C# USB HID example for mbed using hidlibrary

packages.config

<?xml version="1.0" encoding="utf-8"?>
<packages>
  <package id="hidlibrary" version="3.2.29.0" targetFramework="net45" />
</packages>

Program.cs

namespace UsbHid
{
    using System;
    using System.Linq;
    using System.Threading;

    using HidLibrary;

    public class Program
    {
        private const int VendorId = 0x1234;

        private const int ProductId = 0x0006;

        private const int ReportLength = 8;

        private static readonly Random Random = new Random();

        private static HidDevice device;

        public static void Main()
        {
            device = HidDevices.Enumerate(VendorId, ProductId).FirstOrDefault();
            if (device == null)
            {
                Console.WriteLine("No device connected");
                return;
            }

            Console.WriteLine("mbed found");

            device.ReadReport(ReadReportCallback);

            while (true)
            {
                var data = new byte[ReportLength];
                Random.NextBytes(data);
                device.WriteReport(new HidReport(ReportLength, new HidDeviceData(data, HidDeviceData.ReadStatus.Success)));
                Thread.Sleep(TimeSpan.FromSeconds(0.2));
            }
        }

        private static void ReadReportCallback(HidReport report)
        {
            Console.WriteLine("recv: {0}", string.Join(", ", report.Data.Select(b => b.ToString("X2"))));
            device.ReadReport(ReadReportCallback);
        }
    }
}

See https://mbed.org/cookbook/USBHID-bindings- for the mbed side of things.