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USB protocol analyzer runs on PCs

Posted: 05 Sep 2005 ?? ?Print Version ?Bookmark and Share

Keywords:saelig? usb explorerpro? usb bus analyzer? protocol analyzer?

USB ExplorerPRO Professional EditionAlthough the press release from Saelig primarily discusses the latest USB ExplorerPRO Professional Edition bits, it's worth taking a closer look at the USB ExplorerPRO USB bus analyzer box, too. It's a small (5.9-by-4.7-by-2.6-inch) and light (less than 2lb) package that works with a PC as an analyzer, communicating across USB 2.0's 480Mbps connection. It's also powered from the USB port it's connected to.

As you might expect (although it's not mentioned in the press statement) this is a Windows platform product. Also, because the USB Explorer 200 records data to be analyzed in realtime, two host controllers are necessary.

The first one is used to connect the peripheral to be tested and the other PC is used to record the data. One is for analysis and the other for testing. You can also use one computer with two host controllers, but Saelig recommends two computers, one of them fitted with a USB 2.0 high-speed connection.

PC requirements
To run the software, one PC must run at least a Pentium III clocking at 600MHz or higher, and have at least 128 megs of DRAM. The platform must include an 800 x 600-pixel display (256 colors), and run Windows 2000 Service Pack4 or Windows XP Service Pack1, as well as Internet Explorer 5.0 or above. Of course, that PC must also have a USB 2.0 EHCI (enhanced host controller interface) controller.

The analyzer uses your host computer's DRAM to store any recorded traffic using the Visual USB software. As such, the maximum amount of data is limited, but a RecordToDisk tool can be used to record vast amounts of USB data into consecutive files that can later be opened using Visual USB.

Capture elusive intermittents
That can be a boon if you're looking for intermittent problems, especially those that don't occur very often. You can actually use the RecordToDisk tool to record traffic over hours or even weeks. Later, you can return to the correct position in the files using a time stamp or other external event.

As you can surmise, the USB Explorer 200 protocol analyzer is very powerful. It will readily let you display USB bus states, packets sent, and decode descriptors, where it can detect errors in devices and host controllers, as well as in embedded software and drivers.

Once installed, the FIFO-equipped USB ExplorerPRO USB analyzer can accommodate testing of all USB 2.0 speeds, with automatic detection of the link-under-test speed. In operation, the system will non-intrusively measure all USB bus states and low-level protocols.

Realtime analysis
You can download analyzed data in realtime, too. When capturing USB data packets, a realtime statistical display lets you check bus status even before you look at the packets that have been read. These are displayed in a chronological list together with peripheral addressing and endpoint numbering. A second window provides details on the selected item.

A coaxial BNC connector is also provided to feed in triggers. There's also a trigger output function. The USB Explorer 200's adjustable hardware trigger permits triggering of specific actions when external events are occurring, or when repetitive events are taking place, or when specific event sequences are happening. A text mode summary gives a glimpse of events and defined actions.

In addition to that, front-panel indicators are provided to show power and bus activity. An indicator goes green when packets are detected, changing to red when they're recorded. A trigger indicator goes green when a trigger is detected on the input, and it can change to red when a trigger is detected in the output.

Multi-level decode
In use, the system's PC display shows the various USB transactions and transfers layers, with high-level decoding of standard requests and descriptors. There's also a set of display filters (more on them in a moment), and a time stamp with 16.67ns precision.

Low-level error detection reveals bit-stuffing, as well as CRC5/CRC16 (cyclical redundancy check) errors. The high-level states show detection and measurement of Reset, Suspend, Keep Alive and High Speed Handshake states.

To make it easier to identify packets, software provides filtering and packet color-coding.

This gives you a choice of several levels of detail, with information taken from the traffic containing references to the USB specs.

Once acquired, you can also export your findings into various PC-compatible formats, such as XML or text files, or raw data.

- Alex Mendelsohn

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