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.

Dawson Pate has created BitByte, a Teensy 4.1-based handheld console with an easy-to-learn scripting language for creating your own games.

The Micro VM language allows games to be edited as simple text files on a microSD card, which is automatically mounted as a mass storage device when connected via USB.

The handheld features a 2.8″ 320×240 LCD display, an ESP32-S3 coprocessor for wireless multiplayer, dual piezos for sound, and 18 GPIO pins for incorporating additional hardware.

The MicroVM language includes tilemap, ray-casting, texturing, and more, in order to facilitate game development.

Games developed in the language are inherently open for analysis and modification since there is no compiled binary. The Arduino IDE can be used to create your own firmware without the VM. The project is currently crowdfunding on Kickstarter.

ChrisT had an idea for a MIDI pedal board that could send MIDI messages to his laptop while playing guitar, to trigger samples, change effects, and play synth pad chords.

After prototyping in software using HTML and JavaScript, ChrisT built a prototype using plastic multi-purpose compartment organizers that might ordinarily be used for storing hardware of the fastener variety rather than electronics.

In addition to the Teensy 4.1 and the plastic box, the foot pedal controller features ten soft-touch footswitches and a 2.8″ ILI9341 TFT touchscreen. A JSON file is used to configure the GUI and functionality, and copied to the Teensy in mass storage device mode, meaning that changes can be made without having to compile and re-flash the firmware. In the initial prototype, five of the buttons send chords (defined in the JSON file), while the other six are used to adjust settings. See it in action in the video below, and check out the source (including for the HTML version) on GitHub.

MikeSound found two old phones from the 50s and 70s in his parents’ basement. Still in good working order, and visually striking compared to today’s drab black slabs, Mike decided to give them new lives as Microsoft Teams/Zoom-compatible headsets using Teensy 4.0.

In addition to headset functionality via the Teensy Audio Adaptor Board, the phone dialer has been retrofitted to output the corresponding digits as a USB keyboard. The ringer really functions (when an audio signal is detected), and lifting the handset sends the corresponding keyboard macro to to the PC application to answer (or plays the 440Hz dial tone when there is no call).

Replacing the handset similarly ends the call, and of course, there’s a Mute button. Schematics and source are available on GitHub, so you too can surprise and delight your colleagues with a retro re-fit of your favorite old Bakelite or candlestick telephone!

A hybrid piano translates traditional acoustic piano action into MIDI (unlike a purely digital MIDI keyboard), giving pianists the best of both worlds.

Greg Zweigle had long wanted to build his own, and has gotten all 88 keys working, using two Teensy 4.1s and a Kawai grand piano action.

Greg is working on several different architectures in parallel; while the aforementioned uses two Teensy 4.1s to handle all 88 keys, a higher-performance version uses two 4.1s for every eight keys plus two for a pedal unit (i.e. 24 for a complete piano).

The system measures and sends hammer velocity and optionally damper velocity over MIDI and can also output the data to optional Adafruit 2.8″ TFT touch screens. Schematics, firmware, documentation and more can be found in the project’s GitHub repo, and if you want to get really nerdy, Greg has published data from piano and piano action measurements in another repo. Much of the journey is also published on Greg’s YouTube channel, such as the latest progress below.

Benkster had a dream of creating the perfect custom joystick for Elite Dangerous.

The dream was a lengthy one, spanning two years and numerous iterations. The current version is a leviathan 3d-printed affair with two 3-axis joysticks, one 2-axis joystick, a heap of buttons, and a tiny OLED display to tell you what’s going on, all powered by a Teensy 4.0.

But beyond their dream keyboard, Benkster ended up creating a wealth of information of value to anyone looking to create their own custom keyboard – which has now been assembled into a comprehensive guide. Because sometimes it’s not the joystick, but the instructions we make along the way.

Lucian_dusk has created a self-described “functional Teensy 4.1-based breakout board for Eurorack modular synth(s).”

Based around the versatile Cirrus Logic CS42448 audio codec, the board features CV input and multichannel audio I/O, with an auxiliary PCB multiplexing five channels into one analog pin. More detail, including schematics, can be found in the original forum thread.

Madgrizzle’s FloydTheRobot is an ongoing DIY ‘bot project with ever-evolving capabilities, the latest being the addition of two quite versatile-looking Teensy 4.1-powered arms.

The controller has four TI DRV8874 H-bridge motor drivers and four ports for Hiwonder HX-35HM Serial Bus Servos. Two PWM servos control pan/tilt of the robot’s camera, and integrated fan management keeps the servos cool.

See it all in action in the video below, driven by the ROS MoveIt motion planning framework.

Sylvain Van Iniitu has open-sourced their Teensy 4.1-based polyrythmic errorist and stochastic MIDI sequencer, Piccolo meant for generative and process-based music.

Featuring MIDI in and out, tap tempo, 16 channels x 4 layers, and 64 layer memories (save/load as .txt on mSD), the system boasts 1ms precision and unlimited notes per layer and loop duration. Delay, variable delay, transposition, harmonization, modulation and other transformations can be applied to sequences — more than 100 in total.

Source code and schematics are available on GitHub, and over an hour of experimental output during its development can be experienced in the video below.