Hackable oscilloscope with 4 channels and >100Mhz bandwidth? - Page 1
Forum section: electronics / testgear

author: ironcurtain
author_rank: Regular Contributor
timestamp: March 19, 2018, 06:39:42 pm
content: Hey,I'm finally going to buy a new scope... I settled on 4 channels, more than 100MHz bandwidth (I will need to do some RF and digital work with it so 200 would be neat, unless someone wiser can illustrate to me how I could workaround bandwidth limitations...) and decoding functions as I do reverse engineering somewhat regularly, and they help a bunch.I would like to save some money, and I could not find a straight to the point post with a short summary of oscilloscopes presently 'hackable', either through firmware modification or key generation methods.I'm looking into these series:SDS1000X by SiglentDS1054Z by Rigol (only hackable to 100 it seems)The Siglent SDS1204X-E seems like my best option, unless someone can prove otherwise. I'm still not sure whether I will end up needing a built in logic analyzer...

author: LoveToRepair
author_rank: Newbie
timestamp: March 19, 2018, 06:44:27 pm
content: I just Got the Rigol DS1054Z completely unlocked. I love it. I haven't been able to test it past 200Mhz yet But it went up to 200Mhz just fine

author: tggzzz
author_rank: Super Contributor
timestamp: March 19, 2018, 06:55:46 pm
content: A scope is usually the wrong tool for RF work at that kind of frequency, due to limited voltage input ranges, ADC non-linearity, ADC resolution, and non-50ohm input impedance.So, work out what input powers (and therefore voltages) you will be measuring, and what measurements you want to make. Then try to match that with scope specifications.Consider using a decent RF spectrum analyser, i.e. one that is a low-noise high-linearity superheterodyne radio.

author: rstofer
author_rank: Super Contributor
timestamp: March 19, 2018, 07:36:31 pm
content: The SDS1204X-E probably is the best thing going at the entry level but the $760 price tag will keep people in the Rigol DS1054Z for a few more years. There is also the 'newness' bit to get past. It is important to know what issues have yet to be resolved by firmware revisions. It took a couple of years for the DS1054Z firmware to get to a point where most issues are fixed.200 MHz seems like a lot for sine waves. It isn't all that much when you think about the 5th harmonic of a 50 MHz square wave. The sum of the first, 3rd and 5th don't really look all that good.I have the DS1054Z but I am seriously thinking about the SDS1204X-E. I'm not in a hurry so I'll wait on firmware revisions. Maybe in a couple of years...Don't overlook 2 scopes. For your high bandwidth stuff, you probably don't need the features of a DSO. I bought a Tektronix 485 350 MHz analog scope about a dozen years ago for around $200. It was only a year or so back that I bought the Rigol and I bought it for channels and decoding, not bandwidth.The features of a DSO are compelling - except for bandwidth versus dollars.

author: ironcurtain
author_rank: Regular Contributor
timestamp: March 19, 2018, 07:47:10 pm
content: Quote from: tggzzz on March 19, 2018, 06:55:46 pmI have a HP 8924c test set with a GPIB interface and such, for all my RF needs. But I do like the ability to look at FFT/RF related tasks for lower frequencies. I just can't find a newer SA for an acceptable sum of money... the European market sucks for all things second hand in this field.

author: tggzzz
author_rank: Super Contributor
timestamp: March 19, 2018, 08:05:09 pm
content: Quote from: ironcurtain on March 19, 2018, 07:47:10 pmThat's good, but I'm not sure it changes the cautions about using scopes.Apart from that, patience may allow you to find a conventional spectrum analyser; my Tek492 cost £250

author: nctnico
author_rank: Super Contributor
timestamp: March 19, 2018, 08:11:35 pm
content: Quote from: rstofer on March 19, 2018, 07:36:31 pmAgreed but you don't need to buy a 40 year old boat anchor. You can buy a decent 500MHz+ DSO for a reasonable amount of money. Personally I also have multiple DSOs. One for general purpose use and one for specific HF use.

author: joseph nicholas
author_rank: Frequent Contributor
timestamp: March 19, 2018, 08:28:39 pm
content: Quote from: nctnico on March 19, 2018, 08:11:35 pmYes, yes I agree. The hype around the usefulness and value of old scopes are generated by peoples desire to sell you something that is a nightmare to repair and maintain. Don't forget that even if it is good shape and working its full of aging capacitors and unobtainable parts. The old tek scope are especially prone to this. The romantic and nostalgia reality warp effect.

