Synapse - A DIY-friendly CV I/O shield for Arduino

Some Synapse pcbs

Synapse is a simple, diy-friendly Arduino shield that will allow you to expand your modular synthesizer in new and creative ways. Here's the hardware features:

  • 2 x control voltage inputs, 0 to 5V with diode protection
  • 2 x control voltage outputs, individually configurable as 0 to 10V or -5 to 5V via software, with 12bit of resolution
  • 2 x gate inputs
  • 2 x gate outputs
  • 1 x eurorack power connector (10 pin)

Please refer to the github repository for the latest version of the schematic, the BOM and the library. Please note that for the time being I'm not selling kits or pcbs, you'll have to order the pcbs yourself and source all the parts (see the links and infos below).

Assembling the board

If you have basic soldering skills this shield shouldn't take too long to build. Just start with the components with lower height (diodes, resistors), then the IC sockets, the small capacitors and then the connectors.
Please pay attention to the 2x3 SPI female header, it's the only component which needs to be on the bottom side of the pcb.
Unless you plan to use some Arduino pins, you shouldn't need stackable headers since the eurorack connectors would prevent stacking any other shield on top in any case.

Bill of materials

Order from OSH Park

Passive components

  • 2 x ferrite beads (or 10 ohm resistors)
  • 8 x 1K 1% resistor
  • 4 x 10K 1% resistor
  • 6 x 100K 1% resistor
  • 2 x 1M 1% resistor
  • 2 x 47p capacitor
  • 4 x 100n capacitor
  • 1 x 10u 25V electrolytic capacitor

Diodes, transistors, ICs

  • 4 x BAT85 diode
  • 4 x 2N3904 transistor
  • 1 x REF02CP voltage reference
  • 1 x MCP4922E SPI DAC
  • 1 x TL072 dual opamp
  • 1 x 4053N


  • 2 x 8 pin dip socket
  • 1 x 16 pin dip socket
  • 1 x 14 pin dip socket
  • 1 x 5x2 male strip connector (2.54mm pitch)
  • 1 x 3x2 female strip connector (2.54mm pitch)
  • 1 x 10x1 male strip connector (2.54mm pitch)
  • 2 x 8x1 male strip connector (2.54mm pitch)
  • 1 x 6x1 male strip connector (2.54mm pitch)
  • 8 x PJ301BM vertical mount 'Erthenvar' jack

Feel free to use the shopping carts already available for Reichelt and Mouser, but be aware that these don't include the jack connectors (Erthenvar PJ301BM)
You'll need to order them separately, there's plenty of options:

Installing the library

The library is available in the Arduino library manager, to install it simply go to Sketches -> Include Library -> Manage Libraries, look for "Synapse" and click Install. Please refer to the github repository for usage examples.

Compatible Boards

The shield has been tested mainly with Arduino Uno and Arduino Due, it should work fine with any Arduino with onboard 5V regulator which can tolerate up to 12V on the VIN pin (e.g. it will *NOT* work with an Arduino Yun or Tian and will most likely damage the board).
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