Blog Posts

Brace yourselves, because Ted is back with — any guesses? Yep, another drop-in emulator, this time for the 16/32-bit Motorola 68000!

Ted Fried aka MicroCore Labs has been featured a fair number of times on the PJRC blog with his Teensy-based drop-in CPU replacements, including the MCL65-Fast Apple II Accelerator, MCLZ8 Zilog Z80 (RIP!) emulator, and MCL64 Commodore 64 Accelerator.

The MCL68+ emulates both the 68k itself, and the local bus interface (at full speed) thanks to Ted’s prior experience and some new tricks. In the case of the Macintosh 512K, the MCL68+ is able to substitute for the original CPU, while bit-banging the bus at the required 7.8MHz. Byte-wide latches based on 74HCT574 flip-flops are used to power the address and data busses due to the sheer amount of I/O required to emulate the m68k. As always, source code can be found on GitHub, and you can see it in action below.

We’re big fans of Emmanuel Presselin’s original Teensy 3.2-based MiniTouch low-cost synth for children’s music workshops, so we were keen to find out more details when he mentioned a new Teensy 4.0-based MiniTouch 2nd Edition!

The MiniTouch 2.0 features a larger 18-note capacitive touch keyboard, two oscillators (up from one), 8-voice polyphony (from 4), FM and AM “ring” modulation, a noise generator with ladder filter, high- and bandpass filters in addition to the existing low-pass, per-voice filters (with note tracking) vs. a single global filter, and delay and reverb effects. A MIDI interface, EEPROM-backed presets, USB MIDI host, and a new PAM8406 class-D amplifier and larger speaker all bring quality-of-live improvements, while still remaining accessible for workshop participants with around a $35 BOM cost. See it in action below!

ThirdEarthDesign has shared their first project, a sim rig button box.

Based on the Teensy 4.1, it uses a custom joystick interface via USB HID to extend the functionality of an already-impressive rig.

The “box” features 13 momentary buttons, three toggle switches, two eight-way rotary switches (effectively 16 more inputs), X and Y axis inputs via two further rotary encoders, and Z axis via analog Hall effect sensor.

WS2812 RGB LEDs provide backlighting, and two PWM fans simulate the feeling of wind! A 3d-printed enclosure, Cricut-created labels, and a custom PCB round out the professional-looking package. More information and pics on the PJRC forums.

PJRC forum member lokki, who you may recall from their unique MIDI Bass Guitar project, is back with another fun musical creation, this time in the form of an infrared foot controller.

Based on the Teensy 4.0, this project uses USB Host to transmit the X-Y position of an object (such as a foot) inside the frame to a connected computer; sort of like a giant Kaoss Pad for your toes! In addition to the IR frame, WS2812 LEDs along the edges help indicate the detected coordinates, and four big buttons allow the user to switch between modes.

More information and source code can be found on the PJRC forums, and a demonstration can be seen in the video below.

PJRC forum member Nick Culbertson, who you may recall from the (“world’s smallest?”) Mini MIDI Controller project, is back with more Teensy-based synth goodness, this time in the much larger, cigar-box-sixed Teensy Arcade Synth.

Built around the Teensy 4.0 and Audio Adaptor Board, the project incorporates a rotary encoder and LCD display for selecting parameters, and the eponymous eight 30mm arcade buttons to mash out three-layer polyphonic jams. The Teensy Audio Library was used to do all of the heavy DSP lifting, leaving the GUI and parameter implementation as the “hardest” part. Code and wiring details are available on GitHub, and an excellent tutorial and demo can be enjoyed in the video below.

PJRC forum member MarkusGruen has developed RTMC (Real Time Measure and Control), a universal data acquisition, logging and I/O system. The Teensy 4.1-based platform enables data capture from any I2C, SPI, RS-232, or analog sensor.

Data can be sampled from eight sensors simultaneously at up to 4.4KHz, then transmitted via USB to a host PC for further analysis. The I/O aspect of the system means that actuators can also be connected to create closed-loop control systems. Raspberry Pi Pico-based node units connect to the Teensy-powered hub via standard Ethernet cable. More information about the project, as well as Gerbers, BOMs, schematics and firmware source can be found on GitHub.

PJRC forum member DrM is back with another CCD (charge-coupled device) project, this time a controller for the Hamamatsu S11639-01 linear CCD sensor, with the aim of making high-end scientific instruments more affordable and accessible.

A GitHub repo provides KiCad files and firmware for the sensor/controller set. Some optional register-level enhancements take advantage of the Teensy 4.0’s i.MX RT1060 to provide improved interrupt latency and more efficient SPI transfers from the board’s 16-bit ADC. The included firmware presents a command-line interface over serial for easy interaction and operation. A Python utility and class library facilitate integration into other systems.

YouTuber Stuff Made Here has shared the latest evolution of his intelligent basketball hoops, this time in the form of the ball-seeking hoop.

Powered by a Teensy 3.6, this robotic backboard moves through three-dimensional space to ensure every shot ends with a satisfying swish.

A specially modified basketball’s position is tracked via eight OptiTrack motion-tracking cameras, with the resulting data used to calculate its trajectory in real time.

Six large motors and a pulley system allow the hoop to position itself anywhere in the room, ensuring a perfect shot every time.

See it in action and learn more about how it was made in the video below.

After more than a year of development, sucofunk has released the Beatmaker’s Sketchbook, a Teensy 4.1-based sampler and sequencer. Designed as an open-source alternative to OP-1s and MPCs, it follows a “Sample, Sketch, Arrange, Play” workflow to help take your ideas from simple noodling to live performances.

In addition to the Teensy 4.1, the Beatmaker’s Sketchbook features a 24-key (two octave) keyboard, 12 functional keys, four endless rotary encoders, a 10mm fader, 2″ LCD display, and 32 LEDs. A built-in microphone and 3.5mm line-in facilitate sampling, while line out, MIDI in/out, and headphone output help connect to all of your other gear.

The project’s firmware and hardware can both be found on GitHub, and you can see it in action in the video below.

Andrew J. Harvie and John C. de Mello have created OLIA, an open-source digital lock-in amplifier. Digital lock-in is a method for isolating weak signals to facilitate measurement amongst background noise, which is processed away via digital signal processing (DSP).

The Open Lock-In Amplifier (OLIA) is a Teensy 4.0-based system that can outperform far more expensive commercial devices for around $35. OLIA offers dual-phase lock-in detection at multiple harmonic frequencies up to 50KHz, adjustable levels of input gain, and a comprehensive API for remote control. An optional breakout board allows optical detection down to 40 pW. Complete details about the project, as well as firmware, schematics, and BOM can be found in the original research paper.