Oscilloscope Bandwidth Confunsion - Page 1
Forum section: electronics / testgear

author: fabltd
author_rank: Contributor
timestamp: September 01, 2017, 09:31:24 am
content: HiI have some electronics experience and currently use the following scope:https://www.picotech.com/oscilloscope/3425/picoscope-3425-overviewThis would appear to have only a 5 MHz bandwidth.I am a little confused as to why this is so low when compared with the bench scopes i am looking at. I am aware this is a differential scope. It was purchased for mains power work.I am now looking to purchase a bench scope for work with micro controllers:The signals will be:I2C / SPI / UART and maybe USBIs there a reference table for how much bandwidth a signal will need to be displayed properly.So that i can look at purchasing the correct scope.Thanks

author: tggzzz
author_rank: Super Contributor
timestamp: September 01, 2017, 09:46:40 am
content: Quote from: fabltd on September 01, 2017, 09:31:24 amFor digital signals, the rule of thumb is that bandwidth = 0.35/tr, where tr is the transition time. Note that the period/frequency of the signal is completely irrelevant.

author: Ice-Tea
author_rank: Super Contributor
timestamp: September 01, 2017, 09:53:13 am
content: It's not just about the differential and high voltage part. These are 12-bit ADCs. Speed or accuracy. Never both. Unless you have a spare kidney.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: September 01, 2017, 09:58:51 am
content: I keep eye on Pico range but never even noticed this. Must be quite old model. Seems it's very specialized thing12 bits+ quite high voltage tolerance:Maximum safe voltagesDifferentialAny input above scope ground400 V400 V (600 V transient)Current counterpart for mains work seems to be 12/14bit 4444 which is solved differently with protection shifted more to specialized custom probes and is up to 20MHz.These scopes are not optimal for general low voltage tinkering. I have fastest 2000 for that:https://www.eevblog.com/forum/testgear/picoscope-2000/However they started to add some extra features to USB 3.0 scopes (3000+). Currently Deep Measure.2000 is USB 2.0.As for USB 1.1 (1.5Mbps / 12Mbps ) can be looked and decoded with pretty much any general purpose Pico, but not 2.0 (480Mbps). Overall scope is not optimal thing to mess with USB 2.0 due to quite complex protocol. For signal integrity best would be very high analog bw sampling scope and for protocol some specialized analyzer.

author: fabltd
author_rank: Contributor
timestamp: September 01, 2017, 10:04:24 am
content: Thanks for this.Yes my current scope is a few years old. I use it for testing mains dimmers. Its ideal.So i am still confused as to what bandwidth I really need. Does some one have an example of where a 100 MHz scope would be better than say 50 MHz?Jeremy

author: nctnico
author_rank: Super Contributor
timestamp: September 01, 2017, 10:12:46 am
content: More bandwidth is always better. For general purpose work 100MHz is enough unless you are going to use SPI at tens of MHz. Beyond 100MHz you'll need other probes as well to get something meaningfull on the screen so things can get expensive quickly.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: September 01, 2017, 10:14:29 am
content: Quote from: fabltd on September 01, 2017, 10:04:24 amFor analog work you need approx 4x bandwidth. So with 100MHz scope you are fully comfortable with <25MHz signals, above that you can work mainly with timing related stuff (but to high accuracy!) and see only general shape w/o fine detail. Overall I would say 100MHz analog is ok, but more is... moreNote that my 100MHz 2000 measured to be approx 140MHz (-3dB). Others have gotten approx 100MHz from 70MHz variants.Cannot really see USB 2.0 signal integrity inanalogdomain with anything below 1GHz so suppose your only option would be some used boat anchor if truly interested.

author: Eric_S
author_rank: Regular Contributor
timestamp: September 01, 2017, 10:19:57 am
content: Keysight as an appnote or two regarding scope BW that might be interesting for you to review:http://literature.cdn.keysight.com/litweb/pdf/5989-5733EN.pdfhttp://literature.cdn.keysight.com/litweb/pdf/5991-0662EN.pdf

author: fabltd
author_rank: Contributor
timestamp: September 01, 2017, 10:23:46 am
content: Thanks allI was thinking of somthing like this:https://www.siglent.eu/sds1202x-e.htmlIt claims 200 Mhz. Its the decoding that most interests me too.Has any one used one of these?

