Instant Macropad: Just Add QMK

I recently picked up one of those cheap macropads (and wrote about it, of course). It is surprisingly handy and quite inexpensive. But I felt bad about buying it. Something like that should be easy to build yourself. People build keyboards all the time now, and with a small number of keys, you don’t even have to scan a matrix. Just use an I/O pin per switch.

The macropad had some wacky software on it that, luckily, people have replaced with open-source alternatives. But if I were going to roll my own, it would be smart to use something like QMK, just like a big keyboard. But that made me wonder, how much trouble it would be to set up QMK for a simple project. Spoiler: It was pretty easy.

The Hardware

Simple badge or prototype macropad? Why not both?

Since I just wanted to experiment, I was tempted to jam some switches in a breadboard along with a Raspberry Pi Pico. But then I remembered the “simple badge” project I had up on a nearby shelf. It is simplicity itself: an RP2040-Plus (you could just use a regular Pi Pico) and a small add-on board with a switch “joystick,” four buttons, and a small display. You don’t really need the Plus for this project since, unlike the badge, it doesn’t need a battery. The USB cable will power the device and carry keyboard (or even mouse) commands back to the computer.

Practical? No. But it would be easy enough to wire up any kind of switches you like. I didn’t use the display, so there would be no reason to wire one up if you were trying to make a useful copy of this project.

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The Tape Speed Keyboard

For those who experienced any part of the 1960s, even if it’s just experiencing the music from that era here in the future, the sound of the Mellotron is immediately recognizable. The Moody Blues were famous for using the tape-based instrument, and the Beatles and David Bowie produced hits with it as well. It’s haunting sounds are still highly prized today, but the complexity, cost, and maintenance requirement for the tape loops and other moving parts can put many musicians off from owning one. But [Japhy Riddle] has built an instrument without these downsides called the Tape Speed Keyboard.

Unlike the Mellotron which used a tape loop for each of its keys, the Tape Speed Keyboard uses only a single cassette tape. As the name implies, it changes the pitch of the sound by modulating the speed of the single tape housed in its own tape deck. The keyboard itself started off life as a Casio MT-35 but since this is a completely analog instrument, it was rewired so each key is connected to a potentiometer whose output voltage is tuned to a specific tape speed. [Japhy] reports that this is similar to tuning an analog piano and the process can be equally temperamental.

With everything electronic working, [Japhy] turned to making this a more acceptable musical instrument. Predictably, turning the motor on and off for each key press came with a bit of delay, causing the sound to come out goofy and muddy. To solve this problem he changed the design to make the tape play continuously rather than start and stop for a key press, and then modified other keys to be on-off switches for sound output. Since cassette tapes have two sides, he can also play either of two sounds in this way.

With the final polish on, the Tape Speed Keyboard is able to produce completely unique compositions that separate it from even the venerable Mellotron. Be sure to check out the video linked below to hear its sound. There have been plenty of other musical projects based around tape decks as well, including this one inspired by the original Mellotron and this tape deck-based guitar effects pedal.

Thanks to [splashbun] for the tip!

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Phone Keyboard Reverse Engineered

Who knows what you’ll find in a second-hand shop? [Zeal] found some old keyboards made to fit early Alcatel phones from the year 2000 or so. They looked good but, of course, had no documentation. He’s made two videos about his adventure, and you can see them below.

The connector was a cellphone-style phone jack that must carry power and some sort of serial data. Inside, there wasn’t much other than a major chip and a membrane keyboard. There were a few small support chips and components, too.

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Add TouchTone Typing To Your Next Project

The Blackberry made phones with real keyboards popular, and smartphones with touch keyboards made that input method the default. However, the old flip phone crowd had just a few telephone keys to work with. If you have a key-limited project, maybe check out the libt9 library from [FoxMoss].

There were two methods for using these limited keyboards, both of which relied on the letters above a phone key’s number. For example, the number 2 should have “ABC” above it, or, sometimes, below it.

In one scheme, you’d press the two key multiple times quickly to get the letter you wanted. One press was ‘2’ while two rapid presses made up ‘A.’ If you waited too long, you were entering the next letter (so pressing two, pausing, and pressing it again would give you ’22’ instead of ‘A’).

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Split Keyboard Uses No PCB

When [daniely101] wanted a split keyboard, he decided to build his own. It wound up costing $25 to create a wireless board with no custom PCB required. Each half has its own microcontroller, and the whole thing connects via Bluetooth. While we don’t mind making a PCB, we can appreciate that you could change your mind easily with this wiring scheme.

The 3D printed case holds the keys, and then it is just a matter of carefully soldering the keys to the microcontrollers. Of course, each side also has to have its own battery. The ZMK firmware is split in half, one part for each side of the keyboard. The nRF52840 CPUs have plenty of wireless connectivity. The keys are set in rows and columns, so the amount of soldering back to the controller is manageable.

While we applaud the wireless design, it does seem odd that you have to charge both halves and turn them on and off separately. But that’s the nice thing about a design like this — you could modify the design to not have a split. Or, you could allow one flexible wire pair to run across for power. Of course, you could modify the layout, including adding or deleting keys.

You might consider adding a pointing device. At least you don’t have to pull out a saw.

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Taking A One Handed Keyboard To The Next Level

When a wrist mounted keyboard floated past in the Hackaday feed, a mental image surfaced, perhaps something like a Blackberry keyboard mounted on a wrist cuff, maybe with some kind of display. It’s impressive indeed then to open the link and see [AdamLeBlanc]’s Schist01. It’s a wrist mounted keyboard, but with its bracket curving in front of the had to support a custom ergonomic chording keyboard, it’s definitely a break from the norm.

The wrist mount has clearly taken a lot of thought, and despite looking something like the arm of a Star Trek Borg, appears comfortable. It’s extremely adjustable, and can be demounted into several different parts. Meanwhile the keyboard itself has been formed to his hand by a trial and error process involving keycaps and a clay model. there’s even a thumb-operable touchpad.

We like this peripheral a lot, for the huge attention to detail that has gone into its design, for its boldness, and because we can’t help seeing ourselves using it as the input device for a futuristic head-mounted display. For now though we don’t have any futuristic silver clothing in the wardrobe, so that will have to wait. If you’d like to see more, there’s a video.

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Building A Cyberpunk Modular Keyboard

Perhaps you have a tilt towards glowing cyberpunk peripherals. Perhaps you’ve been hunting for a keyboard that you can position perfectly to suit both your left and right hands. In that case, you might just like this nifty design from [Modern Hobbyist].

The first thing you’ll note is the split design, which allows each half of the keyboard to be placed optimally for each arm’s comfort. They’re linked with a cable, which allows the STM32 microcontroller to read the keys on both sides and then spit out the right stuff upstream over its USB-C connection. The microcontroller is also in charge of running the per-key LED lighting and the LCD screens on each half.

The board owes its sleek and slim design at least in part to using Kailh Choc low-profile switches. They plug in to hotswap compatible sockets so the switches can easily be changed if desired. Keycaps are blank off-the-shelf parts because this is a keyboard for those who aren’t afraid to spend the time establishing the right muscle memory. It might take some adaptation if you’re not used to the staggered columnar layout. However, the LCD screens can display a keymap if you need a little help now and then.

We’ve seen a lot of great split keyboards over the years, including one amusing design made by hacking an existing keyboard in half with a saw.

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