The Original Seven (Eight?) Segment Display

The seven-segment LED display is ubiquitous. But how old do you think the fundamental idea behind it is? You nixie tube fans will be thinking of the vacuum-tube era, but a reader sent us this patent filed in 1908 where [Frank W. Wood] builds a numeric display with plain-vanilla light bulbs, slots cut in wood, and lots of wires.

The OCR on the patent is poorly done — you’re going to want to download the PDF and read it locally. But as it states in the patent, “Referring again to Fig. 1, the novel arrangement of the lamp compartments will be readily understood.”

Technically it’s not a seven-segment display at all. [F.W. Wood] designed these really nice-looking “4”s with the diagonal heads, and so he needed eight segments per digit. But the basic idea shines through, if you pardon the pun.

The other figures demonstrate the machine that’s used to send the signals to light up the lights. It’s a rotating drum with the right contacts on the bottom side to make connections and turn on the right lights at the other end. Low tech, but it’s what was available at the time.

We’re stoked that we’re not responsible for wiring this thing up, and we’re a bit awed by how old the spirit behind one of our most ubiquitous technologies is.

Thanks to [mario59] for the nostalgic tip!

Reverse-Engineering a Superior Chinese Product

It makes an Arduino look like a 555.  A 364 Mhz, 32 bit processor. 8 MB RAM. GSM. Bluetooth. LCD controller. PWM. USB and dozens more. Smaller than a Zippo and thinner than corrugated cardboard. And here is the kicker: $3. So why isn’t everyone using it? They can’t.

Adoption would mandate tier after tier of hacks just to figure out what exact hardware is there. Try to buy one and find that suppliers close their doors to foreigners. Try to use one, and only hints of incomplete documentation will be found. Is the problem patents? No, not really.

[Bunnie] has dubbed the phenomenon “Gongkai”, a type of institutionalized, collaborative, infringementesque knowledge-exchange that occupies an IP equivalent of bartering. Not quite open source, not quite proprietary. Legally, this sharing is only grey-market on paper, but widespread and quasi-accepted in practice – even among the rights holders. [Bunnie] figures it is just the way business is done in the East and it is a way that is encouraging innovation by knocking down barriers to entry. Chinese startups can churn out gimmicky trash almost on whim, using hardware most of us could only dream about for a serious project.

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RISC, Tagged Memory, and Minion Cores

Buy a computing device nowadays, and you’re probably getting something that knows x86 or an ARM. There’s more than one architecture out there for general purpose computing with dual-core MIPS boards available and some very strange silicon that’s making its way into dev boards. lowRISC is the latest endeavour from a few notable silicon designers, able to run Linux ‘well’ and adding a few novel security features that haven’t yet been put together this way before.

There are two interesting features that make the lowRISC notable. The first is tagged memory. This has been used before in older, weirder computers as a sort of metadata for memory. Basically, a few bits of each memory address tag each memory address as executable/non-executable, serve as memory watchpoints, garbage collection, and a lock on every word. New instructions are added to the ISA, allowing these tags to be manipulated, watched, and monitored to prevent the most common single security problem: buffer overflows. It’s an extremely interesting application of tagged memory, and something that isn’t really found in a modern architecture.

The second neat feature of the lowRISC are the minions. These are programmable devices tied to the processor’s I/O that work a lot like a Zynq SOC or the PRU inside the BeagleBone. Basically, they’re used for programmable I/O, implementing SPI/I2C/I2S/SDIO in software, offloading work from the main core, and devices that require very precise timing.

The current goal of the lowRISC team is to develop the hardware on an FPGA, releasing some beta silicon in a year’s time. The first complete chip will be an embedded SOC, hopefully release sometime around late 2016 or early 2017. The ultimate goal is an SOC with a GPU that would be used in mobile phones, set-top boxes, and Raspi and BeagleBone-like dev boards. There are enough people on the team, including [Robert Mullins] and [Alex Bradbury] of the University of Cambridge and the Raspberry Pi, researchers at UC Berkeley, and [Bunnie Huang].

It’s a project still in its infancy, but the features these people are going after are very interesting, and something that just isn’t being done with other platforms.

[Alex Bardbury] gave a talk on lowRISC at ORConf last October. You can check out the presentation here.

ESP Gets FCC and CE

The ESP8266 Internet of Things module is the latest and greatest thing to come out of China. It’s ideal for turning plastic Minecraft blocks into Minecraft servers, making your toilet tweet, or for some bizarre home automation scheme. This WiFi module is not, however, certified by the FCC. The chipset, on the other hand, is.

