ULZ logs are proprietary packet capture files generated by USBlyzer, a popular Windows-based software USB protocol analyzer and traffic sniffer. Troubleshooting USB protocols using .ulz logs involves capturing, filtering, and decoding low-level USB request blocks (URBs), I/O Request Packets (IRPs), and device descriptors to find the root cause of enumeration failures, timing timing mismatches, or data corruption.
This troubleshooting methodology is standard practice for embedded developers, system engineers, and IT administrators managing virtualization environments like HP Anyware or VMware Horizon. Step 1: Setting Up the Capture Environment
Before analyzing a protocol failure, you must capture the exact moments the issue occurs (typically during device connection or high-throughput data transfer).
Isolate the Path: In Windows Device Manager, select View > Devices by connection to isolate the target USB Controller and Hub.
Configure USBlyzer: Launch USBlyzer and navigate to the Capture menu. Enable Capture Hot-plugged to ensure the log captures the initial power-on and negotiation phases.
Start Recording: Click Start Capture on the main toolbar before plugging in your problem device. Step 2: Triggering and Saving the Log
Replicate the Failure: Plug the target USB device into the port. Leave the capture running until the protocol error occurs—such as a “Device Descriptor Request Failed” notification or a frozen data stream.
Halt and Export: Click Stop Capture. Go to File > Save As… and save the output as a .ulz file. This file archives raw binary timestamps, pipe handles, endpoints, and data payloads. Step 3: Analyzing the ULZ Log (Protocol Walkthrough)
When you open a .ulz file back inside USBlyzer, the trace window displays sequential protocol layers. You should analyze them using a top-down approach:
[Raw Request / URB] ➔ [USB Descriptor Tree] ➔ [Token / Handshake Packets] USB Ports Not Working – Microsoft Q&A
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