If you are fascinated by stories you read on sites like Hackaday in which people reverse engineer wireless protocols, you may have been tempted to hook up your RTL-SDR stick and have a go for yourself. Unfortunately then you may have encountered the rather steep learning curve that comes with these activities, and been repelled by a world with far more of the 1337 about it than you possess. You give up after an evening spent in command-line dependency hell, and move on to the next thing that catches your eye.
You could then be interested by [Jopohl]’s Universal Radio Hacker. It’s a handy piece of software for investigating unknown wireless protocols. It supports a range of software defined radios including the dirt-cheap RTL-SDR sticks, quickly demodulates any signals you identify, and provides a whole suite of tools to help you extract the data they contain. And for those of you scarred by dependency hell, installation is simple, at least for this Hackaday scribe. If you own an SDR transceiver, it can even send a reply.
To prove how straightforward the package is, we put an RTL stick into a spare USB port and ran the software. A little investigation of the menus found the spectrum analyser, with which we were able to identify the 433 MHz packets coming periodically from a wireless thermometer. Running the record function allowed us to capture several packets, after which we could use the interpretation and analysis screens to look at the binary stream for each one. All in the first ten minutes after installation, which in our view makes it an easy to use piece of software. It didn’t deliver blinding insight into the content of the packets, that still needs brain power, but at least if we were reverse engineering them we wouldn’t have wasted time fighting the software.
We’ve had so many reverse engineering wireless protocol stories over the years, to pick only a couple seems to miss the bulk of the story. However both this temperature sensor and this weather station show how fiddly it can be without a handy software package to make it easy.
The star turn of most hackspaces and other community workshops is usually a laser cutter. An expensive and fiddly device that it makes much more sense to own collectively than to buy yourself.
This isn’t to say that laser cutters are outside the budget of the experimenter though, we’re all familiar with the inexpensive table-top machines from China. Blue and white boxes that can be yours for a few hundred dollars, and hold the promise of a real laser cutter on your table.
Owning one of these machines is not always smooth sailing though, because their construction and choice of components are often highly variable. A thorough check and often a session of fixing the non-functional parts is a must before first power-on.
[Extreme Electronics] bought one, and in a series of posts documented the process from unboxing to cutting. Starting with a full description of the machine and what to watch for out of the box, then a look at the software. A plugin for Corel Draw was supplied, along with a dubious copy of Corel Draw itself. Finally we see the machine in operation, and the process of finding the proper height for beam focus by cutting an inclined plane of acrylic.
The series rounds off with a list of useful links, and should make interesting reading for anyone, whether they are in the market for a cutter or not.
As anyone who has experimented with their own home-made CNC machinery will tell you, precision isn’t cheap. You can assemble a gantry mill using off-the-shelf threading and kitchen drawer slides. But it’s a safe assumption that if you put the tool at a particular position it won’t be quite at the same position next time you return. But if you take your budget from dirt cheap to reasonably priced you can do much better. [Adam Bender] designs high-precision automation systems for a living, so when he needed a precision linear stage for a personal project he achieved micron level accuracy for under $500.
He explains the problem of backlash with an inexpensive lead screw — the wiggle between threaded components that cause positional chaos. His solution uses two nuts preloaded against each other with a spring. There is still a stick-slip issue; a tendency to move in lurches due to differences between the coefficients of static and dynamic friction between the materials. Careful choice of machining stock for the nut to picking materials in which these coefficients were almost identical reduced the stick-slip to as little as possible.
He goes into significant detail on the design, manufacture, and testing of all the components of his stage, its body, sealing system, and control. If you are a precision CNC guru maybe you’ll find it interesting as a cleverly designed component, but if you are a mere dilettante you’ll find it fascinating to read a comprehensive but accessible write-up from a professional in the field.
This build probably goes a step beyond most we’ve featured in the past, but that’s not to say we’ve not seen some pretty good efforts.
One of the designers whose work we see constantly in the world of retrocomputing is [Grant Searle], whose work on minimal chip count microcomputers has spawned a host of implementations across several processor families.
Often a retrocomputer is by necessity quite large, as an inevitable consequence of having integrated circuits in the period-correct dual-in-line packages with 0.1″ spaced pins. Back in the day there were few micros whose PCBs were smaller than a Eurocard (100 mm x 160 mm, 4″ x 6.3″), and many boasted PCBs much larger.
