Send raw ZPL to Zebra printer via USB

You haven't mentioned a language, so I'm going to give you some some hints how to do it with the straight Windows API in C.

First, open a connection to the printer with OpenPrinter. Next, start a document with StartDocPrinter having the pDatatype field of the DOC_INFO_1 structure set to "RAW" - this tells the printer driver not to encode anything going to the printer, but to pass it along unchanged. Use StartPagePrinter to indicate the first page, WritePrinter to send the data to the printer, and close it with EndPagePrinter, EndDocPrinter and ClosePrinter when done.

I found the answer... or at least, the easiest answer (if there are multiple). When I installed the printer, I renamed it to "ICS Label Printer". Here's how to change the options to allow pass-through ZPL commands:

1. Right-click on the "ICS Label Printer" and choose "Properties".
2. On the "General" tab, click on the "Printing Preferences..." button.
3. On the "Advanced Setup" tab, click on the "Other" button.
4. Make sure there is a check in the box labeled "Enable Passthrough Mode".
5. Make sure the "Start sequence:" is "${".
6. Make sure the "End sequence:" is "}$".
7. Click on the "Close" button.
8. Click on the "OK" button.
9. Click on the "OK" button.

In my code, I just have to add "${" to the beginning of my ZPL and "}$" to the end and print it as plain text. This is with the "Windows driver for ZDesigner LP 2844-Z printer Version 2.6.42 (Build 2382)". Works like a charm!

I've found yet an easier way to write to a Zebra printer over a COM port. I went to the Windows control panel and added a new printer. For the port, I chose COM1 (the port the printer was plugged in to). I used a "Generic / Text Only" printer driver. I disabled the print spooler (a standard option in the printer preferences) as well as all advanced printing options. Now, I can just print any string to that printer and if the string contains ZPL, the printer renders the ZPL just fine! No need for special "start sequences" or funky stuff like that. Yay for simplicity!

Visual Studio C# solution (found at http://support.microsoft.com/kb/322091)

Step 1.) Create class RawPrinterHelper...

using System;
using System.IO;
using System.Runtime.InteropServices;

public class RawPrinterHelper
{
    // 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;
    }
}

Step 2.) Create a form with text box and button (text box will hold the ZPL to send in this example). In button click event add code...

private void button1_Click(object sender, EventArgs e)
        {
            // Allow the user to select a printer.
            PrintDialog pd = new PrintDialog();
            pd.PrinterSettings = new PrinterSettings();
            if (DialogResult.OK == pd.ShowDialog(this))
            {
                // Send a printer-specific to the printer.
                RawPrinterHelper.SendStringToPrinter(pd.PrinterSettings.PrinterName, textBox1.Text);
                MessageBox.Show("Data sent to printer.");
            }
            else
            {
                MessageBox.Show("Data not sent to printer.");
            }
        }

With this solution, you can tweak to meet specific requirements. Perhaps hardcode the specific printer. Perhaps derive the ZPL text dynamically rather than from a text box. Whatever. Perhaps you don't need a graphical interface, but this shows how to send the ZPL. Your use depends on your needs.