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Mar 02, 2009, 03:31 AM
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Alison,

while I think a good case can be made for open-sourcing the Rigol, I'd certainly appreciate it, and your points are well-taken, I do suspect that you are dreaming.

I'd guess that any additional sales that Rigol might receive from hobbiest and enthusiast customers that would be attracted would not be perceived as outweighing the competitive loss from that disclosure. Keep in mind that they don't currently even disclose schematics, and their instruments are designed and built in China. In that environment, open-source would surely be a one-way street, where many other manufacturers would simply take that intellectual-property, embed it in their own devices, possibly make some changes and/or improvements, and then keep those proprietary and secret (in violation of GNU requirements). That "gift" of years of R&D would be so big as to likely spawn many more new competitors, whose only claim to fame would be undercutting the cost.

Honestly, I don't see it happening, and I can't even say that it would be in Rigol's self-interest. So my hopes are more limited, in the sense that when an issue is found that Rigol does not plan to rectify (like the LA problem), they release the tech info they gathered to isolate the problem, if for no other reason than so we can be confident that we know what the boundaries and limits are. I don't think that's too much to ask for a professional instrument.

- Mark
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Mar 02, 2009, 05:15 AM
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Quote:
If you're up to it, continuing to inquire to obtain these few pieces of tech info could be very helpful - Mark
I will give this a try, although it took me months just to get info out of them regarding the data file layouts.. and then we had already worked it out ourselves.

Regarding building our own... well I do prefer having a stand alone device and not having to have a PC. Unfortunately Rigol was one of the few that fitted my limited budget. The problem I have with the LA is that I do want to check the actual data on the various data busses. I think the biggest issue regarding building an LA is cost. At a rough guess the hardware will cost about $150us - That would be using an existing board and including things such as probes etc. This will give you an LA capable of about 200mhz sampling and 8MB of memory. But at this price one could simply purchase a system such as the one here: http://www.mcumall.com/comersus/stor...idProduct=4313

So unless Rigol take the unlikely step of providing us with enough info to work around the problem the logical alternative is to purchase something else or.... suffer in silence with the current LA
Mar 02, 2009, 06:28 AM
Quote:
Originally Posted by Mark_O
Alison,

while I think a good case can be made for open-sourcing the Rigol, I'd certainly appreciate it, and your points are well-taken, I do suspect that you are dreaming.

- Mark
Damn, caught.

Quote:
Originally Posted by davidgrm
the logical alternative is to purchase something else or....
Would we be able to pool our 'Googling' ability to bring the alternatives to the surface? I've certainly seen alternatives, but when it comes to finding them again...

The obvious two at the moment are the Owon MSO, and the Leaptronix LA. Does anyone out there have one, or know someone?

I may mail Leaptronix this week, and see if they'd release one for a month, for testing against the Rigol. With a view to posting the outcome on here. I'm in the UK mind, when the USA may be better for their distribution.

1k is about my upper limit. If I spent that then the Rigol could go back based on jittery LA. Again, I'd rather keep the Rigol, but we might find that the Leaptronix is as poorly built as the Owon. Or maybe it might be brilliant.

Having just done some reading... I suspect that they're all rubbish at this end of the market, and Rigol is the best of the bunch. It's looking like a USB pod at this rate (I like standalone).
Last edited by Alison F; Mar 02, 2009 at 06:40 AM.
Mar 02, 2009, 09:56 AM
Registered User
David commented:
> at this price one could simply purchase a system such as the one here <

A couple attractive things about the ZeroPlus you found, David... it does provide a trigger out to allow syncing an analog scope with the digital stream (but no way to integrate the two, for aligned evaluations). It has compression capabilities to take greater advantage of limited memory capacity (critical, since its 32k/channel is anemic compared to the 512k on the Rigol, 16x larger). It provides integrated protocol analysis and display capability, which can be very handy (goes way beyond the Rigol), and now includes 6 protocols (4 stock and 2 user selected). Is reasonably priced (but adds a hefty $30 for shipping to the US). It accepts an external clock, for state mode analysis (up to 100 MHz).

