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

Keebin’ With Kristina: The One With The Cat Keyboard

December 2, 2021 by Kristina Panos 8 Comments

Special thanks to [Maarten], who stumbled upon this old gem of a geekhack thread by [suka]. It’s essentially a show and tell of their DIY keyboard journey, complete with pictures. [suka]’s interest started with a yen for ergonomic keyboard layout alternatives. They soon found the geekhack forum and started lurking around, practicing layouts like Neo and AdNW, which [suka] still uses today.

When it was time to stop lurking and start building something, [suka] got plenty of support from the community. They knew they wanted a split ortho with a trackpoint and plenty of thumb keys. [suka] started by building them from old Cherry keyboards, which are easier to come by in Germany.

The first build was a pair of num pads turned landscape and wired up to a Teensy, but [suka] wanted those sweet, clacky Cherry MX switches instead of MLs. So the second version used a pair of sawed-off num pads from old MX boards.

When the Truly Ergonomic came out, it got [suka] interested in one-piece splits. Plus, they were tired of carrying around a two-piece keyboard. So their next build was a sexy monoblock split with a laser-sintered case and keycaps. But that was ultimately too uncomfortable, so [suka] went back to split-splits.

Everyone takes a different path into and through this hobby, and they’re all likely to be interesting. Is yours documented somewhere? Let us know.

What Could Have Been: The Dygma Raise

I do some streaming here and there, mostly for the sense of focus I get out of being live on camera. I like to find out what my people in chat are clacking on, and one of them told me they have a staggered split called the Dygma Raise. I hadn’t heard of it before that day, but this keyboard has been around for a few years now.

This same person told me that Dygma might make an ortholinear version sometime soon, but apparently Dygma wanted it that way from the beginning. According to the timely video below sent to the tips line by [deʃhipu], Dygma’s original plan was a split ortho with few keys and presumably a layer system.

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LEDs display different pitches in a sunburst pattern

Spiral Music Visualization

November 26, 2021 by Mike Szczys 6 Comments

Displaying notes live as they are being played can be a really powerful learning tool, but it’s usually used to learn how to play a specific instrument. This take on the topic is actually a neat way to learn more about music theory — how pitches work together to build the sounds that we hear. The visual tack chosen arranges each of 12 notes into a spiral. As you continue to go up the scale through more octaves, pitches that share the same name line up into a line like a ray projecting out from the sun. So there are 12 rays for the notes in the scale: C, C#/D♭, D, D#/E♭,F, etc.

[mechatronicsguy] built it a few years back but just now got around to documenting it, and we’re sure glad he did. The layout of notes at first looks just like a colorful visualization. But as he mentions in his description, this assigns a shape to each different type of cord. A major cord will have the same shape whether it is played with C, G#, B♭, or any other note as the root. The shape simply rotates around the axis based on that root note. Higher octaves will be shown further out on the radius, but the chord shape will still be the same. Minor, augmented, even modal chords and those with added pitches all have their own unique shape on the display.

You get the best understanding of the visualization by looking at the Python-rendered version in the video below. It’s a nice touch that notes turn grey and fade away after being released so you kind of see where the current chord came from. This isn’t strictly a perk of pre-recordings. While you can feed it MIDI files, you can also play a MIDI instrument and display the visuals live on the hardware version that uses a Teensy with an audio shield.

If you’re looking for examples on how music visualizers are used to teach the instrument, look no further than this Wurlitzer note visualizer replica. Also for those who don’t know, the song being played in the hardware demo (second video below) is Beethoven’s 7th Symphony. Well worth a full listen, it’ll change your life.

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Run UNIX On Microcontrollers With PDP-11 Emulator

November 19, 2021 by Bryan Cockfield 40 Comments

C and C++ are powerful tools, but not everyone has the patience (or enough semicolons) to use them all the time. For a lot of us, the preference is for something a little higher level than C. While Python is arguably more straightforward, sometimes the best choice is to work within a full-fledged operating system, even if it’s on a microcontroller. For that [Chloe Lunn] decided to port Unix to several popular microcontrollers.

This is an implementation of the PDP-11 minicomputer running a Unix-based operating system as an emulator. The PDP-11 was a popular minicomputer platform from the ’70s until the early 90s, which influenced a lot of computer and operating system designs in its time. [Chloe]’s emulator runs on the SAMD51, SAMD21, Teensy 4.1, and any Arduino Mega and is also easily portable to any other microcontrollers. Right now it is able to boot and run Unix but is currently missing support for some interfaces and other hardware.

[Chloe] reports that performance on some of the less-capable microcontrollers is not great, but that it does run perfectly on the Teensy and the SAMD51. This isn’t the first time that someone has felt the need to port Unix to something small; we featured a build before which uses the same PDP-11 implementation on a 32-bit STM32 microcontroller.

This is a MIDI harp that is played by waving your hands in the air over the infrared distance sensors.

Teensy MIDI Air Harp Sounds Huge

November 15, 2021 by Kristina Panos 4 Comments

Some of the coolest sounds come from wild instruments like orchestra strings, fretless basses, and theremins — instruments that aren’t tied down by the constraints of frets and other kinds of note boundaries. [XenonJohn]’s air harp is definitely among this class of music makers, all of which require a certain level of manual finesse to play well.

Although inspired by Jean-Michel Jarre’s laser harp, there are no lasers here. This is a MIDI aetherharp, aka an air harp, and it is played by interrupting the signals from a set of eight infrared distance sensors. These sensors can be played at three different heights for a total of 24 notes, plus there’s a little joystick for doing pitch bends.

