Squoze Your Data

November 22, 2016 by Al Williams 44 Comments

I have a confession to make. I enjoy the challenge of squeezing software into a tiny space or trying to cut a few more cycles out of a loop. It is like an intricate puzzle. Today, of course, there isn’t nearly as much call for that as there used to be. Today even a “small” microcontroller has a ton of memory and resources.

Even so, there’s still a few cases where you need to squeeze those last few bytes out of memory. Maybe you are trying to maximize memory available for some purpose. Maybe you are anticipating mass production and you are using the smallest microcontroller you can find. Or maybe you’re doing the 1 kB Challenge and just want some advice.

One way to find techniques to maximize resources is to look at what people did “in the old days.” Digital Equipment computers once had a special character set called Squoze (or sometimes DEC Radix-50). This technique can be useful when you need to get a lot of strings into memory. The good news is that you can reliably get 3 characters into 2 bytes (or, as DEC did, 6 characters into 4 bytes). The bad news is that you have to pick a limited character set that you can use. However, that’s not always a big problem.

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IP Over QR Codes

November 22, 2016 by Richard Baguley 41 Comments

We’ve seen networks built over some interesting mediums, but QR codes has to be a new one. [Eric Seifert] decided to try to use QR codes to make an IP connection. He used these visual codes to create a bi-directional connection between two camera-equipped computers. He’s a persistent chap, because it works: in one of his videos, he shows an SSH connection between two devices.

He faced a number of challenges on the way. Although there is plenty of code to read QR codes, the data that can be encoded and read from them is limited. There is a binary mode that can be used with QR codes, but it is really inefficient. [Eric] decided to use base32 coding instead, packing the data into each frame as alphanumeric text. Each QR code image that is created and received is numbered, so the system can keep track and request any lost images. He also had some problems with keeping the data consistent between the encoded and decoded versions, so he had to add some packing to the data before it would work. It uses Python-pytun to create a TUN/TAP device that carries the data.

The speed of the connection is rather slow: in his demo video, the two computers take over a minute to exchange keys for an SSH connection, and [Eric] measured the speed of the connection at about 100 bits per second. But even getting something like this working at all is a significant achievement. He has published his code on GitHub.

We’ve featured the work of [Eric] before: he created a data connection using an iPod FM transmitter.

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Levitating Table Makes The Sound Of This Holochess Jukebox

November 22, 2016 by Dan Maloney 3 Comments

A bubbling Wurlitzer juke would be a prized addition to the classic picture of a man cave — brass-railed bar, kegerator, pool table, tin signs and neon on the walls. But it would take a particularly geeky abode to give a proper home to this Millenium Falcon holochess table jukebox. And a particularly awesome one at that.

It all started with a very detailed and realistic replica of a holochess table made by [Jim Shima]’s friend. A lot of time and care went into the prop, and [Jim] was determined not to alter the look while installing the media player gear, consisting of a Raspberry Pi running OSMC and a 160-watt power amp.

The speakers were problematic – there was nowhere convenient to mount them except under the brushed aluminum playing surface of the table. The sound quality was less than acceptable, so rather than poke unsightly holes in the table, [Jim] devised a servo to lift the table while the music is playing.

An LCD monitor and wireless keyboard slightly detract from the overall look; we’ll give [Jim] a pass until he can come up with a holographic display to finish the build right. But we are disappointed that he didn’t use “Mad About Me” by Figrin D’an and the Modal Nodes as the demo tune in the video below.

It’s a nice build, and you’ll want to check out [Jim]’s Hyperdyne Labs for more drool-worthy props and effects. And for another fandom jukebox, look over this jukebox that’s bigger on the inside.

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