Author Topic: new RIGOL DS1000Z and... MSO4000  (Read 83740 times)

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Offline Bugware

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #125 on: October 10, 2013, 10:52:34 am »
The new Rigol DS2000A-S Series apparently has a Sig-Gen with Arbitrary Waveform Frequency Range 0.1 Hz to 10 MHz and length 2 to 16 kpts in 10 internal Storage locations.

I found a Datasheet here: http://int.rigol.com/download/Oversea/DS/Datasheet/DS2000A_DataSheet_EN.pdf
 

Offline Hydrawerk

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #126 on: October 10, 2013, 07:13:26 pm »
Yes, it is better than signal generator in DSOX2000A series.
Amazing machines. https://www.youtube.com/user/denha (It is not me...)
 

Offline icpart

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #127 on: October 18, 2013, 08:58:45 pm »
Hi guys I have little official information from distributor of Rigol in my country that the new models of oscilloscopes are expected to arrive in the Europe in October 28 and after that they will be distributed among the distributors to fulfill pre-orders.
 

Offline Electro Fan

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #128 on: October 18, 2013, 10:10:15 pm »
Ordered a DS1074Z-S yesterday. Leadtime for stock arrival to emona is towards the end of next week apparently. Should arrive within a couple of weeks I guess. The North America Rigol site lisots 4-6 weeks...

For me, it was 4 channels and function gen for the same price as base model DS2000. The other stuff isn't so important to me. There have been many times where I wished I had at least 3 channels (3 phase BLDC motors etc).

I have to agree here, I really do like the DS2000 series scope but I'm ALWAYS regretting that it's only 2 channels (3000 was out of my price abilities).  I need 3-4 channels especially to get the best use out of some of the decoding options. If anyone in Canada picks one of these models up and wouldn't mind letting me know the costs associated to getting it across the border (if ordered through RigolNA), and their opinion on the device it would be greatly appreciated.


Please tell us more about the specific extra decoding capabilities you would like/enable with 4 channels vs 2 channels.  Thanks
 

Offline Mark_O

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #129 on: October 19, 2013, 03:25:10 am »
For me, it was 4 channels and function gen for the same price as base model DS2000. The other stuff isn't so important to me. There have been many times where I wished I had at least 3 channels (3 phase BLDC motors etc).

I have to agree here, I really do like the DS2000 series scope but I'm ALWAYS regretting that it's only 2 channels (3000 was out of my price abilities).  I need 3-4 channels especially to get the best use out of some of the decoding options.

Please tell us more about the specific extra decoding capabilities you would like/enable with 4 channels vs 2 channels.  Thanks

ElectroFan, I'm not sure if you're being serious or not, but I'll assume so, for the sake of discussion.

First off, the DS2000 series has two Bus Decoders.  I don't know why.  I2C requires an SDA and SCL line, which is two channels.  No channels left for Decoder2.  RS232 has RX and TX lines (self clocking with start/stop bits).  Again, uses both channels 1 and 2.

SPI requires 4 channels, all by itself, which Rigol seems to manage to gloss over by simply referring again to SDA and SCL in their manual.  But SPI is a full-duplex communications link, a 4-wire bus with MOSI, MISO, CLK, and SS/CS (Slave or Chip select) lines.  How are you supposed to handle that with 2 channels?  The DS1000 with 4-channels can support full SPI directly, but the DS2000 can not.  The best it can do is "half-SPI", where you can monitor and decode one side of the data stream (along with a clock).  And even that is crippled, because SPI is a bus, and without a Select line to determine which device is talking, you can't separate out what you want from all the bus chatter.  Unless you limit yourself to Master + SingleSlave-only systems.  And again, only one decoder can be used, because you've exhausted your channels.

I thought perhaps they might have some trick whereby the Ext.Trigger channel could be used to provide a 3rd input (say run the Clock in there, with MOSI on Chan1 and MISO on Chan2), but not according to anything in the manual.  EXT appears to only be available as a Trigger Source in Edge mode.

Lastly is "Parallel Decode", and I can't even figure out what that's supposed to be, from their documentation.  It sounds like it's intended to work with an MSO (not DSO), since it refers to "up to 20 channels".  Presumably 4 analog, and 16 digital.  You assign one channel to a Clock, and the next channel to data, and, well... you're done.  Doesn't seem very parallel to me.

So the 4-channel DS1000Z not only allows for handling full SPI, but can also potentially make use of both Bus Decoders, by handling two protocols at once... e.g., I2C on one, and RS232 on the other.  Have you ever worked on an embedded system where you needed to track comms across more than one interface bus?  With only 2 channels on the DS2000, your options are severely limited.  Even something as simple as running one protocol Decoder on channels 1 & 2, while monitoring channel 3 as a trigger does not seem to be possible.  (The Rigol docs indicate the Ext.Trigger cannot be used as a source when in protocol decoder modes.)  But say you wanted to see the power supply thresholds where comms started or cut out.  Kinda hard to do with only 2 channels.  Or maybe you're probing around trying to correlate some other signal in the system to find where/when a comms channel is picking up glitches.  Again, you're SOL.

So the only use I can see for Decoder2 on the DS2000 is to have two independent sets of parameters config'ed, and be able to turn one or the other on quickly.  On a 4-channel scope like the DS1000Z, you can actually use both decoders at the same time.

