Solving The Final Part Of The IClicker Puzzle

May 21, 2019 by Tom Nardi 9 Comments

The regular Hackaday reader might remember the iClicker from our previous coverage of the classroom quiz device, or perhaps you even had some first hand experience with it during your university days. A number of hackers have worked to reverse engineer the devices over the years, and on the whole, it’s a fairly well understood system. But there are still a few gaps in the hacker’s map of the iClicker, and for some folks, that just won’t do.

[Ammar Askar] took it upon himself to further the state of the art for iClicker hacking, and has put together a very detailed account on his blog. While most efforts have focused on documenting and eventually recreating how the student remotes send their responses to the teacher’s base station, he was curious about looking at the system from the other side. Specifically, he wanted to know how the base station was able to push teacher-supplied welcome messages to the student units, and how it informed the clients that their answers had been acknowledged.

He started by looking through the base station’s software update tool to find out where it was downloading the firmware files from, a trick we’ve seen used to great effect in the past. With the firmware in hand, [Ammar] disassembled the AVR code in IDA and got to work piecing together how the hardware works. He knew from previous group’s exploration of the hardware that the base station’s Semtech XE1203F radio is connected to the processor via SPI, so he started searching for code which was interacting with the SPI control registers.

This line of logic uncovered how the radio is configured over SPI, and ultimately where the data intended for transmission is stored in memory. He then moved over to running the firmware image in simavr. Just like Firmadyne allows you to run ARM or MIPS firmware with an attached debugger, this tool allowed [Ammar] to poke around in memory and do things such as simulate when student responses were coming in over the radio link.

At that point, all he had to do was capture the bytes being sent out and decode what they actually meant. This process was complicated slightly by the fact the system uses to use its own custom encoding rather than ASCII for the messages, but by that point, [Ammar] was too close to let something like that deter him. Nearly a decade after first hearing that hackers had started poking around inside of them, it looks like we can finally close the case on the iClicker.

Integrated Circuits Can Be Easy To Understand With The Right Teachers

May 20, 2019 by Mike Szczys 22 Comments

For years I’ve been trying to wrap my mind around how silicon chips actually work. How does a purposefully contaminated shard of glass wield control over electrons? Every once in a while, someone comes up with a learning aid that makes these abstract concepts really easy to understand, and this was the case with one of the booths at Maker Faire Bay Area. In addition to the insight it gave me (and hundreds of Faire-goers), here is an example of the best of what Maker Faire stands for. You’ll find a video of their presentation embedded below, along with closeup images of the props used at the booth.

The Uncovering the Silicon booth had a banner and a tablecloth, but was otherwise so unassuming that many people I spoke with missed it. Windell Oskay, Lenore Edman, Eric Schlepfer, John McMaster, and Ken Shirriff took a 50-year-old logic chip and laid it bare for anyone who cared to stop and ask what was on display. The Fairchild μL914 is a dual NOR gate, and it’s age matters because the silicon is not just simple, it’s enormous by today’s standards making it relatively easy to peer inside with tools available to the individual hacker.

ATmega328 decapped by John McMaster was also on display at this booth

The first challenge is just getting to the die itself. This is John McMaster’s specialty, and you’re likely familiar from his Silicon Pr0n website. He decapped the chip (as well as an ATmega328 which was running the Arduino blink sketch with it’s silicon exposed). Visitors to the booth could look through the microscope and see the circuit for themselves. But looking doesn’t mean understanding, and that’s where this exhibit shines.

To walk us through how this chip works, a stack-up of laser-cut acrylic demonstrates the base, emitter, and collector of a single transistor. The color coding and shape of this small model makes it easy to pick out the six transistors of the 941 on a full model of the chip. This lets you begin to trace out the function of the circuit.

For me, a real ah-ha moment was the resistors in the design. A resistive layer is produced by doping the semiconductor with impurities, making it conduct more poorly. But how do you zero-in on the desired resistance for each part? It’s not by changing the doping, that remains the same. The trick is to make the resistor itself take up a larger footprint. More physical space for the electrons to travel means a lower resistance, and in the model you can see a nice fat resistor in the lower right. The proof for these models was the final showpiece of the exhibit as the artwork of the silicon die was laid out as a circuit board with discrete transistors used to recreate the functionality of the original chip.

Windell takes us through the booth presentation in the video below. I think you’ll be impressed by the breakdown of these concepts and how well they aid in understanding. This was a brilliant concept for an exhibit; it brought together interdisciplinary experts whom I respect and whose work I follow, and sought to invite everyone to gain a better understanding of the secrets hiding in the chips that underpin this technological age. This is exactly the kind of thing I love to see at a Maker Faire.

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It’s Time To Embrace The Toilet Of The Future

May 19, 2019 by Al Williams 82 Comments

You use things every day that are very different from the same items from even a decade ago. Your car, your cellphone, and your computer all have probably changed a lot in the last ten years. But there’s something you almost certainly use every day that hasn’t changed much in a very long time: your toilet. That is unless you live in Japan where some toilets are a high tech delight. Lifehacker recently did a video about the toilet of the future, which might be coming to the US soon if Toto — one of the Japanese toilet makers — has its way.