author: MrW0lf
author_rank: Frequent Contributor
timestamp: September 01, 2017, 11:09:43 am
content: If decoding is something that you havemostinterest in Id suggest to experiment a little with UART on your Pico and get some feel what it can do. Then carefully observe some YouTube videos about decoding on standalone DSOs in general and think if you are prepared to fiddle with knobs so much. Overall PC based instruments are better for decoding because mouse/keyboard/bigscreen GUI is optimal for data processing type app. Best are of course specialized decoders that support nested protocols etc. That goes for data processing part - as for triggering standalone DSOs offer serial trigger, which Pico and specialized decoders do not tend to offer.I've thinking for some time that currently best option would be cheap DSO that can serial-trigger and feed trigger-out to Pico or logic analyzer. Get best of both. Question is should "trigger slave" be 2ch or maybe 4ch

author: rstofer
author_rank: Super Contributor
timestamp: September 01, 2017, 03:43:46 pm
content: Quote from: fabltd on September 01, 2017, 10:23:46 amThere are two epic threads on this forum re: 1202x-e. There are also a couple of videoshttps://www.eevblog.com/forum/testgear/siglent-sds-1202x-e-review-on-youtube/Personally, I might wait for the 4 channel that was just released in China. And, yes, there is a thread about it here.Nothing is more important than bandwidth except channels.

author: fabltd
author_rank: Contributor
timestamp: September 01, 2017, 03:46:49 pm
content: ThanksIts so confusing to know what to get. They all seem similar but the protocol decoding has to be number 1 on my list.I have a logic analyser but its not real time.Two channels should be OK ( TX / RX) i think.Has any one used the PC application?

author: rstofer
author_rank: Super Contributor
timestamp: September 01, 2017, 04:48:48 pm
content: Quote from: fabltd on September 01, 2017, 03:46:49 pm4 Channels is pretty useful for SPI and the ONLY reason I bought the DS1054Z. I already had a 350 MHz Tek 485 so bandwidth was not a consideration. Playing with a DSO has been pretty interesting. Single shot is a very nice feature.If you want to do USB, look for a purpose specific protocol analyzer.

author: fabltd
author_rank: Contributor
timestamp: September 01, 2017, 05:26:04 pm
content: Thanks this great.Who makes the DS1054Z does it come with protocol analysis or is it an add on.Any one have any opinion on the best scope for my usage case? I have read so many specs and reviews but still cannot decide.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: September 01, 2017, 05:33:11 pm
content: Quote from: fabltd on September 01, 2017, 03:46:49 pmhttps://youtu.be/hlSUF8iCZtM?t=3m57sDefine realtime? As Dave points out correctly analyzing large memory takes time.Most "realtime" in low end are Keysights. But at the cost ofnotanalyzing (very) large memory.Same on Rigol - decodes only whats on screen but much slower than Keysight.Think you should determine what is record size you want to work with...Less than 100 bits? 10M? 100M? Segmented memory or not?

author: fabltd
author_rank: Contributor
timestamp: September 01, 2017, 05:43:11 pm
content: Typically 100 bytes max. It's small packets from IOT devices.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: September 01, 2017, 06:22:00 pm
content: Quote from: fabltd on September 01, 2017, 05:43:11 pmAFAIK Rigol cannot resolve 100bytesat same time from single screen. 100 bytes smells of table style display, not inline. Not sure if Keysight X1000 has this and enough resolution, probably not. If you actually mean 100bitspicture changes...

author: fabltd
author_rank: Contributor
timestamp: September 01, 2017, 06:46:07 pm
content: That's fine I don't need to see all of the message. I can use the logic analyser for that. Need to need verify the right data is being sent a lot of the messages are 4 byte.

author: tautech
author_rank: Super Contributor
timestamp: September 01, 2017, 08:18:39 pm
content: Quote from: fabltd on September 01, 2017, 06:46:07 pmScopes handle this in different ways. Some use Zoom/Split screen to show lots of packets and the in Zoom window you can zero in on the bytes of interest. In this mode you use the Horizontal position of the unzoomed datastream to scroll along the message.These screenshots copied from the US site show the idea.In this image it's apparent I2C Trigger settings have been set to Stop the scope at the start of the packet.