author: ironcurtain
author_rank: Regular Contributor
timestamp: March 20, 2018, 03:25:45 am
content: Quote from: LoveToRepair on March 19, 2018, 06:44:27 pmHow does it compare to the Siglent in that state? How's the sampling? Did you follow any specific 'recipe' posted somewhere you can link to?It's literally 400 EUR less... so my guess is, are the insides the same as the 200MHz model??

author: tautech
author_rank: Super Contributor
timestamp: March 20, 2018, 04:30:01 am
content: Quote from: ironcurtain on March 20, 2018, 03:25:45 amHalf the Sa/s of SDS1004X-E models with 4 channels active.

author: Fungus
author_rank: Super Contributor
timestamp: March 20, 2018, 05:23:19 am
content: Quote from: LoveToRepair on March 19, 2018, 06:44:27 pmThey can show signals up to 300+ MHz but they'll be attenuated.The -3dB point is usually around 130Mhz.

author: ironcurtain
author_rank: Regular Contributor
timestamp: March 20, 2018, 07:30:55 am
content: Almost seems like it is worth saving the extra $ and just buy the Rigol and "upgrade" it to 100MHz, unless the higher end models can also be hacked... Then the Siglent does not seem like a better option anymore. Am I missing something there? It seems the only difference really would be the sampling at 1G when using two channels in two separate ADCs... (c1 and c2 together would also downsample to 500M I read, but c1 and c3 would sample each at 1G).

author: tautech
author_rank: Super Contributor
timestamp: March 20, 2018, 08:03:03 am
content: Quote from: ironcurtain on March 20, 2018, 07:30:55 amYes, combinations of ch 1+3 or 2+4 offer 1Gsa/s for each channel.Any damn DSO will display waveforms waaaaay past their rated -3dB BW.Defpom demonstrated the 2ch X-E to 500 MHz for shits and giggle here:https://youtu.be/64kxGDOg7es?t=1646WRT the additional functionality SDS1004X-E models offer you're really not looking very hard at the datasheets and manuals.

author: JPortici
author_rank: Super Contributor
timestamp: March 20, 2018, 08:42:39 am
content: also if you care about decoding and history mode, siglent is definetly better in that aspectdecoding from screen data is just useless (try to decode more than 6 UART packets with the rigol) because if you move the signal around, the result changes. if you zoom out or in, the result changes (the data is resampled to fit on the screen)