It made us think. For as ubiquitous as the porcelain throne is, we don’t see many hacks related to it. There are several really obvious ones. For example, in the Lifehacker video, the seat automatically raises when you approach. We don’t know how it could figure out if you were going to stand or sit, but maybe that’s a good application for machine learning. What we really want is one that can clean itself. That would be worth something. Every time we see a Sanisette washing itself in Paris we want to take it home.

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Concrete Speakers Are Attractive And Functional

May 17, 2019 by Lewin Day 25 Comments

In a lot of fields – motorsport, space exploration, wearables – lighter is better. But it’s not always the case. When you want to damp vibration, stop things moving around, and give things a nice weighty feel, heavier is the way to go. This is the case for things like machine tools, anvils, and yes – speakers. Using this philosophy, [SoundBlab] built a set of concrete speakers. (Youtube link, embedded below)

The concrete speaker enclsosures are sized for 3″ drivers, and were cast using two measuring jugs as the mold. This gave the final product a smooth and glossy surface finish, thanks to the surface of the plastic used. The concrete was also agitated during the casting process to minimise the presence of air bubbles in the mixture.

Once cast, the enclosures are fitted with plywood end caps which mount the Fountek FE85 speaker drivers. These are a full-range driver, meaning no cross-overs or other drivers are required. The speakers are then mounted on stands constructed from wood edging, which are stained in a contrasting colour for a nice aesthetic touch. Felt pads are placed on the base, and polyfill inside the enclosure to further minimise any unwanted vibrations.

The sound test confirms the speakers perform well, and they look great as a part of a lounge audio setup. We think they make an excellent pair of bookshelf speakers, which would be ideal for comfortable listening at moderate volume levels.

We’ve seen many speaker builds at Hackaday, from 3D-printed omnidirectional builds to the more classical designs. Video after the break.

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Fun With Negative Resistance II: Unobtanium Russian Tunnel Diodes

May 16, 2019 by Ted Yapo 24 Comments

In the first part of this series, we took a look at a “toy” negative-differential-resistance circuit made from two ordinary transistors. Although this circuit allows experimentation with negative-resistance devices without the need to source rare parts, its performance is severely limited. This is not the case for actual tunnel diodes, which exploit quantum tunneling effects to create a negative differential resistance characteristic. While these two-terminal devices once ruled the fastest electronic designs, their use has fallen off dramatically with the rise of other technologies. As a result, the average electronics hacker probably has never encountered one. That ends today.

Due to the efficiencies of the modern on-line marketplace, these rare beasts of the diode world are not completely unobtainable. Although new-production diodes are difficult for individuals to get their hands on, a wide range of surplus tunnel diodes can still be found on eBay for as little as $1 each in lots of ten. While you’d be better off with any number of modern technologies for new designs, exploring the properties of these odd devices can be an interesting learning experience.

For this installment, I dug deep into my collection of semiconductor exotica for some Russian 3И306M gallium arsenide tunnel diodes that I purchased a few years ago. Let’s have a look at what you can do with just a diode — if it’s the right kind, that is.

[Note: the images are all small in the article; click them to get a full-sized version]

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An Open Source ESC For Brushless Motors

May 15, 2019 by Lewin Day 18 Comments

For something basic like a brushed DC motor, speed control can be quite simple, and powering up the motor is a simple matter of just applying voltage. Brushless motors are much more demanding in their requirements however, and won’t spin unless driven just right. [Electronoobs] has been exploring the design of a brushless speed controller, and just released version 1.0 of his open-source ESC design.

The basic design is compact, and very similar to many off-the-shelf brushless ESCs in the low power range. There’s a small PCB packing a bank of MOSFETs to handle switching power to the coils of the motor, and a big capacitor to help deal with current spikes. The hacker staple ATMEGA328 is the microcontroller running the show. It’s a sensorless design, which measures the back EMF of the motor in order to determine when to fire the MOSFETs. This keeps things simple for low-torque, low-power applications.

It’s a tidy build, and the latest revision shows a lot of polish compared to the earlier prototypes. If you’re interested to learn more, try building it yourself, or consider building a thrust testing rig for your bench at home. Video after the break.

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Emotigun Sends A Stinging Message

May 15, 2019 by Lewin Day 11 Comments

Emojis, the graphical descendants of textual emoticons, are everywhere these days. They’re commonly used on social media platforms as a way of indicating a basic emotional response to a post. That wasn’t enough for [Tadas Maksimovas], who built the Emotigun to really get the point across.

Fundamentally, the Emotigun is akin to a Gatling cannon for small foam emojis. Firing over ten rounds per second, it’s built primarily out of wood, using Precise anti-cold rubber bands to fling its ammunition at targets. This was a practical choice, as the original Thera-Band green rubber tubes became inelastic in the cold temperatures of the testing environment. The finer details of the build are laid out in a document for those eager to know more.

The build was a team effort, with many pitching in, and even [Jorg Sprave] lending his expertise to the build. Given [Jorg]’s expertise, we’re not surprised the final result is so impressive. Reports are that filming the machine in action was quite an ordeal, with [Tadas] taking over 200 rounds to the face during the course of the shoot. Video after the break.

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