General Purpose I/O: How To Get More

June 14, 2018 by Inderpreet Singh 28 Comments

The first program anyone writes for a microcontroller is the blinking LED which involves toggling a general-purpose input/output (GPIO) on and off. Consequently, the same GPIO can be used to read digital bits as well. A traditional microcontroller like the 8051 is available in DIP packages ranging from 20 pins to 40 pins. Some trade the number of GPIOs for compactness while other devices offer a larger number of GPIOs at the cost of complexity in fitting the part into your design. In this article, we take a quick look at applications that require a larger number of GPIOs and traditional solutions for the problem.

A GPIO is a generic pin on an integrated circuit or computer board whose behavior, including whether it is an input or output pin, is controllable by the user at runtime. See the internal diagram of the GPIO circuit for the ATmega328 for reference.

Simply put, each GPIO has a latch connected to a drive circuit with transistors for the output part and another latch for the input part. In the case of the ATmega328, there is a direction register as well, whereas, in the case of the 8051, the output register serves as the direction register where writing a 1 to it sets it in output mode.

The important thing to note here is that since all the circuits are on the same piece of silicon, the operations are relatively fast. Having all the latches and registers on the same bus means it takes just one instruction to write or read a byte from any GPIO register.
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VCF East 2018: Cactus, Retro Because It Wants To Be

June 13, 2018 by Tom Nardi 19 Comments

Among the rows of digital dinosaurs, one blinking front panel stood out. It certainly looked the part of a retro computer; with banks of blinking LEDs and multicolored paddle switches. But upon closer inspection, the laser cut wooden front panel betrays the fact that this machine is an impostor. It may have the appearance of a machine from the heady days where home computers looked like they could have doubled as a prop on the bridge of Kirk’s Enterprise, but it’s actually a product of much more modern provenance.

It’s called the Cactus, a love letter to the homebrew microcomputers of the 1970’s, designed and built by somebody at least 20 years too young to have experienced them the first time around. Alexander Pierson created the Cactus not because he had fond memories of putting together an Altair 8800 in 1975, but because he’s fascinated with the retro computer experience: the look of the front panel, the satisfying clunk of era-appropriate switches, and the idea that the computer’s inner workings aren’t an abstract black box but rather something you can interact with and study. Judging by all the attention the Cactus got at VCF East XIII, he’s not the only one.

Let’s take a look at everything Alexander poured into this retrocomputer build.

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The Flight Of The Seagull: Valentina Tereshkova, Cosmonaut

June 12, 2018 by Dan Maloney 47 Comments

That the Cold War was a tense and perilous time in history cannot be denied, and is perhaps a bit of an understatement. The world stood on the edge of Armageddon for most of it, occasionally stepping slightly over the line, and thankfully stepping back before any damage was done.

As nerve-wracking as the Cold War was, it had one redeeming quality: it turned us into a spacefaring species. Propelled by national pride and the need to appear to be the biggest kid on the block, the United States and the Soviet Union consistently ratcheted up their programs, trying to be the first to make the next major milestone. The Soviets made most of the firsts, making Sputnik and Gagarin household names all over the world. But in 1962, they laid down a marker for a first of epic proportions, and one that would sadly stand alone for the next 19 years: they put the first woman, Valentina Tereshkova, into space.

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A Close Eye On Power Exposes Private Keys

June 11, 2018 by Kerry Scharfglass 37 Comments

Hardware wallets are devices used exclusively to store the highly sensitive cryptographic information that authenticates cryptocurrency transactions. They are useful if one is worried about the compromise of a general purpose computer leading to the loss of such secrets (and thus loss of the funds the secrets identify). The idea is to move the critical data away from a more vulnerable network-connected machine and onto a device without a network connection that is unable to run other software. When designing a security focused hardware devices like hardware wallets it’s important to consider what threats need to be protected against. More sophisticated threats warrant more sophisticated defenses and at the extreme end these precautions can become highly involved. In 2015 when [Jochen] took a look around his TREZOR hardware wallet he discovered that maybe all the precautions hadn’t been considered.

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Bike-Driven Scarf Knitter Is An Accessory To Warmth

June 11, 2018 by Kristina Panos 25 Comments

Despite all our technological achievements, humans still spend a lot of time waiting around for trains. Add a stiff winter breeze to the injury of commuting, and you’ve got a classic recipe for misery. [George Barratt-Jones] decided to inject some warmth into this scene by inviting people to knit a free scarf for themselves by riding a bike.

All a person has to do is ride the Cyclo-Knitter for five minutes and marvel at their handiwork. By the time the scarf is finished, they’ve cycled past being cold, and they have something to hold in the warmth. Cyclo-Knitter is essentially an Addi Express knitting machine being belt-driven by a stationary bike. Power is transferred from the bike through large, handmade wooden gears using old bike tire inner tubes as belts. [George] built a wooden tower to hold the machine and give the growing scarf a protected space to dangle.

We love the utility of this project as much as the joy it inspires in everyone who tries it. Check out their scarves and their reactions after the break. We haven’t seen people this happy to see something they weren’t expecting since that billboard that kills Zika mosquitoes.

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Hacking When It Counts: The Magnetron Goes To War

June 11, 2018 by Dan Maloney 36 Comments

In 1940, England was in a dangerous predicament. The Nazi war machine had been sweeping across Europe for almost two years, claiming countries in a crescent from Norway to France and cutting off the island from the Continent. The Battle of Britain was raging in the skies above the English Channel and southern coast of the country, while the Blitz ravaged London with a nightly rain of bombs and terror. The entire country was mobilized, prepared for Hitler’s inevitable invasion force to sweep across the Channel and claim another victim.

We’ve seen before that no idea that could possibly help turn the tide was considered too risky or too wild to take a chance on. Indeed, many of the ideas that sprang from the fertile and desperate minds of British inventors went on to influence the course of the war in ways they could never have been predicted. But there was one invention that not only influenced the war but has a solid claim on being its key invention, one without which the outcome of the war almost certainly would have been far worse, and one that would become a critical technology of the post-war era that would lead directly to innovations in communications, material science, and beyond. And the risks taken to develop this idea, the cavity magnetron, and field usable systems based on it are breathtaking in their scope and audacity. Here’s how the magnetron went to war.

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The Hacky Throttle Repair That Got Me On The Road Again

June 6, 2018 by Zoe Skyforest 82 Comments

Old cars are great. For the nostalgia-obsessed like myself, getting into an old car is like sitting in a living, breathing representation of another time. They also happen to come with their fair share of problems. As the owner of two cars which are nearing their 30th birthdays, you start to face issues that you’d never encounter on a younger automobile. The worst offender of all is plastics. Whether in the interior or in the engine bay, after many years of exposure to the elements, parts become brittle and will crack, snap and shatter at the slightest provocation.

You also get stuck bolts. This was the initial cause of frustration with my Volvo 740 Turbo on a cold Sunday afternoon in May. As I tried in vain to free the fuel rail from its fittings, I tossed a spanner in frustration and I gave up any hope of completing, or indeed, starting the job that day. As I went to move the car back into the driveway, I quickly noticed a new problem. The accelerator was doing approximately nothing. Popping the hood, found the problem and shook my head in resignation. A Volvo 740 Turbo is fitted with a ball-jointed linkage which connects the accelerator cable to the throttle body itself. In my angst, the flying spanner had hit the throttle body and snapped the linkage’s plastic clips. It was at this point that I stormed off, cursing the car that has given me so much trouble over the past year.

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