author: rf-loop
author_rank: Super Contributor
timestamp: March 20, 2018, 12:04:07 pm
content: Quote from: ironcurtain on March 20, 2018, 07:30:55 amYes, you are missing LOT of. How you buy car. Are nearly same if both have 4 wheels and both have 180km/h max speed.If you compare Rigl DS1000Z and Siglent SDS1004X-E fast you can see that they are really from different planet. Of course there are also similar things, 7" 480x800 display and 4 analog input channels. Both have shared vertical adjustments. Both have maximum samplerrate 1GSa/s.If do not argument normal mode wfm/s speed maximum (what is also lot of higher in Siglent)Siglent construction is 2x 1ADC1MEM/2 channel and Rigol 1ADC1MEM/4 channelSiglent 2 channel both 1GSa/s Rigol 1 channel 1GSa/s and 2 channel 500MSa/sSiglent >2 channels simultaneously 500MSa/s Just barely enough for 200MHz and Rigol 250MSa/s Just barely enough for 100MHz. Even if analog front end can pass over this to ADC just for aliasing.If look signals what are not sine, example square, some times linear interpolation is better (exept if user only admire "nice looking image". Least linear interpolation is tool for experienced users for detect what is going on when he can switch between linear, Sinc and dots. In Siglent all is full freedom for user and all is done post processing. And importatntly, Siglent Sinc do not flush real data to toilet, it draw Sinc iterpolation via true ADC data points. And you can always select if it is used or not, also you can change mode afterwards. And dots mode it do not generate fake dots. Also it do not decimate. All real ADC data is mapped for display.But Rigol works here like some kind of entertainment toy. It is unbelievable how they have used this fake Sinc years, they start it with old DS1000E and never repaired it. Still it also looks like there is lot of users who do not even understand this severity IF we talk about real tools and not toys.Many times one good tool for hunting anomalies in signal is mask test. Yes, Rigol have mask test - yes. But there is real trap for users. It can lead to severe false result if exaple do statistics about anomalies occurence. Why, because its speed depends about test result and it depends about it really lot. If mask test result is fail it is extremely slow. Some tests in second and if result is pass, then speed is example up to max wfm/s speed.In Siglent, independent of result, (test is hardware based) test result do not affect speed at all. Always maximum speed.Yes I know mask test is not so popular specially in user segment "hobbyist". Perhaps because just this test have been so crap in low price oscilloscopes, mostly just software based so that sales man can list this feature to AD.Also Siglent mask test is simply and feture poor version if compare to higher grade scopes. But least it is fast and also statistics result is valid and do not include this "hidden" trap what leads to false data.Siglent have real waveform history buffer up to over 50Mpoints, up to 80000 last acquisitions and with realative time stamps and it is not image frame recorder, it keep full raw ADC data. You can stop scope and look what just previously happe. You can do then measurements, even FFT for every single stored waveform, you can change linear or sinc interpolation or just dots. You can play with this history many ways.Rigol do not have nothing like this. And this is real tool after you learn how to work with it for get more power for your work. Many peoples overlook this - just because they have never seen or used this kind of tool. Yes, this can also find in some R&S higher crade scopes (and of course also then more featured also - with high price)Segmented memory acquisition. What Rigol really have?Siglent have real fast sequence mode. Up to 80000 segments with relative time stamps and maximum speed over 400kwfm/s (beats also these cheapest Keysight models just thands down and many times in speed and thousend times with segments max count)Instead of these Rigol have some kind of "frame recorder" like segmented memory acg.Siglent have max 1M FFT. What Rigol have? Yes, FFT is in feature list.Siglent have full ADC sample resolution automatic measurements up to 14Mpts. One tiny example below attached. What Rigol have, some kind of very small second buffer (or perhaps just display memory) for measurements, well under 1000 data points. (it is well explained previously in this forum somewhere and it is really - really poor.Siglent have best ever seen 3 channel SFRA in this scope class and example Keysight 1000X models SFRA is just like toy vs this Siglent version. (but it need external compatible signal generator)But Rigol, nothing.Siglent can also upgrade to full MSO with 4 analog and 16 digital channels.Rigol, not possible.Siglent have real full resoluition full bandwidth 500uV/div sensitivity. Rigol highest sensitivity full resolution full bandwidth is 5mV/div (1mV and 2mV/div are somehow magnified from 5mV/div.(There is somewhere thread where I have tested it using my Rigol and also Sinc "bug" (what include also "mysterious" level error) Perhaps it can name Rig(x)/x instead of Sin(x)/x )Then we can also talk about window zoom performance and trigger jitter and trigger accuracy, perhaps also how good is trigger position fine interpolation between true samples.And simple small fact: Siglent horizontal scale 1ns/div - 100s/div. Rigol 5ns/div - 50s/divThen example some nice things. In Siglent you can select two kind of vertical offset, fixed V level, fixed position. And same for Horizontal, fixed delay time or fixed position.For gated measurtements gate cursors, it do not reserve normal cursors for this.Color gradiend display. Some times help fast observation with eyes.User interface speed. Even with much more brute force needing features it is still like J-16 Red Eagle vs Cessna 150There is couple more things what differentate tools and toys but I think even this is like red for bull and Rigol fans start and and also soldiers who have one mans war against Siglent.And, Siglent is not at all perfect, it is not high grade manufacturer like Teledyne, Keysight, Tektronix or R&S. But what have been one year, two year, four years and more ago, Siglent have developed lot of, but still need develop more themselves and do better. (and why Keysight compare to Rigol but not to Siglent. Reason is natural, They compare all what they can show they looks like win - or if not win then they select some settings what makes competitor loose and looks like Keysight win. They have always done it, even in simple or higher level aplication notes and not only in sales advertisements)Just for very small and simplest example (you can find lot of things from forum and of course all what Rigol do not have they all are not nessessary - of course.).This is impossible with Rigol. Can not do nothing even close this. And this is not at all most important thing - better say that one not so important thing but dry reality.But then you look price, performance and features - these relationship is pretty good.If we look situation what was just after old SDS2000 (no X) was launched and how unmatrure it first was. Today with example SDS1004X-E situation is very different. (as it is also today with SDS2000X series)And yes, signal is 99.7ns wide (at 50% level)

