I’ve been diving into the world of Eurorack format modular synthesizers for a little while now. A terrific, fun, and versatile addition to my rack has been the euroshield 1 by 1010music, a module that brings Arduino and Teensy to Eurorack.
One of the things that attracted me to the Eurorack format is the terrific blend of analog and digital synthesis, control, and processing going on. As I put together my first small rack of equipment — a VCO (voltage controlled oscillator) for generating pitched audible-rate waveforms, VCA (voltage controlled amplifier), envelope generator, filter, and LFO (low frequency oscillator), I started to yearn for a way to inject other modulations, effects, and signal processing experimentally, without necessarily committing to the cost and size of more individual modules. The euroshield does just that.
I met Aaron Higgins at a modular event at Perfect Circuit Audio while he was in beta stages with the euroshield, and he kindly offered for me to test one out and give feedback. I added the euroshield to my rack, plugged in a Teensy 3.2, and installed the latest Teensyduino and excellent PJRC Teensy Audio Library, and the 1010music Euroshield example files.
The euroshield and Teensy are powered by the 5V supply line inside the rack. The demo code let me fire up the four LEDs on the module, test the two trim pots and pushbutton to make sure everything was working. Then, its onto the good stuff — software defined module building! I created low pass filters, bit crushers, saw waves, LFO signals, arpeggios and note sequences, and more to interact over the signal inputs and outputs with the rest of my modules.
The euroshield (or a Teensy + Audio Shield) really shines when you start using the Audio System Design Tool for Teensy Audio Library https://www.pjrc.com/teensy/gui/ which is a visual node-graph GUI for designing audio signal processing code. I had a lot of fun going through the tutorials from the Microcontroller Audio Workshop.
Then, I started cooking up my own bits of code to do things like generate semi-random sequences (turn the knobs to adjust the randomness and note ranges). I used the euroshield with a Teensy 3.6 as a class compliant USB MIDI host to send clock signals to an Arturia Beatstep, my modules, a Pocket Operator drum machine, and other MIDI devices.
I also made a little reverb unit out of it. A friend of mine, Jim Bumgardner, is also using a euroshield in his rack, and wrote a very nice Turing Machine to generate random melodies that are pitch quantized.
Before I got the euroshield I had been experimenting with using a Circuit Playground Express and a Metro M0 with my Eurorack, which also have lots of promise for interfacing with synthesizers, particularly using CircuitPython. My solutions for interfacing these currently involve a lot of alligator clip wires, so I’m very impressed at how nice and neat the euroshield is for tying together all of the wiring and circuits needed to have a microcontroller play nicely with -10V to +10V Eurorack control voltages.
If you’re into Eurorack and microcontrollers, have a look at the 1010music euroshield.