USB Logic Analyzer

Any (dis)recommendations for PC based USB logic analyzers?

I'm looking for something in the order of a few hundred MHz and 16+ channels.

programmable logic thresholds is a bit of a necessity these days.

Fancy triggering & serial bus protocol decoding would be nice, but not essential.

Anything else I should be looking for? Any opinions about how big a memory buffer is reasonable/available?

Reply to
yellow.yeti
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The price leader is probably This is a 16- or 32-channel bare board sampling at up to 200MHz. Some very flexible triggering is built in and supported by the software clients, both the standard one and my work-in-progress at .

I use it. It functions.

Mel.

Reply to
Mel Wilson

Check out the Intronix Logicport. I have used it and it works well. I don't own one however. The $390 price is a bit higher than I would like to pay. If it had one or two oscope channel inputs that would be the ticket! I'd also like to see it with a Linux driver, but they only support Windows.

The software supports a variety of serial protocols and includes the input "probe" meaning the ribbon cable. The grabbers are extra.

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Rick
Reply to
rickman

I've owned a Logicport for years and use it pretty much daily for commercial stuff at work as well as my own fiddle-farting around for hobby projects.

Must-haves, for me, include

- A wide input range (+/- 40 V) and adjustable trigger (+/- 6 V). That's needed to look at RS-232 "on the wire" and not after it has passed through the line receiver. I need it specifically to probe NTDS "A" traffic that runs strictly below the equipment ground reference (0 to -15V) with a -6 V threshold (conveniently), which is a fairly rare protocol but I'd stay far away from anything that could only handle, say, a 0-5V input range or that had a fixed trigger.

- Data compression, being able to run a fast sample clock to look at bursty data over long periods. With direct sampling, even a relatively slow 10 MHz sample rate fills a 1 MB buffer in only 0.1 seconds. Not very useful if one is simultaneously watching, say, 4800 baud serial traffic and high speed digital I/O. That said, having only 2K transitions per channel can occasionally be annoying. I'm astounded that they haven't yet come out with V2 hardware with deeper memory.

- The serial protocols are a nice-to-have until you're trying to decode a new manufacturer's data sheet and it's "Am I not sending the right stuff or is the other chip not happy for some reason?"

Reply to
Rich Webb

Rethink the triggering. Fancy triggering is often essential. If you can't get the desired event in the capture memory, you're SOL.

Reply to
mike

As with USB scopes, it is essential that all high speed processing is done on the device (such as triggering), since there is a severe bottleneck (the USB bus). Thus, only relatively short captured frames can be transferred later on to the host for post processing and display.

Fancy protocol decoding can well be done in the host, but first you must capture (in the device) a part of the data stream containing at least the high level frame (and some extra data) and transfer over USB to the host, where it can be decoded and displayed.

Reply to
upsidedown

Thanks - I've ordered one of these - the price makes it difficult to resist. If it doesn't do the job, it has the potential for a fun toy that I can re-program to do /stuff/

Reply to
yellow.yeti

Yeah, I'd agree to an extent - the problem stops being '2 devices using their own interpretation of the protocol' and becomes '3 devices using their own interpretation of the protocol'

When things have settled down and you're looking at contents of packets rather than timing relationships of wires, it can be useful though - hence 'nice but not essential'

Reply to
yellow.yeti

definition of /fancy/ I guess - generally for an analyzer that is able to handle triggering of complexity N, there will be that time that you need N+1

I'm quite liking the idea of the opensource FPGA thing mentioned above, as it may be possible to use the FPGA itself to generate complex trigger functions if absolutely needed.

Reply to
yellow.yeti

Works great. Back in the days before GA's were FP, we used to put a GAL20v8 on a proto board and program it as a complex trigger/qualification state machine. Easily created trigger sequences far beyond the capabilities of the logic analyzers of the day. But it was a bitch to reprogram with the tools of the day.

Reply to
mike

On Thu, 04 Jul 2013 12:31:37 -0400 in comp.arch.embedded, Mel Wilson wrote,

That's what we call "hard sell."

Reply to
David Harmon

snipped-for-privacy@gmail.com wrote

As usual, I recommend DigiView from

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although I prefer a standalone mixed mode scope for most of my specific tasks.

DigiView uses "compression" (stores only changes and according times), so you get very good recording depth and fast transfer tothe PC.

BTW: You should improve your quoting style (no full quote, no additional line feeds).

Oliver

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Oliver Betz, Munich http://oliverbetz.de/
Reply to
Oliver Betz

:)

But there are th Mel.

Reply to
Mel Wilson

On Mon, 08 Jul 2013 13:36:20 -0400 in comp.arch.embedded, Mel Wilson wrote,

Reply to
David Harmon

channels.

essential.

buffer is reasonable/available?

Might be a delayed reply but have a look at this

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Reply to
gopal_amlekar

That should be

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Roberto Waltman 

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Reply to
Roberto Waltman

oh yes that's right. sorry for the typo error..

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Reply to
gopal_amlekar

I have the top of the line units and I love the complex triggering system so you don't have to wade through tons of garbage to get to what you want to see.

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Reply to
WangoTango

Um, why are you measuring time in units of conductance i.e. Siemens (S), rather than seconds (s)? That's a mistake frequently made by softies :)

Have you had any problems getting a decent clean external 200MHz clock to the chip? (I.e. via a connector that doesn't include a ground connection).

Reply to
Tom Gardner

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