Siglent SDS1102X Serial decoder not decoding properly

[GeorgeOfTheJungle]

Hi, I'm playing with my new SDS1102X and it's refusing to decode, see the pictures, both scopes are connected to the same signal. Any ideas why?

Also there are a few things that I don't get:

1) Why is the memory depth just 1.4MB (and won't let me set it to 14MB) ?
2) Why such a low sample rate 5MSa/s @ 20ms/div ? There are 14 divs/screen, @ 20ms/div= 0,28s, @10MSa/s= 2,8MB, and even @ 50MSa/s 0,28s*50MSa/s= 14MB and it should fit.
3) When horizontal is > 20 ms/div it shuts down for good the serial decoder, why??

The firmware is the latest version. Is it broken or this is just the way it is?

[rf-loop]

Hi, I'm playing with my new SDS1102X and it's refusing to decode, see the pictures, both scopes are connected to the same signal. Any ideas why?

Also there are a few things that I don't get:

1) Why is the memory depth just 1.4MB (and won't let me set it to 14MB) ?
2) Why such a low sample rate 5MSa/s @ 20ms/div ? There are 14 divs/screen, @ 20ms/div= 0,28s, @10MSa/s= 2,8MB, and even @ 50MSa/s 0,28s*50MSa/s= 14MB and it should fit.
3) When horizontal is > 20 ms/div it shuts down for good the serial decoder, why??

The firmware is the latest version. Is it broken or this is just the way it is?

When decode is in use:
maximum acquisition length is 1.4M
lowest horizontal speed is 20ms/div

These are limits (in last FW versions - why, I do not know, 20ms/div also surprise for me).

I have not checked but is it so that this Agilent have hardware decoders?

What is your signal accurate speed (115k ?) and parameters?
(some day I can perhaps also look it bit...)

Old FW can
  NOTE, Attached image is obsolete! (Old FW !!! (Perhaps P06)

[GeorgeOfTheJungle]

Hi rf-loop,

Thanks for the quick response!

Yes, the baud rate is 115200.

So yours can decode @ 50ms/div??? But surely not @ 115Kbaud, have you tried? I need to decode a frame that's almost 2s long, and I need to do that with both channels on. Is that possible with this Siglent?

Why is mem depth just 1.4MB with decode on? What a bugger!

Mine seems to need 10MSa/s to be able o decode properly @115Kbaud which is strange, really, IIRC there were UARTs that did it well with just 16 samples per bit-slot, I don't get why does the siglent need hundreds of points per bit-slot to decode properly. Is it a bug? What do you think?

I'm afraid I'm going to have to return it, if that's the way it is it's useless for me. A pity because I like it very much.

Thanks,

[rf-loop]

So yours can decode @ 50ms/div???

 No, it was very old obsolete FW version. Now 20ms/div is limit.

But surely not @ 115Kbaud, have you tried?
 

not with this acq. speed.

I need to decode a frame that's almost 2s long, and I need to do that with both channels on. Is that possible with this Siglent?

No, it is not.

Why is mem depth just 1.4MB with decode on? What a bugger!

Memory settings are 14k, 140k, 1.4M, 14M (for one channel in use). I do not know reason why max for Decode is 1.4M. Perhaps lack of processing power and it go too slow?

I'm afraid I'm going to have to return it, if that's the way it is it's useless for me. A pity because I like it very much.

All scopes do not meet all users specified needs. If you need  ~>2second  115k speed  Rx Tx   decoded,  this scope is not at all right tool (if you need do this using oscilloscope). If this  is Go - NoGo  question  -  it is end of game with this and you really need something other.

Most important is that you get tools what meet your individual needs.

[nctnico]

If the purpose is to purely look at the data and not timing then a PC with a serial port monitoring program (there are many of them so spend some time testing a couple of them) is a much better tool. At some point the buffer for decoded data in an oscilloscope will be full and it doesn't matter if the oscilloscope costs $400 or $25000 for that to happen.

[rf-loop]

If the purpose is to purely look at the data and not timing then a PC with a serial port monitoring program (there are many of them so spend some time testing a couple of them) is a much better tool. At some point the buffer for decoded data in an oscilloscope will be full and it doesn't matter if the oscilloscope costs $400 or $25000 for that to happen.

These PC tools + oscilloscope for signal signal integrity and form analyzing  is good combination for many this kind of things.

[tautech]

George
You can improve results by using the correct protocol trigger from the Trigger suite. Be sure to set the correct baud rate too.
As advised 20ms/div is the slowest decode speed, slower and the scope drops decode functionality and enters Roll mode.

[GeorgeOfTheJungle]

@rf-loop, thank you very much. The thing is that I bought this siglent to replace a 2 years old 1074Z that's doing exactly that just fine and just because I don't like its UI nor its overall sluggishness. (and to get a new toy :-) I saw videos on youtube and thought wow, that thing flies (comparatively), has serial decode and 14MB is about right for this... but no :-(

@nctnico The other channel is sensing the current into the DUT, the code spits bytes at certain points to correlate execution with power input, the DUT is sleeping most of the time, only awakes every now and then and for less than ~2 seconds.

[GeorgeOfTheJungle]

George
You can improve results by using the correct protocol trigger from the Trigger suite. Be sure to set the correct baud rate too.
As advised 20ns/div is the slowest decode speed, slower and the scope drops decode functionality and enters Roll mode.

I believe that's ok as it is (falling edge), I tried trigger/uart/condition start and it makes no difference, only switching horizontal to 5 ms/div or less makes it decode ok. See the pictures.

EDIT:  This are the wrong pictures (triggering on rising edge), haven't got at hand the right ones, but it makes no difference.