Having a single module that’s able to run code, act as a UART to WiFi transceiver, peek and poke a few GPIOs, all priced at about $4 is a game changer, and all your favorite silicon companies are freaking out wondering how they’re going to beat the ESP8266. Now the chipset is FCC certified, the first step to turning these modules into products.

This announcement does come with a few caveats: the chipset is certified, not the module. Each version of the module must be certified by itself, and there are versions that will never be certified by the FCC. Right now, we’re looking at the ESP8266-06, -07, -08, and -12 modules – the ones with a metal shield – as being the only ones that could potentially pass an FCC cert. Yes, those modules already have an FCC logo on them, but you’re looking at something sold for under $5 in China, here.

Anyone wanting to build a product with the ESP will, of course, also need to certify it with the FCC. This announcement hasn’t broken down any walls, but it has cracked a window.

Clap On! A Breadboard

The Clapper™ is a miracle of the 1980s, turning lights and TVs on and off with the simple clap of the hands, and engraving itself into the collective human unconsciousness with a little jingle that implores – nay, commands – you to Clap On! and Clap Off! [Rutuvij] and [Ayush] bought a clap switch kit, but like so many kits, this one was impossible to understand; building the circuit was out of the question, let alone understanding the circuit. To help [Rutuvij] and [Ayush] out, [Rafale] made his own version of the circuit, and figured out a way to explain how the circuit works.

While not the most important component, the most obvious component inside a Clapper is a microphone. [Rafale] is using a small electret microphone connected to an amplifier block, in this case a single transistor.

The signal from the microphone is then sent to the part of the circuit that will turn a load on and off. For this, a bistable multivibrator was used, or as it’s called in the world of digital logic and Minecraft circuits, an S-R flip-flop. This flip-flop needs two inputs; one to store the value and another to erase the stored value. For that, it’s two more transistors. The first time the circuit senses a clap, it stores the value in the flip-flop. The next time a clap is sensed, the circuit is reset.

Output is as simple as a LED and a buzzer, but once you have that, connecting a relay is a piece of cake. That’s the complete circuit of a clapper using five transistors, something that just can’t be done with other builds centered around a 555 timer chip.

Chaos Theory in Practice: Chua’s Circuit

Chua’s circuit is the simplest electronic circuit that produces chaos—the output of this circuit never repeats the same sequence, and is a truly random signal. If you need a good source of randomness, Chua’s circuit is easy to make and is built around standard components that you might have lying around. [Valentine] wrote a comprehensive guide which walks you through the process of building your own source of chaos.

The chaos of Chua’s circuit is derived from several elements, most importantly a nonlinear negative resistor. Unfortunately for us, this type of resistor doesn’t exist in a discrete form, so we have to model it with several other components. This resistor, also known as Chua’s diode, can be created with an op-amp configured as a negative impedance converter and a couple pairs of diodes and resistors. Other variations such, as the schematic above,22`01 model Chua’s diode using only op-amps and resistors.

The rest of the circuit is quite simple: only two capacitors, an inductor, and a resistor are needed. [Valentine] does note that the circuit is quite sensitive, so you might encounter issues when building it on a breadboard. The circuit is very sensitive to vibration (especially on a breadboard), and good solder connections are essential to a reliable circuit. Be sure to check out the Wikipedia article on Chua’s circuit for a brief overview of the circuit’s functionality and a rabbit trail of information on chaos theory.

Direct Digital Synthesis (DDS) Explained by [Bil Herd]

One of the acronyms you may hear thrown around is DDS which stands for Direct Digital Synthesis. DDS can be as simple as taking a digital value — a collection of ones and zeroes — and processing it through a Digital to Analog Converter (DAC) circuit. For example, if the digital source is the output of a counter that counts up to a maximum value and resets then the output of the DAC would be a ramp (analog signal) that increases in voltage until it resets back to its starting voltage.

This concept can be very useful for creating signals for use in a project or as a poor-man’s version of a signal or function generator. With this in mind I set out here to demonstrate some basic waveforms using programmable logic for flexibility, and a small collection of resistors to act as a cheap DAC. In the end I will also demonstrate an off-the-shelf and inexpensive DDS chip that can be used with any of the popular micro-controller boards available that support SPI serial communication.

All of the topics covered in the video are also discussed further after the break.

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