author: SWR
author_rank: Regular Contributor
timestamp: March 20, 2018, 03:54:54 pm
content: I like the Rigol and Siglent brands you mention. I have a Rigol scope and a Siglent spectrum analyzer, but here's another option that might fit your needs?I'm pretty impressed with a GW Instek MDO-2204EX scope I got this weekend.It's a 6-in-1 multi instrument I bought at Reichelt.de:1 A 4ch 200MHz scope with individual channel controls8" 800x480 TFT with 12 soft keys for quick menu navigation40M sample memory120K waveforms/sHigh resolution 1M FFT with very fast update rate29K memory segments with a very useful search functionAdvanced math with user definable functionsDownloadable apps:Go-nogo with HW output on the back for automated testingDigital volt & frequency meter with readout on screen captureData logger up to 1000h with event counterDigital filter LP/BP/HP up to 500MHzMask function to capture rare eventsBode plot using the built in sweep generator2 Serial bus decoder with UART, SPI, I²C, CAN, LINThe search function can use bin, hex or ASCII with wild-cards3 Spectrum analyzer from DC to 500MHzUseful for audio and vibration (my Siglent SSA3021 only goes down to 9KHz)It's also much easier to operate (no switching between scope/FFT mode)Centre, span, start and stop frequency controlSample, min, max and average detectionLinear, dBV or dBm displayWindows: Rect.(single shot), Hanning/Hamming(periodic), Blackman(amplitude)4 Dual 25MHz 200Ms 14bit Arbitrary Waveform GeneratorOn board waveform editor and PC interfaceAM, FM, FSK and sweep modulation (independent or tracking)5 Independent 5000 count digital multimeterVdc, Vac, Idc, IacOhm, Beep, DiodeThermocouple °C/F type B,E,J,K,N,R,S or TReadout on screen capture6 Dual 5V 1A power supplyIndividually adjustable or 3,3 and 5V presetsOverload protectionIt's also got a calibration output for self-calibration.I haven't had much time to go through all the details yet, but I've been through all 6 instruments and all the things I've tried works as expected. It costs a bit more than the Rigol and Siglent you mention, but considering what you get I think the price is very fair. There's no need to hack it because everything is already unlocked from the factory. It's really easy to include AWG, DVM and DMM readings in your reports with the screen capture instead of taking pictures.It's also a nice form factor if you're working with embedded software development. It will fit on a desk with room for a couple of decent size monitors and power a development board. You've got the AWG for exciting the inputs and a wide selection of measurement options. The only thing I miss is an electronic load to test the outputs, but all-in-all it's pretty complete for the work I'm doing.Best regardsSoren

author: rsjsouza
author_rank: Super Contributor
timestamp: March 20, 2018, 04:42:02 pm
content: Quote from: JPortici on March 20, 2018, 08:42:39 amJust a warning: not all Rigols are the same. The DS4000 series stores decodes the entire stored stream as shown by H.O.here. I can attest to this as well on my DS4014.If the price is right (above $1k and more realistically around $1.5k), this family of scopes has a good bang for the buck - upgradeable to 500MHz and with several decoders (it can be done for free if you are into that). The architecture is a bit older, but what matters is the use you make of it.

author: mrinner
author_rank: Newbie
timestamp: March 20, 2018, 04:48:58 pm
content: I'm also looking DS1054Z VS sds1204 4ch... but now starting thinking about rigol DS2072(hack) + external LA. 2ch yes, but faster...

author: ironcurtain
author_rank: Regular Contributor
timestamp: March 20, 2018, 08:46:54 pm
content: The GW Instek MDO-2204EX looks pretty beefy, is there a cheaper model without the DMM and PSU? How does it compare functionally to the Siglent? Is the SA really worth it? Seems like the Siglent is not that different, from the looks of it, it is not a real SA. The Siglent's FFT functionality can't achieve the same? I assume dynamic range is poor in both.

author: mk_
author_rank: Regular Contributor
timestamp: March 20, 2018, 09:10:01 pm
content: Quote from: ironcurtain on March 19, 2018, 06:39:42 pmGo for the Tektronix MDO3014. Buy it, enable all features (Bandwith up to 500MHz, Spectrum Analyser up to 3GHz, Function Generator, a lot of decoders, a Logic analyser... ) with the code you can finde here on eevblogbeside the ugliy UI it is a fine instrument.good luckMichael

