How to read GC420t printer's status?

Question

I'm using LibUsbDotNet to communicate with my GC420t Zebra printer.

It works great when it comes to printing:

MyUsbDevice = UsbDevice.OpenUsbDevice(MyUsbFinder);
if (MyUsbDevice == null) throw new Exception("Device Not Found.");

IUsbDevice wholeUsbDevice = MyUsbDevice as IUsbDevice;
if (!ReferenceEquals(wholeUsbDevice, null))
{
    wholeUsbDevice.SetConfiguration(1);
    wholeUsbDevice.ClaimInterface(0);
}

UsbEndpointWriter writer = MyUsbDevice.OpenEndpointWriter(WriteEndpointID.Ep01);

int bytesWritten;
if (writer.Write(Encoding.Default.GetBytes(someString), 2000, out bytesWritten) != ErrorCode.None)
    throw new Exception(UsbDevice.LastErrorString);

But I can't find a way to make my reader code work... Always returns 0 bytes read. I put it right at the end of the above code, having my printer's lid opened (which should surely give me some error code).

UsbEndpointReader reader = MyUsbDevice.OpenEndpointReader(ReadEndpointID.Ep01);

// above code...

ErrorCode ec = ErrorCode.None;
byte[] readBuffer = new byte[1024];
while (ec == ErrorCode.None)
{
    int bytesRead;
    ec = reader.Read(readBuffer, 5000, out bytesRead);
    Console.WriteLine("{0} bytes read", bytesRead);
    Console.Write(Encoding.Default.GetString(readBuffer, 0, bytesRead));
}

If you know how to make that work... Or if you know a better/faster/easier way to do that, I'll take it, thanks.

EDIT: So I tried a few more things, did some more research.

Accessing printer status using winspool -> Returned 0 even though I removed the media from my printer, neat. Well, I guess it's just initialized to 0, and receives no value. This code is using the OpenPrinter/GetPrinter/ClosePrinter pattern.

LibUsbDotNet -> Tried every listed way to read status, always 0 bytes read.

RawPrinterHelper -> Works for printing, didn't find a way to get my printer's status though.

Then I read something (can't remember on which site) saying you had to read the status WHILE the printer was printing. How can that be done?

EDIT: For the sake of completeness, here's how I generate my commands for the printer (which will probably not help, since, once more, it works flawlessly when it comes to printing):

StringBuilder sb = new StringBuilder().AppendLine()
    .AppendLine("N")
    .AppendLine("^ee") // The "give me an answer" code, also tested at the end of the commands, or as the only command (with newline and N)
    // more appending...
    .AppendLine(String.Format("P{0},{1}", 1, 1));

EDIT: Just for the record, the reason why I'm quite sure you can get this GC420t's status... is because you just can, with Zebra Setup Utilities. If you send ^ee with the provided tool (Open Communication With Printer), you get the error code properly. I just need to know how it does it.

Answer 1

Try to use the above class:

   public class cPrintHelper
{
    // Structure and API declarions:
    [StructLayout(LayoutKind.Sequential, CharSet=CharSet.Ansi)]
    public class DOCINFOA
    {
        [MarshalAs(UnmanagedType.LPStr)] public string pDocName;
        [MarshalAs(UnmanagedType.LPStr)] public string pOutputFile;
        [MarshalAs(UnmanagedType.LPStr)] public string pDataType;
    }
    [DllImport("winspool.Drv", EntryPoint="OpenPrinterA", SetLastError=true, CharSet=CharSet.Ansi, ExactSpelling=true, CallingConvention=CallingConvention.StdCall)]
    public static extern bool OpenPrinter([MarshalAs(UnmanagedType.LPStr)] string szPrinter, out IntPtr hPrinter, IntPtr pd);

    [DllImport("winspool.Drv", EntryPoint="ClosePrinter", SetLastError=true, ExactSpelling=true, CallingConvention=CallingConvention.StdCall)]
    public static extern bool ClosePrinter(IntPtr hPrinter);

    [DllImport("winspool.Drv", EntryPoint="StartDocPrinterA", SetLastError=true, CharSet=CharSet.Ansi, ExactSpelling=true, CallingConvention=CallingConvention.StdCall)]
    public static extern bool StartDocPrinter( IntPtr hPrinter, Int32 level,  [In, MarshalAs(UnmanagedType.LPStruct)] DOCINFOA di);

    [DllImport("winspool.Drv", EntryPoint="EndDocPrinter", SetLastError=true, ExactSpelling=true, CallingConvention=CallingConvention.StdCall)]
    public static extern bool EndDocPrinter(IntPtr hPrinter);

    [DllImport("winspool.Drv", EntryPoint="StartPagePrinter", SetLastError=true, ExactSpelling=true, CallingConvention=CallingConvention.StdCall)]
    public static extern bool StartPagePrinter(IntPtr hPrinter);

    [DllImport("winspool.Drv", EntryPoint="EndPagePrinter", SetLastError=true, ExactSpelling=true, CallingConvention=CallingConvention.StdCall)]
    public static extern bool EndPagePrinter(IntPtr hPrinter);

