AudioToy – 8×8 Channel Audio Mixer

Thanks to the Teensy Audio Library, palmerr used a Teensy 4.0 to particularly stunning effect with his CS42448-based AudioToy 8×8 channel modular mixer.

This pro-grade piece of kit features fully balanced, software gain-controlled line/instrument inputs and 600 ohm/+8dBm outputs, with combo XLR/TRS sockets whose insertion status can be remotely read over I2C. An ESP32 allows remote control via Wi-Fi, while  WS2812B LED strips indicate channel levels.

Complete hardware details for its component modules, as well as a user manual, can be found on GitHub.

Rotary Dial Numeric Keypad

Jp3141 decided traditional numeric keypad was far too efficient and the rotary dialer from an old AT&T Trimline phone would make any Excel spreadsheet or other data entry task far more enjoyable.

Teensy’s HID functionality makes it a great candidate for your latest rad keyboard project, but as we’ve covered elsewhere, this double-edged sword also means it’s perfect for all manner of bizarre prank input devices as well.

A Teensy 3.x or LC is used to read the pulses from the dialer, then convert the positive pulses to the corresponding number and send the keystroke via USB as if it were a normal keyboard. STL files for the enclosure and source code can be found in the project’s GitHub repo, and you can watch (thankfully only) the first six digits of pi being entered in the video below!

OctoWS2811 Power Injection Board

We love LED projects, and we especially love big LED projects.

But big LED projects require big power, and involve big distances, which is where PJRC forum member bamos’ OctoWS2811 Power Injection Board comes in handy.

This simple board connects to OctoWS2811 Adaptors or bamos’ Teensy Pixel Pusher via Ethernet cable, enabling the connection of up to four LED strands at remote locations, with the added bonus of power injection at the site.

Design files are available on GitHub, and preassembled boards, as well as kits and unpopulated PCBs, are available on Tindie.

APRS Tracker

Rvnash has developed code to output the required tones to transmit APRS (Automatic Packet Reporting System) packets on the Teensy 3.1’s DAC pin, which is then modulated to the required frequency using a Radiometrix HX1 transmitter module.

APRS is a radio-based system for relaying various data of interest to users in the broadcasting region.

As is often the case on the PJRC forums, various other members were inspired by the project, including Malaysian ham enthusiast Stanley, who used it to upgrade their own open-source APRS Tracker, SVTrackR. rvnash’s code, as well as Stanley’s project, are available on GitHub.

Air Quality Monitor

JBeale created a quick solution to monitoring air quality as the 2020 Oregon wildfires raged, eventually burning over 1,000,000 acres.

Tracking indoor CO2 PPM levels emerged early in the pandemic as a way to measure one’s local environment for stale air and the increased likelihood of disease transmission. But measurements such as CO2 levels and the Air Quality Index (AQI) have also entered the public consciousness due to frequent large wildfires in recent years, and the propensity for their effects to spread well beyond their origins.

The system consists of a Teensy 3.1 connected to a Plantower PMS5003 laser particle sensor, with a small OLED display presenting time series data from the sensor. Initial test measurements showed particle pollution levels of 3-5 PM2.5, but the wildfires brought readings to 90 indoors and 380 outdoors. The resulting thread also brought out AQM projects from other forum members, as well as JBeale’s own Teensy 4.1-based evolution that uses the built-in mSD for data logging. The original sketch is available on GitHub as part of JBeale’s DataAcq collection of data acquisition tools.

Replica of the EnsoniQ Mirage Synth

Alessandro Fasan and his team of Ensoniq enthusiasts are bringing this classic synth back to life via Teensy!

The MOS Technology 6581 SID. The Yamaha OPN and OPL chips. General Instruments’ AY-3-8910. These legendary sound chips are perhaps not quite household names, but have obtained a cult following with legions of fans each declaring their allegiance to one as the superior sound generator. When the SID’s designer, Bob Yannes left MOS, he co-founded Ensoniq, and designed the 5503 Digital Oscillator Chip (DOC) at the heart of the groundbreaking Ensoniq Mirage sampler synth.

