"Beyond Obnoxious"
Zoxnoxious is a hardware analog music synthesizer with a software interface. The intent is to provide a platform for card/module development ("card" may be a better term than "module", as the latter is a well established term in the modular synth world). Cards interface to a Raspberry Pi host controller, and the host controller responds to VCV Rack on an external computer.
A card is a circuit board that plugs into the Zoxnoxious backplane. Each card receives digital signals such as I2C and SPI, and the card drives a defined set of pins with analog signals. Cards developed to date include:
- AS3340 VCO
- AS3372 Signal Processor (VCF, VCA)
- SSI2130/AS3394 Dual VCO Synth Voice
The design allows for up to 8 cards to be controlled. The backplane counts as one of the eight. The current physical board is designed with 6 slots.
A Raspberry Pi attaches to the Zoxnoxious backplane. To a host computer, the Pi appears as USB Audio and USB MIDI devices. Incoming USB Audio and MIDI are dispatched to a card's driver, which may choose to send SPI or I2C messages to the card.
The user interacts with the synth through a VCV Rack plugin. Zoxnoxious VCV Rack plugins map the Rack modules to audio channels and MIDI events that are sent via USB to the synthesizer.