OSC (Open Sound Control) is a protocol with which data can be sent between applications. For example sending data from a python script to VCV-Rack, audio DAWs, or even to certain hardware synthesizers. OSC acts as a glue, so to be speak.

In this case we want to go this route [Arduino] -> [USB-Serial] -> [Laptop/Python Script] -> [OSC] -> [Laptop/VCV-Rack].

This is the python part:

#! /usr/bin/python
# -*- coding: utf-8 -*-
import serial
import time
import serial.tools.list_ports
from pythonosc import udp_client

"""
Receives Serial messages in the format "address:value" from Arduino
and forward the value to the given OSC-address

Dependecies:
 - pyserial (install with `pip install pyserial`)
 - python-osc (install with `pip install python-osc`)
"""

# A list of strings which identify a valid "Arduino" for us.
# Use something from the description of list_comport_devices()
PORT_IDENTIFIERS = ["Arduino", "CH340", "USB2.0-Serial", "USB Serial", "Teensyduino"]

# OSC IP to connect to (127.0.0.1 is the IP address of this computer)
OSC_IP = "127.0.0.1"

# OSC Port to connect to (7001 is default)
OSC_PORT = 7001



def list_comport_devices():
    """
    Print a list of devices connected to this computers serial port
    """
    # Get a full list of devices connected
    ports = [p for p in serial.tools.list_ports.comports() if
p.description != "n/a"]

    if len(ports) == 0:
        # If there are no devices connected, print this
        print("Found no devices connected to this computers Serial ports\n")
    else:
        # If there are devices connected...
        print(f"Found the following devices connected to this computers serial ports:")
        # Print each of the devices out
        print(f"   n {'port':<15} {'description':<15} {'manufacturer':<15} {'product':<15}")
        print("-"*120)
        for i, p in enumerate(ports):
            device = f"[{p.device}]"
            print(f"  [{i}]{device:<15} {p.description:<15} {p.manufacturer if not p.manufacturer is None else 'None':<15} {p.product if not p.product is None else 'None':<15}")
        print()


def is_suitable_device(port) -> bool:
    """
    Return true if any of the Strings in the list PORT_IDENTIFIERS is found in
    a ports description or manufacturer
    """
    in_description = any(x in port.description for x in PORT_IDENTIFIERS)
    in_manufacturer = any(x in port.manufacturer for x in PORT_IDENTIFIERS) if not port.manufacturer is None else False
    return in_description or in_manufacturer


def find_first_arduino_port():
    """
    This function returns the first device connected to this computers
serial port, whose description matches with any string in the list
    PORT_IDENTIFIERS. If nothing is found print a message and wait
    """
    # Get a list of devices which have any of the strings from the list
    # PORT_IDENTIFIERS in their description
    ports = [p for p in serial.tools.list_ports.comports() if is_suitable_device(p)]

    # When there are no devices found, just try again every second until
    # a device is found or the program is stopped
    while len(ports) == 0:
        try:
            print("  No serial port with Arduino found, not connected? Stop program with [Ctrl] + [c]", end='\r', flush=True)
            ports = [p for p in serial.tools.list_ports.comports() if is_suitable_device(p)]
            time.sleep(1)
        except KeyboardInterrupt:
            break
    else:
        print("", end='\r', flush=True)

    # If a device is found, print a message and return the first one
    port = ports[0]
    print(f"  Found a suitable device connected at {port.device}: {port.description}")

    return port.device


# -----------------------------------------------------------------------

print("="*120)
print(f"{'serial_to_osc.py':^120}")
print("="*120)
print()


print("Trying to establish a connection to Arduino...")

# List all devices connected to this computers Serial Ports
list_comport_devices()

# Find the first devices that seems to be an Arduino
arduino_port = find_first_arduino_port()
arduino = serial.Serial(port=arduino_port, baudrate=115200, timeout=.1)
arduino.flushInput()
print(f"Established a serial connection to device at {arduino_port}")

print(f"Creating OSC client which will send OSC data to {OSC_IP}:{OSC_PORT}")
client = udp_client.SimpleUDPClient(OSC_IP, OSC_PORT)

print("\nListening for incoming messages:")
while True:
    try:
        # 
        serialdata = arduino.readline()
        received_string = serialdata.decode("utf-8").strip()
        if received_string != "" and ":" in received_string:
            address, value = received_string.split(":")
            print(f"  {arduino_port} ⟶ {value} ⟶ {OSC_IP}:{OSC_PORT}{address}")
            value = float(value)
            client.send_message(address, value)
        elif received_string != "" and not ":" in received_string:
            address = "/chn/1"
            value = float(received_string)
            print(f"  {arduino_port} ⟶ {value} ⟶ {OSC_IP}:{OSC_PORT}{address}")
            client.send_message(address, value)

    except KeyboardInterrupt:
        break

Arduino

This the Arduino Code (upload onto the arduino via Arduino IDE):

int led = 13;

float pot = 0.0;
float increment = 0.1;

// Create a Buffer to hold characters for the messages
String buffer;



void setup() {
  pinMode(led, OUTPUT);
  Serial.begin(115200);

  // Reserve memory for the messages
  buffer.reserve(128);
}



// the loop routine runs over and over again forever:
void loop() {

  pot = analogRead(A0)

  // Send OSC message to this address
  sendOSC("/ch/1", pot);
  delay(10);

}




// /ch/1:5.234
void sendOSC(String address, float value) {
    buffer += address;
    buffer += ":";
    buffer += String(value);
    Serial.println(buffer);
    buffer = "";
}