author: fabltd
author_rank: Contributor
timestamp: September 01, 2017, 08:29:53 pm
content: This is just want I need. So I guess Rigor or Siglet is the question.What's the perference for most here?You guys are great. So much better than the software forums.

author: tautech
author_rank: Super Contributor
timestamp: September 01, 2017, 08:37:36 pm
content: Quote from: fabltd on September 01, 2017, 08:29:53 pmIf youmusthave 4 channels then you'll have to wait a few months for the SDS1204X-E to be released otherwise the SDS1202X-E is available. These are 200 MHz units and Decode is standard.There's plenty of info on this forum if you search for it. Use the Search button not the box.

author: nctnico
author_rank: Super Contributor
timestamp: September 01, 2017, 08:55:44 pm
content: Quote from: fabltd on September 01, 2017, 08:29:53 pmIf this is for work then I'd avoid anything from Owon, Hantek, Rigol and Siglent. Too many bugs which may never get fixed. After all you don't get what you don't pay for. The next step up before getting into Keysight territory is GW Instek (GDS2000E series, MDO2000 series or MSO2000 series) but expect to spend much more.

author: Electric2000
author_rank: Newbie
timestamp: September 01, 2017, 09:02:59 pm
content: If an oscilloscope has a bandwidth of 50MHz and 1gig samples/seconds. What would be the maximum square wave frequency it can display?

author: tautech
author_rank: Super Contributor
timestamp: September 01, 2017, 09:16:44 pm
content: Quote from: Electric2000 on September 01, 2017, 09:02:59 pmMaybe 200 MHz but it won't look like a square wave anymore.Simply, BW ratings presume 2 things, sinewave input and the -3dB amplitude frequency point.Typically most consider 1/5 of the BW rating gives best accuracy/fidelity.If you watch Pt 2 of the vids that rstofer linked earlier you'll see high BW sinewaves diminishing in amplitude as the frequency goes up.

author: nctnico
author_rank: Super Contributor
timestamp: September 01, 2017, 09:40:03 pm
content: Quote from: Electric2000 on September 01, 2017, 09:02:59 pmThat depends on how many harmonics you want to see. A square wave consists of the fundamental frequency and odd harmonics (3rd, 5th, 7th, etc). Seeing the 5th harmonic means you can start to see the shape of a square wave so 50MHz/5=10MHz. A 50MHz oscilloscope is likely to show some higher bandwidth signals so the 7th harmonic will also be shown (attenuated) for a 10MHz square wave making the picture a little bit prettier.

author: rstofer
author_rank: Super Contributor
timestamp: September 01, 2017, 09:56:23 pm
content: Quote from: fabltd on September 01, 2017, 06:46:07 pmYou use the decoder option to see a very few bytes. Just enough to know that the clock and data are properly aligned and that CS' doesn't go inactive before the last byte clears the output (SPI). It's the same kind of thing for I2C and UART. You don't need to decode everything, you just need to see how the data lines up.If you want to decode "War and Peace", use printf(). You'll get much more information from printf() than you will ever get from a scope or logic analyzer. Faster, too!The decoder option on the Rigol DS1054Z comes when you unlock the 50 MHz scope to 100 MHz. The options come along for the ride. I'm not going to go into it, there are EPIC threads around here about the DS1054Z but, basically, the unlocking is trivial.

author: nctnico
author_rank: Super Contributor
timestamp: September 01, 2017, 10:11:36 pm
content: Quote from: rstofer on September 01, 2017, 09:56:23 pmNot so fast! Decoding on an oscilloscope usually has accurate timestamps and (if your scope can search) you can search for specific messages to see where something went wrong. The timing being right for one message doesn't mean it is right for all messages! I have seen intermittent problems for which being able to decode & list thousands of messages was very benificial.

author: fabltd
author_rank: Contributor
timestamp: September 01, 2017, 10:22:04 pm
content: Great stuff but still not sure if the Rigor or Siglet is better for this class of work?Love to know when some chose one or the other ?