The ALFASoniQ Mirage II began development a Teensy 3.5 coupled with Erturk Kocalar’s Retroshield 6809 housing the DOC (Digital Oscillator Chip). The system is capable of booting the alternative Mirage operating system MASOS 3.2 from SD, and while not all of the voices and modes are functional, full polyphony is supported. Source code can be found on GitHub, while the video below gives a demonstration of the project’s state.

More recently, the ALFASoniQ has moved to development on Teensy 4.1 with software emulation of the 6809 chip. This quick video demos show the project’s progression to utilizing the more powerful hardware to implement more Ensoniq capability.

DIY Drum Sequencer

Step sequencers have been around since at least the 1960s, and from the 1980s and beyond became a very common sight as the number and variety of digital instruments exploded.

This DIY Drum Machine from Robert Robert on YouTube is a unique blend of the two, with a huge number of switches and knobs up front, but a Teensy 3.6 and Audio Adaptor Board generating the beats behind the scenes.

Most step sequencers have 16 buttons with LEDs to indicate on/off status, which are reused in order to create multiple tracks and thus produce layered sounds. This device has a dedicated row of 16 switches for each of its ten tracks/samples, with 16 LEDs above them to indicate which note in the sequence is currently playing. Momentary switches on each row allow the same samples to be triggered at any time, and 10 potentiometers allow the volume of each sample to be adjusted, also effectively allowing a track to be muted. Four additional buttons and knobs allow a further four samples to be triggered at corresponding volumes. A 16×2 I2C LCD display and further knob allows configuration of parameters such as BPM. See it in action and learn more about its construction in the video below!

Repeater Controller GPS Time Source

The Arcom RC210 Advanced Repeater Controller is a popular solution for managing multiple amateur radio repeaters. It has a built-in real-time clock (RTC) for scheduling and other features, but extended power outages and other factors can cause it to drift.

MatA came up with a great solution to this problem in the form of their GPS Time Source project.

Initially based on an Arduino, MatA switched to the Teensy LC on recommendation from a friend, greatly enhancing the project’s capabilities thanks to increased memory and processing power over the original. A custom PCB holds the Teensy, GPS module, LCD display, and DB9 connectors for interfacing to the repeater controller. Find out more on the project’s web page.

Aeroponic Garden Monitoring

The idea of aeroponics — growing plants in an air or mist environment rather than soil — has been around for over a century, yet somehow it always appears very high-tech and novel in practice.

To make things even higher-tech, boomish designed a custom aeroponic garden monitoring system, based on a Teensy 4.1.

The system uses a custom PCB, which incorporates an LM2596S buck converter and TI P82B715DR I2C extenders to give the humidity sensors further reach. The TI HDC1080 low-power digital relative humidity sensors used have a single hard-coded I2C address, so an Analog Devices LTC4316CDD#TRPBF I2C address translator is used to allow them to coexist on the same bus. After creating a successful aeroponic monitoring system, boomish went on to create a SQL-backed hardwood floor humidity monitoring and logging system, with the exciting additional feature of Power over Ethernet (PoE).

ThinkPad TrackPoint Translator

ThinkPad keyboards and TrackPoint pointing devices are somewhat legendary, with many connoisseurs preferring older IBM models to current Lenovo products.

It’s no surprise then to see a late 90s IBM ThinkPad 380ED’s peripherals still in use today, although doing so presents a challenge in that unlike newer models, the resistive strain gauge that measures TrackPoint input does not convert it to PS/2.  Frank Adams (thedalles77) has once again solved this challenge as part of the larger USB Laptop Keyboard Controller project.

The project consists of a custom PCB, in order to provide the required connectors, an Analog Devices AD8236 Instrumentation Amplifier reading each channel of the strain gauge, and TI LM358 op-amps providing a reference voltage. Code and documentation can be found on GitHub, with additional detail on Hackaday, and a detailed overview in the video below.