How to auto-detect Arduino COM port?

Question

I'm using an Arduino with the Firmata library for communication to a C# application, and I want to eliminate a COM port configuration component since it can change from machine to machine...

Is it possible to:

1. Enumerate list of COM ports in the system? (In my googling I've seen some fairly ugly Win32 API code, hoping there's maybe a cleaner version now)
2. Auto-detect which COM port(s) are connected to an Arduino?

Answer 1

This little bit of code has performed very well for this (returns the COM port string, i.e. "COM12" if Arduino is detected):

private string AutodetectArduinoPort()
        {
            ManagementScope connectionScope = new ManagementScope();
            SelectQuery serialQuery = new SelectQuery("SELECT * FROM Win32_SerialPort");
            ManagementObjectSearcher searcher = new ManagementObjectSearcher(connectionScope, serialQuery);

            try
            {
                foreach (ManagementObject item in searcher.Get())
                {
                    string desc = item["Description"].ToString();
                    string deviceId = item["DeviceID"].ToString();

                    if (desc.Contains("Arduino"))
                    {
                        return deviceId;
                    }
                }
            }
            catch (ManagementException e)
            {
                /* Do Nothing */
            }

            return null;
        }

Answer 2

1. You can use SerialPort.GetPortNames() to return an array of string COM port names.
2. I dont think you can auto detect the ports, youd have to ping the device in order to see if the device is connected.

Answer 3

Taking the WMI Management route a bit further, I've come up with a wrapper class which hooks on to the Win32_SerialPorts events and dynamically populated a list of SerialPorts for Arduino and Digi International (X-Bee) devices, complete with PortNames and BaudRates.

For now, I've used the devices Description field in the Win32_SerialPorts entry as the Key for the Dictionary, but this can easily be changed.

It has been tested to a limited capacity with an Arduino UNO and it seems to be stable.

// -------------------------------------------------------------------------
//  <copyright file="ArduinoDeviceManager.cs" company="ApacheTech Consultancy">
//      Copyright (c) ApacheTech Consultancy. All rights reserved.
//  </copyright>
//  <license type="GNU General Public License" version="3">
//      This program is free software: you can redistribute it and/or modify
//      it under the terms of the GNU General Public License as published by
//      the Free Software Foundation, either version 3 of the License, or
//      (at your option) any later version.
// 
//      This program is distributed in the hope that it will be useful,
//      but WITHOUT ANY WARRANTY; without even the implied warranty of
//      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//      GNU General Public License for more details.
// 
//      You should have received a copy of the GNU General Public License
//      along with this program. If not, see http://www.gnu.org/licenses
//  <license>
// -------------------------------------------------------------------------

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.IO.Ports;
using System.Linq;
using System.Management;
using System.Runtime.CompilerServices;

// Automatically imported by Jetbeans Resharper
using ArduinoLibrary.Annotations;

namespace ArduinoLibrary
{
    /// <summary>
    ///     Provides automated detection and initiation of Arduino devices. This class cannot be inherited.
    /// </summary>
    public sealed class ArduinoDeviceManager : IDisposable, INotifyPropertyChanged
    {
        /// <summary>
        ///     A System Watcher to hook events from the WMI tree.
        /// </summary>
        private readonly ManagementEventWatcher _deviceWatcher = new ManagementEventWatcher(new WqlEventQuery(
            "SELECT * FROM Win32_DeviceChangeEvent WHERE EventType = 2 OR EventType = 3"));

        /// <summary>
        ///     A list of all dynamically found SerialPorts.
        /// </summary>
        private Dictionary<string, SerialPort> _serialPorts = new Dictionary<string, SerialPort>();

        /// <summary>
        ///     Initialises a new instance of the <see cref="ArduinoDeviceManager"/> class.
        /// </summary>
        public ArduinoDeviceManager()
        {
            // Attach an event listener to the device watcher.
            _deviceWatcher.EventArrived += _deviceWatcher_EventArrived;

            // Start monitoring the WMI tree for changes in SerialPort devices.
            _deviceWatcher.Start();

            // Initially populate the devices list.
            DiscoverArduinoDevices();
        }

        /// <summary>
        ///     Gets a list of all dynamically found SerialPorts.
        /// </summary>
        /// <value>A list of all dynamically found SerialPorts.</value>
        public Dictionary<string, SerialPort> SerialPorts
        {
            get { return _serialPorts; }
            private set
            {
                _serialPorts = value;
                OnPropertyChanged();
            }
        }

        /// <summary>
        ///     Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
        /// </summary>
        public void Dispose()
        {
            // Stop the WMI monitors when this instance is disposed.
            _deviceWatcher.Stop();
        }

        /// <summary>
        ///     Occurs when a property value changes.
        /// </summary>
        public event PropertyChangedEventHandler PropertyChanged;

        /// <summary>
        ///     Handles the EventArrived event of the _deviceWatcher control.
        /// </summary>
        /// <param name="sender">The source of the event.</param>
        /// <param name="e">The <see cref="EventArrivedEventArgs"/> instance containing the event data.</param>
        private void _deviceWatcher_EventArrived(object sender, EventArrivedEventArgs e)
        {
            DiscoverArduinoDevices();
        }

        /// <summary>
        ///     Dynamically populates the SerialPorts property with relevant devices discovered from the WMI Win32_SerialPorts class.
        /// </summary>
        private void DiscoverArduinoDevices()
        {
            // Create a temporary dictionary to superimpose onto the SerialPorts property.
            var dict = new Dictionary<string, SerialPort>();

            try
            {
                // Scan through each SerialPort registered in the WMI.
                foreach (ManagementObject device in
                    new ManagementObjectSearcher("root\\CIMV2", "SELECT * FROM Win32_SerialPort").Get())
                {
                    // Ignore all devices that do not have a relevant VendorID.
                    if (!device["PNPDeviceID"].ToString().Contains("VID_2341") && // Arduino
                        !device["PNPDeviceID"].ToString().Contains("VID_04d0")) continue; // Digi International (X-Bee)

                    // Create a SerialPort to add to the collection.
                    var port = new SerialPort();

                    // Gather related configuration details for the Arduino Device.
                    var config = device.GetRelated("Win32_SerialPortConfiguration")
                                       .Cast<ManagementObject>().ToList().FirstOrDefault();

                    // Set the SerialPort's PortName property.
                    port.PortName = device["DeviceID"].ToString();

                    // Set the SerialPort's BaudRate property. Use the devices maximum BaudRate as a fallback.
                    port.BaudRate = (config != null)
                                        ? int.Parse(config["BaudRate"].ToString())
                                        : int.Parse(device["MaxBaudRate"].ToString());

                    // Add the SerialPort to the dictionary. Key = Arduino device description.
                    dict.Add(device["Description"].ToString(), port);
                }

                // Return the dictionary.
                SerialPorts = dict;
            }
            catch (ManagementException mex)
            {
                // Send a message to debug.
                Debug.WriteLine(@"An error occurred while querying for WMI data: " + mex.Message);
            }
        }

        /// <summary>
        ///     Called when a property is set.
        /// </summary>
        /// <param name="propertyName">Name of the property.</param>
        [NotifyPropertyChangedInvocator]
        private void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            var handler = PropertyChanged;
            if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}