author: SWR
author_rank: Regular Contributor
timestamp: March 20, 2018, 10:02:37 pm
content: Quote from: ironcurtain on March 20, 2018, 08:46:54 pmYes, they have a whole range of cheaper scopes without the DMM & PSU, 2 or 4 channel with different bandwidth, but they all have the deep segmented memory with search function and apps including data logging.QuoteThe Siglent scope also have a high resolution 1M FFT so in this function the main advantage of the Instek is the high update rate. I believe they have achieved this by integrating the microcontroller and FPGA on the same Xilinx chip. It has a much higher transfer bandwidth between the two on chip than the Siglent design with the microcontroller and FPGA in separate chips.Apart from the update rate the Siglent has equally high frequency resolution.QuoteFor me it is, but that really depends on what you want to use it for?The dynamic range is a bit more than 80dB (which is poor compared to the 160dB of my Siglent SSA3021).The advantage of the FFT based approach is that it covers DC to 500MHz (my SSA3021 covers 9K to 3,2GHz).I'm planning to use the Instek for audio, sensor and vibration work. The Siglent SSA is for RF and EMC pre compliance work.I did some measurements with the Instek on a 5KHz LVDT sensor design today that worked out really well. I could feed a 5KHz sine to the TX coil from the built in AWG and measure the A & B receive coils in both time and frequency domain. Here I could play around with different bandpass filters on the scope in real-time, to filter out switching noise from four solenoids that are placed close to the LVDT coil. Using the advanced math to measure the RMS value of the filtered A & B I could calculate the LVDT position as (A-B)/(A+B) in real time without writing any software. This way I could quickly evaluate which filters have to be implemented in software on the embedded micro.It really depends on what you want do do, but the main advantage of the integrated SA is the interface ease-of-use.Normally if you use the FFT function in the math menu the frequency resolution will depend on your sample rate, so I often find myself switching several times between time and frequency domain to get the right image on the Keysight scopes we have at work that doesn't have the SA type interface. On the Instek you can stay in the frequency domain adjusting center, span, start and stop frequencies interactively while looking at the image. It's just much quicker to work with.My needs may be different than yours, and I can really recommend forming your own oppinion based on your own needs. If you're more in love with the Siglent scope then by all means go for it and have fun.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: March 20, 2018, 10:37:02 pm
content: I just got the DS1054Z and I'm very happy with it. A scope is not the ideal tool for looking at long streams of serial data; scopes are useful for checking the data integrity and waveform shape; usually when that's resolved and data is flowing, it make way more sense to change over to a logic analyzer such as the Salae Logic 8/16 (there are cheap clones that seem to work but I bought a real Salae Logic.So my recommendation is buy the Rigol and look for a logic analyzer.

author: ironcurtain
author_rank: Regular Contributor
timestamp: March 20, 2018, 11:19:49 pm
content: I really appreciate your responses, it's always great to see someone putting in some effort and time. I will just list a few of the case scenarios I will likely be involved with, in my lab:Analyze EMI suppression in power supply and amplifier circuits, mostly LF-UHF related projects.Analyze RF components: filter response, attenuation, etc.Troubleshoot radio equipment: figure out if oscillators are working OK, debug receiver stages, etc.Reverse engineering: I2C/SPI/UART and other buses, memory dumping, rewriting, glitches/side channel attacks.Debugging small circuits with the usual run of the mill PIC/AVR/MCU: arduino, STM32.Assorted experiments, like firmware stuff for hard drives, computer equipment, FPGAsVideo signals: sync clocks, conversion....I was initially looking for spending up to 1k EUR, since I have put quite some money into things recently... Considering this, what do you honestly think would suit me best? Siglent or splurge a little and pick the Tektronix? Any decent EU seller that offers discounts? (I'm between jobs now)

author: nctnico
author_rank: Super Contributor
timestamp: March 20, 2018, 11:41:44 pm
content: Quote from: Gandalf_Sr on March 20, 2018, 10:37:02 pmI disagree with that. A good scope has the toolset to decode and deal with lots of messages. That way you can collect data and look (search) for errors. Using two instruments to cover that just makes things more complicated. On a logic analyser you can see something went wrong but you can't see the reason. Therefore a DS1054Z and seperate logic analyser is very far from a good choice.

author: llkiwi2006
author_rank: Regular Contributor
timestamp: March 20, 2018, 11:46:02 pm
content: Quote from: nctnico on March 20, 2018, 11:41:44 pmOf course the "easy" solution is just to get a better scope, maybe even a mixed signal one. But when you don't have the budget for that, a separate usb logic analyzer might just fill in the gap that your cheap scope can't cover (e.g. ds1054z really sucks at decoding).

