Author Topic: Scope that can decode USB  (Read 4256 times)

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Offline NiHaoMike

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Re: Scope that can decode USB
« Reply #25 on: August 26, 2017, 05:19:53 pm »
I remember reading that you could use a Beaglebone - which can do USB 2.0 host and USB 2.0 gadget at the same time - as a USB sniffer.
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Offline Titan 4380

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Re: Scope that can decode USB
« Reply #26 on: August 26, 2017, 09:12:05 pm »
Wanting to read USB2.0 traffic is like a trip down the rabbit hole and gets more complex after each post. I jumped from an early 90's CRO to a DS2000 scope thinking that these new wonder devices would enable me to decode and freeze the data coming from a USB stepper driver. I wasn't so interested in the waveforms, but more the ASCII data being transmitted. I did considerable research (i.e.:looked at this forum) to understand that I could purchase a DS2070 scope and end up with a 300mhz unit with all triggers at no cost . I should have done more research to find out what is involved in monitoring USB transmissions.
 

Offline nctnico

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Re: Scope that can decode USB
« Reply #27 on: August 26, 2017, 09:39:19 pm »
When dealing with USB (or any serial interface like ethernet, PCI express) the electrical interface is the least interesting part. What you need is a USB protocol analyser!
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline Leo Bodnar

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Re: Scope that can decode USB
« Reply #28 on: August 27, 2017, 12:59:22 am »
If you want to decode USB in hardware your best solution is USB protocol analyser with its associated software package.
The device class communications are quite complex and make almost no sense as just hex dumps.  You will drown in raw data.

I am using:
https://www.totalphase.com/products/beagle-usb480/
http://teledynelecroy.com/protocolanalyzer/protocoloverview.aspx?seriesid=414&capid=103&mid=511
There are also
https://www.ellisys.com/products/usbex200/index.php (industry standard)
and few others... http://janaxelson.com/development_tools.htm#analyzers

Before you make a jump make sure you are getting the right device class decoders in your software.
Otherwise you'll be looking at expensive and nicely formatted hex packets of raw data.  Often extra class decoders are extra, e.g. look at Ellisys pricing structure.

Teledyne Lecroy software is free, has lots of decoders and allows you to write your own decoding add-ons so if you are working with some proprietary data you can present it in a sensible way as [huge amounts of] data is streaming past.

Hardware analysers allow capturing sub-microsecond hardware timestamps so you can fix all the subtle problems in your MCU.
I wouldn't use scope unless you:
are syncing or analysing USB traffic interaction with external events on ~microsecond level
are designing low level stuff (PHYs, converters, isolators, etc)
have signal integrity or EMC problems

By the way Mercury T2 has input for external trigger.  It is my favourite analyser to date.

Total Phase software is simple, easy to use and also works on Mac and Linux.

Cheers
Leo
« Last Edit: August 27, 2017, 10:03:02 am by Leo Bodnar »
 

Offline abraxa

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Re: Scope that can decode USB
« Reply #29 on: August 27, 2017, 06:38:04 am »
Thanks for all replies and suggestions. Let me reframe my original question;

What would I need to read or decode ASCII traffic coming from a USB 2.0 device. If for example, If I wanted to read XYZ data from a USB stepper driver, what would I need to do that?

If you just want to sniff the data, you could also use https://wiki.wireshark.org/CaptureSetup/USB to do this on the PC side.
 

Offline Titan 4380

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Re: Scope that can decode USB
« Reply #30 on: August 27, 2017, 09:16:25 am »
Thanks for your suggestions Leo. Its ironic that you should jump in on this thread, because it is one of your devices that I am also interested in monitoring to see how it can be implemented in other ways.Specifically, the BU0836X turned out to be an extremely reliable and robust unit, but I am convinced that its full potential has yet to be unlocked.
 

Offline Howardlong

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Re: Scope that can decode USB
« Reply #31 on: August 30, 2017, 01:10:07 am »
 

Offline Leo Bodnar

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Re: Scope that can decode USB
« Reply #32 on: August 30, 2017, 01:29:57 am »
Which ones offer external trigger (either in or out, but preferably both)?
http://teledynelecroy.com/protocolanalyzer/protocoloverview.aspx?seriesid=414&capid=103&mid=511
They sell a cable for it but it's just a standard DIN connector on the back. It is both IN and OUT.
https://store.teledynelecroy.com/products/ac032xxa-x-mercury-external-trigger-cable

Leo

« Last Edit: August 30, 2017, 01:37:04 am by Leo Bodnar »
 

Offline Howardlong

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Re: Scope that can decode USB
« Reply #33 on: August 30, 2017, 05:31:04 am »
Which ones offer external trigger (either in or out, but preferably both)?
http://teledynelecroy.com/protocolanalyzer/protocoloverview.aspx?seriesid=414&capid=103&mid=511
They sell a cable for it but it's just a standard DIN connector on the back. It is both IN and OUT.
https://store.teledynelecroy.com/products/ac032xxa-x-mercury-external-trigger-cable

Leo



OK, thanks, very useful. I went for the LeCroy Mercury T2C standard, I may well need to do power delivery protocols later, but unlikely to need the advanced option's facilities. Either of those options can be purchased separately.

The ITIC solution is reasonably priced but seems to lack an external trigger: my current use case is figuring out what is happening in an MCU based HS device when performance inexplicably drops, so I need to time correlate MCU telemetry on the scope with the bus analyser. The signal integrity looks fine, it's a firmware problem in a vendor provided USB library under load.

The Ellisys stuff seems to be priced stratospherically as soon as you want external triggers.

The Beagle options appeared about 50% more expensive than the LeCroy T2C.
 

Offline bill@geektrap.com

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Re: Scope that can decode USB
« Reply #34 on: April 02, 2019, 01:27:58 am »
WireShark software is free and open-source and works quite well.  Just add the USB decoders.  I've used it and a LeCroy Catalyst together and have no complaints about it.
 


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