Unfortunately, I'm at a bit of a disadvantage... not having a DS2000 here to play with, I have to go by what's in the manual (and what bits I've read here).  And that may not fully reflect the instrument's capabilities.  E.g., in their screen shots, Rigol doesn't even show SPI decoding as SPI... it's listed as "SDIO".  Sadly, fairly typical of Rigol documents (though they're usually well ahead of the rest of their Chinese competition.)  Unless there's an option to customize the Label set for each decoder, that I missed in the manual.

Hopefully this will give you at least a partial answer to your question.
« Last Edit: October 19, 2013, 03:32:48 am by Mark_O »
 

Offline marmad

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #130 on: October 19, 2013, 04:30:33 am »
I thought perhaps they might have some trick whereby the Ext.Trigger channel could be used to provide a 3rd input (say run the Clock in there, with MOSI on Chan1 and MISO on Chan2), but not according to anything in the manual.  EXT appears to only be available as a Trigger Source in Edge mode.

The complaint about the weak implementation of the External Trigger channel (which should be able to be used as a source for at least a few other trigger modes) was passed on to Rigol a little while before they released the last version of the firmware. They confirmed the 'problem', with promises that they would work on addressing it (although they mentioned it wouldn't be in the [at that time] soon-to-be released v.1.0.0.2). So hopefully it will still be expanded in a later FW version.
 

Offline Mark_O

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #131 on: October 19, 2013, 05:21:14 am »
The complaint about the weak implementation of the External Trigger channel (which should be able to be used as a source for at least a few other trigger modes) was passed on to Rigol a little while before they released the last version of the firmware. They confirmed the 'problem', with promises that they would work on addressing it (although they mentioned it wouldn't be in the [at that time] soon-to-be released v.1.0.0.2). So hopefully it will still be expanded in a later FW version.

Thanks for the info, Mark.  That's good to hear.  Kind of a shame to have a channel so under-utilized.
 

Offline marmad

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #132 on: October 19, 2013, 05:25:38 am »
Thanks for the info, Mark.  That's good to hear.  Kind of a shame to have a channel so under-utilized.

Yes - one of my main disappointments with the DSO. I work with I2C a lot and just being able to use that External Trigger as a source for SDA or SCL would mean a free channel for another signal in the circuit - a big time saver.
« Last Edit: October 19, 2013, 08:35:01 am by marmad »
 

Offline Electro Fan

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #133 on: October 19, 2013, 08:13:19 am »
For me, it was 4 channels and function gen for the same price as base model DS2000. The other stuff isn't so important to me. There have been many times where I wished I had at least 3 channels (3 phase BLDC motors etc).

I have to agree here, I really do like the DS2000 series scope but I'm ALWAYS regretting that it's only 2 channels (3000 was out of my price abilities).  I need 3-4 channels especially to get the best use out of some of the decoding options.

Please tell us more about the specific extra decoding capabilities you would like/enable with 4 channels vs 2 channels.  Thanks

ElectroFan, I'm not sure if you're being serious or not, but I'll assume so, for the sake of discussion.

First off, the DS2000 series has two Bus Decoders.  I don't know why.  I2C requires an SDA and SCL line, which is two channels.  No channels left for Decoder2.  RS232 has RX and TX lines (self clocking with start/stop bits).  Again, uses both channels 1 and 2.

SPI requires 4 channels, all by itself, which Rigol seems to manage to gloss over by simply referring again to SDA and SCL in their manual.  But SPI is a full-duplex communications link, a 4-wire bus with MOSI, MISO, CLK, and SS/CS (Slave or Chip select) lines.  How are you supposed to handle that with 2 channels?  The DS1000 with 4-channels can support full SPI directly, but the DS2000 can not.  The best it can do is "half-SPI", where you can monitor and decode one side of the data stream (along with a clock).  And even that is crippled, because SPI is a bus, and without a Select line to determine which device is talking, you can't separate out what you want from all the bus chatter.  Unless you limit yourself to Master + SingleSlave-only systems.  And again, only one decoder can be used, because you've exhausted your channels.

I thought perhaps they might have some trick whereby the Ext.Trigger channel could be used to provide a 3rd input (say run the Clock in there, with MOSI on Chan1 and MISO on Chan2), but not according to anything in the manual.  EXT appears to only be available as a Trigger Source in Edge mode.

Lastly is "Parallel Decode", and I can't even figure out what that's supposed to be, from their documentation.  It sounds like it's intended to work with an MSO (not DSO), since it refers to "up to 20 channels".  Presumably 4 analog, and 16 digital.  You assign one channel to a Clock, and the next channel to data, and, well... you're done.  Doesn't seem very parallel to me.

So the 4-channel DS1000Z not only allows for handling full SPI, but can also potentially make use of both Bus Decoders, by handling two protocols at once... e.g., I2C on one, and RS232 on the other.  Have you ever worked on an embedded system where you needed to track comms across more than one interface bus?  With only 2 channels on the DS2000, your options are severely limited.  Even something as simple as running one protocol Decoder on channels 1 & 2, while monitoring channel 3 as a trigger does not seem to be possible.  (The Rigol docs indicate the Ext.Trigger cannot be used as a source when in protocol decoder modes.)  But say you wanted to see the power supply thresholds where comms started or cut out.  Kinda hard to do with only 2 channels.  Or maybe you're probing around trying to correlate some other signal in the system to find where/when a comms channel is picking up glitches.  Again, you're SOL.

So the only use I can see for Decoder2 on the DS2000 is to have two independent sets of parameters config'ed, and be able to turn one or the other on quickly.  On a 4-channel scope like the DS1000Z, you can actually use both decoders at the same time.

