Avoiding Repetitive Stress Injury: Invest In Yourself Now, Or Pay Later

July 22, 2021 by Kristina Panos 49 Comments

There I was, thirty years after I first sat down at an Apple IIe , and I suddenly found myself wondering if I would ever use a computer again without pain. How could I work if I couldn’t use a computer anymore? I had to seriously ask myself this question. It took a bit of a winding road to figure out what was going on and two EMGs to confirm it, but after all these years, it was clear to the medical community that I had developed a repetitive stress injury (RSI) called cubital tunnel syndrome in my left arm.

Yeah, it’s about like that. Image via Kinesis

Cubital tunnel syndrome is like carpal tunnel, but in your elbow instead of your wrist. What a misnomer! Sometimes my pain went all the way from my armpit to my fingertips and made me want to gnaw my own arm off. I don’t think you can really understand neuropathy unless you’ve felt this weird, annoying type of pain firsthand. I hope you never do.

Can you stop and seriously imagine not being able to use a computer for the rest of your life? Or at least feeling that way because doing so causes incredibly annoying pain? I feel like we’re all vaguely aware of the standard list of anti-RSI precautions, but let’s review:

maintain good posture — sit with feet flat on the floor, wrists straight, elbows at 90°
put the screen an arm’s length away at eye level
take frequent short breaks

Yes, those are all fine and good. But there are other things you can do to avoid computer-related RSIs, like using ergonomic inputs, and building a custom setup that fits you exactly. This isn’t a study kiosk at the university library we’re talking about — this is your battlestation! The problem is that many people are stubborn, and won’t go out of their way to do anything to proactively prevent these injuries. But you don’t have to cross a bridge when you come to it if you have a map that shows you a way around the body of water.

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Convert Your Mouse Into A Paddle Controller

July 4, 2021 by Danie Conradie 4 Comments

Early game consoles had a wide and interesting variety of controllers, many of which fell by the wayside as consoles evolved. One of these is the Atari 2600 paddle controller, which was the preferred interface for playing games like Kaboom!, Tempest, and Pong. While it is possible to play these games with a mouse, [Retro Gaming I Guess] wanted to do it the historically correct way, so he created a simple hack to convert an optical mouse into a paddle controller.

The main idea Is to attach a rotary knob to the bottom of the mouse, with the optical sensor located just inside the edge of the knob. To the optical sensor, it appears that the bottom surface of the knob is moving in a straight line, so the mouse pointer will move in a straight line as the knob rotates. The 3D printed knob (or bottle cap) is magnetically attached to the bottom of the mouse, by gluing one magnet into the center of the knob, and the other on the inside of the mouse under the PCB. This allows for quick conversion back to a normal mouse. You could off course sacrifice an old mouse to the cause to create a dedicated paddle controller, and make it closer to the original by adding end stops and a spring return.

We really like the simplicity of this hack, and we’re sure our readers can come up with a few other use cases for it in the comments below. You can also approach old Atari games from the opposite end, like adding a machine vision powered laser blaster. While many may think the Atari 2600 was the first gaming console, that honor actually goes to the Magnavox Odyssey, which was the start the of the multi-billion dollar home gaming industry we know today.

Hacking A Thermal Imager For Dual-use Of The Thermal Sensor

July 4, 2021 by Donald Papp 3 Comments

Sometimes a device doesn’t do quite what one needs, and in those cases a bit of tampering might do the trick. That’s what led to being able to record video from a HTI HT-A1 thermal imager despite the device not actually supporting that function, thanks to careful investigation and warranty violation.

Plugging in a custom USB cable allows a mobile phone app to access the thermal sensor, while the host device itself remains ignorant.

We’ve seen a teardown of the HT-A1 in the past, and it turns out that Seek — the manufacturer for the actual thermal sensor inside the device — released an OEM development kit and mobile phone app for their modules. Could this mean that the raw sensor module in the HT-A1 could be accessed via the developer kit app? One hacked together USB cable later showed that the answer is yes! Not only does the app allow viewing thermal imagery, but it makes it possible to do things like record video (a function the HT-A1 itself does not support.)

But even if the HT-A1 doesn’t allow recording, as a handheld thermal sensor with a screen it’s still pretty useful in its own way and it would be shame to gut the unit just for a raw sensor module. The best solution ended up being to put the sensor back into the HT-A1, and install some switching circuitry to disconnect the sensor from the HT-A1’s CPU and divert its data to the USB plug on demand. This means the HT-A1 can be used normally, but by plugging in a custom-made cable while the unit is off, the thermal sensor can be accessed by the mobile phone app instead. Best of both worlds. You can see a brief celebratory thermal cat video embedded below, proving it works.

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Vintage Remote Control Gets Bluetooth Upgrade

July 4, 2021 by Tom Nardi 20 Comments

This swanky Magnavox remote is old enough to predate the use of infrared, and actually relies on ultrasound to communicate with the television. It’s a neat conversation starter, but not terribly useful today. Which is why [Chad Lawson] decided to gut the original electronics and replace it with a Adafruit Feather 32u4 Bluefruit LE that can actually talk to modern devices.

