YouTuber Computer Hardware Tips and Tutorials (CHWTT) wanted a device that could control individual app volumes on their PC. Inspired by the deej project, they created a Teensy 4.1-based five-channel mixer that would look at home in any professional studio.

Mimicking expensive broadcast mixers like the GoXLR, the device features five motorized faders with OLED scribble strips above each. Additional buttons allow mixes to be stored and recalled, as well as channels to be instantly muted. Teensy’s USB MIDI functionality is combined with MIDI Mixer software to allow control over individual PC app volumes via dedicated faders, as well as represent any adjustments made via software, thanks to their motorization.

A wonderfully detailed build guide is available on Instructables, including STEP files for the custom CNC’d faceplates, STL files for the 3D-printed parts, full bill of materials, and source code. Learn more and see it in action in the video below!

Yongsup Park has created a high-speed Teensy-based pulse counter with reliability down to a pulse width of 20ns or less — performance which typically requires equipment costing hundreds, or even thousands of dollars.

Using the FreqCount function, Yongsup iteratively reduced the pulse width until behavior became erratic. The Teensy 4.1’s 600MHz clock gives a theoretical resolution of 1.67ns, and was observed counting as little as 9ns pulse widths at 50MHz. The Rigol DG912 Pro waveform generator being used to test it has a rise/fall of 3ns, so reducing further would have been hard to measure anyway.

The pulse counter is part of a larger data acquisition app that runs in the browser without the need for a computer, using a Teensy 4.1 as a web server, USB device controller, and pulse counter. Testing results, code, and more can be found in the original forum thread.

alnwlsn has used a pair of Teensy boards to take control of a robot arm that they recovered from surplus.

The 70lb lab-grade arm came with no software, but was still in running order. Instead of an FPGA, alnwlsn choose the powerful Teensy 4.1 to replace the embedded 486, FPGAs, and DSP chips that controlled the original. The main control loop is handled via IntervalTimer, which runs PID controllers, reads encoders, and writes to motors.

A custom PCB provides DACs for the ±10V analog signals required by the motor amps. A surplus control box refitted with a Teensy 3.2 provides manual control, and a mini reproduction of the main arm enables mimicry of its manipulation by the larger unit. 16MB of PSRAM allows several minutes of motion recording and playback, and the SD card stores encoder positions between reboots, to prevent the need for calibration each time. alnwlsn says that almost every pin on the Teensy is used for something, and you can see them in use in the video below!

MikeSound has created the midiGPIO MIDI to arbitrary hardware I/O interface.

Often in music or art projects, sensors are used to trigger audio or other events via MIDI, and sometimes in the other direction too. For example, a sound effect of a door creaking that triggers when as it opens on stage, or turning on lights in response to the playing of a particular note. The self-contained unit provides four 3.3V inputs and four 3.3V outputs, and supports USB and serial MIDI. When a rising edge is detected on an input, a MIDI Note-On message is sent; similarly, a Note-Off is sent on a falling edge. The input edge detection can also be used to trigger a MIDI program change. Outputs are controlled via MIDI Note-On and -Off as well.

Check out the GitHub repo for source code, schematics, and more detail.

Ken Shirriff retrofitted Douglas Engelbar’s 1960s era keyset from his famous “Mother of All Demos” to connect to USB so that it can be used with today’s computers.

We love Ken Shirriff projects, and Ken Shirriff seems to love Teensy too, if the number of our boards we’ve seen used in his various retrocomputing restoration projects are anything to go by. Ken apparently managed to get a loan of one of the original “keyset” devices from Douglas Engelbart’s famous “Mother of All Demos,” during which the concept of a computer mouse and GUI were introduced to the public for the first time. That the keyset was also introduced to the public for the first time at the event is perhaps less worthy of mention, since it didn’t catch on in the same way as some of the other demonstrated tech which we now take for granted. While chorded keyboards are still a thing (particularly among stenographers), and we’ve even shared a Teensy 4.1-powered recreation of Engelbart’s chording keyset on the blog before, it’s certainly a niche device, and Ken even concludes his blog post by saying that he found it hard to use, both physically and mentally. But the cool thing is that he made it work, so let’s focus on that!

Ken’s project is based around the Teensy 3.6’s ability to act as both USB device (connecting to the host PC) and USB host (for connecting a standard USB mouse, required to get the full range of outputs, by being pressed in conjunction with the keyset keys). The Teensy is connected to the keyset’s standard DB-25 connector, with a 1kOhm pull-up resistor on one of the lines, in addition to the Teensy’s own onboard pull-ups on each. Code was added to pass through mouse input, except when used in conjunction with the keyset, as well as output the resultant characters as if it were a normal keyboard. Ken goes into glorious detail on the background of the device and its famous demo on his blog, and has shared the code on GitHub. While he may not have fallen in love with the keyset workflow, we are enamoured with the incredible journey he took to reach that conclusion.

