raspberry pi

1631 Articles

What Is Entropy And How Do I Get More Of It?

November 2, 2017 by 55 Comments

Let’s start off with one of my favorite quotes from John von Neumann: “Any one who considers arithmetical methods of producing random digits is, of course, in a state of sin. For, as has been pointed out several times, there is no such thing as a random number — there are only methods to produce random numbers, and a strict arithmetic procedure of course is not such a method.”

What von Neumann is getting at is that the “pseudo” in pseudorandom number generator (PRNG) is really a synonym for “not at all”. Granted, if you come in the middle of a good PRNG sequence, guessing the next number is nearly impossible. But if you know, or can guess, the seed that started the PRNG off, you know all past and future values nearly instantly; it’s a purely deterministic mathematical function. This shouldn’t be taken as a rant against PRNGs, but merely as a reminder that when you use one, the un-guessability of the numbers that it spits out is only as un-guessable as the seed. And while “un-guessability” isn’t a well-defined mathematical concept, or even a real word, entropy is.

That’s why entropy matters to you. Almost anything that your computer wants to keep secret will require the generation of a secret random number at some point, and any series of “random” numbers that a computer generates will have only as much entropy, and thus un-guessability, as the seed used. So how does a computer, a deterministic machine, harvest entropy for that seed in the first place? And how can you make sure you’ve got enough? And did you know that your Raspberry Pi can be turned into a heavy-duty source of entropy? Read on!

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Pi Handheld With A Mindblowing Enclosure

November 2, 2017 by 14 Comments

The Raspberry Pi is possibly the world’s most popular emulation platform these days. While it was never intended to serve this purpose, the fact remains that a small, compact computer with flexible I/O is ideally suited to it. We’ve featured a multitude of builds over the years using a Pi in a mobile form factor to take games on the go. [Michael]’s build, however, offers a lot more than a few Nintendo ROMs and some buttons from eBay. It’s a tour de force in enclosure design.

The build starts with the electronics. In 2017 it’s no longer necessary to cobble together five different accessory boards to handle the controls, battery charging, and display. Boards like Kite’s Super All In One exist, handling everything necessary for a handheld game console. With this as a starting point, he then set out to recreate Nintendo’s classic Game Boy, with a few tweaks to form and function.

It’s a textbook example of smart planning, design, and execution. We are taken through the process of creating the initial CAD drawings, then combining 3D printed parts with wood and carbon fibre for a look that is more akin to a high-end piece of hi-fi gear than anything related to gaming. The attention to detail is superb and the write-up makes it look easy, while [Michael] shares tips on how to safely cut carbon fibre to make your own buttons.

The final results are stunning, and it’s a great example of why a fine piece of wood is always a classy way to go for an enclosure. For another great example, try this walnut keyboard, or check out the roots of the Raspberry Pi Game Boy movement.

Pumpkin Piano Promises A Gourd Time

October 31, 2017 by 9 Comments

Fall – it’s that time of year that brings falling leaves, Hallowe’en, and a pumpkin version of everything that you hold dear. In this case, it’s not a latte – it’s [Robert Vorthman]’s Pumpkin Piano.

[Robert] took a straightforward approach to the build, pressing a Raspberry Pi into service as the backbone of the operation. This is combined with an Adafruit breakout board for the MPR121, which is a chip that provides 12 capacitive touch-sensitive inputs. These are connected to the bountiful produce which make up the piano keys in this fun holiday hack. [Robert] uses some Python code that talks to fluidsynth, a software synthesizer that uses Soundfont files to create different sounds. It’s all wrapped up with some Neopixels that flash when each vegetable is triggered.

The build would make a great party piece for just about any fall gathering, and [Robert] has done a great job of rolling up all the hardware and software required in the write-up. For another take on a vegetable-based orchestra, check out last year’s Harpsi-gourd.

Raspberry Pi Media Streamer Is Combat Ready

October 26, 2017 by 21 Comments

We are truly living in the golden age of media streaming. From the Roku to the Chromecast, there is no shortage of cheap devices to fling your audio and video anywhere you please. Some services and devices may try to get you locked in a bit more than we’d like (Amazon, we’re looking at you), but on the whole if you’ve got media files on your network that you want to enjoy throughout the whole house, there’s a product out there to get it done.

But why buy an easy to use and polished commercial product when you can hack together your own for twice the price and labor over it for hours? While you’re at it, why not build the whole thing into a surplus ammo can? This the line of logic that brought [Zwaffel] to his latest project, and it makes perfect sense to us.