Inside the wooden enclosure of this aetherharp is a Teensy 3.5 and eight infrared distance sensors with particularly long ranges. On top is a layer of red acrylic that doesn’t affect the playability, except in bright sunlight. Although you could use most any MIDI software to produce the actual sounds, [XenonJohn] chose VMPK (Virtual MIDI Piano Keyboard). Be sure to check it out in action after the break.

Not dangerous enough for you? Here’s a laser harp that involves a Tesla coil.

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An animated newspaper image from Harry Potter

Muggle Uses E-Paper For Daily Prophet Replica

October 29, 2021 by Chris Wilkinson 12 Comments

News from the wizarding world is a little hard to come by for common muggles, but [Deep Tronix] has brought us one step closer to our magical counterparts with their electronic replica of the Daily Prophet newspaper.

Those familiar with the Harry Potter series will no doubt be familiar with the Daily Prophet. In the films, the newspaper is especially eye-catching with its spooky animated images, a reflection of the magic present throughout the wizarding world. This was achieved with post-production special effects for the films, but this fan-made front page of the Prophet brings the concept to life using e-paper technology and a few other interesting gadgets, all hidden away in a picture frame.

As mentioned, the heart of this project is the e-paper display and a Teensy microcontroller. While e-paper displays are excellent for displaying static text and simple graphics, they are usually not suitable for moving images due to suffering from a form of ‘burn in’, which can leave errant pixels on the screen. This means that e-paper technology typically has a relatively low frame rate for video. [Deep Tronix] has used a custom dithering library to somewhat mitigate this issue, and the results are impressive. Moving images are loaded from an external SD card, processed, and then displayed on the e-paper display, which is almost indistinguishable from the newspaper print that surrounds it.

The seemingly magical newspaper also has a face detection feature, which is enabled by a hidden camera and the venerable ESP32 microcontroller. This system integrates with the Teensy to record and then display the reader’s face on the e-paper display. A neat trick, which is made all the more eerie when these faces are later displayed at random.

We’ve seen Daily Prophet replicas before using more traditional display technology, however the move to an e-paper display goes a long way to improving the overall aesthetics, despite the lower frame rates. With Halloween just around the corner, you might just end up tricking a few people with this clever prop – check out all the build details here.

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Kinesis + Teensy = QMK Advantage Over Your Keyboard

August 5, 2021 by Kristina Panos 11 Comments

Back in 2013, [Michael Stapelberg] created what is lovingly referred to as the Stapelberg controller: a replacement keyboard controller for the original Kinesis Advantage, the decades-old darling of the ergonomic clacking world. Whether you’re building a new keeb, you’ve got a broken Kinesis, or you simply want to run QMK on the thing and don’t mind getting your hands dirty, there’s a new Stapelberg controller on the block. It’s called the kinT, for Kinesis + Teensy.

[Michael] built kinT in response to the Advantage 2, which came along in 2017 and changed the way the thumb clusters connect to the main board from a soldered cable to an FPC connector. Whereas the original Stapelberg controller was built in Eagle, this one was done in KiCad and is open-source, along with the firmware. You can use a Teensy 4 with this board but if you don’t have one, don’t worry — kinT is backwards-compatible with pretty much every Teensy, and it will even work on the original Advantage.

Are you on the fence about going full ergo? Check out my in-depth review of the original Kinesis Advantage I got that’s almost 20 years old and still clacking along like new. But don’t wait for a repetitive stress injury to go full ergo. Trust me.

MIT’s Knitted Keyboard Is Quite A Flexible MIDI Controller

June 30, 2021 by Kristina Panos 7 Comments

There are only so many ways to make noise on standard instruments such as acoustic pianos. Their rigidity and inputs just don’t allow for a super-wide range of expression. On the other hand, if you knit your interface together, the possibilities are nearly endless. MIT’s new and improved knitted keyboard is an instrument like none other — it responds to touch, pressure, and continuous proximity, meaning that you can play it like a keyboard, a theremin, and something that is somewhere in between the two. Because it’s a MIDI interface, it can ultimately sound like any instrument you’ve got available in software.

The silver keys of this five-octave interface are made of conductive yarn, and the blue background is regular polyester yarn. Underneath that is a conductive knit layer to complete the key circuits, and a piezo-resistive knit layer that responds to pressure and stretch. It runs on a Teensy 4.0 and uses five MPR121 proximity/touch controllers, one per octave.

The really exciting thing about this keyboard is its musical (and physical) versatility. As you might expect, the keyboard takes discrete inputs from keystrokes, but it also takes continuous input from hovering and waving via the proximity sensors, and goes even further by taking physical input from squeezing, pulling, stretching, and twisting the conductive yarns that make up the keys. This means it takes aftertouch (pressure applied after initial contact) into account — something that isn’t possible with most regular instruments. And since this keyboard is mostly yarn and fabric, you can roll it up and take it anywhere, or wrap it around your neck for a varied soundscape.

If you’re looking for more detail, check out the paper for the previous version (PDF), which also used thermochromic yarn to show different colors for various modes of play using a heating element. With the new version, [Irmandy Wicaksono] and team sought to improve the sensing modalities, knitted aesthetics, and the overall tactility of the keyboard. We love both versions! Be sure to check it out after the break.

Want to play around with capacitive touch sensors without leaving the house for parts? Make your own from paper and aluminum foil.

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