Methods for analyzing USB data traffic using a single USB host
Contents
1. is unnecessarily present in the analyzer response If the host controller 10 is sending many packets to the analyzer 12 then this has the potential of overloading the captured analysis traffic with unnecessary information and can also take up bandwidth in the analyzer s response at time t3 Previous products and technologies combated this issue in one of two ways they either avoided the issue entirely by insisting the user put the USB analyzer on a separate host controller or they required the user of the analyzer to know the device address of the analyzer beforehand and set up a filter for it Using a separate host controller for the analysis computer is optimal in all cases it reduces the load on that host con troller and allows both the analyzer and the device under test to have more available bandwidth However this situation is not always possible or practical as it requires the user to include additional hardware on the analysis computer or to obtain another USB capable computer thereby requiring a total of two computers Therefore this requirement excludes users from efficiently using the analyzer in such a situation and does not address the problem Some products give the ability to create a hardware filter that will serve a similar purpose The filter can be configured to discard all data intended for a specific device address In this way the analyzer and the device under test can be on the same host controller without ove2. Jul 2007 entire docu ment relevant Author Unknown Universal Serial Bus Specification specifica tion Apr 27 2000 entire document relevant cited by examiner Primary Examiner Chun Kuan Lee 74 Attorney Agent or Firm Van Pelt Yi amp James LLP 57 ABSTRACT A method is described for capturing USB data traffic for a monitored device by a USB analyzer using a single USB host controller It comprises the steps of generating and storing an address and communication speed associated with the USB analyzer reading a USB packet discarding selected read packets based on the stored analyzer address and communi cation speed and transmitting the remaining packets to an analysis computer 18 Claims 4 Drawing Sheets 46 Read USB Data 48 50 No Write Data to Buffer Is it a Token PID Yes US 8 176 216 B1 Sheet 1 of 4 May 8 2012 U S Patent Joz euy ch O OL Hy 10114 Big wa O rta mmea SOY US 8 176 216 B1 Sheet 2 of 4 May 8 2012 U S Patent Hy 1011d c Di INVZ DId IS3YAJO AZ MN ono JezAjeuy 0 j949ed 9suodsay SAGA 0 JONDB d INVZDId A3UZ Ad owns J0z Jguv JOZ Jeuy 0 JODE d SAQ OF JeyOeY Ji 3 8 3 esuodsey Tc rpm AE AN CDM ds i INVZ Ad Jez Ajeuy 0 JONDE Y A3UZ Md aI 0 19498d 3S3YA30 esuodsey IMMA osuodses JOZ Jeuy ASIHAJO
3. stored in the pass through buffer of the USB ana lyzer 8 The method of claim 3 wherein a graphical user interface is provided for enabling or disabling the filtering step 9 The method of claim 3 wherein in the filtering step filtering is performed as a function of the packet type of the read USB packet 10 The method of claim 1 wherein filtering comprises if the USB packet is a token packet identifier and if the token packet identifier has a target address that is equal to the stored analyzer address and if the first communi cation speed associated with the monitored device matches with the second communication speed associ ated with the USB analyzer entering a state in which one or more subsequent read USB packets are discarded 11 The method of claim 10 wherein the state is exited in the event that a new token packet identifier is received and that the new token packet identifier has a target address that is not equal to the stored analyzer address 12 A method for capturing universal serial bus USB data traffic for a monitored device by a USB analyzer comprising the steps of generating and storing an analyzer address associated with the USB analyzer wherein the storing of the analyzer address is performed automatically upon enumeration of the USB analyzer reading a USB packet filtering the read USB packet at least in part based on whether the read USB packet is a token packet identifier and whether the token p
4. the same host controller DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Presently preferred embodiments of the present invention provide methods for effectively monitoring USB data traffic ona single USB host controller by implementing a preferably hardware based filter that removes packets from a monitor port intended for the analyzer These packets are removed in order to minimize the load on the capture buffers Further more a graphical interface for this filter is provided to greatly simplify the use of the analyzer To apply this filter the graphical interface can have a check box to enable this filter amechanism to call a single function with a single constant in a programming API or other user interface mechanisms to enable this filter This filter can remain valid and functional so long as the settings are saved even ifthe device address ofthe analyzer changes In the preferred embodiment of the present invention the filtering mechanism also takes into account the speed of the monitored bus The USB protocol is defined in such a way that on a single host controller the device address space meaning the set of possible device addresses of full speed FS and low speed LS communication is separate to that of high speed HS Therefore it is possible for HS devices to have the same device address of FS or LS devices on the same a 5 20 25 35 40 45 50 4 host controller Unintentional filtering can t