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: March 21, 2018, 12:04:25 am
content: I've tried to used $10,000, 1GHz scopes for decoding, they suck at it - it's like trying to look at the Great Barrier Reef through the botom of a jam jar - far better to be able to a) check that the signals look like you expect them to with the scope and b) move to the logic analyzer.If you're a masochist, then I suppose the scope might do the job.

author: nctnico
author_rank: Super Contributor
timestamp: March 21, 2018, 12:10:47 am
content: Quote from: Gandalf_Sr on March 21, 2018, 12:04:25 amThe trick is to save the data as CSV and analyse it on a PC. When the 'bad' message is found then go back to the scope and look at the signal. Sometimes a problem only occurs once per hour or more. Deep memory is very useful for these kind of cases.

author: SWR
author_rank: Regular Contributor
timestamp: March 21, 2018, 12:23:17 am
content: Quote from: ironcurtain on March 20, 2018, 11:19:49 pmIMHO none of the 8 bit scopes are gonna cut it on the low signal levels for EMC pre compliance testing.You really need a high dynamic range SA like the SSA3021 or similar with a real tracking generator. Build a LISN for the conducted measurements (there's a nice wide band SMD design here on the forum) and a wide band common-mode clamp with a ferrite torroid for radiated measurements. You can also buy a low cost near-field probe set from Deepace to locate radiation sources on the PCB. All of this will be hidden by the noise-floor of the scope, unless you've got a really serious compliance issue.QuoteIf you have the patience all the scopes mentioned here can be used for this (depending on the frequency range). The andvantage of the Instek I mentioned above is that it has the SA input controls that are easy to work with. Another feature is a Bode plot app (FRA) I didn't mention above. Using the built in tracking AWG it will sweep a circuit and give you the Amplitude & Phase plots on screen.If you're above 200MHz you're out of luck and need a proper SA. I do some work on LoRa (170M, 433M & 868M), GPS and WiFi (2,4G) that none of these lower end scopes will handle. I did need to modify my SA a bit to cover the WiFi range, but that's fairly easy to do if you're ok with that sort of thing.QuoteAll the scopes mentioned here can do this, especially if you don't mind fiddeling with the FFT mode.Having an AWG with AM, FM, FSK and sweep modulation is useful for this as well, but can be bought separately.QuoteFor this type of work it's a big advantage with deep memory and memory decoding. Screen based decoding becomes frustrating really quickly. A flexible content based trigger and search function with wild cards is also a really nice feature. Scrolling through a 10M sample buffer is paralyzing.QuoteAll the scopes mentioned here should be able to do this, but again - it depends on the type of HDD and FPGA signals you need to measure.

author: daybyter
author_rank: Frequent Contributor
timestamp: March 21, 2018, 01:58:57 am
content: https://hackaday.io/project/4327-stretching-the-limits-of-a-rigol-ds-1102e-scopeI guess the 1054z should show the same performance?

author: rsjsouza
author_rank: Super Contributor
timestamp: March 21, 2018, 02:39:03 am
content: Quote from: ironcurtain on March 20, 2018, 11:19:49 pmApart from the higher frequency required by the radio equipment, both a Rigol DS1054Z or the Siglent SDS1204 seem enough. If you max your budget the GW Instek GDS2204E starts to become interesting. Another alternative is theRigol EU clearance bin, which has a DS4014E for €1.2k but probably is net price with no freight. If you go that route, be sure to figure out warranty and accessories.A Tek MDO3014 would put you well into €2.5k...

author: tggzzz
author_rank: Super Contributor
timestamp: March 21, 2018, 08:16:30 am
content: Quote from: Gandalf_Sr on March 21, 2018, 12:04:25 amSo very very true. Use analogue tools for the analogue domain and digital tools for the digital domain.Thoughtful use of sprintf() is a very useful tool as well!

author: tggzzz
author_rank: Super Contributor
timestamp: March 21, 2018, 08:21:19 am
content: Quote from: nctnico on March 21, 2018, 12:10:47 amThe better technique is to use the right tool for the job in the first place: a logic analyser or sprintf(). Both of those are very good at selecting only the interesting information, and discarding the rest.

author: tggzzz
author_rank: Super Contributor
timestamp: March 21, 2018, 08:30:27 am
content: Quote from: ironcurtain on March 20, 2018, 11:19:49 pmEMI: unlikely a scope is much use.RF components: scope not much good if you are characterising the stopbandRadio equipment: scope not much good for oscillator harmonics, spurs, and phase noise, nor if looking for "rf level" signals (consider 5mVpp/50ohm is -36dBm)Reverse engineering: logic analyser has width and depth that a scope doesn't, plus decent triggering/filteringDebugging: analogue tools for analogue problems, digital tools for digital problemsAssorted experiments: assorted tools.Video: analogue or digital?