    [DllImport("winspool.Drv", EntryPoint="WritePrinter", SetLastError=true, ExactSpelling=true, CallingConvention=CallingConvention.StdCall)]
    public static extern bool WritePrinter(IntPtr hPrinter, IntPtr pBytes, Int32 dwCount, out Int32 dwWritten );

    // SendBytesToPrinter()
    // When the function is given a printer name and an unmanaged array
    // of bytes, the function sends those bytes to the print queue.
    // Returns true on success, false on failure.
    public static bool SendBytesToPrinter( string szPrinterName, IntPtr pBytes, Int32 dwCount)
    {
        Int32    dwError = 0, dwWritten = 0;
        IntPtr    hPrinter = new IntPtr(0);
        DOCINFOA    di = new DOCINFOA();
        bool    bSuccess = false; // Assume failure unless you specifically succeed.

        di.pDocName = "My C#.NET RAW Document";
        di.pDataType = "RAW";

        // Open the printer.
        if( OpenPrinter( szPrinterName.Normalize(), out hPrinter, IntPtr.Zero ) )
        {
            // Start a document.
            if( StartDocPrinter(hPrinter, 1, di) )
            {
                // Start a page.
                if( StartPagePrinter(hPrinter) )
                {
                    // Write your bytes.
                    bSuccess = WritePrinter(hPrinter, pBytes, dwCount, out dwWritten);
                    EndPagePrinter(hPrinter);
                }
                EndDocPrinter(hPrinter);
            }
            ClosePrinter(hPrinter);
        }
        // If you did not succeed, GetLastError may give more information
        // about why not.
        if( bSuccess == false )
        {
                dwError = Marshal.GetLastWin32Error();
        }
        return bSuccess;
    }

    public static bool SendFileToPrinter( string szPrinterName, string szFileName )
    {
        // Open the file.
        FileStream fs = new FileStream(szFileName, FileMode.Open);
        // Create a BinaryReader on the file.
        BinaryReader br = new BinaryReader(fs);
        // Dim an array of bytes big enough to hold the file's contents.
        Byte []bytes = new Byte[fs.Length];
        bool bSuccess = false;
        // Your unmanaged pointer.
        IntPtr pUnmanagedBytes = new IntPtr(0);
        int nLength;

        nLength = Convert.ToInt32(fs.Length);
        // Read the contents of the file into the array.
        bytes = br.ReadBytes( nLength );
        // Allocate some unmanaged memory for those bytes.
        pUnmanagedBytes = Marshal.AllocCoTaskMem(nLength);
        // Copy the managed byte array into the unmanaged array.
        Marshal.Copy(bytes, 0, pUnmanagedBytes, nLength);
        // Send the unmanaged bytes to the printer.
        bSuccess = SendBytesToPrinter(szPrinterName, pUnmanagedBytes, nLength);
        // Free the unmanaged memory that you allocated earlier.
        Marshal.FreeCoTaskMem(pUnmanagedBytes);
        return bSuccess;
    }
    public static bool SendStringToPrinter( string szPrinterName, string szString )
    {
        IntPtr pBytes;
        Int32 dwCount;
        // How many characters are in the string?
        dwCount = szString.Length;
        // Assume that the printer is expecting ANSI text, and then convert
        // the string to ANSI text.
        pBytes = Marshal.StringToCoTaskMemAnsi(szString);
        // Send the converted ANSI string to the printer.
        SendBytesToPrinter(szPrinterName, pBytes, dwCount);
        Marshal.FreeCoTaskMem(pBytes);
        return true;
    }
}

And the call:

cPrintHelper.SendStringToPrinter(printerName, fileIn);

fileIn is the escape sequence code.

fileIn should be something like this. N I8,D Q120,24 q245 S4 D12 ZB A100,10,0,3,2,2,N,"A" A140,10,0,3,2,2,N,"B" P1

1

This code works successful 5 years with zebra label printer 2844.

Hope that helps. :)

Answer 2

Wrote a kiosk application using a KR403 last year. I was able to successfully print and poll the status of the printer to see if there was a paper jam low paper etc via usb using the blog post below.

http://danielezanoli.blogspot.com/2010/06/usb-communications-with-zebra-printers.html

var printerStatusCommand = Encoding.GetEncoding(850).GetBytes(@"~HQES");
try
{
    var zebraConnection = new ZebraUsbStream();

    zebraConnection.Write(printerStatusCommand, 0, printerStatusCommand.Length);

    var statusReturn = new byte[800];
    var bytesRead = zebraConnection.Read(statusReturn, 0, 800);

    if (bytesRead >= 132)
    {
        var stringResult = Encoding.Default.GetString(statusReturn.ToArray());
        Console.WriteLine(stringResult);
    }
}
catch
{
    Console.WriteLine("Error");
}

There was a lot of additional string/byte parsing of stringResult since the status values where stored as individual bits inside of of the return bytes but the printer docs covered the formatting pretty well.