Day: November 23, 2020

A CPU-Less Computer With A Single NOR-Gate ALU

November 23, 2020 by 13 Comments

We see a lot of discrete-logic computer builds these days, and we love them all. But after a while, they kind of all blend in with each other. So what’s the discrete logic aficionado to do if they want to stand out from the pack? Perhaps this CPU-less computer with a single NOR-gate instead of an arithmetic-logic unit is enough of a hacker flex? We certainly think so.

We must admit that when we first saw [Dennis Kuschel]’s “MyNor” we thought all the logic would be emulated by discrete NOR gates, which of course can be wired up in various combinations to produce every other logic gate. And while that would be really cool, [Dennis] chose another path. Sitting in the middle of the very nicely designed PCB is a small outcropping, a pair of discrete transistors and a single resistor. These form the NOR gate that is used, along with MyNor’s microcode, to perform all the operations normally done by the ALU.

While making the MyNor very slow, this has the advantage of not needing 74-series chips that are no longer manufactured, like the 74LS181 ALU. It may be slow, but as seen in the video below, with the help of a couple of add-on cards of similar architecture, it still manages to play Minesweeper and Tetris and acts as a decent calculator.

We really like the look of this build, and we congratulate [Dennis] on pulling it off. He has open-sourced everything, so feel free to build your own. Or, check out some of the other CPU-less computers we’ve featured: there’s the Gigatron, the Dis-Integrated 6502, or the jumper-wire jungle of this 8-bit CPU-less machine.

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Roll Your Own Photo Sharing, Minus The Social Networking Baggage

November 23, 2020 by 9 Comments

[Niklas Roy] rolled his own photo diary, because he found the core functionality of something like instagram attractive, but didn’t want the social network baggage that it came with. His simple system is called my own insta ;) and it consists of some javascript and PHP to create a nice progressive web app photo diary and backend that can be accessed just fine from a mobile device. It is available on GitHub for anyone interested in having their own.

This project came up because [Niklas] sometimes found himself working on small projects or experiments that aren’t destined for proper documentation, but nevertheless could benefit from being shared as a photo with a short description. This dovetails with what many social networks offer, except that those platforms also come with other aspects [Niklas] doesn’t particularly want. His online photo diary solves this by having a simple back end with which he can upload, sort, and caption photos in an easy way even from a mobile device.

Rolling one’s own solution to some small core functionality offered by a social network is one way to avoid all the extra baggage, but another method is to simply automate away all the pesky social bits with a robot.

The Mystery Of A Particular ATtiny85 Fuse

November 23, 2020 by 17 Comments

First-timers playing with 8-bit micros such as the AVR and PIC will at some point in their lives, find themselves locked out of their MCUs. This is usually attributed to badly configured fuses that disable certain IO functions rending the device unprogrammable via conventional ICSP methods. [Uri Shaked] shares his story of how his ATtiny85 got locked and became the subject of a lengthy investigation into fuse bit configurations.

[Uri]’s journey started when he accidentally left some pins of the device connected to a second board while he was flashing the firmware. He quickly researched online for a solution for the problem and it turns out, there are a number of recipes to resolve the issue. As it turns out, his problem was not so straight-forward and warranted more digging. [Uri] ended setting up a High Voltage Programming serial programming setup and then probing the communications. He discovered that the chip refused to reset its fuses and would reject attempts to set fuses.

Further investigation of the fuse bits and reading them proved useful in understanding that the memory protection features were preventing alteration of the device. The quick-fix was to erase the ATtiny and things were back to normal thereafter. [Uri] details his pursuit of reading and comparing fuse bits from the impacted chip against a fresh device which is where he makes the discovery. The write-up is a case study in the investigation into the idiosyncrasies of device programming and will be a great resource for many and reduce hair loss for some.

Once you get your hands on an ATTINY, there are a number of small experiments to be done to cure boredom. Be sure to share your experiments and stories with us to inspire the masses.