There is one man whose hour-long sessions in my company give me days of stress and worry. He can be found in a soundless and windowless room deep in the bowels of an anonymous building in a town on the outskirts of London. You’ve probably driven past it or others like it worldwide, without being aware of the sinister instruments that lie within.
The man in question is sometimes there to please the demands of the State, but there’s nothing too scary about him. Instead he’s an engineer and expert in electromagnetic compatibility, and the windowless room is a metal-walled and RF-proof EMC lab lined with ferrite tiles and conductive foam spikes. I’m there with the friend on whose work I lend a hand from time to time, and we’re about to discover whether all our efforts have been in vain as the piece of equipment over which we’ve toiled faces a battery of RF-related tests. As before when I’ve described working on products of this nature the specifics are subject to NDAs and in this case there is a strict no-cameras policy at the EMC lab, so yet again my apologies as any pictures and specifics will be generic.
There are two broadly different sets of tests which our equipment will face: RF radiation, and RF injection. In simple terms: what RF does it emit, and what happens when you push RF into it through its connectors and cables? We’ll look at each in turn as a broad overview pitched at those who’ve never seen inside an EMC lab, sadly there simply isn’t enough space in a Hackaday article to cover every nuance.
One of the miracle technological gadgets of the 1950s and 1960s was the transistor radio. Something that can be had for a few dollars today, but which in its day represented the last word in futuristic sophistication. Of course, it’s worth remembering that portable radios were nothing new when the transistor appeared. There had been tube radios in small attaché cases, but they had never really caught the imagination in the same way. They were bulky, like all tube radios they had to warm up, and they required a pair of hefty batteries to work.
If you have a portable tube radio today, the chances are you won’t be able to use it. The low voltage heater battery can easily be substituted with a modern equivalent, but the 90V anode batteries are long out of production. Your best bet is to build an inverter, and if you’re at a loss for where to start then [Ronald Dekker] has gone through a significant design exercise to produce a variety of routes to achieve that goal. It’s a page that’s a few years old, but still a fascinating read.
A problem with these radios lies with their sensitivity to noise. They are AM receivers from an era with a low electrical noise floor, so they don’t react well to high-frequency switch-mode power supplies. Thus, the inverters usually tasked for projects like this are low-frequency, at 50Hz as this is a European project, to mimic one source of electrical noise that would have been an issue for the designers in the 1950s.
We are taken through transformer selection and a variety of discrete inverter designs using multivibrators, investigating how to maximize efficiency through careful manipulation of switch-on and switch-off times. Then a PIC microcontroller design is presented, and finally a CMOS ring counter.
The final converter is mounted in a diecast box and covered with a printed card shell to mimic a period battery. If you weren’t intimately familiar with battery tube radios, you might mistake it for the real thing.
You might think that our community would always strive to be at the cutting edge of computing and use only the latest and fastest hardware, except for the steady stream of retrocomputing projects that appear. These minimalist platforms hark back to the first and second generation of accessible microcomputers, often with text displays if they have a display at all, and a simple keyboard interface to a language interpreter.
Often these machines strive to use the hardware of the day, and are covered with 74 logic chips and 8-bit processors in 40-pin dual-in-line packages, but there are projects that implement retrocomputers on more modern hardware. An example is [Sebastian]’s machine based upon a couple of PIC microcontrollers, one of which is an application processor with a PS/2 keyboard interface, and the other of which handles a VGA display interface. The application it runs calculates whether a 4-digit number is a prime and displays its results.
His write-up gives a fascinating overview of the challenges he found in creating a reliable VGA output from such limited hardware, and how he solved them. Though this one-sentence description makes a ton of work sound easy, horizontal sync pulses are generated as hardware PWM, and pixel data is streamed from the SPI bus. The VGA resolution is 640×480, upon which he could initially place a 10×10 block of text. Later optimizations extend it to 14×14.
Sometimes it’s not the power of the hardware but the challenge of making it perform the impossible that provides the attraction in a project, and on this front [Sebastian]’s retrocomputer certainly delivers. We’ve featured many other retrocomputers before here, some of which follow [Sebastian]’s example using modern silicon throughout, while others mix-and-match old and new.