Teensy forum member and M.CU.M.E retrocomputing emulator innovator Jean-Marc is back with yet another emulation project, this time in the form of a MAME (Multiple Arcade Machine Emulator) port and accompanying handheld hardware.

Memory limitations mean that games are spread across several projects, but several hundred are supported overall.

Hardware consists of a Teensy 4.0 and ILI9341 or ST7789 SPI display plus an analog thumb joystick and three buttons. While pictures show a perfboard assembly, there is a KiCad PCB file in the repo, which should facilitate reproduction of the optional I2C keyboard, itself powered by a dedicated ATmega328P.

While sound is not yet supported, and emulation is limited to fairly old hardware, it’s still pretty cool to see Konami’s 1981 hit Scramble running on a DIY handheld. Watch more classics demoed in the videos below, and grab the source and pinout/PCB on GitHub.

ROM emulators have become extremely common for classic consoles like the NES and Game Boy, but what about earlier computers that also used edge-connector-style expansions?

 

HP Series 80 group member Tim Nye developed a Teensy 3.6-based ROM-emulating plug-in module that allows users of the early 1980s pre-PC HP 83/85 and 86/87 to select any of the systems’ available ROMs to be loaded from flash memory.

The board includes some unique features, such as a 6V level shifter to bridge the HP’s bus with the Teensy’s 3.3V logic, and a diode to prevent the HP’s 5V power from flowing via USB to a connected computer during programming. One interesting challenge was that the Teensy needs to boot before the HP, but the /HALT line on the HP’s bus can be driven by the Teensy to only permit the CPU to start once it’s ready.

The board appears to be a one-off with no information on purchasing or creating one’s own, but the HP Series 80 group is an active community, so drop them a note if you have a Series 80 with an empty expansion slot!

With over ten thousand Eurorack modules already available in the world, you’d want to be MAD to create a whole new suite of them.

But Michele Perla is just our type of bonkers, and has created a set of Modular Audio Devices that work together as a bridge between analog synths, MIDI keyboards, PCs, and audio interfaces.

The Teensy 3.6-powered CORE module features USB communication with a host PC, 5-pin DIN MIDI in and out jacks, eight CV outs, 8 gate outs, one clock in and one clock out, and a TFT display with four potentiometers for configuration. The “lite” version features a Teensy 3.2.

The CTRL module connects to the CORE via I2C, and adds up to 24 analog sensors, buttons and LEDs, with three address bit jumpers allowing up to eight CTRL modules to be used together. The intuitively-named CODEC module adds an AK4558 CODEC featuring stereo inputs and outputs, as well as a headphone jack, and aux in/out connectors. VCO, VCF, and VCA modules flesh out the line completely.

A demonstration of the CORE prototype can be found in the video below, with more information available on Hackaday, Facebook, and Instagram.

While the Teensy 4.1 includes a 5-pin USB host header, the smaller 4.0 board, which intrinsically supports the same USB host functionality, exposes bottom-side pads to do so.

The Teensy 4.0 also foregoes the current-limiting circuitry that allows the safe hot-swapping of USB devices. Enter the Teensy 4.0 Minimalist USB Host Shield, the creation of Dave Madison aka Parts Not Included.

The Minimalist USB Host Shield (hereon: MUHS) adds a soft-start current limiter, allowing the host port to slowly ramp up current and handle small surges. It also features ESD protection, a power-conditioning LC filter, and a 500 mA polyfuse to protect the attached Teensy board.

Using standard headers and 12mm pogo pins, all required pads can be connected without any soldering, and a second set of headers enables the resultant stack to be used for breadboarding. Two M3 holes facilitate case mounting of the unified USB unit. KiCAD files, Gerbers, and the complete BOM can be found in the MUHS GitHub repo, and our own USB Host Library is all you need to interface with any connected devices!

While nowadays it’s possible to carry an entire studio in your pocket thanks to smartphone apps like FL Studio Mobile and Cubasis, not long ago the idea of computerizing analog studios was still a relatively new and expensive proposition.

King among such solutions was Digidesign’s Pro Tools — a hardware/software hybrid that cost thousands or even tens of thousands of dollars, yet quickly established itself as the industry standard. As Digidesign opened their software platform to other hardware vendors, the Human User Interface (HUI) was developed in order to facilitate communication with 3rd-party control surfaces. Rather than scoring an old Procontrol off of eBay, PJRC forum member rotabox took the ambitious path of creating their own HUI-compatible automated MIDI controller, powered by dual Teensy 3.6s.

