Are USB logic analysers typically single-shot only?!

[Bassman59]

Why not get a (used) MSO which works?

Because I think the PC connectivity is important for a logic analyzer (heck, the 24" screen for all those digital signals and a mouse with a scroll wheel blow away a standalone unit immediately, before all of the extra analysis options are considered); because bench space is limited here, and because I have other projects in mind which call for a PC-connected 100MHz 4-channel DAC. Nevertheless, thanks for the suggestion -- it's worth a look, maybe I can find a really cheap "throwaway" MSO that'll tide me over in the mean time.

Look for a used HP 1660. Seriously.

[Electro Fan]

The vintage units have a nostalgic appeal and probably have some decent utility if they are working A-OK.
If you would like a HP 1660 or other HP models there are about half a buzillion various units, modules, and parts out there:

http://www.ebay.com/itm/HP-Agilent-1660A-Logic-Analyzer-Analysis-System-/301273126207?hash=item462547153f:m:mL8lpU3YGVxHHSSOCxoLusw

http://www.ebay.com/itm/HP-16500B-Logic-Analysis-System-with-16550A-Module-Working-/301538848432?hash=item46351daeb0:g:ZgMAAOSweW5U6Sdn

http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313.TR0.TRC0.H0.Xhp+16500+logic.TRS0&_nkw=hp+16500+logic&_sacat=0

Pretty nice if you are into toggle switches and mechanical counters:
http://www.ebay.com/itm/HP-1607A-Logic-State-Analyzer-with-10230C-clock-probe-cables-manual-/151638870841?hash=item234e618b39:m:mpNtXQy6DqWZtnJhx7WReCQ

[Dubbie]

Or you could just solve your problem with a spare gpio or three. Just set them high when whatever axis is > threshold. It seems like you need to think outside the box a little here.


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[rs20]

Or you could just solve your problem with a spare gpio or three. Just set them high when whatever axis is > threshold. It seems like you need to think outside the box a little here.

I want a tool to effectively solve current and future problems, not a hack to get me past the next little hurdle. I recently bought a drill press and I massively regret the time I wasted carefully lining up hand-held drills in the time before I got the drill press; by analogy I want to understand the best tools for the job and the responses on this thread have been wonderfully helpful to this end.

Also, that was just an example of the utility of auto-run; I can already see live SPI feeds on my Rigol DS2202 logic decoding feature. The real problem prompting this thread was another one where I'd like to see at least 5 lines at once.

Thirdly, the bug I found that way was that the endianness of the bytes from the ADXL345 were not what I expected, which would have been difficult to debug with a simple threshold! It's all very well to suggest ways of achieving a goal under the assumption that everything is working fine; but the tools that reveal unexpected problems are the best.

[BloodyCactus]

the newer stand alone LA's are pc's with keyboard + mouse. like the Agilent 1683. hook up external monitor if you want 24". its windows xp.

they also do state analysis + transitional timing and triggering which all these usb things dont do. they just dump X megabytes of  data over usb to the pc to analyse.

[Electro Fan]

Or you could just solve your problem with a spare gpio or three. Just set them high when whatever axis is > threshold. It seems like you need to think outside the box a little here.

I want a tool to effectively solve current and future problems, not a hack to get me past the next little hurdle. I recently bought a drill press and I massively regret the time I wasted carefully lining up hand-held drills in the time before I got the drill press; by analogy I want to understand the best tools for the job and the responses on this thread have been wonderfully helpful to this end.

Also, that was just an example of the utility of auto-run; I can already see live SPI feeds on my Rigol DS2202 logic decoding feature. The real problem prompting this thread was another one where I'd like to see at least 5 lines at once.

Thirdly, the bug I found that way was that the endianness of the bytes from the ADXL345 were not what I expected, which would have been difficult to debug with a simple threshold! It's all very well to suggest ways of achieving a goal under the assumption that everything is working fine; but the tools that reveal unexpected problems are the best.

