How Do I Monitor and Analyze a USB Bus Without Data Packets?

Photo by cottonbro

Question from the Customer:

I have a manufacturing problem to take care of and it looks like the Beagle USB 5000 v2 SuperSpeed Protocol Analyzer - Standard Edition could do the job. The product I am working on is a measuring device that transfers data to a computer through the USB bus. Here are the known issues I have to troubleshoot and debug:

  • Some devices record a transmission pause of approximately 5 seconds after operating about 2 hours in which no data is transmitted.
  • After 5 seconds, however, the "missing data" is transferred.

What I need to determine - what happens during these 5 seconds? Note - The data packets are of less interest since no data transmission occurs during these 5 seconds.

My question is, as the issue occurs when there are no data packets to capture and analyze, can the Beagle USB 5000 v2 analyzer help find the problem at the lowest protocol level, such as a hold command?

Response from Technical Support:

Thanks for your question! The Beagle USB 5000 v2 SuperSpeed Protocol Analyzer - Standard Edition with our Data Center Software can help you capture, analyze, and successfully debug low-level events. First, we will talk about the possible causes of the issues you identified, and then we will go over how the Beagle USB 5000 v2 standard analyzer can help you get your devices back in production.

Low-Level Events

When developing/testing USB products, it is common to experience bus issues that can lead to USB communication errors. While some errors will cause system failures, other issues may still allow the system to operate, but with potentially erratic behavior.

Here are some example USB bus issues that can occur:

  • Improper USB Packet Data and Data Sequencing
  • USB Transmissions/Re-transmission
  • Power/VBUS Related Issues
  • Problems with Enumeration
  • Speed Negotiation Issues
  • Reset, Suspend, and Resume Events

How the Beagle 5000 USB Analyzer Monitors Low-Level Events

The Beagle USB 5000 v2 standard analyzer can capture, decode, and debug low-level bus events and errors, as well as high-traffic data.

  • Low-level bus events include K/J chirps, Reset, Suspend, Resume, In/NAKs, SOF.
  • Beagle USB 5000 v2 analyzer also provides visibility into the USB 3.0 bus, detecting low-level bus events including link training, LFPS polling, training sequences.
  • Sometimes, the cause is also a PHY error which is a special-case bus event and can also occur due to electrical inconsistencies.

The Beagle USB 5000 v2 standard analyzer should help you determine to the cause of issues you described.

 Advanced Features for USB Troubleshooting and Analysis

For more advanced features, consider the Beagle USB 5000 v2 SuperSpeed Protocol Analyzer - Ultimate Edition. The Beagle USB 5000 v2 ultimate analyzer supports everything that the standard edition provides, plus the following:

  • Simultaneous Capture Option for USB 3.0 and 2.0 Monitoring
  • SuperSpeed Downlink Upgrade
  • Advanced USB 3.0 Triggers (only USB 2.0 Included with Standard)
  • USB 3.0 Advanced State-Based Matching Option
  • Multi-Analyzer Synchronization Option

You can also obtain a view into the LTSSM, which tracks upstream and downstream link state transitions. In addition to the article, here is a video that you can watch:

This next video shows an example of troubleshooting with the Beagle USB 480 Protocol Analyzer. The same concepts can be applied to the Beagle USB 5000 v2 analyzers.

To compare the features of our USB analyzers and other devices, please refer to the USB Product Comparison chart.

We hope this answers your questions. Additional resources that you may find helpful include the following:

If you want more information, feel free to contact us with your questions, or request a demo that applies to your application.