This work is licensed under CC BY-SA 4.0.

Eurorack Teensy/Arduino parameters library

Work-in-progress, classes designed for handling Eurorack inputs in Arduino platform projects and mapping values to object-setter functions.

Based on code extracted from my envor2 and talkie projects, currently used by sidenhancy and usb_midi_clocker and Microlidian.

Classes and structure

• ADCDevices set up a hardware ADC device (eg ADS1x15 library + Pimoroni +/-24v board), possibly with multiple channels
• VoltageSources read from the ADCDevice, represents one channel of the device
• ParameterInputs fetches values from VoltageSources (so in theory can have multiple ParameterInputs feeding from the same VoltageSource)
  • if a ParameterInput supports_pitch then it can also generate a note corresponding to the 1v/oct value for the voltage
• Parameters fetch values from ParameterInputs (currently up to 3 ParameterInputs can be attached to each Parameter)
  • Amount % modulation for each connected ParameterInput is mixed together
  • Result is sent to target objects (eg MIDI output, envelope, variable, etc)
• ParameterMenuItem is a way to interact directly with that Parameter value.
  • asks the Parameter how to render the value, how to increment/decrement, etc..
  • select from available ParameterInputs, and set Amount % modulation
  • ParameterInputViewItem is a graphical display of input

Options

Build flags:

• -DPARAMETER_INPUTS_USE_CALLBACKS to use callbacks for parameter input value changes in ParameterInputDisplay, instead of polling from menu
• -DDISABLE_PARAMETER_INPUT_SELECTORS to disable parameter input selectors on the 'heavyweight' parameter controls

Current status

Currently working

• Teensy 4.1 and RP2040 (Pico/XIAO)
• 3x analogue inputs using the i2c Pimoroni +/-24v ADC breakout and Rob Tillaart's ADS1X15 library
  • Multiple ADCDevices also works (so getting 6x inputs using two Pimoroni boards on different i2c addresses is possible)
• MenuItems for mymenu that allow changing Parameter values and ParameterInput-Parameter mappings
  • graph of modulation amount/history
  • selectable 3 ParameterInputs per Parameter
  • change how much each selected ParameterInput affects the Parameter, from -100% to +100%
  • switch between bipolar/unipolar ranges on per-ParameterInput level, for both input and output
• Incoming MIDI CC as a modulation source
• Convert incoming analogue level to frequency in 1v/oct fashion, and output of corresponding MIDI note (with midihelpers)
• Simple LFO/random source types (VirtualParameterInputs)

Probably working, but untested

• Analogue inputs for other boards via Rob Tillaart's ADS1X15 library
  • todo: write a class in 'devices' to set this up, based on include/devices/ADCPimoroni24v.h

Probably not currently working / untested

• Arduino
• analogRead()-based inputs on Arduino analog pins
• Gate inputs

Todo

• todo: implement corrected voltage calculation based on https://github.com/pimoroni/ads1015-python/blob/9ae775bc0a4a148771ef1d36a98adb76cc6cf54e/library/ads1015/__init__.py#L375
• Make the usual analogRead()-based classes work again think done, just needs testing?
• Make the GateInput classes work again, to trigger on/offs think done, just needs testing?
• Move the MIDICCParameter and MIDICCProxiedParameter stuff out of usb_midi_clocker into this library
• Provide scaling logic for eg opamp-scaled inputs
• Make envor2 and talkie use this library
  • Hmm, adapted envor2 to use this, but doesn't work; suspect requires too much memory for the Nano to handle?
• Docs/examples how to use the library in a project from scratch
• Provide a manager class that encapsulates all the annoying stuff like setting up and checking the values (currently need to add code to do this in your app, see sidenhancy and usb_midi_clocker for examples)
• Back port so it can be used by sidenhancy again
• Inputs from non-voltage sources, eg network, MIDI, LFOs
• Better handling of how calibration is saved + loaded, ie more rigorously defined slots
• Allow to de-select (ie set to None) from a ParameterInputSelectorControl