted a case that was simple, cheap and did the job. Thankfully, the folks over at http://h2database.com/raspi have provided a printable template that folds into a Raspberry Pi case. The coolest print stock is a clear mylar sheet. Figure 1 shows how cool a foldable clear case can look.

Figure 1. This foldable case is simple, cheap and pretty cool-looking (image from http://h2database.com).

Case Option: Crazy Go Nuts

You have a computer with a silly name, so why not compliment that with a silly case? The Raspberry Pi is small enough to fit inside a Pop-Tart box, an old shoe, a DVD case, a hollowed-out book or a carved Halloween pumpkin. Of course, any case that is wet likely will damage or destroy your Pi, but it's awful tempting to make a "Raspberry Pumpkin Pi", isn't it? The possibilities are endless with RPi case mods, so let your creativity lead the way.

Figure 2. I am probably the only kid on the block with a bootable box of Pop-Tarts.

Getting the Boot

First off, the Raspberry Pi will not PXE boot. It also won't boot directly from a USB device. Both of those things really bum me out, but nonetheless, the RPi does boot quite nicely from the included SD slot. Because it won't boot from USB, installing an operating system is easiest from a second computer. Several Linux distributions are compiled for the ARM-based RPi, but the most popular by far is the Debian-based Raspbian OS.

For best performance, a class 10 SD card is recommended. Once you get the SD card, instructions for copying the Raspbian OS are available at http://www.raspberrypi.org. The good news is that even if your SD card is small and slow, once the unit is booted, there's no reason the OS can't live largely on a USB drive. If you want to experiment with moving the bulk of the OS off the SD card, the Raspberry Pi Web site has some great tutorials.

Splitting Your Brain

The Raspberry Pi comes with a shared system for system RAM and GPU RAM. Because the GPU is a powerful device capable of driving a high-resolution monitor and hardware rendering several types of video, if you're using the RPi in a multimedia setting, you'll want to be sure the GPU gets plenty of RAM. If you're running the Pi in a headless server mode, you'll likely want to use as little of the RAM as possible for the GPU, reserving the bulk for the system.

The absolute minimum the GPU needs is 16MB. That doesn't seem like a lot, but because the system maxes out at 256MB or 512MB, even 16MB can be significant. As the Raspberry Pi doesn't have a BIOS, the only way to allocate RAM is to put a binary file named start.elf into the /boot directory. Due to the proprietary nature of the GPU, those various .elf files are downloaded from http://www.raspberrypi.org. If you're running headless, you'll want to grab the .elf binary with only 16MB dedicated to GPU. Otherwise, you'll have to decide how much GPU RAM your application will require. Trial and error might be the only way to figure out the best split. The good news is that the new model B units come with 512MB of RAM instead of 256, so it allows for much more flexibility with the memory split.

______________________

Shawn Powers is an Associate Editor for Linux Journal. You might find him chatting on the IRC channel, or Twitter

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raspberry

galant's picture

I have a raspberry pi and a old screen from my phone and plenty other screens from other devices and some random screens. Could someone give me a link or instructions on how to do so. spelmaskiner

Anne, best wishes from the

ma's picture

Anne, best wishes from the Corporate Email SolutionJust wanted to drop a comment and say I am new to your blog and really like what I am reading. Thanks for the great content. Look forward to coming back for more......

I like your point which you

Debora's picture

I like your point which you given in your blogs specially Case Option: Buy One, Case Option: Steal from the Nursery, Case Option: 3-D Printing, Case Option: Regular Printing. http://www.usacoverage.com

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CK's picture

http://www.lovewigs88.com
Your blog is a great one. What really impresses me is that you are correctly mentioned that there are thousands of tools that are available to create a website or launch one but what matters is that you choose the right one, the one that gives you all that is actually needed

One question about linux in

anony's picture

One question about linux in Modelos de Currículo

first bite

roger gull's picture

Here in dotMobi we found ourselves repeatedly switching UAs and reloading pages in our testing of our own products lipo 6 black, lipo 6 unlimited and dhea

No, better check this out

Andrey's picture

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raspberry

Andreole's picture

The van has always been difficult to start but when I asked a mechanic I was told some vehicles are just like that lipo 6 black ultra

good sd card?

miltonhonsten's picture

Seems like a nice little toy, but I don't really like the fact that it does not boot from USB. Can you recommend a good SD-Card?
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is that usb card come inside

dennishobson's picture

is that usb card come inside an cereal box ? ... i really think that they sould put those in brasilian cereal ... i would be so happy ahahah

have a nice day !!

zadi

olivery's picture

The observation or line!

Electrical current

absolutely.geek.nz's picture

Electrical current and therefore power supply capacity is measured in Amps or mA.

Power supplies are rated in Watts which is V x A = W, there is no unit of time involved.

Energy has a time component W x s = Joules.

If you consider a battery is rated at a Voltage it is able to provide then a simplification of the power that it can supply is in Amp-Hours or Ah / mAh. Power supplies by definition do not have an Ah rating as they don't run out....execpt in a power cut etc.

missie

olivery's picture

in the line, in the horizont, in the tv online

Can you help me?

Anonymous's picture

Do you think you could perhaps make a simpler explanation on the steps to split the brain to allocate the preffered RAM to GPU

Swap on a network filesystem

Brian Likosar's picture

Have you given any thought/consideration to swapping on NFS or the like? I wonder if that would address your concerns about limited memory...

Dear Shawn, Please note that

Janne's picture

Dear Shawn,

Please note that current is not measured in mAh but in mAh/h, or just mA. But who cares?

Best regards
/Janne

Power and current

Anonymous's picture

But who cares?

I care, Janne, because I have a selection of power supplies that can deliver this voltage, but would like to know the max. current expected before fitting one. Why blow a functioning PS unnecessarily.

test

عين العرب's picture

thank you about this blog
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