Pressing start button again after stopping the capture

Posted: 3 years ago Quote
Hi,

A USB device was connected in FS mode. The data captured by the analyzer showed that device requests and IN/OUT transactions were at FS speed.  Just after stopping the analizer software, I pressed the start button to re-capture the data. And I sent data to the device. This time, however, the analyzer software said the packet speed was in LS.

Is this the expected behavior, and what was the actual speed?

Thanks and regards,

Hiroshi
Posted: 2 years ago Quote
Hi, this is not an error but correct behavior. Please note that the device must be disconnected when the capture is started or else the 1480A will not see the connection sequence and, consequently, will not be able to detect the correct link speed. This is per the USB specification. Please see the below support forum post for details:

http://www.internationaltestinstruments.com/boards/t/113/the-1480a-capture-must-be-started-before-the-device-under-test-is-connected.aspx