When monitoring data on the USB bus, how do I tell which data is from the host computer and which is from the device under test?

Question from the Customer:
I’m using the Beagle USB 480 Power Protocol Analyzer - Standard Edition to monitor data between devices and the host computer. Looking at the data transactions in the block view of the Data Center Software, I see “IN” and “OUT” transaction types – does that tell me the direction of the data flow?

Response from Technical Support:
Thanks for your question! Yes, when using the Beagle USB analyzers with the Data Center Software, you can easily determine the flow of data. Everything is from the perspective of the Host - the type of the transaction is one of these two:

  • OUT txn, the data is flowingfrom the Host to the Device.
  • IN txn, the data is flowing from the Device to the Host.

Below is an example of viewing the data:



 For details about the Device that is communicating, take a look at the Bus Pane in Navigator Window of the Data Center Software. In the example to the right, we selected the Memory Stick, the device that is transmitting the largest number of bytes.
The Enumeration tab shows the details of the Memory Stick.



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

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