Thea Flowers' Winterbloom Sol Module Offers Eurorack Compatibility and CircuitPython Programmability

Designed for easy re-programmability via CircuitPython, the 8HP Eurorack module is a flexible piece of open source hardware.

Synthesizer enthusiast Thea Flowers has opened pre-orders for the world's first Eurorack module designed to be programmable via CircuitPython, Adafruit's popular fork of the microcontroller-focused MicroPython programming language.

"Sol is a uniquely customizable USB MIDI to CV/Gate module. It's designed to be useful right out of the box but flexible enough to accommodate a ton of different CV/Gate generation needs," Flowers explains. "It is an unusual module, though: Sol is the first Eurorack module that can be re-programmed using CircuitPython. It's designed from the ground up to be customized by you. You are not limited by what we’ve programmed the module to do and you don't have to become an embedded developer to impart your own magic into this module.

"How does it work? Well, when you connect Sol to your computer you'll both see both a MIDI device as well as a very small external drive. This drive has a file that you can edit with any text editor and customize how this module works. No complicated developer tools to install!"

The 8HP-wide Eurorack-compatible device features four 16-bit control voltage outputs, offering a range of -5V to +8V, and four gate/trigger outputs. Programming is handled by a USB B port, with a bundled cable, and an RGB LED is provided for user control. The entire design — hardware and software - is open source, published under the Creative Commons Attribution-ShareAlike 4.0 and MIT Licence respectively.

"Sol can do everything you'd expect a MIDI to CV/Gate module to do," Flowers continues. "It can do multiple channels, portamento, polyphony, MIDI clock & transport, etc. Sol comes with examples on how to do most of these common use cases. However, the real power is that Sol is basically a teeny re-programmable computer with CV and Gate outputs. That means it can act as an envelope generator, an LFO, a random CV/gate source, and even more! It comes with some examples on how to do things other than just MIDI conversion."

Sol is available to pre-order now, with May shipping, from the Winterbloom website for $169; the source code and design files, meanwhile, can be found on Flowers' GitHub repository.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire:
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