Unfortunately, I'm at a bit of a disadvantage... not having a DS2000 here to play with, I have to go by what's in the manual (and what bits I've read here).  And that may not fully reflect the instrument's capabilities.  E.g., in their screen shots, Rigol doesn't even show SPI decoding as SPI... it's listed as "SDIO".  Sadly, fairly typical of Rigol documents (though they're usually well ahead of the rest of their Chinese competition.)  Unless there's an option to customize the Label set for each decoder, that I missed in the manual.

Hopefully this will give you at least a partial answer to your question.

Hi Mark_O,

Thanks!  I was definitely being serious and your reply was outstanding.  I've been trying to gain a better understanding of the practical capabilities and limitations of the decode functions on the DS2000 series for a while now and your reply is the most definitive discussion of this topic I've seen.

I've also been trying to figure out the 2 decode button layout and like you have been trying to decipher the manual and other documentation.

I had just about decided that the DS2000 was the right scope given that most of my work initially will probably be RS232 and I2C with SPI as the likely 3rd decode protocol I'd like to work with.  I realize that SPI would be (much) better with 4 channels but I was thinking maybe the DS2000 get the job done to some extent in "workaround mode"; you and Marmad and others have me wondering if 2  channels will become a notable limitation sooner than later.  The DS2000 seems like a pretty good step up from the DS1000Z in several respects such as waveforms per second, memory, screen size, and maybe the big Nav dial too but maybe those are worth giving up for the 2 extra channels on the DS1000Z.
 
I don't think I'll be needing to work with 2 different protocols at once but I understand your views with respect to SPI and triggering/signal correlation and I appreciate the time you took to type out specifics.  I hope you will be up for adding more thoughts as they come to you.  Thanks again, EF
 

Offline marmad

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #134 on: October 19, 2013, 08:48:18 am »
I had just about decided that the DS2000 was the right scope given that most of my work initially will probably be RS232 and I2C with SPI as the likely 3rd decode protocol I'd like to work with.  I realize that SPI would be (much) better with 4 channels but I was thinking maybe the DS2000 get the job done to some extent in "workaround mode"; you and Marmad and others have me wondering if 2  channels will become a notable limitation sooner than later.  The DS2000 seems like a pretty good step up from the DS1000Z in several respects such as waveforms per second, memory, screen size, and maybe the big Nav dial too but maybe those are worth giving up for the 2 extra channels on the DS1000Z.

In reality, it's nice to be able to do some simple decoding on the DSO, but if you need to do a serious amount of it - or you need something more than the VERY simple trigger definitions built into MSOs - you really need a logic analyzer. IMO, you should concentrate mostly on the oscilloscope functions you need/want when buying a DSO - and worry about the bus decoding aspect less.
 

Offline grego

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #135 on: October 19, 2013, 12:32:24 pm »
I had just about decided that the DS2000 was the right scope given that most of my work initially will probably be RS232 and I2C with SPI as the likely 3rd decode protocol I'd like to work with.  I realize that SPI would be (much) better with 4 channels but I was thinking maybe the DS2000 get the job done to some extent in "workaround mode"; you and Marmad and others have me wondering if 2  channels will become a notable limitation sooner than later.  The DS2000 seems like a pretty good step up from the DS1000Z in several respects such as waveforms per second, memory, screen size, and maybe the big Nav dial too but maybe those are worth giving up for the 2 extra channels on the DS1000Z.

In reality, it's nice to be able to do some simple decoding on the DSO, but if you need to do a serious amount of it - or you need something more than the VERY simple trigger definitions built into MSOs - you really need a logic analyzer. IMO, you should concentrate mostly on the oscilloscope functions you need/want when buying a DSO - and worry about the bus decoding aspect less.

What he said.

You buy a scope for the scope part, not the decodes.  At least that's the primary category.

In my case I look at the decodes because I have two separate signals - one CAN and one square wave AC that are present. So I need to be able to trigger off specific CAN messages and see the resulting DCC signal (the square wave AC) so having MSO options is important to me.
 

Offline Mark_O

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #136 on: October 19, 2013, 04:58:23 pm »
Hi Mark_O, Thanks!  I was definitely being serious and your reply was outstanding.

You're welcome.  I'm glad your question wasn't tongue-in-cheek, and my reply was useful.

Quote
I've been trying to gain a better understanding of the practical capabilities and limitations of the decode functions on the DS2000 series for a while now and your reply is the most definitive discussion of this topic I've seen.

I'll admit that when you're trying to make a buying decision based on anticipating what you might need, to handle things you haven't encountered yet, it can be difficult.  Especially when you're getting started.  "What do I chose?  What do I chose?"   :scared:

Quote
I've also been trying to figure out the 2 decode button layout and like you have been trying to decipher the manual and other documentation.

I was kind of hoping that someone who actually has a DS2000 would jump in and tell me I was FOS :), and that the limitations implied by the manual were not present in the scope itself.

Quote
I had just about decided that the DS2000 was the right scope given that most of my work initially will probably be RS232 and I2C with SPI as the likely 3rd decode protocol I'd like to work with.  I realize that SPI would be (much) better with 4 channels but I was thinking maybe the DS2000 get the job done to some extent in "workaround mode"

Well, it's certainly possible to "work around" many limitations in your test instruments.  All of us have done it at one point or another, and some of us have to do it every day.  But just because you can finagle things around doesn't mean that you'd want to, or it would be a productive solution.  Let me illustrate the problem with half-SPI on the DS2000 with a very specific example (analogy) that's probably closer to home for you, and may be easier to grok.

