Year: 2017

Phase Modulation With An FPGA

May 6, 2017 by 29 Comments

There are two radio modulation schemes everyone should know. Amplitude modulation changes the amplitude — or ‘volume’, if you will — of a carrier frequency and turns all radio into channels owned and operated by a church. Frequency modulation changes the pitch of a carrier frequency and is completely run by Clear Channel. Amateur radio operators are familiar with dozens of other modulation schemes, but there’s one hardly anyone touches. Phase modulation is weird and almost unheard of, but that doesn’t mean you can’t implement it on an FPGA. [nckm] is transmitting audio using phase modulation on an FPGA (Russian, here’s the Google Translatrix).

This hardware is just an Altera MAX10 board, with a single input used for serial data of the audio to be transmitted, and two outputs, each connected to a few bits of wire for a quarter-wave antenna. No, there’s no output filter or anything else except for a few bits of wire. It’s an experiment, chillax.

The Verilog for this project receives an audio signal as serial data in mono, 22050 BPS, 8-bit unsigned samples. These samples are fed into a dynamic PLL with phase shift in the FPGA. Shifting the phases also changes the frequency, so [nckm] can receive this audio signal with the FM transmitter on his phone.

Is this really phase modulation if it’s being received by an FM radio? Eh, maybe. PM and FM are closely related, but certainly distinguishable as modulation schemes in their own right. You can grab [nckm]’s code over on the gits, or check out the video demo below.

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Hackaday Prize Entry: Device For Seismic Noise Analysis

May 6, 2017 by 24 Comments

Whenever there is an earthquake somewhere in the world, our TV screens fill with images of seismic data. Those news report graphics with simplified bite-sized diagrams that inform the masses, but usually get something wrong. Among the images there will invariably be one of a chart recorder drawing a significant earthquake trace on paper, which makes good TV, but is probably miles away from the state of the art in seismology.

We are not seismologists here at Hackaday, so it was extremely interesting to find [Michael D]’s project, Device for Seismic Noise Analysis. In it, he gives a basic primer in seismic sensors, and outlines his take on the subject, a sensitive wideband seismic sensor designed to capture the seismic background noise. It seems that many seismic sensors are designed to capture big events, yet ignore the noise between them from which using suitable software one can glean advance warning of seismic events.

The sensor is a simple design, a ball of significant mass rests upon three piezoelectric microphone elements spaced at 120 degree intervals. An extremely high impedance op-amp circuit converts and integrates the charge from the piezo element to a voltage that can be read by an Arduino Yun which harvests the data. It is a bold claim, but the device is said to have already given advance warning of minor seismic events near its Tennessee test site.

Seismology has featured here a few times before. There was this seismometer using a subwoofer as its sensor, and this project using commercial geophones, just to name a couple of examples.

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The Nintendo PlayStation: Finally Working

May 6, 2017 by 19 Comments

The Nintendo PlayStation is not a misnomer. Before the PS1, Sony teamed up with Nintendo to produce a video game console that used CD-ROMs as a distribution platform. These plans fell through, Sony went on to design the PS1, Nintendo the N64, but a few prototype ‘Nintendo PlayStations’ made it out into the wild. One of these unbelievably rare consoles was shipped to a company that eventually went into bankruptcy. The console was found when the contents of an office building were put up for auction, and last year, [Ben Heck] tore it apart.

It’s taken a year, but now this Nintendo PlayStation is finally working. This console now plays audio CDs and games written by homebrewers. The hardware lives, and a console once forgotten lives once more.

The last time [Ben Heck] took a look at the Nintendo PlayStation, the CD-ROM portion of the console was non-functional. The Super Nintendo was still functional, but for this prototype, the CD-ROM was completely self-contained and required a ‘boot cartridge’ of sorts to access anything on a CD. Somehow or another — [Ben] thinks it was a wonky cable or a dead cap — The CD-ROM came to life. Yes, jiggling a cable was the extent of the repair, after spending an inordinate amount of time reverse engineering the console.

With the CD-ROM working, [Ben] got audio playing and tried out of the few homebrew games for this PlayStation prototype. Super Boss Gaiden didn’t quite work because this game was designed to load in chunks. Another game written for this console, Magic Floor, was small enough to fit in the entirety of the CD-ROM’s buffer and loaded correctly. That doesn’t mean the game worked; there are some slight differences between the Nintendo PlayStation emulator and the actual hardware that now exists. [Ben] emailed the author of Magic Floor, and now, after a quarter-century, the Nintendo PlayStation works.

What’s next for the Nintendo PlayStation? Well, now the emulator for this system can correctly reflect the actual hardware, and hopefully the homebrewers can figure out how to write a game for this system.

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Reverse Engineering Space Invaders Sound Chip

May 6, 2017 by 7 Comments

Around here, a new blog post from [Ken Shirriff] is almost as exciting as a new Star Trek movie. This time, [Ken] tears apart a 76477 sound effects chip. This chip was state-of-the-art in 1978 and used in Space Invaders, along with plenty of other pinball machines and games.

