What's the deal with logic analyzers on scopes?  (Hantek MSO5102D) - Page 1
Forum section: electronics / testgear

author: scurrier
author_rank: Newbie
timestamp: April 09, 2013, 05:10:53 am
content: My question is pretty much what the title says. I am in the market for a mid-hundreds up to $1k scope, and it seems like the LA functions on them are quite weak. For example, I looks like the Hantek MSO5102D that I am interested in can't decode any protocols or trigger off of a specific string of bits. This seems to make it quite useless in my opinion. What's the deal? Who buys these MSO's with crippled LA's? What's the general feeling that people have about them? What is considered to be the best strategy for covering both analog and digital signals (ex: digital oscilloscope + PC based LA)?Some background about me. I plan to use the scope for my electronics hobby, which entails programming my propeller microcontroller and troubleshooting electronics. I also want to build a quadrocopter in the future and basically design and program it from scratch (except for the speed controllers). I have a deep interest in electronics and a master's in mechanical engineering with a controls focus, so it seems feasible. (and fun!) I just found EEVblog last week and I have been ADDICTED since then. I love the teardowns and troubleshooting. It's great just to hear the thoughts of someone experienced as they look at different things.P.S. The MSO5102D manual says it has what's called a "code-pattern trigger" and a "queue trigger" specifically for the LA. What are these? You have to select a pattern of H, L, or X for them. What are those?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 09, 2013, 09:16:30 am
content: MSO functions aren't really logic analysers, they're just more channels.In some cases you get functions like bus grouping (e.g. showing hex values on a group of signals) , and the additional channels often allow simple pattern triggering, but you generally don't get the advanced triggering modes of a real LA, and AFAIK none of them offer state analysis (except maybe very crudely using segmented memory) .

author: Gunb
author_rank: Regular Contributor
timestamp: April 09, 2013, 10:01:46 am
content: Looking back there was no decoding functionality offered a few years ago for many scopes/logic analyzers but that doesn't mean that it is useless. During my studies I remember well that I've developed µC circuitries with external memory. Checking the address bus after I had some trouble to get it working right, I've connected the LA and could decode the address manually. Of course, that meant more efforts, but in the end I had a tool to see something.Today you might implement firmware on FPGAs which have replaced a bunch of CMOS circuitries and you would like to measure a few inputs/outputs in parallel, where timing is an issue. In this case you're glad to have an LA, even without decoding options.I use my Hameg HMO2524 with 16 channels (of course not your intended budget), and I've all the options for decoding. But there are still cases where to apply the probes to the circuitry and see the channels in parallel on screen without activation of any decoding. You can see if ports are set right at a certain point of time very easely. So, this is an option that I won't miss at all, especially when working with embedded systems.So, there are still reasons to have the LA included without decoding options. I decided a few years ago for the HMO series since they are very powerful especially at this point, and I'm using it mainly for hobby purposes, too.Kind regardsGunb

author: nctnico
author_rank: Super Contributor
timestamp: April 09, 2013, 01:12:44 pm
content: Quote from: mikeselectricstuff on April 09, 2013, 09:16:30 amI agree. Back in the days when I did a lot of FPGA work I used an MSO for most regular debugging work. If you need fancy triggering, state analysis or timestamped recording then its time to pull out a real logic analyser.

author: scurrier
author_rank: Newbie
timestamp: April 09, 2013, 05:06:05 pm
content: Thanks guys, this is some good information. I really appreciate the guidance.With respect to the MSO5102D.... does anyone have an idea what the code-pattern triggering or queue triggering might be? Or what the pattern selections of H, L, or X that you have to make for the trigger could be?

author: Gunb
author_rank: Regular Contributor
timestamp: April 09, 2013, 07:00:37 pm
content: Hi,did not study the manual of the MSO5102D, but usually the pattern selection enables you to define the pattern which should trigger the scope. Let's assume digital probe pins D0 AND D4 should both be high, D2 low to trigger the scope, all remaining pins are "don't cares", then you set D0 to H, D4 to H and D2 to L, all other pins to X. That's a comfortable way to trigger the scope with special events on the logic channels.With my HMO2524 I can use up to 16 channels plus the 4 analog channels and design either an AND or OR pattern as described above, the output of the FF can be set to TRUE or FALSE. Additionally a filter can be specified where the output pulse must meet certain pulse length (minimum, maximum, equal, unequal,....).Kind regardsGunb

author: wojt
author_rank: Newbie
timestamp: April 09, 2013, 07:21:57 pm
content: Once I became familiar with SCPI commands, things became much easier. If the scope does not decode the protocol, I do it on the PC. Recently I built the USB decoder for Hameg HMO. I use scope for triggering and data acquisition. Then my script on the PC retrieves the waveforms and analyses them. It all can be done automatically using only free tools. My favourite is Python(x,y). It has awesome math and plotting libraries.

author: scurrier
author_rank: Newbie
timestamp: April 10, 2013, 02:54:49 am
content: Great input, thanks guys.I had a feeling H and L stood for hi and lo, but didn't know what X was. Ha! Thanks.