author: rstofer
author_rank: Super Contributor
timestamp: September 02, 2017, 01:24:52 pm
content: Quote from: fabltd on September 01, 2017, 10:22:04 pmYou're missing something. The Rigol has been around for three years or so and several firmware revisions. The Siglent is only a couple of months old and one firmware revision.So, those of us that bought a scope a year or so back didn't have a choice; the Siglent wasn't available.Since I already had bandwidth covered with my analog scope (2 channel), I bought the Rigol specifically for the 4 channels. I would do the same today (maybe) or I would wait for the release of the new 4 channel 1204X-E.More bandwidth is always good but so is more channels. Realistically, most of what I do is a low frequency. Last night I was decoding a 115200 baud serial signal. Not exactly high frequency work but I wanted to prove that the USB->Serial gadget was doing the right thing. And, with RS232, there is ALWAYS the DCE vs DTE issue. Did I need a null modem to reorient the pins? Scope showed that I did. The output from the terminal program showed up on pin 3 and I needed it on pin 2.If you don't already have bandwidth covered with something else, you have a tough decision to make. How important is decoding SPI? To me, it was the ONLY reason for buying the DS1054Z. I've gotten along with analog scopes for more than 50 years so the modern DSO, even if a lowly entry level scope, was a real eye-opener. But I didn't sell my Tek 485...And, somehow, for the last dozen years or so, I have been able to get SPI to work with just a 2 channel analog scope. Four channels is easier...

author: fabltd
author_rank: Contributor
timestamp: September 02, 2017, 01:31:53 pm
content: @rstofer Thank for a great post.Your doing exactly what I need todo a lot of the time. How do you find the Ui on the Rigor I have seen posts that point to it being not as good as the Siglet.

author: nctnico
author_rank: Super Contributor
timestamp: September 02, 2017, 01:34:08 pm
content: Quote from: fabltd on September 01, 2017, 10:22:04 pmAt this moment the DS1054Z is a very good choice because it has 4 channels and the firmware works. Personally I don't ever want to buy a 2 channel scope again because 4 channels makes life so much easier. However if you can wait a bit (and don't have a bigger budget) it might be worthwhile to see what Rigol and/or Siglent are going to introduce. Another option is to get a MicSig TO1000 tablet scope. These aren't expensive either and have mature firmware.

author: rstofer
author_rank: Super Contributor
timestamp: September 02, 2017, 03:43:29 pm
content: Quote from: fabltd on September 02, 2017, 01:31:53 pmIt's crap but I find it acceptable because I don't care. Moving the trace up or down, even with only one trace on the screen, is not anywhere near what I get with an analog scope where I simply turn a knob and change the voltage on the deflection circuit. But once I get the trace where I want it on the screen, I don't tend to move it again. I spend more time pressing the button for single shot capture. That works well!In fact, this is a PERFECT example of where analog controls are better than digital controls.I don't have the Siglent so I can't make a comparison.

author: fabltd
author_rank: Contributor
timestamp: September 02, 2017, 03:53:18 pm
content: Thanks the MicSig looks like a option as well. Any one using one of these?

author: nctnico
author_rank: Super Contributor
timestamp: September 02, 2017, 04:20:51 pm
content: Quote from: rstofer on September 02, 2017, 03:43:29 pmYou have to keep in mind that (AFAIK) the DS1054Z is your only reference! On most DSOs moving the traces works just as quick as on an analog scope.

author: rstofer
author_rank: Super Contributor
timestamp: September 02, 2017, 06:23:49 pm
content: Quote from: nctnico on September 02, 2017, 04:20:51 pmYou are correct, the DS1054Z is my ONLY DSO reference and I am a complete newbie with DSOs. But there is no way a digital control works in real time. It may be microseconds but it isn't real time. On a high end DSO, can the trace be adjusted vertically mid-scan? Say a 1s/div scale and you decide to shift it up 3 seconds in when you decide the position isn't where you want it. Or do you have to wait for another scan (12 seconds/scan)? On the entry level DS1054Z, if you turn the vertical position knob or change the V/div during a scan, the display quits updating until what would be the end of the scan and then restarts at the next trigger. This makes sense since it prevents taking an image of nonsense but it does go to the point of real time updating. Not so much of a problem at 1us/div.On my Tek 485, I can indeed adjust the trace mid-scan. In real time... Except for the bit where the 'cursor' won't bounce, I can play pong with the trace. Bounce it off the top and bottom of the screen. But left always scores!

author: fabltd
author_rank: Contributor
timestamp: September 02, 2017, 06:29:01 pm
content: The more I look into is it seems the Siglent is great but two channels if it had 4 it would be the best at this price point ?