I do have to admit that attempting to decode their Taiwan-glish is a bit challenging. But it does seem to provide the most bang-for-the-buck in an affordable LA, without sacrificing critical features or specifications. It might make a useful companion to the Rigol.

The Leaptronix looks like an attractive product (I was aware of it before I got my Rigol), but its price-tag is so far out of my range for an LA-only device that it's not worth evaluating for me.

- Mark
Mar 02, 2009, 10:08 AM
Registered User
Alison had written:
> The obvious two at the moment are the Owon MSO, and the Leaptronix LA <

I've already commented on the Leaptronix (though others may find it more affordable than I do).

But I must point out that having looked at the Owon, it must be said that it's NOT an MSO at all. You can operate it in digital mode as an LA, OR analog mode as a DSO. But you can't have both at the same time, or data from both on-screen at once. So for them to describe it as an MSO is stretching things. It also suffers from the typical Owon build quality. All of which make it not an option in my book.

Which comes back to why I'd like to find a workaround that lets the features of the Rigo LA be utilized.

- Mark
Mar 02, 2009, 01:07 PM
Ermmm ok

Next step, to open up one of the Rigol LA pods? Admittedly I did look at doing that to mine, but I think it's one of these things that are sealed by ultrasound or whatever it is. The join is pretty secure. I don't think it snaps shut with hidden clips.

I wonder how much a replacement pod actually would be? As the leads are quite good quality really and it would be handy to have some.

The LA cable btw, is a 68-pin SCSI cable ;-)

Certainly on the Rohde & Schwarz, and the Thurlby here, you can cut out the pod altogether.... You just lose the ability of variable threshold voltages, and the distance from the LA. The R&S pod cables are about 1.5metres long. The only downside of the R&S is that while it's a dual processor CP/M machine with an incredible amount of possibilities, ..you have to practically program it using a scripting language before you can capture anything.

I actually have FULL circuit diagrams and service manuals for both the R&S and the Thurlby................

Rigol pods? Replacements?
Mar 02, 2009, 03:01 PM
Registered User
I think that the Rigol LA pod possibly has screws under the label. Perhaps heating the label with a hair-dryer before trying to pry it off might help???? My guess is that there will be an FPGA sitting in the pod with some sort of voltage level control on the inputs. Just regarding the actual issue with the LA, when I first picked it up I was only using a few input lines. I did notice that the problem seemed to be crosstalk between them and if I only used every second or third line the problem went away. This could indicate that somewhere there is poor PCB layout. If this is on the main PCB it would explain why they cant fix it... anyway that just my guess
Here is another USB LA - might be even nicer than the ZeroPlus but costs more. You can download there software and run it in demo mode.
http://www.pctestinstruments.com/index.htm

Alison just as a matter of interest, you say you have the diagrams for your other LA's what do they use for the input stage on the pods?
Last edited by davidgrm; Mar 02, 2009 at 04:57 PM.
Mar 02, 2009, 05:22 PM
David, you have mail. Links to the Service Manuals. I scanned them in a while back, every now and then someone with a LA4800 emails me.

Page 44. 74HC393 74ACT572 74HC165

Page 45. 74HCT573

Schematics at about 61.

I also have the original Service Manual here (not a copy) and an A3 scanner if you'd like 1200/600/300dpi scans.
Last edited by Alison F; Mar 02, 2009 at 05:30 PM.
Mar 03, 2009, 06:29 AM
Registered User
David commented:
> My guess is that there will be an FPGA sitting in the pod with some sort of voltage level control on the inputs. <

I think that's a good guess.

> Just regarding the actual issue with the LA, when I first picked it up I was only using a few input lines. I did notice that the problem seemed to be crosstalk between them and if I only used every second or third line the problem went away. <

Ah, I wasn't aware of that. Thanks!

