View this project on CADLAB.io.

Synapse

Synapse is an Arduino shield (and the corresponding library) which provides CV and Gate I/O for Arduino boards.

Features

• 2 x control voltage inputs, 0 to 5V
• 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 (with interrupt)
• 2 x gate outputs
• 1 x eurorack power connector (10 pin)
• An easy to use software library

Compatible Boards

The shield 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 Yùn or Tian and will most likely damage the board).

Verified Boards

• Arduino Uno
• Arduino Due
• Arduino 101 (requires a small modification to the shield)

Hardware

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

Mechanical

• 2 x 8 pin dip socket
• 1 x 16 pin dip socket
• 1 x 14 pin dip socket
• 1 x 5x2 male strip connector (angled if you want to stack another shield on top) (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

Software library usage

The library can be installed using Arduino Library Manager (Sketch -> Include Library -> Library Manager), just search for "synapse".

Once the library is installed (please remember to install the dependencies, as well - see the last paragraph below), you can call SynapseShield.begin() in the setup() function to initialize the library and the shield

#include <Synapse.h>
using namespace sl;

void setup()
{
  SynapseShield.begin();
  // ...
}

when calling the begin() function you can optionally specify the SPI divider (by default it's set to 8)

Optionally, you can configure a callback function for each gate input channel which will be called when a specific condition is met.

#include <Synapse.h>
using namespace sl;

void onGateAChanged();
void onGateBRisingEdge();

void setup()
{
  SynapseShield.begin();

  SynapseShield.gateInputInterrupt(
    Synapse::GateChannel::A,
    onGateAChanged,
    Synapse::GateInterrupt::ValueChange
  );

  SynapseShield.gateInputInterrupt(
    Synapse::GateChannel::B,
    onGateBRisingEdge,
    Synapse::GateInterrupt::RisingEdge
  );
  // ...
}
void loop()
{
  // ...
}

void onGateAChanged()
{
  // Do something when the logic value of gate input A changes
  // WARNING: keep this function as unexpensive as possible
}

void onGateBRisingEdge()
{
  // Do something when the logic value of gate input B goes from LOW to HIGH
  // WARNING: keep this function as unexpensive as possible
}

The range of each CV output channel can be individually configured (even dinamically)

#include <Synapse.h>
using namespace sl;

void setup()
{
  SynapseShield.begin();

  SynapseShield.setCVRange(
    Synapse::CVChannel::A,
    Synapse::Range::ZeroToTenVolts
  );

  SynapseShield.setCVRange(
    Synapse::CVChannel::B,
    Synapse::Range::MinusFiveToFiveVolts
  );
  // ...
}

void loop()
{
  Synapse::Range rangeA = SynapseShield.getCVRange( Synapse::CVChannel::A );

  if(rangeA == Synapse::Range::MinusFiveToFiveVolts)
  {
    SynapseShield.setCVRange(
      Synapse::CVChannel::A,
      Synapse::Range::ZeroToTenVolts
    );
  }
  else
  {
    SynapseShield.setCVRange(
      Synapse::CVChannel::A,
      Synapse::Range::MinusFiveToFiveVolts
    );
  }
  delay(1000);
}

CV and Gate I/O operations are also very easy:

#include <Synapse.h>
using namespace sl;

bool gateInA{false};
unsigned cvInA{0};

void setup()
{
  SynapseShield.begin();
  // ...
}

void loop()
{
  gateInA = SynapseShield.readGate(Synapse::GateChannel::A);
  cvInA = SynapseShield.readCV(Synapse::CVChannel::A);

  if(gateInA)
  {
    SynapseShield.writeCV(Synapse::CVChannel::A, 4095);
    SynapseShield.writeCV(Synapse::CVChannel::B, 0);
  }
  else
  {
    SynapseShield.writeCV(Synapse::CVChannel::A, 0);
    SynapseShield.writeCV(Synapse::CVChannel::B, 4095);
  }

  if(cvInA > 2047)
  {
    SynapseShield.writeGate(Synapse::GateChannel::A, false);
    SynapseShield.writeGate(Synapse::GateChannel::B, true);
  }
  else
  {
    SynapseShield.writeGate(Synapse::GateChannel::A, true);
    SynapseShield.writeGate(Synapse::GateChannel::B, false);
  }
}

Dependencies

• DirectIO, for fast digital pin access