Connect Zebra and Printronix printers via USB using Device Interface GUIDs

Starting with Zebra SDK#

Initially, I thought using Zebra's official SDK would be the best solution since it directly supports USB connections. I installed Zebra SDK 3.0 in Visual Studio Community Edition 2022 and quickly managed to connect and print barcodes. This worked with a Zebra ZD500 printer, proving that Zebra's SDK was reliable for standard printing tasks.

I faced issues when trying to connect to the Printronix T820 printer. It was set up differently than the Zebra device.

Problems with Printronix Compatibility#

The Printronix T820 printer was set up on another computer using Zebra's Browser Print software. Unfortunately, this setup identified the printer through drivers rather than as a straightforward USB printer. Zebra's SDK couldn't recognize it because it specifically works with printers recognized as USBPRINT devices.

Next, I tried using Printronix's own uniPRT library (version 1.0), but found that it only supported TCP connections, not USB. This meant I had to find another solution.

Testing Other Libraries#

After some research, I discovered wrapper libraries that used libUSB drivers. However, these wrappers didn't help. LibUSB requires devices to use special drivers, whereas our printers used standard Windows drivers like WinUSB. This left me with one complex option: using Windows native DLL functions to connect directly to USB devices.

Working Directly with Native USB Functions#

Connecting through native Windows functions like usbcomm.dll seemed like a good solution initially. However, due to time constraints, implementing these native DLLs was not practical. Instead, I chose a quicker and simpler approach: using symbolic links created from Device Interface GUIDs. To better understand this, I explored the Windows Device Manager. I learned how the Windows Registry and device descriptors categorize USB devices such as Generic USB, USB Printer, and HID devices.

Understanding USB Symbolic Links#

By examining Zebra's demo application code, I learned about symbolic links or descriptors. These symbolic links provide essential details like vendor ID, product ID, and serial number required to establish a direct connection. A typical symbolic link looks like this:

//?/usb#vid_[VendorID]&pid_[ProductID]#[SerialNumber]#{DeviceInterfaceGUID}

A concrete example from an actual device:

//?/usb#vid_0b1f&pid_1e20#90y163510385#{36fc9e60-c465-11cf-8056-444553540000}

Initially, I thought the last part of this symbolic link was a class GUID. Further investigation revealed it was actually a Device Interface GUID.

Learning About Device Interface GUIDs#

A Device Interface GUID uniquely identifies types of device interfaces within Windows. These identifiers help connect specific devices, such as printers or mice, with appropriate drivers. Some common GUIDs include:

• Generic USB Device: {A5DCBF10-6530-11D2-901F-00C04FB951ED}
• USB Printer: {28D78FAD-5A12-11D1-AE5B-0000F803A8C2}
• HID Devices: {4D1E55B2-F16F-11CF-88CB-001111000030}
• USB Host Controller: {3ABF6F2D-71C4-462A-8A92-1E6861E6AF27}
• USB Hub: {F18A0E88-C30C-11D0-8815-00A0C906BED8}

These GUIDs stay the same across all Windows systems, acting as standard identifiers that Windows uses consistently.

Successful Connection#

Once I understood the importance of Device Interface GUIDs, I combined the correct GUID ({28D78FAD-5A12-11D1-AE5B-0000F803A8C2} for USB printers) with the symbolic link. Using Zebra SDK's USBConnection(symbolicLink) function with this corrected symbolic link allowed me to communicate with the Zebra ZD500 printer successfully.

This approach also resolved the Printronix T820 connection challenge. The symbolic link method works across different printer types when you use the appropriate Device Interface GUID.

Final Thoughts#

Connecting printers via USB in Windows involves unexpected complexity, especially due to compatibility and device identification issues. Some printers work with straightforward methods like Zebra's SDK, while others require deeper technical understanding. You need knowledge of USB standards, Windows device management, and how device drivers interact with symbolic links. Understanding symbolic links and Device Interface GUIDs helped me establish reliable USB connections for printer applications on Windows.