How to read the weight from a Weight USB Scale - asp-classic

Question

I have a USB weighing from stamps.com (Model 510: http://www.stamps.com/postage-online/digital-postage-scales/)
I was able to find the drivers to make it stand alone online, but my next question is how do I read the weight of the object on the scale in my classic ASP page / VBScript.
Does anyone have any suggestions where I should begin my search?

Answer 1

I'm not sure if this is applicable to your specific model but there's an article at http://nicholas.piasecki.name/blog/2008/11/reading-a-stamps-com-usb-scale-from-c-sharp/ where the author has written C# code to read from the scale because it conforms to basic USB HID (human input device) standards. The author made use of Mike OBrien's HID library https://github.com/mikeobrien/HidLibrary
They start off getting the raw bytes:
HidDeviceData inData;
HidDevice[] hidDeviceList;
HidDevice scale;
hidDeviceList = HidDevices.Enumerate(0x1446, 0x6A73);
if (hidDeviceList.Length > 0)
{
int waitTries;
scale = hidDeviceList[0];
waitTries = 0;
scale.Open();
if (scale.IsConnected)
{
inData = scale.Read(250);
for (int i = 0; i < inData.Data.Length; ++i)
{
Console.WriteLine("Byte {0}: {1:X}", i, inData.Data[i]);
}
}
scale.Close();
scale.Dispose();
}
Then go on to reverse engineer the payload and construct a function to get the weight in ounces:
private void GetStampsComModel2500iScaleWeight(out decimal? ounces, out bool? isStable)
{
HidDeviceData inData;
HidDevice[] hidDeviceList;
HidDevice scale;
isStable = null;
ounces = null;
hidDeviceList = HidDevices.Enumerate(0x1446, 0x6A73);
if (hidDeviceList.Length > 0)
{
int waitTries;
scale = hidDeviceList[0];
waitTries = 0;
scale.Open();
// For some reason, the scale isn't always immediately available
// after calling Open(). Let's wait for a few milliseconds before
// giving up.
while (!scale.IsConnected && waitTries < 10)
{
Thread.Sleep(50);
waitTries++;
}
if (scale.IsConnected)
{
inData = scale.Read(250);
ounces = (Convert.ToDecimal(inData.Data[4]) +
Convert.ToDecimal(inData.Data[5]) * 256) / 10;
isStable = inData.Data[1] == 0x4;
}
scale.Close();
scale.Dispose();
}
}
In order to read the weight from your classic ASP page/VBScript (on the server, right?) the easiest solution looks to be turning the working C# class into a COM component. There are tutorials you can follow to create the C# COM Component and register it on the server, then you would call it from VBScript like:
Dim app
Set app = Server.CreateObject("MyScaleComponent")