When you're working on a system with an RS232 comms channel, you're monitoring RX and TX lines.  You may be looking at Requests or Commands on the TX, and seeing the replies on the RX.  The two are pretty closely tied together, and being able to see the specific response to the specific request may be fundamental.  Now imagine if you could only hear (see) half the conversation.  You could either monitor outbound requests, but not see what was being sent back.  OR you could see responses, not knowing what request they were relating to.  AND you could not see the time-interval between the two.  Does that slow you down any?  How much fun will you have moving your probes around, to check RX and then TX, one at a time?

That's what's going on with SPI on the DS2000.  You only get to see half the conversation at one time, because one of your two available channels HAS to be used for the Clock.  On a SPI bus, the CPOL and CPHA are critical (polarity and phase), because they determine when to sample the data bits.  That leaves only one channel for data, yet there are two (MISO and MOSI, similar to RX and TX).  Not only can you not see both sides at the same time, you also can't see the timing relationship between them.  To me, that's like working in the dark.  And why I was hoping the DS2000 had an undocumented capability (missing from the manual) to use the Ext.Trig for say, Clocking, leaving Chan1 and 2 open for MISO/MOSI.  Not having the 4-th channel (a Select line, for CS or SS) will certainly be detrimental on a multi-slave SPI bus, but that at least you can find ways to work around (have the other slave devices shut-up).  With the DS1000Z, you don't have to.

That's why it seemed like a bit of a stretch to me for Rigol to claim that the DS2000 even handles SPI.  Sure, it can trigger on it (and handle CPOL and CPHA), and decode the bit-stream to turn n-bits into bytes or words... for one half of the comms.  But that's pretty crippled, in my book.

Quote
...you and Marmad and others have me wondering if 2  channels will become a notable limitation sooner than later.  The DS2000 seems like a pretty good step up from the DS1000Z in several respects such as waveforms per second, memory, screen size, and maybe the big Nav dial too but maybe those are worth giving up for the 2 extra channels on the DS1000Z.

That's one area where I think you and many others are making a fairly big mistake.  There's no doubt that the DS2000 IS a good step up from the 1000Z in many key performance metrics.  It's an excellent device.  Greater bandwidth, higher sample rates, deeper memory, etc.  But unless you're a "more is always better" kind of guy, you have to put that into some perspective.  Do you really need 200 MHz?  Or would 100 MHz be enough?  The answer isn't the same for everybody, but even the lower specs of the 1000Z, coupled with 4-channels, would be incredible for many, many users.  Especially hobbyists or beginners.  And 4-channels at under $600?  Are you nuts?  That was simply unheard of.  There's a reason you don't see very many 4-channel scopes out there... until recently they cost an arm and a leg, and they simply weren't an option for anybody without deep pockets.  That doesn't mean we didn't want to have one!  :)  And cursed our bad luck the minute we needed to have channel #3 in a test setup.

Quote
I don't think I'll be needing to work with 2 different protocols at once...

You probably won't, at least not right away.  But consider that if you'll be doing any embedded systems work, or working on devices that are uProc-controlled, there's often a lot of internal communicating going on between subsystems (a huge amount of I2C and SPI, in my experience).  And being able to see the interactions between two separate comms channels will sometimes be fundamental to finding your problem.  Even just monitoring ONE internal comms bus, the minute you need to see and coordinate it with any other external signal you come up short.

And if you're doing your own embedded-systems development work (as opposed to trouble-shooting existing systems), one thing you may find exceptionally useful is to have your micro emit your own trigger pulses at specific points, as markers, to flag when some condition or event has occurred (or the interval where it's active, as a Gate signal).  No digging through a long trace trying to find a correlation, you flagged it yourself in your code, triggered on it, and can see what's happening at the exact spot, as well as the timing.  How do you do that when you have only 2 channels, and they're already tied up?  You don't.  :( 

How does having twice the bandwidth you needed, or 10x the memory depth you needed, or being able to oversample 5x higher than required help you out there?   :-//

Quote
...but I understand your views with respect to SPI and triggering/signal correlation and I appreciate the time you took to type out specifics.  I hope you will be up for adding more thoughts as they come to you.  Thanks again, EF

Well, this was a bit more.  Enough for one posting.  Possibly more later, as time allows.
 

Offline Electro Fan

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #137 on: October 22, 2013, 04:19:52 am »
Hi Mark_O,

Thanks for your most recent post (#136 above) - it is excellent - exactly the type of info I have been hungry for.

I think you might have brought me around from the DS2000 series to the DS1000 series.

You should probably be a four channel scope sales rep -- the two channel scope sales reps would have a hard time selling against you  :)

Your use case examples were clear and meaningful, and compelling.  I get all these concepts I just haven't had the chance to work hands-on with some of these things and I can see from your discussions much more clearly why 4 channels are going to provide a lot more headroom for signal analysis including the abilty to observe signal relationships/correlations.   

I'm familiar with MISO and MOSI but CPOL and CPHA were terms I had to research; I found this (in case anyone is interested):  http://www.diolan.com/dln_doc/spi-transfer-modes.html

I think I can live with the smaller screen and hopefully the lesser memory, and in studying the 1000Z User Guide it looks like maybe the lack of the big Nav knob on the DS2000 isn't going to be a major give-up (but if anyone thinks different, I'd be happy to hear why).
 
Overall, I have a hunch that your post is probably going to influence other scope buyers trying to make the 2 vs 4 channel decision.

