DIY Vocoder

If you’re familiar with songs like Daft Punk’s Digital Love, then you’re familiar with the way a vocoder can transform the human voice by isolating and filtering multiple frequency bands which can then have their pitch manipulated by a synthesizer.

Synth hacker Chip Audette was curious about using one, so he made his own 16-band vocoder, based on the Teensy 3.6-powered Blackaddr Teensy Guitar Audio Pro.

Chip provides an excellent blog post complete with background on how vocoders work, as well as how he applied this hardware theory to his Teensy software, based on the Teensy Audio Library and Blackaddr’s BALibrary.

The resultant sketch is available on GitHub, though the author suggests it be used as more of a starting point, since many of the choices he made (such as filter frequency bands) were arbitrary. A fun demonstration of his results can be found in the video below.

Cadetwriter – Vintage Typewriter to USB Printer

Early computers like the PDP-8 or Altair 8800 did not include the basic I/O that we take for granted today, such as a keyboard and monitor. Instead, a separate ASCII terminal and printer was connected for input and output, as was the case with IBM’s 1959-vintage scientific computer, the 1620.

The wonderful team at the Computer History Museum in Mountain View, California have recreated the experience of using the 1620, but with more reliable modern hardware, yet when it came to I/O, suitable period candidates were becoming harder and harder to find. So, they created their own console typewriter by modifying the far more available IBM/Lexmark Wheelwriter 1000 with a custom serial interface board, based around a Teensy 3.5.

The hybrid Cadetwriter can connect via RS-232 or USB to any retro minicomputer or mainframe as a substitute for harder-to-find vintage teleprinters. Configuration via jumpers extends its utility as a standard ASCII terminal or standalone typewriter. Complete details on how to create your own can be found on the GitHub repo, with PCBs conveniently available to order via OSH Park. An extensive presentation from 2019’s VCF West event can also be found on YouTube.

Spiral Music Visualization

Remember when MP3 players used to have music visualizers, so that you could see what you’re hearing?

Neither do we, because we’re totally not that old, but maybe there are other folks out there who do, and this project appeals not only to them, but to music students and anyone wishing to gain insight into chords and music theory. Teensy forum user gav shared a unique device that not only synthesizes MIDI data as audio, but also displays it via a 12-note spiral LED visualization.

Using MIDI file playback on a PC with the Teensy plugged into it, or a USB MIDI device plugged into the board’s USB Host Port (or both), it’s possible to observe chords as the same “shape” around the spiral, regardless of key. The brief persistence of notes as a histogram also enables the inference of key signatures.

Additional details and code can be found on GitHub, and a demonstration of this incredible visualization technique can be seen in the video below.


Classic Arcade Game Color Vector Display Controller

The number of gamers who recall vector-based games like Tempest (not to mention entire vector-based consoles like the Vectrex) is perhaps dwindling in a pixel-based world, but Robin Champion remembers.

Building on Trammell Hudson’s Teensy 3.2-based vector board, the 4.1-based VSTCM ( Colour Mod) allows use of an RGB monitor to bring color vector-based games like Star Wars to life, thanks in part to a custom interface to AdvanceMAME.


A built-in 6502 emulator also allows games like Battlezone and Asteroids to be played completely within the system.

The schematic, Gerbers, BOM, firmware, and even instructions for a bonus IR remote can all be found on the project’s GitHub repo.

Church Organ MIDI Control

We’ve all been there: you pick some random anachronistic object up from the thrift store, with vague intentions of sticking a microcontroller in it and giving it a new life, but usually its an old telephone or phonograph; not an entire church organ!?

That is, unless you’re Sam Battle, better known as Look Mum No Computer, who drove halfway across the UK to extract an organ he bought on eBay that had been fairly comprehensively plumbed into a small house.

Sam then designed a custom organ/MIDI interface board, based around the Teensy 2.0 ++ plus a handful of ULN2803A Darlington transistor arrays to control the many, many, many solenoids used by the organ. See it in action in the video below, or grab the Gerbers and source code from the LMNC site, should you find yourself in a similarly absurd situation!


Quantum Jungle

What do you get when you cross 12,000 LEDs with a pile of Teensy 4.1s and ESP32s, then toss in  Schrödinger’s Equation for good measure?

If you guessed something along the lines of “Robin Baumgarten’s latest project” then we will gladly award you full credit, plus bonus points if your guess was based on having read about his Teensy 3.2-powered Quantum Garden project on our blog back in 2018. Robin’s latest project is overgrown with even more LEDs, even more spring door stopper things, and even more all-around awesomeness in the form of a Quantum Jungle!

Like the Garden, the Quantum Jungle uses the three Teensy boards to render LED data. Using the TriantaduoWS2811 library, they are able to realize 1.065 million LED updates per second while using zero CPU cycles. A PC running a custom C# application sends the LED data over the Teensy’s 100Mbit Ethernet, as well as handling all the fancy quantum stuff in Python. The springs are connected to NXP MPR121 capacitive touch sensor controllers, which are in turn connected to ESP8266s in order to overcome I2C address limitations involved in connecting the controllers directly to the three Teensy boards. An additional ESP8266 reads their data over Wi-Fi frequencies using ESP-NOW, without the need for a router. This in turn is connected to one of the Teensy 4.1s, which sends the touch data back to the PC over Ethernet for processing.

More information about the project can be found on Robin’s web site, as well as in the video below.