Year: 2020

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.

The Cost Of Moving Atoms In Space; Unpacking The Dubious Claims Of A $10 Quintillion Space Asteroid

November 23, 2020 by 43 Comments

The rest of the media were reporting on an asteroid named 16 Psyche last month worth $10 quintillion. Oddly enough they reported in July 2019 and again in February 2018 that the same asteroid was worth $700 quintillion, so it seems the space rock market is similar to cryptocurrency in its wild speculation. Those numbers are ridiculous, but it had us thinking about the economies of space transportation, and what atoms are worth based on where they are. Let’s break down how gravity wells, distance, and arbitrage work to figure out how much of this $10-$700 quintillion we can leverage for ourselves.

The value assigned to everything has to do with where a thing is, AND how much someone needs that thing to be somewhere else. If they need it in a different place, someone must pay for the transportation of it.

In international (and interplanetary) trade, this is where Incoterms come in. These are the terms used to describe who pays for and has responsibility for the goods between where they are and where they need to be. In this case, all those materials are sitting on an asteroid, and someone has to pay for all the transport and insurance and duties. Note that on the asteroid these materials need to be mined and refined as well; they’re not just sitting in a box on some space dock. On the other end of the spectrum, order something from Amazon and it’s Amazon that takes care of everything until it’s dropped on your doorstep. The buyer is paying for shipping either way; it’s just a matter of whether that cost is built into the price or handled separately. Another important term is arbitrage, which is the practice of taking a thing from one market and selling it in a different market at a higher price. In this case the two markets are Earth and space.

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Full 8-Bit Computer On Breadboards

November 23, 2020 by 13 Comments

Getting into a big electronics project often involves the use of specialized tools, namely the use of some sort of soldering iron or other way to apply solder to often intricate, tiny, and heat-sensitive parts. While it’s best to learn to pick up this skill at some point, it’s not always necessary, even for big, complicated projects like [DerULF1]’s full 8-bit computer that he built entirely on breadboards.

For a fully featured 8-bit computer, this build goes deep into the details of how the computer works. The clock allows programs to be stepped through one cycle at a time, and even the memory can be individually accessed with a set of switches. There are plenty of other interesting features as well, such as using registers to access extra memory. It features an SPI port and PS/2 keyboard controller and also loads programs from an SD card.

The build was inspired by some of [Ben Eater]’s projects which famously focus on using logic gates and TTL chips to perform complex tasks, such as another breadboard computer which plays snake on a small display. It’s certainly a great way to learn about the inner function of computers, and better still that no soldering is required. But you may need a few extra breadboards.

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