author: alank2
author_rank: Super Contributor
timestamp: September 02, 2017, 06:38:45 pm
content: Quote from: fabltd on September 01, 2017, 09:31:24 amMy take is that for looking at I2C/SPI/UART/USB is that scopes are great for looking at the specifics of the signal, is it being produced accurately, etc., but the scopes acquisition model (multiple captures with no common timeline between them) is much less than optimal for looking at a "transaction" of signals. What I truly love for that is something like Saleae model that allows you to capture/decode everything on a single timeline. So, I recommend a Saleae for that, AND a capable scope of looking at the actual voltage levels/waveforms if you need to do that as well.As to your question about the low bandwidth picoscope, I think some of their models were made for different applications like audio use where bandwidth wasn't the primary goal and a higher bit ADC for more important. Pico does have an excellend 2000 series with much higher bandwidths, but as much as I like my picos, they are a desktop scope style in their acquisitions and still lack the single timeline for logic analysis that the Saleae has.

author: nctnico
author_rank: Super Contributor
timestamp: September 02, 2017, 06:45:46 pm
content: Quote from: rstofer on September 02, 2017, 06:23:49 pmAnd you think there is no such delay if you turn the pot on an analog scope? I'm sure there is. For starters to filter the offset voltage. Besides that in a user interface anything below 200ms is realtime. I forgot which DSO it was but I recall one where I could draw a signal using the offset controls. The bottom line is: it greatly depends on the implementation where each has it's pros and cons. On some you can 'draw a signal', some move the entire trace up/down and some restart the acquisition.

author: fabltd
author_rank: Contributor
timestamp: September 02, 2017, 06:55:51 pm
content: Quote from: alank2 on September 02, 2017, 06:38:45 pmThanksI have a Saleae it's great but you need to know that your on the right pins etc. That was my reasoning behind a scope with decide. I love my Pico it's great for a lot of the work I don but need something to compliment. So maybe 2 channels won't be such an issue.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: September 02, 2017, 07:18:38 pm
content: Quote from: fabltd on September 02, 2017, 06:55:51 pmOut of curiosity, what exactly is missing in your Pico decoder? Bandwidth due to analog part, serial trigger or some other functionality? I had Rigol for some months and could not find anything besides serial trigger where it would outperform.BTW if you just want some othertypeof gear for a change it quite ok to admitI even have Velleman HPS140 and in matter of fact used it recently to double check some signal levels before plugging in to expensive equipment.

author: fabltd
author_rank: Contributor
timestamp: September 02, 2017, 07:33:45 pm
content: Bandwidth and portability are the main things.

author: rstofer
author_rank: Super Contributor
timestamp: September 02, 2017, 08:28:53 pm
content: Quote from: fabltd on September 02, 2017, 06:29:01 pmIt's a toss-up. A few months back, there wasn't a choice to make. Now here we are agonizing over:1) Siglent 2 channel 200 MHz versus Rigol 4 channel 100 MHzand2) waiting for the Siglent 4 channel 200 MHz version to be released.Now, if somebody could say how long was the 1202X-E available in China before worlwide release, we could add that duration to the China release of the 1204X-E and see when it might be available to us.Or, a hybrid solution: Buy the 2 channel 200 MHz Siglent and get used to running it. When the 4 channel becomes available, sell the 2 channel and buy the 4 channel, you'll already be familiar with the UI. There, best of both worlds! Even better, do the same thing but delay the 4 channel until there absolutely isn't any other way to get the job done. You'll still have bandwidth.Geez, it's only money!Sidebar: I used to work for a fellow who said "Never use 'only' and 'money' in the same sentence!"

author: tautech
author_rank: Super Contributor
timestamp: September 02, 2017, 08:36:48 pm
content: Quote from: rstofer on September 02, 2017, 06:23:49 pmAt slow timebase settings a DSO is typically in ROLL mode and the display is being updated in real time, the only reference one has is the channel 0V indicator and some have a temporary line on the display that disappears once vertical adjustment has finished.The Siglent models Vertical position control has a dual function, a press of the encoder sets the 0V position to mid screen and in a similar way the Trigger level control when pressed sets the Trigger level to 50% of the waveform, whatever amplitude it is.Properly implemented, DSO's do these 2 things much better than a CRO.Quote from: rstofer on September 02, 2017, 01:24:52 pmYesterday I spent some time refreshing my familiarity (upcoming project) with SPI with 2 and 4 ch DSO's and the only difference was not being able to decode both MOSI and MISO together.

