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Flat Line waveforms during free running mode

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Flat Line waveforms during free running mode

Postby bawebb » Wed Mar 01, 2017 5:34 pm

Hi, I am running PicoScope 6 version 6.11.12.1692 with a 5444B scope. All 4 channels running with a math waveform of ~B+A for 1 waveform and ~D+C for the other waveform. I am running at 8 bits, and I am not using any triggering, just starting and letting it free-run collecting the waveforms. Both on the screen real time, and when I look through the collected waveform buffers, there are several buffers that have "flat line" waveforms. I.E. data is missing. I have adjusted the #bits, the samples per second, the number of waveform buffers etc... and nothing really seems to help, I still see this lost data. I have attached the saved waveform data so you can look through it and see. Do you have any idea what could be happening?
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flatlines.psdata
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Re: Flat Line waveforms during free running mode

Postby Martyn » Fri Mar 03, 2017 11:55 am

That looks unusual, particularly the flat parts in buffer 8.

Can run the test again and, if/when you see the same error, locate the trace.xml file , see section 3 of this guide and either post it here, or email it to support@picotech.com

Can you also take a photograph of your hardware setup, showing what you are monitoring.
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Re: Flat Line waveforms during free running mode

Postby bawebb » Mon Mar 06, 2017 3:12 pm

Martyn, thanks for the response. I ran the system this morning and more or less got the same thing, every other waveform buffer was missing. I checked the data with a different external o-scope and all is well. Also the capture card is showing no problems with the data so I know the data stream is good, I'm just missing some waveform buffers. I have included the trace xml file and the data file from this run. I cannot however provide a picture due to the lab I am running in. I can tell you what I am capturing. It is a manchester encoded data bus. Very similar to mil std 1553, except there is a 20 bit data word instead of 16, and some other differences in the command word etc.... But it is a 1 microsecond bus (1 bit per microsecond) and it is commonly called manchester bi-phase 2. I have another 5444B scope so I tried that to see if it made a difference and it didnt. I also switched USB ports.....that didnt help.....I took the channel off the math and just displayed 1 line of the 4 probes to see if the math on the channels was messing it up......that didnt help either
thanks for looking into this.
Attachments
trace.xml
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flatlines2.psdata
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Re: Flat Line waveforms during free running mode

Postby Martyn » Thu Mar 09, 2017 8:31 am

DO you also see the flat lines if you don't have the Maths Channels enabled ?

Can you try with the latest release of the software 6.12.7 which you can download from the website, this will help to see if this is a hardware issue, or a driver issue.
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Re: Flat Line waveforms during free running mode

Postby bawebb » Thu Mar 09, 2017 4:15 pm

Martyn,
yes it still happens when I take the math off the channels. In fact I turned off channels 2, 3, & 4 and just ran channel 1 with no math and get the same thing. Again I adjusted sample rate, took the voltage setting off of auto and set it to +/-5vdc....nothing seems to help.
Loaded the 6.12.7.2681 version of picoscope and ran all the same tests again, again there was no change. I changed out the USB cable and again no change. I also took an app I wrote that configures the scope, and streams data to a buffer then out to a file (much like one of the sample programs from your SDK), I can then post process that file and look at the waveforms, in my self made viewer. When I do that the data is just fine....all the data is there and the waveforms in my custom software are perfect, but when I go back to running the picoscope software (to use the system like a standalone scope) again there are flatlines.....usually every other buffer is completely flat. I have included the trace.xml file for the run with the new picoscope 6.12.7 software.
thanks
Brent
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Re: Flat Line waveforms during free running mode

Postby Martyn » Thu Mar 09, 2017 9:27 pm

Can you let me know the exact settings you are using in your application, you say streaming data which may be different to how the scope is set up when using PicoScope 6.

Are the settings comparable with the way the scope is set up using our software, View-> ViewProperties will give this information.
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Re: Flat Line waveforms during free running mode

Postby bawebb » Fri Mar 10, 2017 3:57 pm

Martyn,

in the application, it is set for
8 bits resolution
DC Coupled
PS5000A_2V
ETS OFF
Time Units to PS5000A_NS
Sample Interval = 16

The PicoScope app, is set for (normally)
8 bits resolution
+/-2V DC
Sample 4 NS (fastest it will go with my 4 channels)
Rate 250 MS/s
No Samples 12,500

but I have tested to 16 ns sample rate, 56 ns, all the way down to
8 bits resolution
+/- 2V DC
Sample 504 ns
Rate 1.984 MS/s
No Samples 99

and I still get the flatlined waveforms
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Re: Flat Line waveforms during free running mode

Postby Martyn » Fri Mar 17, 2017 12:44 pm

At the moment I am unsure as to where the issue could be, so some additional questions releated to your streaming application.

Is it a 64bit or 32bit application ?
What development language is it written in ?
What versions of ps5000a.dll and picoipp.dll are you using ?
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Re: Flat Line waveforms during free running mode

Postby bawebb » Mon Mar 27, 2017 7:51 pm

my streaming app is a 32 bit app, C++ and the dll and lib are dated 6/8/2015. I want to make sure we don't stray too far away from the problem here. Remember the issue I'm having is with the PicoScope software.....not my streaming app. My streaming app I get a full memory load of samples....no gaps in the waveforms, its the picoscope app that seems to be dropping waveforms. I want to make sure since we are so far down the line from the original problem statement we remember what the actual issue was. Tomorrow I plan to hook a simple sign wave generator up to the scope and see if I get the same dropped waveforms using a different input source. thanks

Brent
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Re: Flat Line waveforms during free running mode

Postby Martyn » Tue Mar 28, 2017 6:41 am

This could be an issue with the scope hardware, your application is streaming data so will only use part of the memory as a FIFO. The PicoScope application is running in block mode, so will have segmented the whole memory to match the application settings (by default 32 segments), and will collect a waveform to each block.

It would be worth trying PicoScope 6 in streaming mode
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streaming112ns.psdata
Streaming at 112ns
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