OUT OF STOCK, follow https://apfelaudio.com/ for updates!

NOTE: as this is a small batch and I only have 1 shipping box size, please do not order more than 2 units. If we sell out we'll do another run :)

Get started with FPGA-based audio synthesis

Eurorack PMOD makes it easy for you to combine the world of FPGAs and hardware electronic music synthesis. It is an expansion board for FPGA development boards that allows them to interface with a Eurorack hardware synthesizer. This board exposes 8 (4 in + 4 out) DC-coupled audio channels, 192KHz / 32bit sampling supported, at a -8V to +8V swing, amongst many more features.

This project is:

• An open hardware eurorack-compatible module compatible with many FPGA development boards (this listing).
• Various example DSP cores. Examples include calibration, sampling, effects, synthesis sources and so on.
• A VCV Rack plugin so you can simulate your Verilog designs in a completely virtual modular system, no hardware required.

Included examples

The GitHub repository contains a bunch of example DSP cores which are continuously being updated:

• Bitcrusher
• Filter (high pass / low pass / band pass)
• Clock divider
• .wav sampler
• Pitch shifter
• Sequential routing switch
• Echo/delay effect
• VCA (voltage controlled amplifier)
• VCO (voltage controlled oscillator)

These examples can all run out of the box on the development boards listed below. The repository currently only supports a Linux-based development environment, however porting to Mac / Windows should be fairly trivial and maybe the community can do it :).

Choosing an FPGA development board

An FPGA development board itself is NOT included! Essentially anything iCE40 or ECP5 based that has a PMOD connector will support the open-source tools and the examples in this project. Just make sure you have enough LUTS, >3K is enough to do interesting things.

The following development boards have been tested with eurorack-pmod and are supported by the examples in the github repository

• iCEbreaker (iCE40 based)
• TinyVision pico-ice-v3 (iCE40 based)
• ECPIX-5 (ECP5 based)
• Colorlight i5 (ECP5 based)
• Colorlight i9 (ECP5 based)

What's in the box?

• 1x Eurorack PMOD R3.1 PCBA, front panel, front panel nuts (assembled + tested)
  • Units are NOT calibrated, but you can easily do this yourself from the instructions in the repository. All you need is a stable +5V and -5V power supply. A switched multiple is also good to have.
• 1x 30cm 10-pin to 16-pin IDC Eurorack power connector to connect this module to a Eurorack power backplane in your case.
• 1x 20cm 12-pin IDC ribbon to connect the Eurorack PMOD to your FPGA development board.
• 1x extra long 2.54mm dual row pin header strip for gender changing the 12-pin IDC ribbon for your FPGA development board if necessary

Technical details

• 3HP module compatible with modular synthesizer systems.
  • Module depth is 47mm with both ribbon cables attached.
  • This fits nicely in for example a 4MS POD 48X (pictured in product photos)
• PMOD connector compatible with many FPGA development boards.
• 8 (4 in + 4 out) DC-coupled audio channels, 192KHz / 32bit sampling supported.
• PWM-controlled, user-programmable red/green LEDs on each output channel.
• Jack insertion detection on input & output jacks.
• Calibration EEPROM for unique ID and storing calibration data. (not actually used by gateware yet)

R3.1 limitations

• These boards are all tested and fully functional, but there are some things I would like to improve for the next batch. For the gruesome details, see https://github.com/apfelaudio/eurorack-pmod/issues/21

All orders are normally shipped within 5 business days. I tend to bundle shipments on Wednesdays, CEST.