Download the source code and project files (Visual C# 2013 Desktop/Arduino)

This project connects to a USB postal scale (A Dymo 25 lb. postal scale in this example) and spews out readings every few seconds in a console. It's a very simple program, obviously, just to make sure I could connect to and get readings from a scale. The program is made up two files - Program.cs and Scale.cs.

Scale.cs is almost totally derived from the code located in this stackoverflow question. Thanks very much, "user1599271"!

//Program.cs
using System;
using System.Threading;
using HidLibrary;
using Scale;
using System.Timers;

namespace ScaleReader
{
    class Program
    {
        private static System.Timers.Timer aTimer;

        public static void Main(string[] args)
        {
            aTimer = new System.Timers.Timer(1000);
            aTimer.Elapsed += OnTimedEvent;
            aTimer.Enabled = true;

            Console.WriteLine("Let the scale do it's thing...");
            Console.ReadLine();
            
        }

        static void OnTimedEvent(object sender, System.EventArgs e)
        {
            decimal? weightInLb, weightInG, weightInOz;
            bool? isStable;

            USBScale s = new USBScale();
            s.Connect();

            if (s.IsConnected)
            {
                s.GetWeight(out weightInLb, out weightInG, out weightInOz, out isStable);
                s.DebugScaleData();
                Console.WriteLine("Weight: {0:0.00} g", weightInG);
                Console.WriteLine("Weight: {0:0.00} LBS", weightInLb);
                Console.WriteLine("Weight: {0:0.00} oz", weightInOz);
                Console.WriteLine("--------------------- {0}", DateTime.Now);
                s.Disconnect(); 
            }
            else
            {
                Console.WriteLine("No Scale Connected.");
            }
        }
    }
}

//Scale.cs
//Original code source: http://stackoverflow.com/questions/11961412/read-weight-from-a-fairbanks-scb-9000-usb-scale
using HidLibrary;
using System.Threading;
using System;
using System.Collections.Generic;
using System.Text;
using System.Linq;

namespace Scale
{
    class USBScale
    {
        public bool IsConnected
        {
            get
            {
                return scale == null ? false : scale.IsConnected;
            }
        }
		
        public decimal ScaleStatus
        {
            get
            {
                return inData.Data[1];
            }
        }
		
        public decimal ScaleWeightUnits
        {
            get
            {
                return inData.Data[2];
            }
        }
		
        private HidDevice scale;
        private HidDeviceData inData;

        public HidDevice[] GetDevices()
        {
            //The next line contains the product/vendor ID numbers for the Dymo 25lb Postal Scale, change these depdending on what scale you're using 
            return HidDevices.Enumerate(0x0922, 0x8004).Cast().ToArray();    
        }

        public bool Connect()
        {
            // Find a Scale
            HidDevice[] deviceList = GetDevices();

            if (deviceList.Length > 0)

                return Connect(deviceList[0]);

            else

                return false;
        }

        public bool Connect(HidDevice device)
        {
            scale = device;
            int waitTries = 0;
            scale.OpenDevice();

            // sometimes the scale is not ready immedietly after
            // Open() so wait till its ready
            while (!scale.IsConnected && waitTries < 10)
            {
                Thread.Sleep(50);
                waitTries++;
            }
            return scale.IsConnected;
        }

        public void Disconnect()
        {
            if (scale.IsConnected)
            {
                scale.CloseDevice();
                scale.Dispose();
            }
        }

        public void DebugScaleData()
        {
            for (int i = 0; i < inData.Data.Length; ++i)
            {
                Console.WriteLine("Byte {0}: {1}", i, inData.Data[i]);
            }
        }

        public void GetWeight(out decimal? weightInLb, out decimal? weightInG, out decimal? weightInOz, out bool? isStable)
        {
            decimal? weight;
            weight = null;
            weightInG = null;
            weightInLb = null;
            weightInOz = null;
            isStable = false;

            if (scale.IsConnected)
            {
                inData = scale.Read(250);
                // Byte 0 == Report ID?
                // Byte 1 == Scale Status (1 == Fault, 2 == Stable @ 0, 3 == In Motion, 4 == Stable, 5 == Under 0, 6 == Over Weight, 7 == Requires Calibration, 8 == Requires Re-Zeroing)
                // Byte 2 == Weight Unit
                // Byte 3 == Data Scaling (decimal placement)
                // Byte 4 == Weight LSB
                // Byte 5 == Weight MSB

                // FIXME: dividing by 100 probably wont work with
                // every scale, need to figure out what to do with
                // Byte 3
                //weight = (Convert.ToDecimal(inData.Data[4]) + Convert.ToDecimal(inData.Data[5]) * 256) / 10;

                switch (Convert.ToInt16(inData.Data[2]))
                {
                    case 2:  // Scale reading in g
                        weight = (Convert.ToDecimal(inData.Data[4]) + Convert.ToDecimal(inData.Data[5]) * 256);
                        weightInG = weight;
                        weightInLb = weight * (decimal?)0.00220462;
                        weightInOz = weight * (decimal?)0.035274;
                        //weightInG = weightInG * (decimal?)0.625;
                        break;
                    case 11: // Ounces
                        weight = (Convert.ToDecimal(inData.Data[4]) + Convert.ToDecimal(inData.Data[5]) * 256) / 10;
                        weightInLb = weight * (decimal?)0.0625;
                        weightInOz = weight;
                        weightInG = weight * (decimal?)28.3495;
                        break;
                    case 12: // Pounds
                        // already in pounds, do nothing
                        break;
                }
                isStable = inData.Data[1] == 0x4;
            }
        }
    }
}