5. traffic is being cap tured It should be noted that this positive feedback occurs only during particular configurations ofthe analyzer 12 and device 20 25 30 35 40 45 50 55 60 65 2 14 on a single host controller 10 High speed HS commu nication devices are electrically isolated from full speed FS and low speed LS devices even if connected to the same host controller Thus packets to the analyzer 12 will only be perceived on the monitor port 15 if the monitor port 15 is HS and the communication port 11 is HS or if they are both not HS FIG 2 illustrates the data traffic at various times for an analyzer and a device on the same host controller Each con nection to the host controller 10 effectively has a logical Send and Receive unit All packets sent by the host con troller 10 see times t0 and t2 are received by all attached peripherals i e the device 14 and the analyzer 12 The responses from the peripherals see times t1 and t3 are only seen on the physical communication interface between the particular peripheral and the host controller 10 When the host controller 10 sends a packet with the data PKT2ANL to the analyzer 12 at time t2 the analyzer 12 receives the packet on its receive logical port ofthe commu nication port 11 as well as on its monitor port 15 Therefore when the analyzer 12 responds with the monitored data at time t3 that piece of data PKT2ANL
6. Enable Disable Filtering Ea Begin Capture 40 ls filtering enabled Write data to Buffer Catalyst Enterprises Inc Bus amp Protocol Analyzers product speci fication 2005 entire document relevant Catalyst Enterprises Inc USB 1 x 2 0 Analyzer Exerciser Tester product specification entire document relevant Ellisys Ellisys USB Explorer 260 Getting Started Guide manual Nov 22 2007 entire document relevant Ellisys Ellisys USB Explorer 200 Getting Started Guide manual Feb 13 2006 entire document relevant Ellisys Ellisys USB Tracker 110 Getting Started Guide manual Feb 13 2006 entire document relevant Finisar Corporation Bus Doctor RX Analyzer product specifi cation entire document relevant Hitex USB Agent Explores the secrets of USB brochure Jun 2001 entire document relevant Lecroy Corporation LeCroy AdvisorTM USB 2 0 Bus and Protocol Analyzer User Manual user manual Jul 2007 entire document relevant Computer Access Technology Corporation CATC USB Chief Bus amp Protocol Analyzer User s Manual user manual Nov 9 2001 entire document relevant Lecroy Corporation LeCroy USBMobileHS Protocol Analyzer User Manual user manual Jul 2007 entire document relevant Lecroy Corporation LeCroy USBTracer USB 2 0 Design amp Veri fication System User Manual user manual
7. SB data from the stream 42 write it to the buffer 44 and check again to see if filtering is enabled 40 If the filter is enabled 40 then special filtering techniques can be used to remove those packets intended for the analyzer from the captured data stream In one example of such special filtering techniques each packet in the USB data traffic is read 46 to determine whether it is a Token packet identifier 48 herein referred to as a Token PID If itis not a Token PID 48 or it is a Token PID that does not match the analyzer s device address 52 or if the speed does not match then the analyzer writes the data to an outbound buffer 50 and reads the next piece of USB data 40 In comparing the speed of the communication port and the monitor port they are considered US 8 176 216 BI 5 matched ifthe communication port is HS and the monitor port is HS orifthe communication port is not HS and the monitor port is not HS However if the packet is a Token PID 48 that matches the analyzer s device address 52 and the communication speed of the analyzer then the analyzer does not write that data to the outbound buffer Instead it transitions to a new state and reads the next piece of USB data 54 Once in this new state the analyzer will not write any ofthe new USB data into the buffer until a new Token PID is received that does not match the analyzer s device address since all interim non Token pack ets are taken to be intended for t
8. acket identifier has a target address that is equal to the stored analyzer address and whether a first communication speed associated with the monitored device matches with a second communica tion speed associated with the USB analyzer and transmitting the filtered USB packet to an analysis com puter 13 The method of claim 12 wherein in the filtering step further comprising the substep if the USB packet is a token packet identifier and if the token packet identifier has a target address not equaling to the analyzer address storing the USB packet US 8 176 216 B1 7 14 The method of claim 13 wherein in the filtering substep ifthe USB packet is a corrupted packet identifier storing the USB packet 15 The method of claim 12 wherein the USB analyzer has a pass through buffer and if a token packet identifier has a target address not equaling to the analyzer address the USB packet is stored in the pass through buffer of the USB ana lyzer 16 The method of claim 12 wherein in the storing step the analyzer address is assigned by the analysis computer having a USB host controller 17 The method of claim 16 wherein the monitored device and the USB analyzer utilize the same USB host controller 18 A USB analyzer for capturing universal serial bus USB data traffic for a monitored device comprising a processor configured to 15 8 generate and store an analyzer address associated with the USB analyzer wherein the
