Blog Posts

Behringer’s 2001 FCB1010 “MIDI Foot Controller” is a curious device. Ten assignable control pedals and expression pedals let you do — well, anything that you can do using MIDI, from controlling instruments, to lighting and effects, to automation.

But what if it could do even more? This was the question the PJRC forum user Expensive Notes asked themselves as they hatched a plan to gut and replace the internals with a Teensy 4.1 and Teensy Audio Adaptor Board.

The project’s forum thread and accompanying videos detail its evolution into a mono synth, drum machine, and sequencer with SD storage. More detail and generously-documented code can be found in the project’s GitHub repository.

DragonSF has created a Web GUI for Teensy 4.1 with a focus on audio projects. The system consists of a Node server (with some HTML/JS/CSS magic) and a Teensy library, which communicate via Ethernet to allow interactions with the GUI to affect firmware on the Teensy board.

As such, the project requires the Ethernet Kit for Teensy 4.1, as well as 8MB PSRAM and our USB Host Cable for MIDI. The web server and library code can be found on GitHub, and an example implementation, TMSidekick2, is also available on GitHub, including source code and schematics.

Marius4560 created a pretty rad project for their Human-Computer Interaction course assignment: a Teensy 4.0-based looping pedal that even provides its own unique ideas for beats!

The Audio Adaptor Board-based project generates random rhythms and drum sounds, plus lets the user record a chord progression to jam along to. An HTML template generator expands options even further. The video below gives a great overview of its usage, and the GitHub repo contains not just source code, but also more detail on the project.

Douglas Engelbart gave “The Mother of All Demos” in 1968, introducing concepts such as the computer mouse, highlighting text, and hyperlinking documents, which profoundly impacted computing.

Less well-remembered, however, was Engelbart’s chording keyset, a five-button keyboard-like device that allows the input of characters when pressed in specific combinations. Russ Nelson wanted to bring awareness to the forgotten device with his entry in the Odd Inputs and Peculiar Peripherals contest.

Consisting of a Teensy 4.1, a custom PCB, and five mechanical key switches, all wrapped up in a custom enclosure housing the five keys, the hardware is actually quite simple. The Teensy’s USB Host capabilities are leveraged to incorporate mouse inputs before passing fused key codes to a PC, expanding the 5 buttons’ 32 combinations (enough for A-Z) to 256 thanks to the three additional buttons on the mouse. Further information, as well as source code and schematics can be found on the project’s Hackaday page.

Visual Micro, creators of a Visual Studio extension that enables Arduino development in the powerful Microsoft IDE, have created a serial debugging tool compatible with the Teensyduino platform.

The plug-in allows you to use breakpoints for step-by-step execution, monitor execution time between breakpoints, and set conditional breakpoints based on data or hit count.

The software, which works with Teensy boards, also allows variable monitoring and value setting at runtime, automatic visual pin monitoring, and easy-to-use charting. It works by injecting serial statements based on breakpoint configuration, when in debug mode. More information can be found on the Visual Micro web site, and a walkthrough of installation and setup can be found in the video below.

Nick Culbertson, aka Moby Pixel on YouTube, recently acquired a Teensy 4.0 and some tiny breadboards. Nick liked the aesthetics of the Teensy/tiny combo so much that it turned into a “world’s smallest MIDI controller” attempt!

Nick had been eyeing Teenage Engineering’s new EP-133 K.O. II sampler, but decided to put some of those funds toward a Teensy DIY project instead (note that the K.O. costs about as much as twelve and a half Teensy 4.0s, so there should be enough left for nearly a dozen more DIY Pocket Operators!). The code uses the Control Surface Arduino library for building MIDI controllers and control surfaces, plus USB MIDI. A couple of buttons and jumper wires complete the hardware setup. Two buttons doesn’t give a ton of expression, but the sound that Nick creates with them in the video is pretty impressive — and then, for an even more diminutive setup, the breadboard is removed, and the Teensy’s headers themselves are played with a jumper wire, creating the ultimate minimalist MIDI rig! See it in action below, and grab the code from Nick’s GitHub gist.

CryHam, creator of the Kacey and KC4 Keyboard Controllers, has created the “Fancy” PC fan controller based on the same code.

The device can regulate seven analog or PWM fans, with RPM detection and display, automated fan power adjustment based on DS18B20 temperature sensors, and an ST7735 1.8″ color TFT LCD display to show the GUI and graphs. Code is available on GitHub, and more detail can be found on CryHam’s web site.

What do you get when you cross a Raspberry Pi 4 with a Teensy 4.1 with a Teenage Engineering OP-1? Perhaps something like the LMN3 from Fundamental Frequency!

This self-described “open source DAW-in-a-box” leverages the Pi-based Tracktion Engine DAW tools with a Pimoroni HyperPixel 4.0 display, and a Teensy interfacing with the hardware layer.

An extremely impressive GitHub organization houses the DAW software, Teensy firmware, FreeCAD and KiCad files, a detailed build guide, and even a MIDI-enabled emulator!

The current functionality includes multitrack recording and editing, plugins, sampler, sequencer, effects, clip cut/paste, loop controls, and project rendering. Check out the video below, then head over to the BOM and pick up the parts to make your own today!

Mjd2dh and their friends were headed to a bachelor party, but how would they survive without their Discord soundboard?

Thanks to mjd2dh’s Teensy 4.1-based hardware soundboard, this was not a question that they ever had to answer, since the friends could now play their favorite sounds at will in real life!

“This project is stupid. Maybe the dumbest thing I’ve ever spent my time on.” states PJRC forum member mjd2dh. With that disclaimer out of the way, mjd2dh added 16MB of PSRAM for storing samples after they’d been loaded from mSD card. A MAX98357 Class D 3W amplifier connected via I2S, and a 4-Ohm 3W speaker provide the sound. Four wireless numeric keypads with their dongles connected to a 4-port USB hub, in turn connected to the Teensy’s USB Host pads give the friends their soundboard buttons. A custom C# utility facilitates sample management. See it in action in the video below!

Econjack (ham radio call sign W8TEE) and Al Peter (AC8GY) have created the T41-EP Software Defined Transceiver (SDT) based on Frank Dziock (DD4WH)’s Convolution SDR code.

The T41-EP is an HF 7-band Single Sideband (SSB) voice and continuous wave (CW) Morse code transmitter, building on the receiver capabilities of the original project.

Unlike other systems, which require an external PC, the system is entirely powered by a Teensy 4.1. Similar systems also often cost ten times as much. The project is open source, with source code and more information available on the project’s Groups.io site.