Kosmo multitool

Kosmo Multitool

This repository contains schematics, PCB and source code for a synthesizer module in Kosmo format. This module consists of an Arduino Nano Every, CV and gate input and output options, MIDI, rotary encoder and an OLED display. It is meant as a development platform for DIY synthesizer enthusiasts.

Here is a full list of features:

• 4x CV input (0-10V)
• 4x CV output (0-10V)
• 4x gate/trigger in
• 4x gate/trigger out
• 1.3" OLED display
• DIN serial MIDI in/through/out
• Rotary encoder with switch
• 3 switches
• 2 LEDs

Modules

• ADSR
• Arpeggiator
• MIDI to CV
• Multiple
• Quantizer

Building

Gerbers for the main PCB can be found here and for the front panel here.

BOM

* match in pairs to get more accurate ADC readings

Installation and calibration

Clone the repository and open up the src/main folder in the Arduino IDE or whatever you use for compiling. You need to install the libraries mentioned below into you Arduino library folder. The ADC and the DAC need calibration to get proper results.

ADC calibration

Set CALIBRATE_CV_IN variable in main file to 1. Apply a fixed, known voltage to CV1 input, eg. 5.000V. On USB serial console (9600 baud) you get the actual reading from the ADC. Calculate the correction factor FIXED VOLTAGE / ACTUAL VOLTAGE, eg. 5.000 / 4.9884 = 1.0023. Enter the value in the CV_IN_CORRECTION array in the top lines of main.ino. Repeat this procedure for all CV inputs. In the end it should look something like this:

float CV_IN_CORRECTION[4] = {0.9995f, 0.9956f, 1.0013f, 1.0009f};

Notice the trailing f to tell the compiler that these are float values. Don't forget to set CALIBRATE_CV_IN back to 0.

DAC calibration

Make sure to calibrate the ADC first. Set CALIBRATE_CV_OUT variable in main file to 1. Plug in patch cables from all four CV inputs to the CV outputs. Calibration is done automatically and stored in a look-up table. Set CALIBRATE_CV_OUT back to 0. This step is only needed once, from now on calibration values are loaded from EEPROM on start up.

Development

Source code is in src/main. If you want to develop your own module just copy the files example_module.h and example_module.ino and rename all functions and variables that are globally available. Include your header file in the main.ino file and add your entry to the main menu. Take a look at the already existing modules on how it works in general. If you created a nice module please file a pull request and I would be happy to merge it.

Libraries

https://github.com/adafruit/Adafruit_MCP4728

https://github.com/adafruit/Adafruit_ADS1X15

https://github.com/olikraus/u8g2

https://github.com/FortySevenEffects/arduino_midi_library

https://github.com/neu-rah/ArduinoMenu

https://github.com/thomasfredericks/Bounce2

https://github.com/mathertel/RotaryEncoder

https://github.com/ivanseidel/LinkedList

References

https://www.lookmumnocomputer.com/modular

https://www.ti.com/lit/ds/symlink/ads1115.pdf

http://ww1.microchip.com/downloads/en/devicedoc/22187e.pdf

https://github.com/DylanMeeus/GoAudio

License

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.