It should come as no surprise that a military ammo can has quite a bit more space inside than is strictly required for the Raspberry Pi 3 [Zwaffel] based his project on. But it does make for a very comfortable wiring arrangement, and offers plenty of breathing room for the monstrous 60 watt power supply he has pumping into his HiFiBerry AMP+ and speakers.

On the software side the Pi is running Max2Play, a Linux distro designed specifically for streaming audio and video remotely. [Zwaffel] says that with this setup he is able to listen to music on his Squeezebox server as well as watch movies via Kodi.

While none are quite as battle-hardened as this, we have seen several other Raspberry Pi Squeezebox clients over the years if you’re looking for more inspiration.

Remote controlled Billy from the Saw movies

Pi-Controlled Billy From The Saw Horror Flicks

October 26, 2017 by 5 Comments

[David0429] has made a very scary Raspberry Pi controlled puppet. Scary that is if you’ve seen the Saw movies where a serial killer uses one like it, called Billy, to communicate with his victims. If you haven’t, then it’s a pretty neat remote-controlled puppet-on-a-tricycle hack.

A stepper motor hidden under the front fender moves the trike by rotating the front wheel. It does this using a small 3D printed wheel that’s attached to the motor’s shaft and that presses against the trike’s wheel. Steering is done using a 3D printed gear mounted above the fender and attached to the steering column. That gear is turned by a servo motor through another gear. And another servo motor in the puppet’s head moves its mouth up and down.

All these servos and motors are wired to an Adafruit stepper motor HAT stacked on a Raspberry Pi hidden under the seat. Remote control is done from a webpage in any browser. The Flask python web framework runs on the Pi to both serve up the webpage and communicate with it in order to receive commands.

[David0429] took great care to make the puppet and tricycle look like the one in the movie. Besides cutting away excess parts of the trike and painting it, he also ran all the wires inside the tubular frame, drilling and grinding out holes where needed.  The puppet’s skeleton is made of wood, zip ties and hinges but with the clothes on, it’s pretty convincing. Interestingly, the puppet in the first movie was constructed with less sophistication, having been made out of paper towel rolls and papier-mâché. The only things [david0429] would like to do for next time are to quieten the motors for maximum creepiness, and to make it drive faster. However, the need for a drive system that could be hidden under the fender resulted one that could only work going slowly. We’re thinking maybe driving it using the rear wheels may make it possible provide both speed and stealth. Ideas anyone?

In any case, as you can see in the video below, the result is suitably creepy.

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Hackaday Prize Entry: CNC Mill Lets Kids Engrave On The Fly

October 25, 2017 by 17 Comments

The manufacturing revolution has already begun, and there are 3D printers, CNC machines, and laser cutters popping up in garages and workspaces all around the world. The trouble with these machines is that they’re fiddly to use, and you don’t want a kid playing around with them.

[moritz.messerschmidt]’s Hackaday Prize entry is a desktop Badgemaker that engraves acrylic name badges for kids. Under the hood, an Arduino with a custom-built shield with 3 SilentStepStick stepper drivers on it operates the three NEMA-11 motors. Meanwhile, the kids interact with a 7” touchscreen powered by a Raspberry Pi.

Once the kid selects what to engrave, motors move the piece of acrylic against a rotary tool’s milling bit, carving the acrylic as instructed. These cards are then equipped with watch batteries and LEDs to light up.

The touch screen is key. Bummed out by basic CNC machines that were difficult to use — like hobbyist 3D printers with a newbie-befuddling interface — [moritz.messerschmidt] went out of his way to make the interface kid-friendly, with just a simple set of choices necessary for creating one’s own name badge.

Is this a feature-packed CNC machine with all the bells and whistles? No, but that’s not the point. The purpose of the Badgemaker is to introduce a new generation to personal fabrication technology. It’s a toy, but that’s the point: a CNC machine that’s so easy to use, even a child can do it.

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Alas, Poor Yorick! He Hath Not Amazon Prime

October 25, 2017 by 15 Comments

If you are looking around for a Halloween project, you might consider The Yorick Project from [ViennaMike]. As you can see in the video below, it marries a Raspberry Pi acting as an Amazon Alexa with an animatronic skull.

This isn’t the most technically demanding project, but it has a lot of potential for further hacking. The project includes a USB microphone, a servo controller, and an audio servo driver board. It looks like the audio servo board is controlling the jaw movement and based on the video, we wondered if you might do better running it completely in software.

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