Blog Posts

LED and pixel art have become ubiquitous, but have you ever thought about how difficult something like this would have been to achieve in 1973? Andrew Seawright has, as a necessity of recreating his father James Seawright’s Network IV sculpture.

The original was installed in Concourse B of the Seattle-Tacoma Airport, and used 1024 GE R6A neon glow lamps. It was controlled by a Data General Nova 1210 minicomputer and featured three Moog-style analog synthesizers. Instead of recreating the piece with modern code, Andrew emulated the Nova on a Raspberry Pi 4B, then ran the original code, extracted from paper tape. A Teensy 4.0 using the OctoWS2811 library controls LEDs in place of the original lamps, replacing the GPIO peripheral of the original. A second Teensy emulates the analogue sounds and handles inputs from a miniature version of the original’s 8×8 button matrix. Source code (original and “rebooted”!) is available on GitHub, and videos of both the original and modern incarnation can be enjoyed below.

Synth DIY Facebook group member Craig Barnes has created a bi-timbral synth controller. With 64 split upper/lower channels of Control Voltage (CV), this Teensy 4.1-based wonder also features 56 channels of shift registers for digital control.

The controller features four LFOs for FM, TM, AM, and PWM (upper and lower). Two noise circuits and Voltage Controlled Amplifiers (VCAs) provide further sonic possibilities. This is a seriously impressive thing to do on protoboard, as attested by the sheer volume of wiring around back.

Yang Zhang, Gierad Laput, and Chris Harrison have developed Electrick: low-cost touch sensing using Electric Field Tomography (EFT). In their paper on the topic, the authors show techniques and examples for adding interactivity to otherwise static objects.

The electrically conductive material used can be spray or brush-coated into irregularly-shaped objects (compared to more typical applications like smartphones and tablets), including laser-cut or 3d-printed items.

A custom PCB featuring a Kinetis K20 MCU running Teensy 3.2 firmware hosts the voltage-controlled current source (VCCS), direct digital synthesizer (DDS), an ADC preamp, and a Bluetooth module for wireless data transmission. Read more on Chris or Yang‘s web sites, or check out the video below.

Trevor Flowers has a tiny computing obsession. To be clear, it’s not the obsession that’s small — it’s the computers themselves, which Trevor painstaking recreates in miniature to look — and even function — just like their full-size counterparts.

Trevor’s work can be seen all over Mastodon, as well as in Mountain View’s Computer History Museum. But the lilliputian marvel that caught our eye was a 1/3 scale replica of the 1978 DEC VT100 computer terminal, complete with functional Teensy 4.1-powered keyboard! Thanks to Teensy’s USB HID (Human Interface Device) capabilities, the diminutive DEC’s typing apparatus can be used with any modern computer, although it is intended to be paired with an SBC, like the Raspberry Pi, which can be concealed in the terminal’s case. A 3.5″ 640×480 TFT display provides sufficient resolution to emulate the VT100’s 80×24 character mode.

A pager motor inside the keyboard provides haptic feedback to give users confidence that their keystrokes were recognized, and USB serial allows the LEDs to be controlled by the connected SBC. More information about the project can be found on Hackaday, and a wide range of tiny art machines, from TRS-80s to NeXT workstations to Cray 1 supercomputers, can be found on Trevor’s web site. If you don’t have space for a tiny retrocomputer on your desk, you can also support Trevor’s art on Patreon, or by commissioning your own custom piece!

While many-channel audio solutions have existed for Teensy for some time, they were mostly based on the Cirrus Logic CS42448 codec, which has sadly been discontinued.

Australian PJRC forum member palmerr has taken up the mantle of multi-channel support with a new board based on the TI TLV320AIC3104 stereo codec. With four multiplexed codecs, each board features four “wing” boards for connecting pairs of TRS, XLR, or combo XLR connectors. The board is stackable, for up to 16 inputs and 16 outputs. The design is very CPU-efficient, using just 0.12% on a Teensy 4.0 to drive 16 output channels from a single sine generator.

Finished boards are available on Tindie, with Gerbers and a board-specific library available on GitHub. An extensive thread detailing the project’s evolution can be found on the PJRC forums.

Muse Electronic Instruments’ Keith Baxter has created a unique device named the Zen Flute.

Perhaps best described as a “mouth Theramin” of sorts, the instrument uses changes in the shape of your mouth to control the pitch (and not, as the “flute” part of the name might imply, blowing into the mouthpiece and covering or uncovering holes). A small speaker near the mouthpiece causes the air in your mouth to resonate, which is picked up by a mic, processed by the Teensy, and used to produce sound using the Zen Flute’s Shakuhachi-like synthesizer system. It also outputs MIDI, and can be used with Ableton. A joystick controls volume and expression, as well as enabling selection of various operation modes.

More information, including schematics, KiCad files, and more can be found on the project’s web page. Hear it in action below, or on the 2023 Guthman Musical Instrument Competition web site, where it was awarded first place!

Cathy Fang, Yang Zhang, Matthew Dworman and Chris Harrison have created Wireality: a haptic system that enables tangible VR interactions by limiting the dexterity of the wearer.

Most virtual reality systems have hand-tracking controllers with buttons and “rumble pack”-style haptic feedback — a feeble facsimile of authentic interaction with real-world objects. Utilizing a shoulder-mounted system that connects to various points of the wearer’s hands, Wireality employs spring-loaded wires to physically prevent motion, simulating the experience of encountering physical obstacles.

A Teensy 3.2 controls two L298 H-Bridge motor drivers, based on commands received over USB from custom VR software. This activates a solenoid which arrests the wearer’s motion to provide a sensation of physical interaction. More information can be found on Chris’s web site, in the original paper, and in the video below.

Karan Ahuja, Sujeath Pareddy, Robert Xiao, Mayank Goel and Chris Harrison have created LightAnchors — a new technology for AR anchoring and data transmission using existing light sources such as LEDs and light bulbs.

Whereas typical AR solutions require the manual placement of physical markers, LightAnchors can take advantage of the LEDs already found in, for example, most appliances. And by rapidly blinking that LED, kind of like Timex Datalink watches in the 90s, which used flashes from a CRT to receive its data, the LightAnchors team have created a glue gun that transmits its temperature, a parking meter that transmits rate info, and a security camera that broadcasts its own privacy policy. A Teensy 3.2 is used to modulate light sources at 120 FPS using the built-in DAC, which is imperceptible to most humans. Learn more on Chris’s web site, in the original paper, or in the video below.

Carlos has converted a small Harbor Freight Predator 212 engine from carburetion to Electronic Fuel Injection (EFI) using a Teensy 4.0. By monitoring intake air pressure (MAP) and crankshaft position, the system is able to accurately drive a fuel injector.

Carlos designed and fabricated all of the engine peripherals himself, including the fuel cell, the fuel pumping/delivery system, the intake manifold, and the trigger wheel system to measure crankshaft position. Despite having a fair amount of mechanical engineering experience, this was his first electronics project. More information can be found on the project’s web page, with source available on GitHub, and a demonstration in the video below.

Teensy hobbyist 1101010 has created a charming project named “Dial-a-Memory.” The system uses a Teensy 3.2 plus Audio Adaptor Board to play various audio files depending on the number dialed on the attached telephone.

Examples include files from archive.org, Morse code “fortune cookies”, spoken versions of numbers like e and pi, and even a Choose Your Own Adventure-style game. After initial experiments with the Teensy wired directly into the phone, 1101010 switched to a SLIC (subscriber line interface) module that allows any phone to be plugged into the system.

More information and source code can be found on GitHub, with the latest hardware in development on EasyEDA.