So I'm almost there but now I'm somewhat back to a question that got me started about half a year ago when I first discovered EEVblog:  Is there any reason to maybe quit trying to turn a low end DSO into a low end MSO (scope + 8/16 channel logic analyzer) or pseudo MSO (4 channel scope without a LA but with protocol triggering and decoding), and just get a decent DSO (again, maybe the DS2000 series) and add a decent USB logic analyzer (such as the Intronix LogicPort - at less than $400)?

One of the things that started me on this journey was a desire to see analog signals and digital signals well correlated, which I'm not sure a scope plus LogicPort does quite as well/seamlessly as say the DS1000Z (at least up to the point that 4 channels is sufficent vs. 4+16).  [So, the question might be framed as:  would you rather have a DS2000 + a LogicPort, or a DS1000Z?, or is the answer start with a DS1000Z and see if a need for a LogicPort develops later?].  Any more thoughts you might have along these lines?

Thanks again!  EF
« Last Edit: October 22, 2013, 04:34:07 am by Electro Fan »
 

Offline nowlan

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #138 on: October 22, 2013, 04:52:48 am »
Wasnt there a hack to let the logic analyser trigger your scope?
 

Offline Pinkus

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #139 on: October 22, 2013, 07:09:29 am »
Exactly: buy the 2072 and then the Intronix Logicport. The result: you will have best of breed and you are not limited!
The decoding part of the scope is always a nice to have but it is often NOT useful as it is much easier to work with a dedicated logic analyzer. And yes, the Logicport can be enhanced to trigger the scope.
 

Offline Electro Fan

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #140 on: November 11, 2013, 04:52:27 pm »
Hi Mark_O, Thanks!  I was definitely being serious and your reply was outstanding.

You're welcome.  I'm glad your question wasn't tongue-in-cheek, and my reply was useful.

Quote
I've been trying to gain a better understanding of the practical capabilities and limitations of the decode functions on the DS2000 series for a while now and your reply is the most definitive discussion of this topic I've seen.

I'll admit that when you're trying to make a buying decision based on anticipating what you might need, to handle things you haven't encountered yet, it can be difficult.  Especially when you're getting started.  "What do I chose?  What do I chose?"   :scared:

Quote
I've also been trying to figure out the 2 decode button layout and like you have been trying to decipher the manual and other documentation.

I was kind of hoping that someone who actually has a DS2000 would jump in and tell me I was FOS :), and that the limitations implied by the manual were not present in the scope itself.

Quote
I had just about decided that the DS2000 was the right scope given that most of my work initially will probably be RS232 and I2C with SPI as the likely 3rd decode protocol I'd like to work with.  I realize that SPI would be (much) better with 4 channels but I was thinking maybe the DS2000 get the job done to some extent in "workaround mode"

Well, it's certainly possible to "work around" many limitations in your test instruments.  All of us have done it at one point or another, and some of us have to do it every day.  But just because you can finagle things around doesn't mean that you'd want to, or it would be a productive solution.  Let me illustrate the problem with half-SPI on the DS2000 with a very specific example (analogy) that's probably closer to home for you, and may be easier to grok.

When you're working on a system with an RS232 comms channel, you're monitoring RX and TX lines.  You may be looking at Requests or Commands on the TX, and seeing the replies on the RX.  The two are pretty closely tied together, and being able to see the specific response to the specific request may be fundamental.  Now imagine if you could only hear (see) half the conversation.  You could either monitor outbound requests, but not see what was being sent back.  OR you could see responses, not knowing what request they were relating to.  AND you could not see the time-interval between the two.  Does that slow you down any?  How much fun will you have moving your probes around, to check RX and then TX, one at a time?

That's what's going on with SPI on the DS2000.  You only get to see half the conversation at one time, because one of your two available channels HAS to be used for the Clock.  On a SPI bus, the CPOL and CPHA are critical (polarity and phase), because they determine when to sample the data bits.  That leaves only one channel for data, yet there are two (MISO and MOSI, similar to RX and TX).  Not only can you not see both sides at the same time, you also can't see the timing relationship between them.  To me, that's like working in the dark.  And why I was hoping the DS2000 had an undocumented capability (missing from the manual) to use the Ext.Trig for say, Clocking, leaving Chan1 and 2 open for MISO/MOSI.  Not having the 4-th channel (a Select line, for CS or SS) will certainly be detrimental on a multi-slave SPI bus, but that at least you can find ways to work around (have the other slave devices shut-up).  With the DS1000Z, you don't have to.

That's why it seemed like a bit of a stretch to me for Rigol to claim that the DS2000 even handles SPI.  Sure, it can trigger on it (and handle CPOL and CPHA), and decode the bit-stream to turn n-bits into bytes or words... for one half of the comms.  But that's pretty crippled, in my book.

Quote
...you and Marmad and others have me wondering if 2  channels will become a notable limitation sooner than later.  The DS2000 seems like a pretty good step up from the DS1000Z in several respects such as waveforms per second, memory, screen size, and maybe the big Nav dial too but maybe those are worth giving up for the 2 extra channels on the DS1000Z.

That's one area where I think you and many others are making a fairly big mistake.  There's no doubt that the DS2000 IS a good step up from the 1000Z in many key performance metrics.  It's an excellent device.  Greater bandwidth, higher sample rates, deeper memory, etc.  But unless you're a "more is always better" kind of guy, you have to put that into some perspective.  Do you really need 200 MHz?  Or would 100 MHz be enough?  The answer isn't the same for everybody, but even the lower specs of the 1000Z, coupled with 4-channels, would be incredible for many, many users.  Especially hobbyists or beginners.  And 4-channels at under $600?  Are you nuts?  That was simply unheard of.  There's a reason you don't see very many 4-channel scopes out there... until recently they cost an arm and a leg, and they simply weren't an option for anybody without deep pockets.  That doesn't mean we didn't want to have one!  :)  And cursed our bad luck the minute we needed to have channel #3 in a test setup.

