Which scope?  - Page 1
Forum section: electronics / projects

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: February 19, 2020, 09:57:02 pm
content: Looking at these scopes:Rigol DS1202Z-ERigol DS1054ZSDS1202X-EThe most demanding use would probably be decoding SPI, and then general troubleshooting/debugging/general use.One particular project I have in mind is to catch a cam sensor signal on an engine so I can re-create it digitally, but its a diesel, so less than 3k RPM and a 28 hole cam gear. Not particularly demanding.They are all similarly priced and similar features. Which one do I want?

author: DaJMasta
author_rank: Super Contributor
timestamp: February 19, 2020, 11:25:14 pm
content: Probably not the best subforum for the question, but all the same:My UI preference is Siglent's between the two, though both will work fine. The DS1054Z is the oldest design of the three, so if Rigol hasn't updated it since then, it may feel the least responsive of the three. I also really prioritize 4 channels over 2, when possible, though. Since bandwidth doesn't seem to be a concern, what about Siglent's SDS1104X-E? I think it's even had a price drop recently.

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: February 19, 2020, 11:35:52 pm
content: Looks like the SDS1104X-E is going to be about $100 more.Probably worth it, but I'd rather not spend it.I was considering the DS1054Z simply because it was 4 channel. But starting with a 50 MHz scope and dividing that by 4, its getting kind of low on bandwidth. Maybe it still good enough though? At least at this point, I'm no power user.I have an old analog Tektronix 2235, so if I really need more than 2 channels, I could fire that back up. I can't say its been calibrated recently though.I've also though about selling the 2235 to put into the new digital scope. I can't see where an analog is better than even these cheaper Rigol and Siglent, but if its a good idea to hold onto it, I will. It still works fine.

author: thm_w
author_rank: Super Contributor
timestamp: February 19, 2020, 11:44:22 pm
content: Sell the tek if you can get anything for it.For decoding SPI I would get a cheap $10 saleae clone.

author: DaJMasta
author_rank: Super Contributor
timestamp: February 20, 2020, 12:00:21 am
content: The nice thing about the 1054Z is that the hacks to get full bandwidth and options are well documented, so as long as you don't mind running through some software stuff, you can get a lot more bandwidth out of it (and I think more memory and all decoding options) relatively easily.The 1104X-E may very well be more expensive, I think it's like $440 on amazon right now. In the same vein as the Rigol, I believe it's software hackable pretty easily to 200MHz bandwidth.Also worth mentioning (since I managed to miss it the first time), 2 channels isn't really enough to decode SPI. You can get both data channels, sure, but it's much easier when you can get the clock (and the chip select, why not!) on your inputs. Certainly helps in making sure things are being selected right and that the whole system is acting in a way you expect. Alternatively, you could measure a data line or two and a power rail to correlate some reset failure, or an output of a DAC being driven by the SPI line, or whatnot.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: February 20, 2020, 12:34:08 am
content: Quote from: Rat_Patrol on February 19, 2020, 11:35:52 pmThat's not the way it works. Each channel has a 50MHz -3dB point, it's the scope's total samples/sec that will get divided up.Plus if you want to decode a logic signal... use a logic analyzer. Smaller, cheaper, faster, easier. Solved.

author: TK
author_rank: Super Contributor
timestamp: February 20, 2020, 12:56:54 am
content: Quote from: DaJMasta on February 20, 2020, 12:00:21 amTo decode SPI you need clock on one channel and MISO or MOSI on the other channel. You can leave one data line and CS out, but not the clock. I also prefer 4-channel scope for SPI decoding, but as others said, a scope is usually the wrong tool for SPI decoding besides signal integrity. After you check the signals are there and they look correct (integrity wise), it gets cumbersome if you want to do a lot of protocol analysis on a long capture.

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 20, 2020, 01:03:31 am
content: Quote from: Alex Eisenhut on February 20, 2020, 12:34:08 amAt $6 or so, a FX2 board along with the free Sigrok software is a must have.

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: February 20, 2020, 04:37:29 am
content: I still need a scope, the SPI decoding and cam signal capture were the only projects I had waiting in line for it.

author: aheid
author_rank: Regular Contributor
timestamp: February 20, 2020, 08:09:14 am
content: The protocol decoding on the 1054z is limited to what is in view at any time, unlike the X-E from Siglent. Its interface is also sluggish compared to the Siglent.I just used my Siglent 1104X-E to debug some SPI and it worked quite well, but for serious debugging that is not related to signal integrity a cheap logic analyzer as mentioned is much more ergonomic.

author: tautech
author_rank: Super Contributor
timestamp: February 20, 2020, 09:04:22 am
content: Quote from: Rat_Patrol on February 20, 2020, 04:37:29 amYou can do basic SPI decoding with the 2ch SDS1202X-E just using the clock and data line and instead of clock sense (CS) use CLK Timeout.This screenshot is from a much higher spec SDS5054X and although the UI is different the same settings will apply:

author: Prehistoricman
author_rank: Regular Contributor
timestamp: February 20, 2020, 01:19:23 pm
content: The 1054Z's interface is not just sluggish. The horiz and vertical movement is particularly bad because the acceleration feature usually kicks in at the worst moment. You're nudging your signal over to get it in the right place and all of a sudden it teleports off screen. FW doesn't get updates any more AFAIK but it still has bugs. I've experienced memory corruption on the trace in normal/stop mode.

author: TK
author_rank: Super Contributor
timestamp: February 20, 2020, 02:46:11 pm
content: Quote from: tautech on February 20, 2020, 09:04:22 amIs the screen showing a single shot? Why MOSI is showing transitions after SIGLENT_ ? All screenshot posts of the SDS5000X and SDS2000X Plus show the same behavior