author: nctnico
author_rank: Super Contributor
timestamp: March 21, 2018, 08:50:13 am
content: Quote from: tggzzz on March 21, 2018, 08:21:19 amAs I wrote before: that way you know something is wrong but not exactly what is wrong. IOW: you learn nothing new! A lot of communication related problems are rooted in the analog domain and a problem may not repeat itself often. An oscilloscope with deep memory and good decoding tools really is very useful because it offers an all in one solution.A couple of years ago I was involved in a project where someone had to interface with a circuit my customer provided. This was a half duplex UART over RS485 interface. After 3 weeks (or so) the engineer at the third party still was unable to get it to work. He followed your advice: look at the signals in the digital domain only. That way he was completely oblivious to the fact he got the RS485 rx/tx switching timing all wrong. I had to come over and connect his scope and on that the problem was immediately visible.

author: tggzzz
author_rank: Super Contributor
timestamp: March 21, 2018, 08:57:20 am
content: Quote from: nctnico on March 21, 2018, 08:50:13 amI'm not entirely sure what use-cases you mean, but it sounds like an infinite-persistence eye diagram is appropriate.

author: nctnico
author_rank: Super Contributor
timestamp: March 21, 2018, 09:29:47 am
content: Any eye diagram won't work well for SPI, I2C, UART, etc. And then you still don't know when & what happened in relation with other signals.

author: tggzzz
author_rank: Super Contributor
timestamp: March 21, 2018, 10:00:45 am
content: Quote from: nctnico on March 21, 2018, 09:29:47 amI'm still not sure of what use-cases you have in mind.I've used eye diagrams with UARTs perfectly successfully w.r.t. signal integrity - once that is assured, flip to the digital domain.The analogue/digital cross-correlation can be important, hence mixed signal oscilloscopes - but low-end DSOs aren't MSOs. Personally my generic strategy is to:use scope to assure signal integrityuse LA/sprintf() to discard "noise" and decode messagesuse LA to trigger scope, or vice versa

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: March 21, 2018, 11:03:02 am
content: Quote from: nctnico on March 21, 2018, 08:50:13 amI think we may be in violent agreement. I'm an embedded designer - usually my I2C / SPI doesn't work first time, so I look at it with analogue scope, often with decoding too. Then I see that the voltage levels are wrong, or that my code is failing to send a restart - I fix this and data is now flowing as expected. I then switch to the LA to capture the actual data exchange.

author: SWR
author_rank: Regular Contributor
timestamp: March 21, 2018, 01:19:35 pm
content: Quote from: tggzzz on March 21, 2018, 08:57:20 amIt can work well if you have stable timing, but if your protocol have random delays between bytes or messages it's not really working well with the eye diagram or mask function.You get deep memory and good search functions with the low cost digital bus decoders, but like nctnico points out you won't get the full analog picture of what's going on at the physical protocol layer. I just wanted to point out that not all scopes suck totally at serial decoding. If you've got a deep segmented memory with memory based decoding and flexible content based trigger and search functions, it sucks less than screen based decoding without search functions. There are degrees of totality.

author: Fungus
author_rank: Super Contributor
timestamp: March 21, 2018, 02:09:02 pm
content: Quote from: SWR on March 21, 2018, 01:19:35 pmThe logic analyzers cost $6 so there's no reason not to get both. Combine the two.

author: tggzzz
author_rank: Super Contributor
timestamp: March 21, 2018, 02:43:10 pm
content: Quote from: Gandalf_Sr on March 21, 2018, 11:03:02 amYup. Standard operating practice for the past 30 years.individual technologies change rapidly, but fundamental strategies change very slowly.

author: tggzzz
author_rank: Super Contributor
timestamp: March 21, 2018, 02:53:42 pm
content: Quote from: SWR on March 21, 2018, 01:19:35 pmThe "full analog picture of what's going on at the physical protocol layer"issignal integrity. No doubt you have noticed that I have explicitly stated (reply #36) that my first step is to use a scope to ensure signal integrity. There's little point at examining bits until SI is solid! But after that, flipping tothe digital domain is often advantageous.Something has to cause a receiver to synchronise on the bytes, and in many common cases that is sufficient to trigger a scope for an eye diagram. Obvious example with a UART is the leading edge of the start bit.