[Ken] started out with a die photo from [Sean Riddle] and mapped its functions. Unlike a modern sound chip, this one created sounds based on networks of attached resistors and capacitors. Even if you aren’t interested in the chip, per se, [Ken] explains how the die implements active and passive devices, along with some key analog design principles like current mirrors (although we are pretty sure he got his right and his left mixed up, or maybe it was a very subtle mirror joke).

Before electronics magazines were full of computer projects, they were full of music synthesis projects and the 76477 is like a crude synthesizer on a chip. It has voltage controlled oscillators (VCOs),  and generates envelopes with specific attack and decay times to create the sounds of interest.

This reminded us a little of the sounds from the more advanced MOS6581. [Ken] has looked inside a lot of ICs, including at the 2016 Hackaday SuperConference.

Hackaday Prize Bring-a-Hack Munich Was Great

May 6, 2017 by 9 Comments

Thanks to everyone who came to the Hackaday Prize Make Munich Meetup and Bring-a-Hack last night! We had a great time, and there were a bunch of cool projects on display, some of which we even got pictures of. Frankly, we were enjoying chatting too much to be peering through a camera lens.

Around 30 people made it over to the Munich CCC, including some familiar faces from the last time we had a party in Munich. Although it was a mostly local crowd, we also had visitors from Switzerland, Austria, and even the US of A: TV-B-Gone inventor, HaD Prize judge, and mad hacker [Mitch Altmann] was in the house.

After we got a little food and drink, we opened up the floor for the projects, lightning-talk style. The largest projects were probably a tie between an own-design CoreXY 3D printer and a boombox with some serious sound output. One guest’s automated bacterial culture apparatus probably wouldn’t have fit on the table, so it’s OK that it got left in the lab. The smallest hack? Probably [Alex]‘s super-mini USB LED clock gizmo, complete with hand-soldered 0402 LEDs, and “even smaller stuff on the backside”.

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DIY Lap Counters For Drone Racing

May 6, 2017 by 5 Comments

Drone racing is a very exciting sport, in which there is a lot of room for hackers and makers to add that special sauce into the mix. Usually the aerial finish line requires special race-timing hardware to do the lap counting, and there are timing gate transponders available for around $40. In his project CoreIR and CoreIR-Uplink, [Michael Rickert] decided to reverse engineer the IR Protocol that goes into these beacons and made a homebrew version that mimics the original. The transponders send a 7-digit number out repeatedly to a receiver at the finish line as the UAV passes by and that helps track how fast drone pilots flew around a race track. The hack involves flipping an IR LED ON and OFF with the correct timing, and [Michael Rickert] confesses that it was not as easy as he had imagined.

Using a logic analyser he was able to capture the modulated 38Khz carrier signal and extract the timing from the original beacon, but it took a number of iterations to get the code just right. The IRRemote library has a ‘sendRaw’ function which is quite helpful in these situations and was employed for the task. He experimented with a number of Arduino boards to power the project, before finally going with the Arduino Pro Mini. He has shared the code on github, along with photos of the finished hack which replaces the original circuit. The final sketches include functions to generate the 7-digit code to uniquely identify the quadcopter, which completes the hack in itself.

If that was not enough, he’s gone a step further by coding and sharing a desktop client as well, which turns this hack into a full-fledged project and should prove quite useful for drone racers on a budget. The app is written in NodeJS and packaged using the electron framework, a choice that makes for a very simple way to create cross-platform desktop applications.

A build tutorial is available for you to get started, and if drone racing seems a bit tame, check out Drone Wars for a little more carnage.

Measuring Gait Speed Passively To Diagnose Diseases

May 6, 2017 by 5 Comments

You may not realize it, but how fast a person walks is an important indicator of overall health. We all instinctively know that we lag noticeably when a cold or the flu hits, but monitoring gait speed can help diagnose a plethora of chronic diseases and conditions. Wearables like Fitbit would be one way to monitor gait speed, but the Computer Science and Artificial Intelligence Lab at MIT thinks there’s a better way:  a wireless appliance that measures gait speed passively.

CSAIL’s sensor, dubbed WiTrack (PDF), is a wall-mounted plaque that could be easily concealed as a picture or mirror. It sends out low-power RF signals between about 5- and 7-GHz to perform 3D motion tracking in real time. The WiTrack sensor has a resolution of about 8 cm at those frequencies. With their WiGait algorithms (PDF), the CSAIL team led by [Chen-Yu Hsu] is able to measure not only overall walking speed, but also stride length. That turns out to be critical to predicting the onset of such diseases as Parkinson’s, which has a very characteristic shuffling gait in the early phase of the disease. Mobility impairments from other diseases, like ALS and multiple sclerosis, could also be identified.

WiTrack builds on [Hsu]’s previous work with through-wall RF tracking. It’s nice to see a novel technique coming closer to a useful product, and we’ll be watching to see where this one goes.

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