If you’ve ever wondered how a guitar tuner works, a recent post by forum user jpk unravels the mystery through a project in which they built their own DIY instrument tuner using a Teensy 3.6 and the Teensy audio library.

In the project, jpk uses fft frequency estimation and the Yin algorithm from the Teensy audio library to determine the accuracy of the incoming frequency in hertz. The device also includes a metronome so musicians can keep time, an LED indicator that responds to the note’s accuracy, and a display.The Teensy 3.6 version includes an LED indicator and display. A newer Teensy 4.0 version includes a speaker, rotary encoder, button, and lithium-ion battery charger. Jpk even made custom wood enclosures with transparent lids (so you can see the handiwork) to house both models. If you’d like to try it out yourself, jpk generously shared the project files to our forum.

Jeremy dePrisco has designed and fabricated a Teensy breakout printed circuit board that allows easy access to I/O pins with nearby ground and voltage rails.

Jeremy dePrisco is a musician and electronics tinkerer who uses Teensy in a number of his projects. He wanted a an easy way to connect in sensors to his Teensy boards, so he made a simple but effective breakout board. You can read about the design process on dePrisco’s website, and you can also buy the board on his Tindie page.

Retired Boeing engineer turned microcontroller tinkerer Frank Adams posted this Instructable showing how to build your own USB laptop keyboard controller using a Teensy LC for over seventeen different models of keyboards.

The tutorial includes step-by-step guidance with detailed, annotated photos walking makers through the process from start to finish including in-depth technical information about keyboard design and control. Frank’s instructions are so detailed that even ambitious beginners could likely follow along with this challenging hardware project while learning a ton about how keyboards work, PCB design, and hardware manufacture. Frank includes software control files for over seventeen different keyboards from Dell, HP, Sony, Lenovo, IBM, Acer, Toshiba, and MSI. In his post to our forum, you can see a beautiful wooden case that Warren made using basic carpentry tools and a link to the source code for the Teensy LC. For those who would like to replicate Frank’s PCB, those files are included at the bottom of the tutorial. Frank also includes a video with the tutorial which he posted to Youtube that shows the process from the design of the circuit board for the Teensy through to programming and final install.

 

Interactive artist and sound designer Josh Wilkinson’s project Harp of the City is an installation made up of fourteen carved wooden harps with playable LED-illuminated strings.

As Josh explains in his post to our forum, each harp is powered by a Teensy 3.6 which generates a PWM signal in keeping with the amplitude of the person’s touch. This is used to increase the brightness of the LEDs behind each string while at the same time triggering polyphonic sound samples via the Teensy audio library. The installation was built for the Vivid festival in Sydney Australia which was hosted in 2019. You can explore more of Wilkinson’s sound and interactive installation work on his website.

In the 1970s, personal computers entered into the household market for the first time. You’ve likely heard of or even owned earlier Apple or IBM models, but the Exidy Sorcerer might not ring a bell despite it possessing some truly innovative features not to mention a theatrical name.

The Exidy Sorcerer was released in 1978 shortly after the Apple II and was the first computer to come with an onboard cassette tape player. The player’s interface is, by modern standards, lacking with a baud rate of 300 or 1200, but that didn’t stop forum user Citabria from developing a really interesting upgrade solution using a Teensy 3.5.

Citabria describes the process of replacing the cassette interface with a Teensy 3.5, using the onboard SD card reader to transmit the software at a baud rate of 20833. In the forum post linked above, Citabria illustrates how to connect the Teensy to the Sorcerer’s motherboard (replacing the daughterboard used by the original interface) over UART and explains a bit about the development process.

 

 

Software Engineer by day, DIY synth hobbyist by night, Mark Culross invented this 16 note, 2 voice MIDI synthesizer

based on a Teensy 4.0 and the Teensy audio board.

Culross, who develops hardware in his spare time, was ordering a PCB from OSHPark when a Teensy board popped up as a optional add on. Mark had never heard of a Teensy before but thought he might as well go ahead and order it to see what he could make with it.

When he discovered the Teensy audio board, he knew immediately what he wanted to make. Mark’s project and his reflections on the trials and tribulations of the build are well documented in his forum post where in addition to the technical details he also shares the link to his source files, schematics, and photos on drive. To help provide an idea of the synth’s capabilities, Mark has recorded and shared numerous videos of the synth in action playing everything from circus music to Bach’s Toccata and Fugue.

 

Forum user gi1mic has developed a low cost animated 128 x 32 display which can be used as a marquee for a full-sized MAME cabinet.

Gi1mic generously shared their source code which allows users to create the full 128 x 32 display or with some small changes use single panels or level up to a 256 x 32 layout. Instructions for assembling the hardware are also provided in the same repository.

Gi1mic used Teensy3.6 with the SmartMatrix library and SmartMatrixvV4 interface to create a simple command line protocol that allows users to browse the contents of the attached SD card, upload and download files using the ZMODEM protocol, change directories, display text messages and display animated GIF’s on the attached LED panels. Users can upload any GIF with a resolution of 132 x 64 and see it faithfully animated across the panels.

MAME (or Multiple Arcade Machine Emulator) is a command-line application that documents and replicates the hardware of antique arcade cabinets through software, enabling users to play thousands of classic arcade games like PacMan, Galaga, and Bubble Bobble using their own hardware. A fourth release was just announced for the MAME software which you can can download via their website or you can keep up with the latest development on their Github.

Some things are more complicated than they appear at first glance. Take, for example, the metal strings of a musical instrument.

How are these made? Forum user jpk generously shared the results of the two years he spent building his own metal musical string winder.

To accomplish the project, jpk used a Teensy 3.5 to handle button input, display output, and calculations and a Teensy 3.6 that handles motor movements, both set into custom PCBs. The machine can also be used to spool wire. Jpk has made his source code for the project available on Github as well as a timing library and a debouncing library he developed for use with the project. Below is a photo of a completed wound wire that uses copper and aluminum to produce a string that is 0.7mm in diameter.

MIT Media Lab have developed the new and improved Knitted Keyboard II using electrically conductive, capacitive and piezoresistive fabrics and fibers.

The Knitted Keyboard II, from Irmandy Wicaksono and team, is a multi-modal, soft and stretchable e-textile musical interface. It responds to touch, including keystrokes, pressure, squeezing and pulling, and continuous proximity, such as hovering and waving. This means that you can play it in a range of ways: like a keyboard, a theremin or as something that is a mixture of the two. You can even wear it like a scarf.

MIT’s Knitted Keyboard II runs on a Teensy 4.0 and uses five MPR121 proximity/touch controllers. It uses MIDI and can therefore sound like any software instrument you have access to, making it incredibly versatile.

Check out Hackaday’s coverage of the Knitted Keyboard II or read the MIT project overview for more detail on this project.

The Audio shield is on sale for Black Friday (sale has ended), with sockets and a flash memory chip included.