author: nctnico
author_rank: Super Contributor
timestamp: March 21, 2018, 07:50:27 pm
content: Quote from: tggzzz on March 21, 2018, 02:53:42 pmThe problem in this reasoning is that it assumes there is no outside influence and the software is 100% bug free. Neither is the case so you can't discard the analog domain. Over the years I have come across several situations where looking at digital domain only confirmed there is a problem but doesn't tell what the problem is. A modern DSO with deep memory and decoding speeds up debugging these kinds of cases significantly.

author: tggzzz
author_rank: Super Contributor
timestamp: March 21, 2018, 10:53:01 pm
content: Quote from: nctnico on March 21, 2018, 07:50:27 pmNobody has suggested that, and most of my experience is with hardware/software systems wherebothare buggy!QuoteThat's a strawman argument. I've always stated that if you have an analogue domain problem, use analogue tools.QuoteI'm sure that's the case with specific DSOs and specific problems. But there are many DSOs and many problems where the tools' limitation make them less than helpful. Examples:where you have a, say, 8-bit bus to capture, or when specifying the trigger, or filtering out uninteresting datawhere the trigger is a sequence of stateswhere the decoding is so slow that the input is ignored for a substantial proportion of the timewhere the decoding only covers a small proportion of the captured signal, e.g. merely what's on the screen at that timeNaturally a full-featured and correspondingly expensive "professional" DSO is more likely to avoid limitations, but this forum is biassed towards hobbyists with limited money.In contrast, the strategy I outlined is pretty general purpose, provided you haveminimalequipment ofeachtype.

author: nctnico
author_rank: Super Contributor
timestamp: March 22, 2018, 07:05:35 am
content: Quote from: tggzzz on March 21, 2018, 10:53:01 pmNow you are just moving goalposts. Not everyone has to make-do. There are lots of people with money (or their boss' money) to buy scopes in the sub $10k range. Starting at around $2k you can buy a decent new scope which has good decoding and analysis features. Also the higher end scopes are available on the used market.

author: tggzzz
author_rank: Super Contributor
timestamp: March 22, 2018, 08:04:31 am
content: Quote from: nctnico on March 22, 2018, 07:05:35 amYou have chosen to comment on a tangential financial point, and to not comment on the substantive technical points. We presume that means you don't disagree with the technical points.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: March 22, 2018, 09:52:29 am
content: mctnico -This isn't even a proper argument!

author: nctnico
author_rank: Super Contributor
timestamp: March 22, 2018, 10:39:28 pm
content: Quote from: tggzzz on March 22, 2018, 08:04:31 amYour technical points discussion is circular and now you try to justify your odd reasoning by moving the goalposts. Hint: it is not working.The OP is asking what kind of amount of money he/she would need to spend to tackle a certain set of problems. Spending more money means getting the job done faster. Spending too much money means getting unnecessary features. Spending too little money could mean ending up with crap which takes all the fun out of building a circuit.

author: SWR
author_rank: Regular Contributor
timestamp: March 23, 2018, 06:12:35 pm
content: Quote from: tggzzz on March 21, 2018, 10:53:01 pmI fully agree. To maximize usability you need deep segmented memory, quick content triggers with wild cards and a search function with the same capabilities.QuoteYes, but the nice thing for us hobbyists is that these features are now becomming available in low cost scopes. The MDO-2204EX costs $1922 at Saelig.com.If I wanted the same features in the Keysight scopes we use at work it would be more than 4 times that price - and I would still only have 1/10th of sample memory depth. These used to be expensive features, but some of the less known brands are putting some pretty useful bargins on the market compared to the better known brands.

author: tggzzz
author_rank: Super Contributor
timestamp: March 23, 2018, 11:33:14 pm
content: Quote from: SWR on March 23, 2018, 06:12:35 pmAgreed.IMNSHO, while expensive full-featured equipment can be used, often if you use imagination and skill then the same ends can be achieved with cheap basic equipment. Plus, for non-repetitive tasks the time saved using full-featured equipment has to be balanced against the time taken to acquire and learn how to use such equipment.Of course, you can't buy skill and imagination off-the-shelf.

author: RogerClark
author_rank: Contributor
timestamp: May 10, 2018, 02:15:55 am
content: Quote from: mrinner on March 20, 2018, 04:48:58 pmDid you end up getting a DS2072???I'm contemplating buying one, but only if the upgrade hack still works on the latest firmware that its shipped with