HexeFX, whose Jaws-themed guitar effects pedal we’ve featured in the past, is back with the fully open-source TGX4 amp modeler and multi-FX pedal.

The project consists of both software and hardware. The software is designed to be compatible with a range of Teensy-based platforms beyond the dedicated TGX4 hardware, including a simple Teensy 4.0 with the Audio Adaptor board installed. The project’s hardware design encapsulates a high-quality audio DSP designed specifically for use with guitar and bass instruments in a pedal-form device. Combined, they feature eight amplifier models, ten cabinet impulse responses for sound reproduction, a stereo enhancer for double track emulation, a compressor, wah, noise gate, three-band EQ with high-pass filter, three types of reverb, and more. Assignable expression pedal input, three assignable potentiometers, and a 3.5″ touch screen provide the interface to all of this. An SD card allows storage of 128 presets, and MIDI control, including via web page, enables interaction with other devices.

More information on the software development can be found on the PJRC Forum

Firmware, hardware, and many more details can be found on GitHub, and a demonstration of the pedal’s capabilities can be enjoyed in the video below.

Christopher Rees loves LEDs. So when he got the request to put together a display for the Tremonton City Lions Club Pumpkin Walk, he of course went all-in.

His Teensy 3.2-powered display features 184 RGB 5050 LEDs, three 10-watt RGB floods, three 20-watt RGB floods, and a whole bunch of PVC pipes and custom wiring. A rack-mounted controller manages the system using xLights.

The show is choreographed to a custom mix of Ghosts ‘n’ Stuff by deadmau5, as can be heard in the video below!

Folkert van Heusden has added Teensy 4.1 support to a microcontroller-focused PDP11/70 emulator.

The system is capable of running UNIX 5 with disk, tape, and serial support, plus 4MB of RAM, an MMU (memory management unit) and high-performance 16-bit 11/70 CPU. It takes around a minute to boot, though can create snapshots for resumption of previous sessions. Teensy 4.1 Ethernet is supported, and a simulated front panel provides plenty of lovely (and functional!) blinkenlights.

More information can be found on the project’s web page, and the source is on GitHub. You can also reach an instance of the software via telnet on pdp.komputilo.nl (username: guest), and via HTTP at http://pdp.komputilo.nl:8080/

Nick Culbertson is back, with an attempt at recreating the “world’s most iconic” analogue synth using a Teensy 4.1.

If you haven’t guessed yet, we’re talking about the Bob Moog’s 1970 Minimoog Model D — the “world’s first” portable synthesizer, which could be played easily and instantly with no complex patches to deal with. You may recall Nick, aka Mob Pixel on YouTube, from the Teensy 4.0-powered “world’s smallest MIDI controller,”

In his video, Nick walks through the fundamental concepts of subtractive synthesis, highlighting oscillators, filters, envelopes, and more, and how they relate to his Teensy implementation of the original Minimoog. The resulting instrument is a six-voice polyphonic synth with three oscillators per voice and six waveforms per oscillator, a 24dB Moog-style ladder filter with ADSR envelopes, and independent LFO with pitch/filter/amp targets, and power, MIDI data and audio all flowing over Teensy USB. Twenty rotary encoders and a 16×2 LCD provide hands-on control.

Code, bill of materials, pinouts and more can be found in the project’s GitHub repo, and a detailed walk-through can be enjoyed in the video below.

Ben Gruver’s lalboard is inspired by one of the most unconventional commercial keyboards of all time: the magnetic/optical two-piece DataHand.

We’ve seen a number of interesting and unique Teensy-based keyboards over the years, such as one that only has two keys, or one that uses individual floppy disks to input each letter. The lalboard is among the more unique keyboards that we’ve seen.

A long-time user of the original DataHand, Ben sought to create an affordable replacement in response to the rising cost of second-hand units. While the layout, functionality, and use of magnets for key return force and optointerrupters to sense position are all directly inspired by the DataHand, the primary goal of the project was to ensure that it could be reproduced using a standard FFF 3d printer. The project improves on the adjustability of the original, with each key cluster gaining six degrees of freedom. The handrests were moulded using plasticine clay, and then scanned using photogrammetry software. Each half of the keyboard uses its own Teensy 2.0 running a modified version of Ben’s original teensyhand firmware, and connected via I2C so that only one USB connection is required for the attached PC. Find the BOM, instructions, and more on the project’s GitHub repo.