We know, we know. Some in the audience will probably take offense to such a cool gadget being unceremoniously torn apart, but to be fair, [Chad] does say he has a second one that will remain in its original state. Plus a quick check on eBay shows these old remotes don’t seem to be particularly rare or valuable. In fact, after some browsing through the recently concluded auctions, we’re fairly sure he paid $27 USD for both of these remotes.

Anyway, [Chad] found that a piece of perfboard in his collection just happened to be nearly the same size as the PCB from the remote, which made the rest of the conversion pretty straightforward. He simply had to mount tactile switches on one side of the perfboard so the remote’s original buttons would hit them when pressed, and then wire those to the Adafruit on the other side. We know there’s a 3.7 V 500 mAh pouch battery in there someplace as well, though it’s not immediately clear where he hid it in the images.

The code [Chad] came up with tells the Adafruit to mimic a Bluetooth Human Interface Device (HID) and send standard key codes to whatever device pairs with it. That makes it easy to use as a media remote on the computer, for example. We’ve seen something similar done with the ESP32, if you’ve already got one in the parts bin and are looking to revamp a remote control of your own.

At the end of the write-up, [Chad] mentions he may try developing an ultrasonic receiver that can pick up the signals from the unmodified remote control. That would be a nice way to bring this whole thing full circle, and should appease even the most hardcore vintage remote control aficionados.

Your PC Sound Card As A Sensor Input

July 3, 2021 by Jenny List 21 Comments

The commoditised PC is the most versatile tool many of us will own, and since it has been around for a very long time it is also something that can be found for free or very cheaply if the latest components aren’t a concern. It’s not without limitations though, while it’s designed for expansion it no longer has any ports that can easily be repurposed as GPIOs for reading sensors. A solution for some sensors comes courtesy of [Ruslan Nagimov], who shows us how the PC sound card can become a measurement interface.

The idea is that simple resistive or capacitive sensors can be read through their AC characteristics by sending out a sine wave on one channel of the card and reading the result on the other from a divider circuit. He goes extensively into the code, both for the resistive example and for reactive components, and we can see that it forms a handy extension to the PC capabilities.

We’re sure this technique will find applications for some readers, but it interests us for another platform. Measurement using a mobile phone’s audio jack doesn’t have an inspiring history, but perhaps this could be used as well for mobile sensors.

Coding A Custom Driver For The Adafruit Mini Thermal Printer

June 26, 2021 by Lewin Day 6 Comments

Thermal printers are cool… or, uh, warm actually. They use heat to make images, so they never need ink and they print on receipt rolls. The thermal printer available from Adafruit is a particularly tasty example, as it comes fully documented for the budding hacker. [Ed] is one such person, who set about writing his own driver to use the hardware with Linux on a Raspberry Pi.

The project came about as [Ed] didn’t like the halftone output from the standard Adafruit CUPS driver. Thus, a dithering-capable driver was needed instead. The first step of the project was to get dithering working via running such an algorithm into a custom driver, as well as to vary the heating time of the print head to gain greyscale capability. From there, the driver was integrated with CUPS and could be used with the Linux lp command. Finally, measures to deal with the paper running out were coded in as well.

It’s a fun dive into the nitty-gritty of talking to printers at the low level, something that few of us think about when printing concert tickets in a rush. There’s a lot that goes on to get a page to print successfully, and [Ed]’s work leaves us more respect for everything that goes on to get an image on the paper. The driver is available for keen tinkerers over at Github.

Meanwhile, consider a thermal printer for all your banner-printing needs.

Breaking Down The USB Keyboard Interface With Old-Fashioned Pen And Paper

June 24, 2021 by Stephen Ogier 37 Comments

What is better for gaming, old PS/2 style keyboards, or modern USB devices? [Ben Eater] sets out to answer this question, but along the way he ends up breaking down the entire USB keyboard interface.

It turns out that PS/2 and USB are very, very different. A PS/2 keyboard sends your keystroke every time you press a key, as long as it has power. A USB keyboard is more polite, it won’t send your keystrokes to the PC until it asks for them.

To help us make sense of USB’s more complicated transactions, [Ben] prints out the oscilloscope trace of a USB exchange between a PC and keyboard and deciphers it using just a pen and the USB specification. We were surprised to see that USB D+ and D- lines are not just a differential pair but also have more complicated signaling behavior. To investigate how USB handles multi-key rollover, [Ben] even borrowed a fancy oscilloscope that automatically decodes the USB data packets.

It turns out that newer isn’t always better—the cheap low-speed USB keyboard [Ben] tested is much slower than his trusty PS/2 model, and even a much nicer keyboard that uses the faster full-speed USB protocol is still only just about as fast as PS/2.

If you’d like to delve deeper into keyboard protocols, check out [Ben]’s guide to the PS/2 keyboard interface, complete with a breadboarded hardware decoder. If these keyboards have too many keys for your taste, you might consider this USB Morse code keyboard. Thanks to Peter Martin for the Tip!