I think you're headed down a good path.  Frame the requirements considering what you know so far, what you currently need, and what you think you will need, then ask questions, get comments, revise and refine your requirements, wash, rinse, dry, repeat until ready.  You are getting lots of good thoughts here - combined with your questions and comments, at the end of the day you will likely have the best sense of what you need.  Per your example, it's no doubt gratifying to know that as much time as you spent drilling holes manually now you can happily automate the process.  Without having experienced the single shot approach and without doing your homework it would be hard to be in the position to appreciate your drill press.  Having said all that, I've found that sometimes I think I understand where I'm headed but I wind up somewhere else because I didn't understand what I didn't understand - fortunately there are often enough patient and persistent EEVers here to straighten me out  .

Part of the beauty of EEVblog is that after you finally select your solution and you tell us what you learned others will gain some insight from your journey. 

[Electro Fan]

the newer stand alone LA's are pc's with keyboard + mouse. like the Agilent 1683. hook up external monitor if you want 24". its windows xp.

they also do state analysis + transitional timing and triggering which all these usb things dont do. they just dump X megabytes of  data over usb to the pc to analyse.

The 1683 may do some very good stuff the Intronix LogicPort doesn't do (and the LogicPort's memory might or might not be sufficient) but the LogicPort does state analysis, and transitional sampling (and triggering)
- just sayin' 

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http://www.pctestinstruments.com/logicport/faqs.htm

How many full-speed channels does the LogicPort support?
The LogicPort will simultaneously sample all 34 channels with full buffer depth at 500MHz in timing mode, 200MHz in state mode. This is in direct contrast with competing products which sample at full speed on only a fraction of their available channels, or with only a fraction of their marketed buffer depth. When sampling in state-mode, one channel is used as a state-clock input allowing the remaining 33 channels to be sampled at the state-clock rate.

What is the benefit of real-time sample compression?
Real-time sample compression or "transitional sampling" allows the LogicPort to utilize its sample buffer much more efficiently. The data is first sampled, then compressed in real-time using a lossless compression algorithm, then written to the sample buffer. The sampled data remains compressed until the software expands it back to its uncompressed form for display.

This entire process is transparent to the user and has zero impact on measurement accuracy, yet allows the LogicPort to pack much more data into its sample buffer. Compression is particularly effective for high-resolution capture of high-speed bursts separated by long periods of low or slow signal activity. That's because during periods when signals have little activity, the LogicPort can continue to sample at high speeds without  filling its sample buffer with thousands of copies of identical data. Only meaningful data is stored in the buffer - memory addresses are not incremented simply to mark time.

The degree of compression varies depending upon the nature of the data, but typically ranges from significant to dramatic. Our proprietary compression algorithm insures that the LogicPort's compression feature never imposes a performance penalty, regardless of signal activity or speed. As a result, the LogicPort enjoys a significant advantage over traditional transitional sampling systems which simply assign half of all available memory locations as storage for time stamps (thereby reducing the effective buffer depth by half for very active signals). To see the LogicPort's sample compression in action take a look at the screenshots, or download the free software and explore the sample projects which are included. As you'll see, it’s not uncommon to collect many times the size of the sample buffer.

http://www.pctestinstruments.com/logicport/specifications.htm

Sampled channels: 34
Timing mode sample rate: 1KHz to 500MHz (uses internal clock)
State mode sample rate: 0 to 200MHz (clock provided by circuit under test)
Sample buffer: 34 x 2048 samples
Maximum sample compression: 2^33 to 1 (sample rates to 200MHz)
Trigger sequencer: 250MHz max, 4ns minimum pulse width
Trigger capability: 
    Edges - Rising, Falling, Either (multiple channels, any combination)
    Patterns - True, False, Entered, Exited (across any / all channels)
    Bus Value - Equal, Not Equal, Less Than, Greater Than, In Range, Not in Range
    Occurrence Count - Range of 1 to 1,048,576 Consecutive or Cumulative
    Duration - Equal, Less Than, Greater Than, Within Range (samples or time)

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Having said all that, if you can get one of these or a similar model (this is a 1663 rather than a 1683) it looks like a deal:

http://www.ebay.com/itm/HP-Agilent-1663A-Logic-Analyzer-with-accessories-/321884393529?hash=item4af1ce1039%3Ag%3A9JMAAOSw4HVWEaLm&nma=true&si=EMI%252B7m1hl%252FlGFOe5Ntx01RCRabI%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557