Quote
I don't think I'll be needing to work with 2 different protocols at once...

You probably won't, at least not right away.  But consider that if you'll be doing any embedded systems work, or working on devices that are uProc-controlled, there's often a lot of internal communicating going on between subsystems (a huge amount of I2C and SPI, in my experience).  And being able to see the interactions between two separate comms channels will sometimes be fundamental to finding your problem.  Even just monitoring ONE internal comms bus, the minute you need to see and coordinate it with any other external signal you come up short.

And if you're doing your own embedded-systems development work (as opposed to trouble-shooting existing systems), one thing you may find exceptionally useful is to have your micro emit your own trigger pulses at specific points, as markers, to flag when some condition or event has occurred (or the interval where it's active, as a Gate signal).  No digging through a long trace trying to find a correlation, you flagged it yourself in your code, triggered on it, and can see what's happening at the exact spot, as well as the timing.  How do you do that when you have only 2 channels, and they're already tied up?  You don't.  :( 

How does having twice the bandwidth you needed, or 10x the memory depth you needed, or being able to oversample 5x higher than required help you out there?   :-//

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...but I understand your views with respect to SPI and triggering/signal correlation and I appreciate the time you took to type out specifics.  I hope you will be up for adding more thoughts as they come to you.  Thanks again, EF

Well, this was a bit more.  Enough for one posting.  Possibly more later, as time allows.

Hi Mark_O,

One more revisit on the 4 channel (DS1000Z) vs 2 channel (DS2000) question(s).

I've discovered that the Decoder functionality gives you not just two Decode channels, but that each Decoder channel allows you to set the decode simultaneously for two Decodes - one for receive and one for transmit.  So, in total, you can show 4 decodes at the same time.  This could be two for TX/RX for binary and two for TX/RX ASCII on channel 1 all at the same time, for example.  Or, you could have TX/RX for binary on channel 1 and TX/RX for binary on channel 2 all at the same time, for example.

The user can only decode on two of the 4 analog scope channels - so you don't have the ability to decode across 3 or 4 analog channels at the same time, but you could be looking at two analog channels without decodes and two more analog with decodes (each showing the TX and RX decodes) for 6 total "views" into signal information.

Given that the decodes do only work on two of the 4 analog channels at one time and given that those two channels can each observe the TX and RX at the same time (for 4 total simultaneous decodes), is it still your firm opinion that the 4 channel scope (DS1000Z) would be needed to do the type of work you described above, or is it possible that with the TX/RX x 2 capability that maybe the 2 channel scope (DS2000) could get closer to being sufficient?

The reason for asking is that I think part of the challenge is to simultaneously observe desired signals and see them time correlated, but part of the challenge is then being able to subsequently navigate through the signals (and here I think the DS2000 might have some either small or medium size advantages).

Thanks!  EF
 

Offline iDevice

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #141 on: November 11, 2013, 06:12:58 pm »
I've discovered that the Decoder functionality gives you not just two Decode channels, but that each Decoder channel allows you to set the decode simultaneously for two Decodes - one for receive and one for transmit.  So, in total, you can show 4 decodes at the same time.  This could be two for TX/RX for binary and two for TX/RX ASCII on channel 1 all at the same time, for example.  Or, you could have TX/RX for binary on channel 1 and TX/RX for binary on channel 2 all at the same time, for example.

The user can only decode on two of the 4 analog scope channels - so you don't have the ability to decode across 3 or 4 analog channels at the same time, but you could be looking at two analog channels without decodes and two more analog with decodes (each showing the TX and RX decodes) for 6 total "views" into signal information.

Given that the decodes do only work on two of the 4 analog channels at one time and given that those two channels can each observe the TX and RX at the same time (for 4 total simultaneous decodes), is it still your firm opinion that the 4 channel scope (DS1000Z) would be needed to do the type of work you described above, or is it possible that with the TX/RX x 2 capability that maybe the 2 channel scope (DS2000) could get closer to being sufficient?
I guess you are confusing channels and decoders.
You have 4 input channels and 2 decoders.
If you take as example the serial decoder for RS-232, one decoder can simultaneously decode and display TX and RX, that is correct.
But to be able to do that, it will uses two channels, one for TX and one for RX.
Now if you want to fully decode 2 rs-232 streams simultaneously, you will have to use the second decoder which will need the 2 remaining channels, one for TX and one for RX.
So you will have something like:
  TXa on ch1
  RXa on ch2
  TXb on ch3
  RXb on ch4
So all your channels will be used for 2  rx/tx rs-232 decoders.
 

Offline Electro Fan

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #142 on: November 11, 2013, 10:18:15 pm »
I've discovered that the Decoder functionality gives you not just two Decode channels, but that each Decoder channel allows you to set the decode simultaneously for two Decodes - one for receive and one for transmit.  So, in total, you can show 4 decodes at the same time.  This could be two for TX/RX for binary and two for TX/RX ASCII on channel 1 all at the same time, for example.  Or, you could have TX/RX for binary on channel 1 and TX/RX for binary on channel 2 all at the same time, for example.

The user can only decode on two of the 4 analog scope channels - so you don't have the ability to decode across 3 or 4 analog channels at the same time, but you could be looking at two analog channels without decodes and two more analog with decodes (each showing the TX and RX decodes) for 6 total "views" into signal information.

