MIDI to CV/Gate The Easy Way

Let’s say you’ve got a modular synthesizer. You’re probably a pretty cool person. But all your cool laptop DJ friends keep showing off their MIDI-controlled hardware, and you’re getting jealous. Well, [little-scale] has the build for you.

The Teensy 3.6 is the current top-of-the-line Teensy from PJRC, and it’s [little-scale]’s weapon of choice here. With USB-MIDI and two 12-bit DACs on board, it’s made creating an interface between the worlds of analog and digital music into a remarkably simple job. Control voltages for pitch and velocity are pushed out over the analog pins, while pin 29 is used for gate signals.

It’s a testament to the amount of development that has gone into the Teensy platform that such projects can be built with virtually no off-board components. The build is a further step forward in simplicity from [little-scale]’s previous work, using a Teensy 2 with an offboard DAC to generate the output voltages.

Here at Hackaday, we’ve always been big fans of adding computer control to analog hardware. This CNC mod to a guitar pickup winding machine is a great example.

The Monolith Brings the Boom to Maker Faire

[Ross Fish], [Darcy Neal], [Ben Davis], and [Paul Stoffregen] created “the Monolith”, an interactive synth sculpture designed to showcase capabilities of the Teensy 3.6 microcontroller.

The Monolith consists of a clear acrylic box covered in LED-lit arcade buttons. The forty buttons in front serve as an 8-step sequencer with five different voices, while touch sensors on the left and right panels serve as a polyphonic arpeggiator and preset controller, respectively.

In order to control all of those buttons, the team designed breakout boards equipped with a port expander, 16-channel PWM driver chip, and N-channel MOSFETs allowing the entire synth to be controlled from a single Teensy 3.6.

In terms of software, [Paul] made improvements to the Teensy Audio Library to accommodate the hardware, improving the way signal-controlled PWM waveforms are handled and enhancing the way envelopes work. Ultimately they combined three Arduino sketches into one to get the finished code.

After showing off the project on Tested, the team set up the Monolith in the Kickstarter booth at Maker Faire Bay Area. The project was a hit at the Faire, earning a coveted red ribbon and inspiring countless adults and kids to check it out. We love a project that inspires so much interaction. Not only can three people play with the Monolith at once, but they can see through the clear case and get an idea of what’s going on.

If you want to learn more you can download project files from [Paul]’s GitHub. In the meantime, check out some other synth projects we’ve published on Hackaday: we’ve grooved on a synth-violin, a 3D-printed synth, and a single-PCB synth, among many others.

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A Full Speed, Portable Apple //e

A while back, [Jorj] caught wind of a Hackaday post from December. It was a handheld Apple IIe, emulated on an ATMega1284p. An impressive feat, no doubt, but it’s all wrong. This ATapple only has 12k of RAM and only runs at 70% of the correct speed. The ATapple is impressive, but [Jorj] knew he could do better. He set out to create the ultimate portable Apple IIe. By all accounts, he succeeded.

This project and its inspiration have a few things in common. They’re both assembled on perfboard, using tiny tact switches for the keyboard. The display is a standard TFT display easily sourced from eBay, Amazon, or Aliexpress. There’s a speaker for terribad Apple II audio on both, and gigantic 5 1/4″ floppies have been shrunk down to the size of an SD card. That’s where the similarities end.

[Jorj] knew he needed horsepower for this build, so he turned to the most powerful microcontroller development board he had on his workbench: the Teensy 3.6. This is a 180 MHz ARM Cortex M4 running a full-speed Apple IIe emulator. Writing a simple 6502 emulator is straightforward, but Apple IIe emulation also requires an MMU. the complete emulator is available in [Jorj]’s repo, and passes all the tests for 6502 functionality.

The project runs all Apple II software with ease, but we’re really struck by how simple the entire circuit is. Aside from the Teensy, there really isn’t much to this build. It’s an off-the-shelf display, a dead simple keyboard matrix, and a little bit of miscellaneous circuitry. It’s simple enough to be built on a piece of perfboard, and we hope simple enough for someone to clone the circuit and share the PCBs.

Introducing The Teensy 3.5 And 3.6

Paul Stoffregen has built a new Teensy. The latest in the line of very powerful, USB-capable microcontrollers is the Teensy 3.5 and 3.6 development boards. It’s faster, more capable, and bigger putting even more pins on a solderless breadboard.

The first Teensy was one of the first Arduino compatible boards with native USB. The Teensy 2.0 was even better with support for USB keyboards, mice, and MIDI. Even today, the Teensy 2.0 is the de facto board to use if you want to build anything like a USB keyboard. The Teensy 2.0 was followed by the exceptionally powerful Teensy 3.0, the first 32-bit Arduino compatible board, and thanks to Paul’s contributions of a pile of Arduino libraries, doing cool stuff faster has never been easier. Since the launch of the Teensy 3.0, its successors, the 3.1 and 3.2 have launched. If you want the power of an ARM microcontroller with the deepest Arduino library support, there’s only one board you should consider.

Like the launch of the Teensy 3.0, Paul is Kickstarting the launch of the latest Teensys with a crowdfunding campaign. Let’s dig into everything these new boards have to offer.

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