Coaxial Connectors, Starting With The PL259

November 23, 2020 by 30 Comments

For the casual breadboard experimenter with a microcontroller and a few peripherals, there’s little concern over interconnects as a set of jumper wires will suffice. But as any radio amateur will tell you though, at higher frequencies it’s a very different affair. [Ria Jairam N2RJ] has embarked upon a series of videos exploring co-axial cable and its various connectors, and her first offering features the humble UHF connector, sometimes known as the PL259. Though it’s one of the older choices and its design flaws mean that “UHF” is more of an aspiration for it than a reality, it remains a common connector at the lower end of the amateur radio frequency range.

She starts with a brief history of co-axial cable, before introducing the UHF connector. We’re the introduced to its major flaw, in that it doesn’t present a constant impedance. The resulting mismatch presents a significant problem to a transmitter, especially at higher frequencies. We’re then taken through the various different models of UHF connector, including those with honeycomb dielectric to minimize the mismatch, and the fancy expensive plugs with strain relief. Finally she takes us through the proper fitting of a PL259 plug, something that there’s a bit more to than most of us might think. Altogether it’s an interesting and informative watch from an engaging and knowledgeable host, and we look forward to more.

Meanwhile, the field of RF connectors is something we’ve dipped a to into from time to time ourselves.

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Wireless Mouse Gets A Charging House

November 23, 2020 by 10 Comments

Mouse batteries always seem to die at the worst possible moment, like when you’re in the middle of pwning noobs or giving a presentation at work. [AyhamAS] was tired of having to look around for a replacement battery and decided to build a nice little charging dock for their mouse.

At the heart of this build is a TC4056A charging board inside the dock. Since this board is designed to charge 3.7 V batteries, [AyhamAS] removed the charge current-limiting resistor and replaced it with a pair of through-hole resistors. A switch on the back of the dock lets [AyhamAS] choose between the two values for fast or slow charging.

On the mouse side, [AyhamAS] cleverly used the receiver storage cubbyhole to house the contacts. Magnets in in the mouse and the dock and spring-loaded contacts add even more tactile feedback to the whole experience. The dock itself looks great, too — it’s made from acrylic that’s been sanded down to a matte finish. Check out the build video after the break.

If your mouse has a battery pack, you could always upgrade to a bigger one as long as there’s room.

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Linux Fu: VPN For Free With SSH

November 23, 2020 by 44 Comments

If you see a lot of banner ads on certain websites, you know that without a Virtual Private Network (VPN), hackers will quickly ravage your computer and burn down your house. Well, that seems to be what they imply. In reality, though, there are two main reasons you might want a VPN connection. You can pay for a service, of course, but if you have ssh access to a computer somewhere on the public Internet, you can set up your own VPN service for no additional cost.

The basic idea is that you connect to a remote computer on another network and it makes it look like all your network traffic is local to that network. The first case for this is to sidestep or enhance security. For example, you might want to print to a network printer without exposing that printer to the public Internet. While you are at the coffee shop you can VPN to your network and print just like you were a meter away from the printer at your desk. Your traffic on the shop’s WiFi will also be encrypted.

The second reason is to hide your location from snooping. For example, if you like watching the BBC videos but you live in Ecuador, you might want to VPN to a network in the UK so the videos are not blocked. If your local authorities monitor and censor your Internet, you might also want your traffic coming from somewhere else.

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Escape Tunnel In Your Living Room: A Different Take On The Infinity Mirror

November 23, 2020 by 26 Comments

Most infinity mirrors are just minor variations on the same old recipe. Take a frame, add a normal mirror in the back, a one-way mirror on the front, and put some LEDs between them. [Stevens Workshop] took a slightly different approach and built an escape tunnel coffee table that really caught our attention.

To create the tunnel and ladder illusion, [Steven] kept the mirrors, but made a deeper wood frame, installed a light bulb in an industrial-looking socket instead of the usual LEDs, and added a single ladder rung. The end result makes for a very interesting conversation piece, and some of us prefer it to the multicolored LED look. Though he added his own touches, the idea was actually borrowed from from [asthhvdrt36] and [BreezleSprouts] on Reddit who used slightly different light and ladder designs.

While there’s nothing groundbreaking here, it’s certainly a case of “why didn’t I think of that”. Sometimes the old and familiar just needs a different perspective to create something fascinating. One of the advantages of the classic infinity mirror is the thin profile, which we’ve seen integrated into everything from guitars to coasters.