9. az United States Patent Santhanam et al US008176216B1 US 8 176 216 B1 May 8 2012 10 Patent No 45 Date of Patent 54 METHODS FOR ANALYZING USB DATA TRAFFIC USING A SINGLE USB HOST CONTROLLER 75 Inventors Gopal Santhanam Sunnyvale CA US Etai Bruhis Palo Alto CA US Kumaran Santhanam Sunnyvale CA US 73 Assignee Total Phase Inc Sunnyvale CA US Notice Subject to any disclaimer the term of this patent is extended or adjusted under 35 U S C 154 b by 226 days 21 Appl No 12 416 107 22 Filed Mar 31 2009 Related U S Application Data 60 Provisional application No 61 041 080 filed on Mar 31 2008 51 Int CI G06F 3 00 2006 01 32 US SEL aee ias 710 15 58 Field of Classification Search 710 15 See application file for complete search history 56 References Cited U S PATENT DOCUMENTS 5 787 253 A 7 1998 McCreery et al 709 231 6 526 044 B1 2 2003 Cookmeyer et al 370 352 6 615 370 B1 9 2003 Edwards et al 2 714 45 7 017 003 B2 3 2006 Broberg III 714 724 2007 0079288 Al 4 2007 Willwerth et al 717 124 OTHER PUBLICATIONS Catalyst Enterprises Inc Conquest Series USB Protocol Analyz ers product specification 2006 entire document relevant A e Plug in Analyzer y es Enumerate Analyzer Store Analyzer s Device Address and Analyzer s Communication Speed
10. esented by this invention Display filters work only on already cap tured data and only filter what has already been downloaded to the analysis computer This invention filters the packets before they reach the capture buffer thus reducing the hard ware buffer usage the load on the analysis computer and the intrusiveness of the analyzer Display filters cannot prevent the capture buffer from being overloaded and exhausted by the unnecessary traffic described previously While the present invention has been described with refer ence to certain preferred embodiments or methods it is to be understood that the present invention is not limited to such specific embodiments or methods Rather it is the inventor s contention that the invention be understood and construed in its broadest meaning as reflected by the following claims Thus these claims are to be understood as incorporating not only the preferred methods described herein but all those other and further alterations and modifications as would be apparent to those ordinary skilled in the art We claim 1 A method for capturing universal serial bus USB data traffic for a monitored device by a USB analyzer comprising the steps of generating and storing an analyzer address associated with the USB analyzer wherein the storing of the analyzer address is performed automatically upon enumeration of the USB analyzer reading a USB packet and filtering the read USB packet at lea
11. esuodsey ool e AREA A302 1d 921A9 0 JONDE Y INVZ Dd JozAjeuy 0 JONDB 4 beamed pl i T p Japon uo 180H JOPOBUOD ISOH ot ol el n M the e o 9 9 Am o o c A A A A A wasi A ha Me M We Nee Q ee TA v te s v M e amn wa hm aee e a mee Da tae Tu mi Mme e um ee eom Hm uum ue m m m d ooo T re V U S Patent May 8 2012 Sheet 3 of 4 US 8 176 216 B1 30 Plug in Analyzer 32 Enumerate Analyzer 34 Store Analyzer s Device Address and Analyzer s Communication Speed 36 Enable Disable Filtering 38 Begin Capture goo Is filtering enabled bis 42 Read USB Data 44 Write data to Buffer em Fig 3a U S Patent May 8 2012 Sheet 4 of 4 US 8 176 216 B1 46 Read USB Data CR 48 No Write Data to Buffer 50 Is ita Token PID Does the Requested Device Address Match the Analyzer s Address and Do the Speeds Match Read USB Data Is Token PID 54 Is Corrupted PID Fig 3b Yes US 8 176 216 BI 1 METHODS FOR ANALYZING USB DATA TRAFFIC USING A SINGLE USB HOST CONTROLLER CROSS REFERENCE This application claims priority from a provi
12. he analyzer After the next piece of USB data is read the analyzer determines whether the read USB data is a Token PID 56 If the data is a Token PID then the requested device address in the Token PID is compared to the analyzer s address and speed to determine if the addresses match 52 Ifthe addresses and speed do not match then the data is written to the buffer 50 If the addresses and speed match the analyzer does not write that data to the outbound buffer and the next USB data is read 54 If the read USB data is not a Token PID then it is deter mined whether the data is a corrupted PID 58 If the data is a corrupted PID then the data is written to the buffer 50 If the data is not a corrupted PID then the next USB data is read 54 Tn an alternative embodiment the analyzer can filter only a subset of packets e g those packets only matching certain packet types intended for its device address The data in the buffer is then transmitted to the analysis computer via the host controller and thereby the USB traffic to the device can be seen on the analysis computer and ana lyzed As a general case data to the analyzer itself would be filtered out and as an option traffic to the analyzer can also be transmitted to the analysis computer if so desired Itis important to note that other products and technologies employ display filters to aid with the visualization ofthe data This is not to be confused with the type of filtering pr
