A man's hands are shown holding a black device. A white knob is in the center of the device, and above the knob in a central protrusion from the rest of the device is a small, circular LCD device.

Simplifying The SmartKnob

January 10, 2026 by Aaron Beckendorf 5 Comments

A knob can make a surprisingly versatile interface, particularly if it’s the SmartKnob, which builds a knob around a BLDC motor for programmable haptic response. It can rotate freely or with a set resistance, spring back to a fixed point when released, stick at detent points, and completely change its behavior as the interface demands. For people inexperienced in electronic assembly, though, smartknobs can be difficult to assemble. That’s why [Kokensha Tech] designed a simpler version, while at the same time letting it use a wider range of BLDC motors.

In addition to a motor, the original design used a magnetic encoder to detect position and a strain gauge to detect pressure on the knob. A circular LCD on the knob itself provided visual feedback, but it also required the motor to have a hollow center shaft. The LCD control wires running through the shaft proved tricky to assemble. [Kokensha Tech] moved the display out of the knob and onto a separate breakout board, which plugs into the controller board. This greatly broadens the range of compatible motors, since they no longer need a hollow shaft.

The motor now fits on a separate carrier board, which makes it easier to swap out different motors. The carrier board has mounting holes sized for a wide variety of motors, and four different types of motor connectors. [Kokensha Tech] also redesigned the rest of the PCB for easier soldering, while avoiding components with narrow pin spacing whenever possible. The original design used a LILYGO T-micro32 Plus MCU. The ESP32 is both cheaper and easier to solder, so it was a no-brainer to swap it in.

We’ve covered the original SmartKnob before, including a more in-depth look at its design. We’ve also seen another project use BLDCs and field-oriented control to make haptic knobs.

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Graphing Calculator Gets USB-C Upgrade

January 7, 2026 by Bryan Cockfield 17 Comments

Unlike Texas Instruments, whose graphing calculators have famously not made technological improvements in decades despite keeping the same price tag, HP has made a few more modern graphing calculators in the last few years. One of which is the HP Prime which boasts hardware from the mid-2010s including an ARM processor, a color screen, and rechargeable lithium battery. But despite this updated hardware it’s still using micro-USB for data and charging. [David] wanted to fix that by giving this calculator a USB-C port.

The first steps were disassembling the calculator case and removing the micro-USB port. The PCB is glued to the LCD screen which isn’t ideal, but he was able to work on it with everything attached. The parts are small enough to need a microscope, and with a hot air station he was quickly able to remove the USB port. His replacements from a generic online retailer were able to be soldered without much effort, but there was one major complication. The new USB-C ports didn’t account for the “On The Go” mode supported by micro-USB and were shorting a pin to ground which put the calculator into “host” mode instead of acting as a device. But using the microscope and cutting a trace on the PCB disabled this mode permanently and got the calculator working properly.

As far as modernizing calculators go, it seems like the HP Prime checks a lot of boxes, with the major downside that the LCD screen and more powerful processor means that the battery needs to be charged more often than the old TI calculators. Rather than carry a dongle around everywhere, [David] found this to be a much more efficient change to his trusty HP. If you’re still stuck using TI calculators, though, there are a few ways to modernize those as well like this build which adds a lithium battery or this one which ports a few Game Boy games to the platform.

TULIP: The Ultimate Intelligent Peripheral For The HP-41 Handheld Calculator

December 30, 2025 by John Elliot V 8 Comments

[Andrew Menadue] wrote in to let us know about the TULIP-DevBoard and TULIP-Module being developed on GitHub.

TULIP is short for “The Ultimate Intelligent Peripheral” and it’s an everything expansion board for the HP-41 line of handheld calculators sold by HP from 1979 to 1990. These particular calculators support Reverse Polish notation which seems to be one of those things, like the Dvorak keyboard, where once you get used to it you can never go back.

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The Confusing World Of Bus Mice

December 30, 2025 by Jenny List 33 Comments

The USB port which first appeared on our computers some time in the mid-1990s has made interfacing peripherals an easy task, save for the occasional upside down connector. But in the days before USB there were a plethora of plugs and sockets for peripherals, often requiring their own expansion card. Among these were mice, and [Robert Smallshire] is here with a potted history of the many incompatible standards which confuse the retrocomputing enthusiast to this day.

The first widely available mice in the 1980s used a quadrature interface, in which the output from mechanical encoders coupled to the mouse ball is fed directly to the computer interface which contains some form of hardware or microcontroller decoder. These were gradually superseded by serial mice that used an RS-232 port, then PS/2 mice, and finally the USB variant you probably use today.