[nctnico]

@nctnico The other channel is sensing the current into the DUT, the code spits bytes at certain points to correlate execution with power input, the DUT is sleeping most of the time, only awakes every now and then and for less than ~2 seconds.

Then I guess your only option is to get a different oscilloscope with more memory and better decoding. Segmented recording won't be helpfull either for these kind of measurements.

[MrW0lf]

I'm afraid I'm going to have to return it, if that's the way it is it's useless for me. A pity because I like it very much.

Do no suffer unneeded pain. Look at this as opportunity get even more gear. Just use your new scope for simple debugging and serial trigger for some large memory USB device that can capture and decode mega, if not gigabits in single shot and analyze in proper manner with search, sorting etc.

[GeorgeOfTheJungle]

Then I guess your only option is to get a different oscilloscope with more memory and better decoding. Segmented recording won't be helpfull either for these kind of measurements.

The funny thing is the 1000z that's cheaper can do it well, huh, I wasn't expecting that.

[tautech]

Brand new unit straight out of the box, UART from Siglent test board, STB3
http://siglentamerica.com/prodcut-fjxx.aspx?fjid=4990&id=4688&tid=1&T=2

Decode and Serial trigger in use.



Edit
Oh yeah, 10x probes used but 1x set on inputs. 

[GeorgeOfTheJungle]

@tautech: Please try that @ 115200 baud

[tautech]

@tautech: Please try that @ 115200 baud

The UART source I have is 9600 baud only, sorry.

[GeorgeOfTheJungle]

Do no suffer unneeded pain. Look at this as opportunity get even more gear. Just use your new scope for simple debugging and serial trigger for some large memory USB device that can capture and decode mega, if not gigabits in single shot and analyze in proper manner with search, sorting etc.

That sounds good ! :-) Any particular device do you have in mind?

[GeorgeOfTheJungle]

@tautech: Please try that @ 115200 baud

The UART source I have is 9600 baud only, sorry.

No problem, I have an espruino here, let me check it out, one second...

[MrW0lf]

That sounds good ! :-) Any particular device do you have in mind?

If you want additional 2 analog channels + digitals then there is scope/analyzer hybrid 2206B MSO from Pico (first model with large memory of 32MB, Pico MSOs go up to 512MB). If want only large mem digitals then look Digilent Digital Discovery and Saleae stuff*. Digilent Analog Discovery (2) is not suitable because of only tiny memory.

*Looking at the specs Saleae does not have oboard mem spec anywhere to be seen... Streaming only? That would explain why sample rates drop heavily when enabling many channels.

[GeorgeOfTheJungle]

All goes well up to 38400 baud, any more than that and it misbehaves.

var baud= 38400;
var str= "George"+ baud;
Serial4.setup(baud);
setInterval(function () { Serial4.write(str); }, 500);

[ebastler]

The thing is that I bought this siglent to replace a 2 years old 1074Z that's doing exactly that just fine and just because I don't like its UI nor its overall sluggishness. (and to get a new toy :-) I saw videos on youtube and thought wow, that thing flies (comparatively), has serial decode and 14MB is about right for this... but no :-(

What?! The "it's-useless-because-it-only-decodes-from-the-screen-buffer" Rigol can do something in the decoding department which the "only-way-to-do-it-right" Siglent can't?! Heresy! 

Kidding aside, this seems to be a nice example that design decisions usually imply some trade-offs. In this particular use case, the Rigol's approach (capture it all, then decode piecemeal what is displayed on the screen) turns out to be less limiting. In other scenarios, the Siglent is ahead.

A good one to remember when the next round of "scope wars" unfurls in some other thread... 
(And yes -- I still like my DS1054Z very much, but agree that its user interface can become annoyingly slow with decodes, math, etc. enabled!)

[MrW0lf]

Seems I was giving wrong advice regarding Saleae analyzers. Seems they do not have onboard memory, at that price!? 
"All data is streamed in real time over USB. The maximum sample rates depends on the number of digital and analog channels used."
Pretty small list then remains.

[nctnico]

All goes well up to 38400 baud, any more than that and it misbehaves.

var baud= 38400;
var str= "George"+ baud;
Serial4.setup(baud);
setInterval(function () { Serial4.write(str); }, 500);

The problem is clearly in the amount of oversampling needed by Siglent's decoding algorithm. It is one of the things I tested when I got the GW Instek GDS2204E and 13 samples per bit seemed to be the limit.

[GeorgeOfTheJungle]

The problem is clearly in the amount of oversampling needed by Siglent's decoding algorithm. It is one of the things I tested when I got the GW Instek GDS2204E and 13 samples per bit seemed to be the limit.

Yes, that to me sounds about right, a paleolithic 6551 UART sampled (IIRC) 16 times per bit but this siglent seems to need hundreds to do it right.

[GeorgeOfTheJungle]

If you want additional 2 analog channels + digitals then there is scope/analyzer hybrid 2206B MSO from Pico (first model with large memory of 32MB, Pico MSOs go up to 512MB). If want only large mem digitals then look Digilent Digital Discovery and Saleae stuff*. Digilent Analog Discovery (2) is not suitable because of only tiny memory.

*Looking at the specs Saleae does not have oboard mem spec anywhere to be seen... Streaming only? That would explain why sample rates drop heavily when enabling many channels.

Correct me if I'm wrong, but isn't it that most of these USB scopes come with Windows only software? And I'm a Mac-man. I wonder why don't they provide a web interface, browsers nowadays have websockets and that would make them chooch fine everywhere (Linux, Mac and Windows).

[JPortici]

not those three.
you have osx software for pico, digilent, selae.

pico is a bit behind in terms of updates, unfortunately.