Audio Guestbook

As things finally start to warm up slightly in the northern hemisphere, it feels like only a matter of time until spring celebrations are in full swing.

But how does one stand out among all the “DIY wedding hacks”? One idea that stood out to us is Playful Technology’s Audio Guestbook — an upcycled handset that allows guests to record fun, personal messages.

Hardware-wise, it’s a relatively simple affair: in addition to the Teensy Audio Board and Teensy 4.0, just a few connectors are required to interface with the old copper-network dog-and-bone. Software and detailed instructions are available on GitHub, including numerous community-contributed enhancements to the original project.

The accompanying how-to video’s comments are littered with folks who successfully recreated the project for their weddings — let us know if you’ve made something similar with a Teensy for your upcoming special event … and don’t forget our invite! <3

Smart Cup Holder

The thirst is real, but the question is: how real is it? Are you experiencing a particularly thirsty Thursday, or an unusually dry Sunday? Unless you have the metrics, it can be hard to say for sure.

Pepijn de Vos set out to answer questions like these with the advent of his Teensy 3.1-based Smart Cup Holder.

The device consists of a LEGO chassis, plus a straight bar load cell and HX711 amplifier. Each time the cup is placed on the holder, it is measured, with a negative differential implying hydration, and an increase in weight implying replenishment, with a new threshold to measure against.

Hydration monitoring is accomplished via a GNOME Shell Extension that reads from TTY, or InfluxDB using Telegraf/tail. A write-up about the project can be found on Pepijn’s blog, with source code for the Teensy and Gnome portions, plus building instructions, found on the GitHub repo.

Melodicade MX – 6+ Octave MIDI Keyboard

While QWERTY dominates the world of computer keyboards, there exist many less-common layouts such as DVORAK and various chorded offerings that tout numerous advantages over the dominant format.

Similarly, in the world of musical keyboards, the traditional piano layout dominates, but sundry alternative input layouts offer potential advantages to their users. The Wicki-Hayden layout groups notes in a more logical fashion, and it was this unique arrangement that KOOP Instruments look to explore with their Teensy 4.1-based Melodicade MX.

Building on the arcade-button-based Melodicade, the MX uses Cherry MX-compatible mechanical key switches, which are both smaller and less expensive than arcade buttons, allowing 6+ octaves to fit in the space of 4.5 octaves’ worth of 24mm arcade buttons (while saving about $100!).

A complete build guide, including code, CAD Files, and BOM can be found on the KOOP Instruments web site, and a detailed demonstration of the instrument’s capabilities, as well as a delightful rendition of the Pokke Village theme from Monster Hunter Freedom Unite can be found in the video below.

Netflix “Maniac” GRTA Mainframe

The main antagonist in Netflix’s 2018 series Maniac, the GRTA mainframe computer, is described as the most advanced artificial intelligence ever created.

It seems fitting then, that when forum user waltsatan aka Alan Watts received the call to bring production designer Alex DiGerlando’s vision to life, he selected a Teensy 3.1 to power it.

Gertie, as she is more affectionately known, consists of 1,476 addressable RGB LEDs, along with 7-segment numerical displays, analog meters, and “hard drive” activity lights. The resultant visual output matches the camera’s frame rate in order to allow the computer’s “actual” animations to be used directly, rather than simulated in post. Time-based animations are generated via a custom GUI and PHP script, and run autonomously or in a user-controlled “puppet” mode.

Much like the show’s Dr. James Mantleray, we fell hopelessly in love with this more modern and empathetic version of HAL 9000, and were blown away to learn that Alan created her in under 5 weeks!

IBM Mainframe Console Restoration

We’re big fans of Ken Shirriff, as evidenced elsewhere on our blog, and we like to think he’s maybe a fan of us too, as evidenced by another Teensy-based project in the form of his IBM System/360 Model 50 mainframe marginal check console.

This tactile panel reads knobs and drives a meter over I2C, which in turn connect to Ken’s IBM 360/50 Simulator via the host Teensy 4.1.

As Ken reminds us, The IBM System/360 Model 50 was a powerful mainframe computer in 1964 that could be rented at a modern-day equivalent cost of $150,000 a month, weighed 3 tons, and used 7600 watts, yet has less than a millionth of the processing power of a modern smartphone.

Spectrum Analyzer and VU Meter

The heyday of the Hi-Fi is lamentably behind us, with elaborate consoles that once took pride of place in the living room replaced by slim soundbars under TVs, or often obviated completely as tinny handheld devices become peoples’ only multimedia interface.

But if you want to add a VU meter or spectrum analyser (or both!) to your system, Mark “The Electronic Engineer” Donners has just the (Teensy-based, of course!) thing!

Mark’s solution consists of a custom PCB that houses a Teensy 4.1 (with PSRAM), our Audio Adaptor board, and dual ILI9341 displays.

Source audio can be via stereo line in, or an optional mono electret microphone. Gerbers and firmware are available on GitHub, with complete instructions on Instructables.

MCLZ8 – Zilog Z80 Emulator in TRS-80 Model III

Ted Fried aka MicroCore Labs is back with another Teensy-powered retro rocket! In January we featured the “world’s fastest” Commodore 64, which used Ted’s drop-in 6510 CPU replacement, the MCL64.

With the C64 already off and breaking records, it was time to turn his tuning skills on the TRS-80 Model III.

Like the MCL64, the MCLZ8 is a drop-in replacement for the machine’s original CPU, in this case the 8-bit Zilog Z80. With cycle-accurate emulation already in place, Ted is of course already scheming ways to improve performance, like moving the Model III’s RAM/ROM inside the Teensy 4.1 as well.

Be sure to check the MicroCore Labs blog for updates, and as always, the Projects GitHub repo for schematics and firmware.

MjpegTFT_t4 – Motion JPEG Player

The lines between Single Board Computers and microcontrollers are starting to blur, especially when it comes to powerful boards like the Teensy 4.1.

While displaying video may be trivial on an SBC like the Raspberry Pi — which has all the facilities of a full Linux operating system — a similar task on a MCU typically requires rolling one’s own firmware and potentially even creating custom codecs. PJRC forum member 1337Misom had a go at rolling their own with the MjpegTFT_t4 Mjpeg-like Video Player for the Teensy 4.1 development Boards.

Encoding a file for MjpegTFT_t4 requires ffmpeg and Python, as well as the Teensy Audio Library and forked versions of the Teensy Audio Codecs and ILI9341_t3n, plus Larry Bank’s JPEGDEC library. Add a simple header and AAC audio, and you have a beautifully performant series of JPEGs on your TFT, just like the video below!

Jeannie DIY Synthesizer

Inspired by the Shruthi Synthesizer from Mutable Instruments, German maker and synth enthusiast Rolf Degen set out to create a small, portable, Teensy 4.1-based polyphonic synthesizer.

The entire journey is documented in a 10-page thread on our forum, and represents not only Rolf’s quest to create his dream instrument, but also a great coming together of the Teensy community as folks jumped in to debug, optimize, and provide encouragement.

Rolf’s Jeannie kit produces an incredibly sophisticated 8-voice polyphonic synthesizer, with 15 banks of 63 waveforms, a waveshaper for refining the sound further, and a multimode filter with low/high/band-pass functions. A built-in 16-step sequencer transforms the synth into a tiny groovebox, capable of producing entire tracks.

While the Jeannie is a DIY kit, the surface mount work is done for you, so users get the satisfaction of creating their own instrument without the chore of SMD soldering. Jeannie is available in small batches from Tubeohhm in Germany. Firmware and schematics can can be found on GitHub, while example tracks created with Jeannie are available  on Soundcloud, and Facebook hosts a user support group.