author: tautech
author_rank: Super Contributor
timestamp: September 02, 2017, 08:53:14 pm
content: Quote from: rstofer on September 02, 2017, 08:28:53 pmMost wouldn't want to do this but yes I find with all the Siglent units I handle the very similar UI is of great benefit.However the SDS1204X-E will have some features that no other Siglent models have and it will be interesting to get to grips with these......hopefully I'll get a pre-release unit to put through its paces.

author: fabltd
author_rank: Contributor
timestamp: September 02, 2017, 08:54:40 pm
content: Quote from: rstofer on September 02, 2017, 08:28:53 pmOk so I am leaning towards the Siglent. I know some of the more expensive scopes have signal generators built in. Any one recommend a signal generator for training. I am thinking it would be good to have a signal generator as a reference.

author: fabltd
author_rank: Contributor
timestamp: September 02, 2017, 08:56:03 pm
content: Quote from: tautech on September 02, 2017, 08:53:14 pmDo you know who the UK distributor is ?

author: tautech
author_rank: Super Contributor
timestamp: September 02, 2017, 09:13:42 pm
content: Quote from: fabltd on September 02, 2017, 08:56:03 pmThere's 2 according to the Siglent Hamburg branch HTB link:http://www.siglenteu.com/howtobuy.aspxLabtronixPass Ltd.Quote from: fabltd on September 02, 2017, 08:54:40 pmWhile not as widely useful as a proper AWG I find that Siglents STB3 very good for gaining familiarity with a large # of different usage cases and practice with trigger settings on tricky signals.http://www.siglenteu.com/prodcut-fjxx.aspx?fjid=2641&id=2771&tid=1&T=2The image shows the PCB underside but the topside and connection points is shown in the User manual.Download the User manual for it to get an idea of all its functions.IIRC it's US$100+I've used it a demo signal source on many occasions when customers have dropped by.

author: rstofer
author_rank: Super Contributor
timestamp: September 02, 2017, 11:03:46 pm
content: For a signal generator, I chose the Siglent SDG2082X - an 80 MHz unit. I bought it specifically to produce the Valentine Heart in this thread:https://www.eevblog.com/forum/chat/a-valentine's-day-activity-for-your-scope-and-function-generator/msg1136847/#msg1136847Here's the thing about real signal generators, most all of them: They can make some fairly complex waveforms. Any time you can take a fundamental frequency and add in various odd or even harmonics at selected amplitudes and phase shift, you have a real tool. The Siglent can do this and so can a lot of others. Dual channels are absolutely required.The Valentine Heart wasn't really the only reason, I thought I should have an AWG at some point and the time seemed right. But what a cool thing to display when the boss-of-the-house asks what you bought this time! It comes in a big box, it's not like you can slip it through the door without getting spotted.There are a lot of cheap signal generators that can basically produce a fundamental and even that looks like trash. It's worth it to have decent tools. The only reason I am so late to the signal generator game is that my interest lies in digital and I don't play with analog all that often. But I'm coming around...

author: alank2
author_rank: Super Contributor
timestamp: September 02, 2017, 11:33:36 pm
content: Quote from: fabltd on September 02, 2017, 06:55:51 pmI'm not sure I'm following you exactly - what do you mean?Quote from: fabltd on September 02, 2017, 06:55:51 pmPersonally I find decoding with a scope is a lesson in frustration, but that might just be me.

author: rstofer
author_rank: Super Contributor
timestamp: September 03, 2017, 12:36:41 pm
content: Quote from: alank2 on September 02, 2017, 11:33:36 pmI agree! I use the feature just long enough to know that I have the configuration right. Playing with the USB->Serial adapter, all I wanted to know was that PuTTY had indeed set the baudrate to 115k and, for sure, which pin of the DB9 was outputting the signal. All I needed was a single character on the scope that matched the character I typed.When I bring up a new project that uses RS232 signalling, I find it helpful to KNOW that one end of the conversation is working and that the Tx/Rx thing is squared away. When you're waiting to see that "Hello World" string it is helpful to know that at least the wiring is correct.