Given that the decodes do only work on two of the 4 analog channels at one time and given that those two channels can each observe the TX and RX at the same time (for 4 total simultaneous decodes), is it still your firm opinion that the 4 channel scope (DS1000Z) would be needed to do the type of work you described above, or is it possible that with the TX/RX x 2 capability that maybe the 2 channel scope (DS2000) could get closer to being sufficient?
I guess you are confusing channels and decoders.
You have 4 input channels and 2 decoders.
If you take as example the serial decoder for RS-232, one decoder can simultaneously decode and display TX and RX, that is correct.
But to be able to do that, it will uses two channels, one for TX and one for RX.
Now if you want to fully decode 2 rs-232 streams simultaneously, you will have to use the second decoder which will need the 2 remaining channels, one for TX and one for RX.
So you will have something like:
  TXa on ch1
  RXa on ch2
  TXb on ch3
  RXb on ch4
So all your channels will be used for 2  rx/tx rs-232 decoders.

I get that; I understand:

With a DS1000Z you could have two rx/tx rs232 decoders, and also have two more analog channels free, no doubt.

With a DS2000 you just have the two rx/tx rs232 decoders (4 paths decoded), but no more channels available, of course.  The question is (what I don't understand/know) is whether the ability to decode 4 paths (2 TX and 2 RX) might somehow address the needs of say, SPI where you have clock, MOSI, and MISO.  I am presuming SPI is a clear cut case where a 3rd or 4th analog channel might be needed in addition to the 4 paths (2 TX and 2 RX) that can be decoded by both the DS1000Z and the DS2000.

"But to be able to do that, it will uses two channels, one for TX and one for RX."  It is not clear to me that this is how it works - it might, of course, however it is my impression (based on the labeling and overall decoder setup process) that one analog input channel can decode a TX and a RX signal, as opposed to one channel providing 2 TX decoders and another channel providing 2 RX decoders.  To be square, I don't quite see how it might do this as the probe is attached to one pin for TX and one pin for GND, and yet the 1000Z decoders (1 and/or 2) ask you to specify both TX and RX and they both display both as if they are two separate pieces of info.

I guess it comes down to getting my head around how probing two pins (TX and GND) can somehow provide a signal that the scope decodes as both Send and Receive (maybe those are just two labels - but why have two labels if it is only decoding one thing?).  It seems like we are just probing a simplex transmission (not a half-duplex signal, and definitely not a full-duplex transmission).  The scope setup process asks for both the TX and RX setup info on a single channel but I can't see how it can derive both from two pins being probed.  That, I think is the source of my confusion. :-//
« Last Edit: November 11, 2013, 10:47:14 pm by Electro Fan »
 

Offline iDevice

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #143 on: November 11, 2013, 11:27:36 pm »
I get that; I understand:
I'm afraid you aren't...
Quote
With a DS1000Z you could have two rx/tx rs232 decoders, and also have two more analog channels free, no doubt.
Nope, 2 x rx+tx means 4 channels, it's elementary math, so you don't have two more analog channel free.
Quote
With a DS2000 you just have the two rx/tx rs232 decoders (4 paths decoded), but no more channels available, of course.
I'm sorry wrong again, with a 2000, you can only decode one rs-232.
Quote
The question is (what I don't understand/know) is whether the ability to decode 4 paths (2 TX and 2 RX) might somehow address the needs of say, SPI where you have clock, MOSI, and MISO.
That's why it is not possible to decode a full SPI with a DS2000, only two channel ! So it is either MISO +CLK or MOSI + CLK
Quote
I am presuming SPI is a clear cut case where a 3rd or 4th analog channel might be needed in addition to the 4 paths (2 TX and 2 RX) that can be decoded by both the DS1000Z and the DS2000.
What you call path is a channel. 2 channels on a 2000, 4 on a 1000Z or 4000.
So for full SPI decoding you need a 1000Z or a 4000 (the fourth channel is used for CS if you have a multi slave bus)
Quote
"But to be able to do that, it will uses two channels, one for TX and one for RX."  It is not clear to me that this is how it works - it might, of course, however it is my impression (based on the labeling and overall decoder setup process) that one analog input channel can decode a TX and a RX signal, as opposed to one channel providing 2 TX decoders and another channel providing 2 RX decoders.

This is where you have your problem, I guess.
RS-232 uses at least 3 wires, TX, RX and GND.
RX and TX are 2 different signals referenced to GND, so you need 2 scope channel to display/decode them.
Quote
To be square, I don't quite see how it might do this as the probe is attached to one pin for TX and one pin for GND, and yet the 1000Z decoders (1 and/or 2) ask you to specify both TX and RX and they both display both as if they are two separate pieces of info.
Well it seems you answer yourself ! RX and TX are indeed two pieces of different signals, thats why you have to specify on which channel you connect each of them. One channel for Tx one different channel for Rx.
Of course the scope allows you to specify two times the same channel without warning, which might be confusing, but it is an operator error. It will still function but you will decode 2 times the same signal which is useless.
Quote
I guess it comes down to getting my head around how probing two pins (TX and GND) can somehow provide a signal that the scope decodes as both Send and Receive (maybe those are just two labels - but why have two labels if it is only decoding one thing?).  It seems like we are just probing a simplex transmission (not a half-duplex signal, and definitely not a full-duplex transmission).  The scope setup process asks for both the TX and RX setup info on a single channel but I can't see how it can derive both from two pins being probed.  That, I think is the source of my confusion. :-//
I hope it clearer now !
 

