[sdiy] Logic Analyzer Advice

[Didrik Madheden]

A name you'll hear when it comes to logic analyzers is Saleae. They got
their business started by noticing that there was a certain Cypress
microcontroller that was very good at copying the state of the digital IO
pins into memory using DMA and then transferring that over USB to the host
computer. They have since graduated from that method of data acquisition,
but their original product lives on in the form of clones from China. These
little clone devices are a very cheap way to get started, as you can find
them on AliExpress etc for about $20. These devices can be used with
Sigrok, which other people already mentioned. These devices will happily
stream 8 digital channels at a sample rate of 8-12 MHz, meaning that
essentially only your computer's RAM is the limit for how much data can be
captured. The sample rate is probably overkill for your application but
perhaps 8 channels could be limiting. The other downside of these devices
is that they can be a bit fiddly to set up with drivers.

Saleae's own products today are a bit pricey. If you're looking for
something a bit better, I'd instead suggest DSLogic's products. Their
baseline offering is a 16 channel/400 MHz logic analyzer for $200. It's
using a fork of the open source Sigrok software.

I have their DSLogic U3Pro32 which I use for probing the full bus of an 8
bit CPU. It's ok but a pet peeve of mine is that the protocol decoders are
using Python, which makes them pretty slow when you have a capture of
multiple hundred megabytes.

The upside of Python decoders is that you could even make a custom decoder
that could warn you about invalid states, which could help you in
debugging. Although just displaying the state if the lines as hex is
trivial to do.

As for connectivity, DSLogic has a pretty well thought out system with
shielded fly wires which terminate into a 2.54 mm socket which you can
optionally connect to a clip that you can clip onto component legs. It also
supports variable logic thresholds for different voltage standards.

If you want something a little more serious, DSLogic's products would be my
suggestion. If you want something cheap to play around with go for the
Saleae clone. I would not consider standalone devices personally. As much
as the device may be a beautiful piece of tech, it's fixed function and the
functionality can't be improved or extended.

/Didrik

On Fri, 16 May 2025, 19:28 Terry Bowman via Synth-diy, <
synth-diy at synth-diy.org> wrote:

> I need to repair some old frequency counters and whatnot. It sounds like a
> job for a logic analyzer but I've never actually used one.  What would be
> wonderful is the ability to put a clip on the counter DIP, tell it what
> chip it is and then watch it count away in hexadecimal. Someone told me
> that this is "decoding" the data which makes sense. Anything that doesn't
> require me to do any mental gymnastics is ESSENTIAL. I'm not rich but I'll
> pay for what I need. Anything less is a waste of time.
>
> What would be best for this? I'm sure there are factors that I'm not even
> aware of. PC based is an option as I'm going to put a 32" monitor on my
> bench. I have a line on a beautiful old HP DSO that's a dream to use and
> has one built in but there's no "decoding".
>
> The counters in question have Nixie tubes in them. Some go down to 1Hz so
> they're not bad for fooling around with trans-AF. I have an LED model that
> I'll practice on first.
>
>
> Terry Bowman, KA4HJH
> "The Mac Doctor"
>
> https://www.astarcloseup.com
>
> #1: There is no substitute for good tools;
>
> #2: Always use the right tool for the job.
>
> Linn Westcott
>
> ________________________________________________________
> This is the Synth-diy mailing list
> Submit email to: Synth-diy at synth-diy.org
> View archive at: https://synth-diy.org/pipermail/synth-diy/
> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20250517/6d7b4309/attachment.htm>