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Support Question of the Week: Using the Beagle USB Protocol Analyzer to Monitor an Embedded System

Q: I would like to monitor the traffic on a single USB 2.0 bus between two microcontrollers on a printed circuit board. I have a Beagle USB 480 Protocol Analyzer at my disposal. I went through the datasheet. Can you provide more details about using the Beagle analyzer on an embedded system? I would greatly appreciate it.

A: Thanks for your question!  The Beagle USB 480 Protocol Analyzer is non-intrusive high-speed USB 2.0 bus monitor. Looking at the Beagle Protocol Analyzer User Manual, it shows the four main architectures for connecting devices to the Beagle protocol analyzer.


Beagle USB Protocol Analyzer Connections Figure 1: Beagle USB Protocol Analyzer Connections


Sections (a), (b) and (c) of the figure show connecting a Beagle inline between the USB device and the host being monitored. If you would like more information about this type of setup, please refer to section 3.1 of the Beagle USB Protocol Analyzer User Manual.

Section (d) shows the setup you are looking for: the target bus is fully internal to an embedded system. In this case, you will need to tap off the lines using a parallel connector, and then plug in the tapped off cable into either the Target host or the Target device port of the analyzer. Connecting to either port will produce the same results.

Knowledge Base Article: Monitoring an embedded USB with a Beagle USB Protocol Analyzer provides details about connecting the Beagle USB 480 Protocol analyzer to embedded USB devices. Following is a summary of the instructions.

  1. The D+/D- signal path of a universal serial bus (USB) does not have to be broken to be monitored by the Beagle USB protocol analyzer. The VBUS, GND, D+, and D- lines can be connected to either the Type A or Type B connector on the Beagle analyzer using "T" connections.
  2. How you connect the Beagle USB protocol analyzer to the embedded bus depends on how the target system signals can be accessed.

    • If the signal lines are accessible through a header or test pads, then connecting to the bus is straightforward. If the signals are not easily accessible, the wires may need to be soldered directly to IC pins or copper on the printed circuit board.
    • If there is no header or test pads, the USB cable may need to be cut open to attach the wires to  the target system.
  3. Use caution when you connect to and monitor an embedded system. Also, please note that Total Phase cannot be held responsible if equipment is damaged from such methods.

Additional information is provided in the article that may be useful for this or other projects, including signal integrity and supplying 5V on the VBUS.

For more information about our Beagle USB 480 protocol analyzer and other products, please see the following:

Beagle USB 480 Protocol Analyzer

Beagle Protocol Analyzer Data Sheet

Total Phase Products

Knowledge Base Articles

We hope this answers your question. If you have other questions about our Protocol Analyzers or other Total Phase products, feel free to email us at sales@totalphase.com or support@totalphase.com.