13. herefore occur when the analyzer is connected to a HS bus and monitoring FS LS devices on a single host controller or vice versa Therefore the speed of the monitored bus should be checked against the speed of the communication bus For example if the analyzer s device address is set to 0x01 and it is communicating at HS it is possible that a FS device being monitored will also have a device address of Ox01 even if on the same host controller If self filtering was enabled and the speed of the bus was not taken into account then the user would not see any monitored traffic as all packets would match that device address and be filtered out Therefore to aid in this situation the analyzer would take into account its own communication speed and that of the monitored bus Only if the device address and the speed of communication match would the packet would be filtered out The speed of the monitor port would be detected automati cally through mechanisms not relevant to this invention The speed of communication port is determined before the cap ture begins It could therefore be automatically detected by the analyzer or transmitted to the analyzer through other mechanisms during the capture start up process Using this mechanism users could safely analyze USB with a single host controller even as they test multiple devices of any speed during a single capture FIGS 3a 3b illustrate a flow chart for a preferred embodi ment of the i
14. nvention for capturing USB data traffic for an analyzer and a device on the same host controller When an analyzer is connected to a host controller via a USB cable 30 the analyzer is enumerated 32 During the enumeration 32 the host controller allocates an address to the analyzer in order to prepare for transmission of data to the analyzer and for the reception of data from the analyzer Upon enumeration of the USB analyzer 32 the analyzer stores its address for future use 34 as well as its communi cation speed In an alternative embodiment the analyzer s device address does not need to be stored upon enumeration It can also be determined by the analysis computer and then transmitted to the analyzer upon starting the capture of USB data traffic Similarly the analyzer s communication speed could be configured the same way The analyzer can then be configured with a single input from the user via a user interface to enable or disable the filtering of packets intended for the analyzer s device address 36 When the capture is started 38 the analyzer checks if the filtering of its device address is enabled 40 The analyzer can check if the filter is enabled at the beginning of the USB data capture or alternatively it can check whether the filter is enabled at the reception of each packet If the filter is not enabled 40 then the analyzer allows all packets through to the rest of the system The analyzer will continuously read U
15. ontroller and hubs that are directly connected on the return path to the host controller This feature of the USB architecture is especially signifi cant for USB analyzers which communicate to an analysis computer through the USB system FIG 1 illustrates atypical setup for connecting an analyzer to a USB system wherein the analyzer and a device are connected to the same host controller An analyzer 12 is setup to monitor the communi cations between a host controller 10 and a device 14 The analyzer 12 can be setup such that the host controller 10 and the device 14 are unaware of the analyzer s presence on the communication line Since the analyzer 12 and the device 14 are connected to the same host controller 10 the analyzer 12 will receive traffic e g packet 16 intended for itself and for the device on the communication port 11 and on the monitor port 15 Since packets intended for the communication port 11 of the ana lyzer 12 are also perceived on the monitor port 15 this creates a positive feedback loop Every time the computer requests data from the analyzer 12 it actually creates more traffic on the monitor port 15 to be sent back to the computer The traffic can overwhelm the user with unnecessary data and will also putunnecessary load on the analyzer s buffer memory and the analysis computer This is especially true when the analyzer 12 sends large volumes of analysis data back to the analysis computer simultaneously to when the
16. rloading the capture buffers However these products require the user to know the device address of the analyzer in order to configure the filter This filter would potentially have to be reconfigured each time the analyzer is used since the device address of the analyzer can change every time it is plugged into a computer While serv ing a similar purpose to the present invention this approach also puts unnecessary strain on the user to maintain the func tionality of the filter Therefore it is desirable to provide methods for analyzing USB data traffic using a USB analyzer on a single USB host controller by automatically filtering the USB data traffic SUMMARY OF INVENTION An object of this invention is to provide methods for rec ognizing packets received on a monitor port intended for an analyzer s device address and then discarding those packets US 8 176 216 BI 3 Another object of this invention is to provide methods for analyzing USB data traffic without requiring the analyzer to be on a separate bus or requiring a manually configured filter Yet another object of this invention is to provide methods for an easy and maintainable interface for a user of an ana lyzer to automatically filter USB traffic Briefly USB data traffic for a monitored device is captured by a USB analyzer wherein the monitored device and the USB analyzer utilize only one USB host controller compris ing the steps of storing an analyzer address as