The custom control surface features eight motorized faders and OLED displays, a total of 31 buttons, and a custom PCB and enclosure to tie them all together. The video below demonstrates the controller being used with Pro Tools — somehow it’s still just as cool watching those faders fly today!

Sometimes projects just need a little help from the community to get over the finish line. Forum user letNic posted to our Audio Projects category asking how to monitor a user’s voice while recording it from the microphone, for a more authentic and intuitive “phone” experience.

Veteran forum user oddson jumped in with some suggestions, which worked great and allowed letNic to complete their project. We in turn thought it looked very impressive and worthy of featuring on our blog, hence the post that you are currently reading! So there we have it: another Teensy forums success story! Maybe yours will be the next we feature — send us a tip via the Blog Project Submission category!

Sophisticated, mature home automation systems like Home Assistant allow us to easily set up and monitor sensors around our houses without writing code or developing custom hardware. But where’s the fun in that!?

We think these are the types of thoughts Teensy forum user Fenichel may have been having when he decided to create his own data logging system from scratch, and deploy it around his house in various ways.

The system consists of multiple Teensy 3.5 sensor stations, each based on the same design, though evolving as requirements and applications develop over time. Data is logged to the Teensy’s onboard mSD card, or sent to a Teensy-based base station over XBee. Real-time clocks on the stations’ custom PCBs help keep things in sync.

Bespoke Windows software provides detailed reporting on the collected data, as well as a board manager for configuring the stations. The project is extensively documented in a 46-page user manual, and schematics can be found on the author’s web site.

If you’re familiar with songs like Daft Punk’s Digital Love, then you’re familiar with the way a vocoder can transform the human voice by isolating and filtering multiple frequency bands which can then have their pitch manipulated by a synthesizer.

Synth hacker Chip Audette was curious about using one, so he made his own 16-band vocoder, based on the Teensy 3.6-powered Blackaddr Teensy Guitar Audio Pro.

Chip provides an excellent blog post complete with background on how vocoders work, as well as how he applied this hardware theory to his Teensy software, based on the Teensy Audio Library and Blackaddr’s BALibrary.

The resultant sketch is available on GitHub, though the author suggests it be used as more of a starting point, since many of the choices he made (such as filter frequency bands) were arbitrary. A fun demonstration of his results can be found in the video below.

Early computers like the PDP-8 or Altair 8800 did not include the basic I/O that we take for granted today, such as a keyboard and monitor. Instead, a separate ASCII terminal and printer was connected for input and output, as was the case with IBM’s 1959-vintage scientific computer, the 1620.

The wonderful team at the Computer History Museum in Mountain View, California have recreated the experience of using the 1620, but with more reliable modern hardware, yet when it came to I/O, suitable period candidates were becoming harder and harder to find. So, they created their own console typewriter by modifying the far more available IBM/Lexmark Wheelwriter 1000 with a custom serial interface board, based around a Teensy 3.5.

The hybrid Cadetwriter can connect via RS-232 or USB to any retro minicomputer or mainframe as a substitute for harder-to-find vintage teleprinters. Configuration via jumpers extends its utility as a standard ASCII terminal or standalone typewriter. Complete details on how to create your own can be found on the GitHub repo, with PCBs conveniently available to order via OSH Park. An extensive presentation from 2019’s VCF West event can also be found on YouTube.

Remember when MP3 players used to have music visualizers, so that you could see what you’re hearing?

Neither do we, because we’re totally not that old, but maybe there are other folks out there who do, and this project appeals not only to them, but to music students and anyone wishing to gain insight into chords and music theory. Teensy forum user gav shared a unique device that not only synthesizes MIDI data as audio, but also displays it via a 12-note spiral LED visualization.

Using MIDI file playback on a PC with the Teensy plugged into it, or a USB MIDI device plugged into the board’s USB Host Port (or both), it’s possible to observe chords as the same “shape” around the spiral, regardless of key. The brief persistence of notes as a histogram also enables the inference of key signatures.

Additional details and code can be found on GitHub, and a demonstration of this incredible visualization technique can be seen in the video below.