> This could indicate that somewhere there is poor PCB layout. If this is on the main PCB it would explain why they cant fix it... <

True, although if the problem is simply the PCB, laying out another one with proper grounding (perhaps a 3-layer board, with an internal ground plane, and alternating lines running top & bottom), might be a solution (for us). Certainly vastly easier than building an LA circuit from scratch.

It would also mean that Rigol themselves could someday come up with a new model pod replacement that would eliminate the problem. I believe that was an idea I suggested several months back.

If I get a chance, I'll investigate the crosstalk issue. Unfortunately, I've got quite a bit of other stuff on my plate at the moment.

- Mark
Mar 03, 2009, 08:04 AM
Registered User
Trevor_G's Avatar
As my Rigol nearly out of warranty anyway deicided to have a peek at the LA. Three screws under the label.

Good news no dedicated controller. The top side uses 4 National DS90LV047A 3V LVDS Quad CMOS Differential Line Drivers. The lower side has 8 six pin ICs labelled C7K (I have not identified them yet). Other than that its al Rs & Cs.

See the pics for layout.

Trevor
Mar 03, 2009, 11:44 AM
Registered User
Trevor_G's Avatar
I have identified the SC70-6 ICs marked as C7K as an 74LVC2G17 dual schmitt I/P buffer.

I have done a rough sketch of the i/p cct showing two inputs.

It would appear that being to cheap skate to use a comparator Rigol have used a summing junction on the i/p of a schmitt trigger

So now a level change on an i/p is passed via C1/R3 to the schmitt i/p. At the same time this spike will be passed via R4 to ALL the other schmitt triggers.

Of course I could be wrong

Trevor
Mar 03, 2009, 03:28 PM
Registered User
Mark regarding the cross talk - It might not be an actual issue. I just remembered that when I first had those troubles I exchanged the LA POD I have not tested that again
Although looking at the images above does suggest this might be possible. A lot would of course depend on what is driving the line coming from the DSO side into R4 /C3 - Thanks for the images Trevor


Alison thanks for the info - check your mail
Last edited by davidgrm; Mar 03, 2009 at 03:41 PM.
Mar 03, 2009, 03:53 PM
Registered User
I think the next think that one needs to do is replicate the problem with the pod open and monitor 2 of the channels with a scope and see if the problem is in the pod or in the main PCB
Mar 03, 2009, 05:03 PM
I do definitely get crosstalk... If I leave the lines unconnected, even on basic signals of a few Hz. Which doesn't affect either the R&S or the Thurlby. They don't pick up on what the lines next to them are doing if floating.

I submit top tec pcb in the UK for making PCBs... http://www.top-tec-pcb.co.uk/ . They'll take Eagle files too.. 180 for 5 Eurocards with multiple identical circuits, and scoring/milling.

David, I've resent your mail. I posted the ftp address...

Give me a while, and I'll do a proper scan of one of the Thurlby schematics.

TBH, I certainly wouldn't mind a couple of Rigol pods... Main requirements would be that the parts could be bought from Farnell.
Last edited by Alison F; Mar 03, 2009 at 05:49 PM.
Mar 03, 2009, 05:22 PM
Oh, and EXCELLENT WORK Trevor!!





HARTING - 6001 068 5132 - SOCKET, SCSI, 68WAY - 9.44
http://uk.farnell.com/harting/6001-0...way/dp/1142821

TYCO ELECTRONICS / AMP - 5787170-7 - CONN, PCB RECEPT. R. ANG 68 PINS - 4.68
http://uk.farnell.com/tyco-electroni...ins/dp/1654613





TEXAS INSTRUMENTS - SN74LVC2G17DBVR - BUFFER/DRIVER/RECEIVER, SMD - 0.35
http://uk.farnell.com/texas-instrume...smd/dp/1470776





NATIONAL SEMICONDUCTOR - DS90LV047ATMTC - LINE DRIVER QUAD LVDS 3V, 90LV047 - 2.57
http://uk.farnell.com/national-semic...047/dp/9778659



PDF datasheets available by following the URLs on the product pages.
Last edited by Alison F; Mar 03, 2009 at 05:47 PM.


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