[sdiy] Logic Analyzers

ASSI Stromeko at NexGo.DE
Thu Dec 28 12:37:10 CET 2017

Am 28.12.2017 um 03:22 schrieb Michael Zacherl:
> In the not so distant future I’ll be probably in the market for a not too expensive logic analyser.
> Just browsed the Saleae site, looks good at the first glance.
> What’s too have? What’s too avoid, feature-wise?

You really need to define your objectives in more detail, make a list of 
"musts", "nice-to-haves" and "don't cares" and just fill that out for 
each of the options you come across.  What's "not too expensive" for 
you?  How many channels do you want, do you need hardware buffering or 
hardware triggering, target synchronous sampling.  Is protocol analysis 
in the viewer software enough or do you need to trigger on protocol 
events?  What protocols do you need to analyze, do you also need to be 
able to inject protocol events?  How about the higher levels of the 
protocol stack?  Is Windows only OK or do you want Linux software also? 
Etc. pp.

At home I have an original Saleae Logic/8, an Intronix LogicPort and a 
PropScope.  All three would somehow fit your description, but of course 
they are very different things even though there is overlapping 
functionality.  The LogicPort software fortunately works with Win98SE 
and doesn't really need much in the way of USB and CPU performance, so I 
use it with an old 10" laptop that already had a touchscreen at the 
time.  That combination is a lot more usable than some hardware LA out 
there and I've used a few.

For all software based instruments you also need to consider how the 
necessary PC or laptop fits into your work area.  I recommend to use a 
dedicated box so that you can freeze the software stack in a known 
working state if you need to.  Keep in mind that those analyzers having 
no hardware buffers (like the Saleae Logic) need pretty much all the USB 
performance they can get if you use them at speed and won't work nicely 
through most USB hubs (either due to bugs in the hub or the additional 
latency).  Unfortunately that description includes many laptop USB ports 
these days, so unless you buy that laptop specifically with those 
requirements in mind you may end up with the only port working well in 
an entirely inconvenient location for instance.


(on the road :-)

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