Methods for embedding an out-of-band signal into a USB capture stream

摘要

One or more out-of-band input signals (GPIO) are handled and efficiently embedded into a USB capture stream. In order to conserve resources, the state of the input signals can be sent only when a change occurs. The signals are accurately time-stamped, and then presented within the context of the captured USB data. In order to provide maximum visibility, if the digital inputs occur during a normally filtered multi-packet sequence, the filter is canceled and the surrounding packets will also be sent to an analysis computer. Furthermore, because digital inputs may happen during a USB packet, the digital inputs are queued in a FIFO buffer until there is an opportunity to send the digital inputs. Even though the state of the inputs may be sent at a later time, the state of the inputs may be time-stamped when the state of the inputs is perceived by the analyzer.

主权项

1. A method for monitoring a USB data stream between a source and a destination, wherein said USB data stream comprises of a plurality of USB packets, comprising the steps of:
receiving a stream of one or more USB packets from a USB input line; receiving non-USB-related signals from a general purpose input line; processing with a processor the stream of one or more USB packets and the non-USB-related signals; interleaving change of state information of the non-USB-related signals with the stream of one or more processed USB packets as an analysis stream without interleaving the non-USB-related signals with the stream, wherein the change of state information includes a change of state in the non-USB-related signals and a timestamp corresponding to the change of state, and wherein the change of state information of the non-USB-related signals is different from the non-USB-related signals; and sending the analysis stream to an analysis computer.