author: Fungus
author_rank: Super Contributor
timestamp: September 03, 2017, 12:43:37 pm
content: Quote from: alank2 on September 02, 2017, 11:33:36 pmMaybe your expectations are wrong. Oscilloscopes aren't really designed for massive protocol-debugging sessions, they're more to check if the electronics are correct and the signals are getting through. You can do this by decoding some simple packets.Once the electronics is correct and data is being transmitted you can either use printf() on the devices or get a logic analyzer.nb. Logic analyzers are mostly useless for finding out if the electronics are correct so the two are complementary.I think Sigrok can probably grab serial data from a 'scope and decode it on your PC.It's free:https://sigrok.org/

author: alank2
author_rank: Super Contributor
timestamp: September 03, 2017, 03:12:40 pm
content: Quote from: rstofer on September 03, 2017, 12:36:41 pmI'll use a scope to verify the voltage levels are what I expect, that there isn't noise, to measure the speed of the signal with more precision, but once I'm satisfied with these things, then the single timeline of the Saleae is the way to go. I've made the mistake of NOT looking at signals first with a scope and because they didn't meet certain voltage thresholds, there were misrepresented on the logic analzyer - so it can be an important step if you aren't sure of the signals.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: September 03, 2017, 04:22:15 pm
content: Quote from: alank2 on September 03, 2017, 03:12:40 pmWould that not roughly equal to just dumping it single shot into scopes quite large memory? Think soon 100+MB will be norm and 500+MB common. Or need even larger?

author: Fungus
author_rank: Super Contributor
timestamp: September 03, 2017, 05:10:38 pm
content: Quote from: MrW0lf on September 03, 2017, 04:22:15 pmIt probably wouldn't be much different really.The DS1054Z can trigger on all sorts of serial events. Setting them up via the knobs on the 'scope is a pain but a PC application could make it easy. 24Mb of memory with good triggering is quite a lot, and it's free (so long as you have the app).

author: alank2
author_rank: Super Contributor
timestamp: September 03, 2017, 05:59:41 pm
content: Quote from: MrW0lf on September 03, 2017, 04:22:15 pmI tried this and found it to be a bit less than desirable. To accomplish this you have to use a slower timebase, and that usually comes with a slower sample rate and less memory usage. Sometimes you can manually adjust the sample rate and memory, but sometimes not. You also have to have an idea of how much you want to capture ahead of time and can't change that mid capture. The bigger issue comes along when you have any sort of space between the data as is common in i2c/spi/uart/usb because you are wasting precious memory because it has no compression. Still, it is the best way to do you on a scope if you need a single timeline.

author: nctnico
author_rank: Super Contributor
timestamp: September 03, 2017, 09:44:50 pm
content: Quote from: alank2 on September 03, 2017, 05:59:41 pmThere is such a thing as segmented recording which does the same especially if you set a trigger for a specific message.

author: alank2
author_rank: Super Contributor
timestamp: September 03, 2017, 10:20:25 pm
content: Quote from: nctnico on September 03, 2017, 09:44:50 pmDoesn't segmented recording involve multiple triggering? Then it isn't a single timeline then, right?

author: nctnico
author_rank: Super Contributor
timestamp: September 03, 2017, 10:29:25 pm
content: Quote from: alank2 on September 03, 2017, 10:20:25 pmEach segment is timestamped and on the better oscilloscopes (Keysight for example) you can have the messages from all segment in one list which basically means you'll have the decoding on one timeline.

author: fabltd
author_rank: Contributor
timestamp: September 04, 2017, 06:07:53 pm
content: Hi AllSo i have purchased the Siglent sds1202x-e.I will revert with my thoughts once it arrives.Thanks

author: tautech
author_rank: Super Contributor
timestamp: September 04, 2017, 09:18:56 pm
content: Quote from: fabltd on September 04, 2017, 06:07:53 pmShortly after release further shipments from the factory had the firmware updated to what's now the current version so check that you do indeed have this version or higher installed: V5.1.3.13.

author: hermit
author_rank: Frequent Contributor
timestamp: September 06, 2017, 12:53:05 am
content: Quote from: Fungus on September 03, 2017, 12:43:37 pmThe guy who started the front end, Pulsview, has a video where he mentions spending way too much of his life analyzing the scope output.