Offline JDubU

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #144 on: November 12, 2013, 12:29:24 am »
I've been using the RS232, I2S and SPI smart triggers on my DS2000 to synchronize a Saleae logic analyser via the scope's trigger output.  The Saleae currently only has edge triggering so the scope can provide data based trigger conditions.  The obvious limitation is that the DS2000 cannot be used to view addition analog waveforms when both channels are being used for the trigger function.  Also, the Saleae's max sampling rate is only 24 Msps.  The upside is that I can display seven data channels (in addition to the eighth channel used for trigger input from the scope).  Also, the interactive user interface on the Saleae is far better than that of the scope's.
 

Offline Smokey

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #145 on: November 12, 2013, 03:33:03 am »
I've been using the RS232, I2S and SPI smart triggers on my DS2000 to synchronize a Saleae logic analyser via the scope's trigger output.  The Saleae currently only has edge triggering so the scope can provide data based trigger conditions.  The obvious limitation is that the DS2000 cannot be used to view addition analog waveforms when both channels are being used for the trigger function.  Also, the Saleae's max sampling rate is only 24 Msps.  The upside is that I can display seven data channels (in addition to the eighth channel used for trigger input from the scope).  Also, the interactive user interface on the Saleae is far better than that of the scope's.

Great idea! 
 

Offline Mark_O

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #146 on: November 12, 2013, 04:09:09 am »

Hi, EF.  I see that iDevice has done all the heavy lifting of explaining the details to you.  Just a few additions...

I guess it comes down to getting my head around how probing two pins (TX and GND) can somehow provide a signal that the scope decodes as both Send and Receive

It cannot do so.  Probing TX and Gnd can provide only Tx, not Rx at all.

Quote
(maybe those are just two labels - but why have two labels if it is only decoding one thing?).

I can see why you might be confused.  However, the scope does not know what signal is on each channel.  So it lets you define the labels.  Just because you set the labels for RX and TX on (say) Channel one, doesn't change the fact that channel one would only be TX.  So the RX assignment you made (which should have been assigned to Channel 2), is just a duplicate of TX.  You're seeing exactly the same thing, with two different labels (one of which is wrong).  This will not be helpful to you in troubleshooting.  ;)
 

Offline Electro Fan

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #147 on: November 12, 2013, 04:31:16 am »

Hi, EF.  I see that iDevice has done all the heavy lifting of explaining the details to you.  Just a few additions...

I guess it comes down to getting my head around how probing two pins (TX and GND) can somehow provide a signal that the scope decodes as both Send and Receive

It cannot do so.  Probing TX and Gnd can provide only Tx, not Rx at all.

Quote
(maybe those are just two labels - but why have two labels if it is only decoding one thing?).

I can see why you might be confused.  However, the scope does not know what signal is on each channel.  So it lets you define the labels.  Just because you set the labels for RX and TX on (say) Channel one, doesn't change the fact that channel one would only be TX.  So the RX assignment you made (which should have been assigned to Channel 2), is just a duplicate of TX.  You're seeing exactly the same thing, with two different labels (one of which is wrong).  This will not be helpful to you in troubleshooting.  ;)

Hi Mark_O and iDevice,

Thanks again to you guys for getting me squared away.  You guys are good teachers.

I think the labeling flexibility might have got me off the track but with your help I'm getting it sorted out.

So, where I've just been probing the TX pin and the GND pin on a PC RS232 port, is there a practical way to probe and monitor the RS232 comminications between two PCs with the 2 decoders? 

iDevice suggested this:
  TXa on ch1
  RXa on ch2
  TXb on ch3
  RXb on ch4

Seems like it might require a special cable where the TX and RX lines/pins could exposed and probed?

 

Offline Electro Fan

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #148 on: November 12, 2013, 04:33:16 am »
I've been using the RS232, I2S and SPI smart triggers on my DS2000 to synchronize a Saleae logic analyser via the scope's trigger output.  The Saleae currently only has edge triggering so the scope can provide data based trigger conditions.  The obvious limitation is that the DS2000 cannot be used to view addition analog waveforms when both channels are being used for the trigger function.  Also, the Saleae's max sampling rate is only 24 Msps.  The upside is that I can display seven data channels (in addition to the eighth channel used for trigger input from the scope).  Also, the interactive user interface on the Saleae is far better than that of the scope's.

JDubU,

If you ever get a chance to make a video showing how you have configured and operated this setup, that would make for a great post here.  Thanks, EF
 

Offline Mark_O

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Re: new RIGOL DS1000Z and... MSO4000
« Reply #149 on: November 12, 2013, 05:22:52 am »
So, where I've just been probing the TX pin and the GND pin on a PC RS232 port, is there a practical way to probe and monitor the RS232 comminications between two PCs with the 2 decoders? 

iDevice suggested this:
  TXa on ch1
  RXa on ch2
  TXb on ch3
  RXb on ch4

That's for two complete RS232 links.  To monitor comms between 2 PCs (or any two devices), you only need to use two channels.  That's because the TX from Dev1 goes to RX on Dev2, and vice-versa.

Quote
Seems like it might require a special cable where the TX and RX lines/pins could exposed and probed?

A "special cable" would do the job.  And you could certainly splice one together yourself.  Even easier would be a non-molded cable, with screw shells on each end.  Just open one end and voila!, your signal lines exposed for probing.

Other options would be a breakout box.  Or an RS232 switch-box you may have laying around, which would expose the signal lines on the wiring inside.
« Last Edit: November 12, 2013, 05:25:24 am by Mark_O »
 


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