17. sional patent application entitled Method and Circuits for Analyzing USB Data Traffic Using a Hardware USB Analyzer on a Single USB Host Controller filed on Mar 31 2008 and having an application No 61 041 080 Said application is incorporated herein by reference FIELD OF INVENTION This invention relates to methods for analyzing USB data traffic and in particular to methods for capturing USB data traffic using a USB analyzer on a single USB host controller BACKGROUND Universal Serial Bus USB is a serial bus standard used for connecting peripheral devices to a host computer A USB system comprises a USB host a plurality of downstream USB ports and one or more peripheral devices A USB host may have multiple USB host controllers the host controllers wherein each host controller may provide for one or more USB ports Specifically the USB 2 0 architecture offers high speed communications and is capable of connecting multiple devices to a hub that is further connected to a port of the host computer The USB 2 0 architecture employs a unidirectional broadcast system In such a system when a host controller or hub sends a packet all devices downstream from the origi nating point ofthe data will receive the packet When the host controller communicates with a specific device it must include the address of the device in the Token packet Upstream traffic i e the responses from the devices is only received by the host c
18. sociated with the USB analyzer and the speed of the analyzer s communi cation port reading a USB packet and filtering the read packet as a function of the stored analyzer address and its communication speed An advantage of this invention is that methods for recog nizing packets received on a monitor port intended for an analyzer s device address and then discarding those packets are provided Another advantage of this invention is that methods for analyzing USB data traffic without requiring the analyzer to beon a separate bus or requiring a manually configured filter are provided Yet another advantage is that methods for an easy and maintainable interface for a user of an analyzer to automati cally filter USB traffic are provided DESCRIPTION OF THE DRAWINGS The foregoing and other objects aspects and advantages ofthe invention will be better understood from the following detailed description of the preferred embodiment of the invention when taken in conjunction with the accompanying drawings in which FIG 1 illustrates a typical setup for connecting an analyzer to a USB system wherein the analyzer and a device are connected to the same host controller FIG 2 illustrates USB data traffic at various times for an analyzer and a device connected to the same host controller FIGS 3a 3b illustrate a flow chart for a preferred embodi ment of the invention for capturing USB data traffic for an analyzer and a device connected to
19. st in part based on whether the read USB packet is a token packet identifier and whether the token packet identifier has a target 5 ha 5 20 25 40 45 50 55 65 6 address that is equal to the stored analyzer address and whether a first communication speed associated with the monitored device matches with a second communica tion speed associated with the USB analyzer 2 The method of claim 1 further comprising the step of transmitting the filtered USB packet to an analysis computer 3 The method of claim 1 wherein the monitored device and the USB analyzer utilize the same USB host controller 4 The method of claim 3 wherein in the filtering step further comprising the substep if the USB packet is a token packet identifier and if the token packet identifier has a target address not equaling to the analyzer address storing the USB packet 5 The method of claim 3 wherein in the filtering step further comprising the substep if the USB packet is a token packet identifier and if the token packet identifier has a target address equaling to the analyzer address discarding the USB packet 6 The method of claim 4 wherein in the filtering substep if the USB packet is a corrupted packet identifier storing the USB packet 7 The method of claim 3 wherein the USB analyzer has a pass through buffer and if a token packet identifier has a target address not equaling to the analyzer address the USB packet is
20. storing of the analyzer address is performed automatically upon enumera tion of the USB analyzer read a USB packet and filter the read USB packet at least in part based on whether the read USB packet is a token packet iden tifier and whether the token packet identifier has a target address that is equal to the stored analyzer address and whether a first communication speed associated with the monitored device matches with a second communication speed associated with the USB analyzer and a memory coupled to the processor and configured to pro vide the processor with instructions
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