Sebastian Holzapfel's Tiliqua Puts a Little Lattice FPGA in Your Eurorack Synth Setup
With eight audio channels as standard, expandable to 24, MIDI, and USB connectivity, the Tiliqua targets flexibility.
Sebastian Holzapfel, of German open source audio hardware specialist apfelaudio, wants to put a little FPGA in your Eurorack synthesizer setup — literally, with the Tiliqua module.
"Tiliqua aims to make FPGA-based audio and video synthesis accessible to everyone," Holzapfel explains of his creation. "The Tiliqua hardware architecture, alongside a comprehensive collection of example projects built in Python (Amaranth HDL [Hardware Description Language]), allows you to experiment with synthesis techniques that are out of reach of embedded microcontroller-based platforms. Think extreme oversampling for alias-free audio-rate modulation, low-latency effects, video synthesis, and high-speed USB audio."
The Tiliqua itself, designed to slot straight in to a Eurorack setup, is based on an open-hardware FPGA module dubbed the soldiercrab and built around the Lattice ECP5 field-programmable gate array chip, with 25k logic elements, 16MB of HyperRAM/octal-SPI RAM, 16MB of SPI flash, and a high-speed USB PHY. This connects to a motherboard that offers a switched rotary encoder with bar-graph display, the FPGA's USB port and a debug port handled by a Raspberry Pi RP2040 microcontroller, two expansion ports, a 720p60 display output, and a MIDI input jack.
A third board, the audio interface, completes the Tiliqua's design, delivering four input and four output DC-coupled audio channels supporting up to 24-bit audio at 192kHz sampling rates. For compositions that don't need that many channels, any input or output can double as a touch or proximity sensor input, while each channel has user-programmable red/green LEDs with pulse-width modulation (PWM) support.
"Tiliqua can store up to 8 projects (bitstreams) simultaneously — you can switch between them at runtime without needing a PC," Holzapfel notes of the FPGA's flexibility. "Out of the box, Tiliqua can be: a video synthesizer (vectorscope display with audio-rate beam modulation); a multichannel wavetable oscillator (1MHz oversampling for audio-rate FM [Frequency Modulation]); a high-speed 4 in/4 out USB 2.0 audio interface; a polyphonic MIDI/touch synthesizer; a multichannel diffusion delay; a multichannel pitch shifter; a MIDI/CV converter; [and] a matrix mixer."
Design files for the project have been published on GitHub under the Strongly Reciprocal variant of the CERN Open Hardware License Version 2; Holzapfel is preparing to launch a crowdfunding campaign for the Tiliqua on Crowd Supply soon.