Among those quadrature mice — or bus mice, as early Microsoft marketing referred to them — were an annoying variety of interfaces. Microsoft, Commodore, and Atari mice are similar electrically and have the same 9-pin D connector, yet remain incompatible with each other. The write-up takes a dive into the interface cards, where we find the familiar 8255 I/O port at play. We’d quite like to have heard about the Sun optical mice with their special mouse pad too, but perhaps their omission illustrates the breadth of the bus mouse world.

This piece has certainly broadened our knowledge of quadrature mice, and we used a few of them back in the day. If you only have a USB mouse and your computer expects one of these rarities, don’t worry, there’s an adapter for that.

Illustrated Kristina with an IBM Model M keyboard floating between her hands.

Keebin’ With Kristina: The One With The Keyboard-Mouse, Again

December 29, 2025 by Kristina Panos 8 Comments

The astute among you may remember an earlier version of this Russian beauty, the Lapa, which I featured last year around this time. Creator [lemosbor] claims that the worry was less about visual beauty and more about ergonomics. Way more. Well then, let this serve rather nicely as a textbook definition of that old form-follows-function principle.

A splendidly ergonomic split with few keys, large openings under the palms and wrists, and mouse control on the thumbs. — The lovely Lapa.

See, [lemosbor] believes that the keyboard must adapt to the hands and not the other way around. The main goals were to minimize hand and finger movement as well as the visual attention required of the keyboard itself. No, there were never going to be any screens or RGB, and there likely never will be.

But I refuse to sidestep the obvious beauty in this keyboard, which from the side resembles a stylish and expensive pair of slightly-heeled shoes that were tailored to the contours of the human hand. And let’s not forget those handmade, oval keycaps, which again are a product of form-follows-function.

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Moving Mousepad Is An Elegant Aimbot

December 27, 2025 by Lewin Day 12 Comments

These days, it can be hard to remain competitive in online shooters without spending your entire life dedicated to the sport. This leads some to explore the world of competitive aids. (AKA: cheating.) A great example is [Nick], who built a mechanical aimbot to help in this regard.

[Nick’s] build moves a mousepad underneath the mouse opposite to the desired movement direction, in order to simulate the mouse movements required to aim at targets in game. This is achieved with the aid of a XDraw A4 pen plotter, which served as a cheap prebuilt X-Y motion platform. The plotter responds to simple serial commands, which makes it easy to control. The X-Y gantry was mounted underneath the desk so the mousepad sits seamlessly on top of the desk, sliding neatly on low-friction mouse skate stickers.

With the mousepad control system built, it was then necessary to figure out how to turn it into an aimbot. [Nick] already had a machine vision tool to detect enemies in shooting game, so it was merely modified to make the right mousepad movements to get the crosshairs right where they needed to be before firing. In testing, it proved more than capable at helping a new player achieve far superior aim, as a good aimbot should.

We’ve featured similar projects before that use complex mechanical contraptions to aim for you. Yes, it’s still cheating, but it’s a lot harder to detect than a traditional aimbot. That doesn’t make it right, per se, just more subtle. Video after the break. Continue reading “Moving Mousepad Is An Elegant Aimbot” →

a torn-up printer with a very long image of different frames

Playing DOOM On A Receipt Printer

December 27, 2025 by Ian Bos 33 Comments

Gaming is a wonderful thing. Unfortunately for many of us, work takes up our valuable time, which should be allocated to our gaming. What if there was a better way? Well, printers can print an image quickly, and receipt printers can print a lot of images. This sounds like an effective display for DOOM in a pinch. [Bringus Studios] managed to find such a printer and got the classic shooter running.

Getting the printer’s attached computer, which was only designed for printing the cost of your chicken sandwich, to run Half-Life was far from easy. [Bringus] struggled through the process of swapping operating systems from Windows 7 to Linux just to return to Windows 7 after a painful process of maintaining compatibility between 32 and 64 bit software. Driver issues followed through the entire process just to get anything running at all.

But we can’t play DOOM while at work on a normal screen. The printer MUST display our glorious 480p gameplay. To achieve such a workflow, [Bringus] implemented a script to print out a frame of the display, allowing for “visible gameplay”. Along with some heat issues from the nature of thermal receipts, eventually the printer displayed the glory of DOOM.

Playing games on a thermal printer might be one of the weirdest things you’ve seen today, but what if we could reverse the script a bit and create a printer from something else? Here at Hackaday, we have exactly the thing for you: a printer made from a vintage typewriter!

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