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Invalid values in streaming mode

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Invalid values in streaming mode

Postby daniel.ketel » Thu Nov 27, 2014 10:50 am

Greetings,

I am working on an application using the PicoScope SDK with a PicoScope 2204A.

My software is written in C#, I am using the "wrapper" functions supplied in the C# example.
When I enter streaming mode, after a certain (reproducible) period, the driver starts to return -32767, even though the input of that channel is definitely on ground potential.

This first happened to me when streaming with a sampling period of 160ns, it also happens when I go down to 1us. The driver reports that the overview buffer is overrunning, also my callback function to read the data does not seem to get called anymore. This is the portion of code telling the scope what callback function to use:
Code: Select all
while (true)
                {
                    ImportPS2000.GetStreamingLastValues(handle, callbackFunction);

                    ImportPS2000.OverviewBufferStatus(handle, out overrun);

                    if (overrun != 0)
                    {
                        Console.Write("Overrun!");
                    }
                }

Are there any known performance issues with the driver for the 2000 series?

Any other ideas?

Best regards,
Daniel
daniel.ketel
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Re: Invalid values in streaming mode

Postby Karunen » Tue Dec 09, 2014 12:58 pm

Hi Daniel,

In streaming mode overview buffer can overrun if the data is not removed from the device fast enough.

As the 2204A is our low memory device is will run out of memory very quickly at the faster sampling rates.

Using the wrapper might add another layer which could cause a delay.
Which might be causing the overview buffer to overrun.

I have updated the C# example to use the callback directly in fast streaming mode.
Which should reduce the likelihood of data corruption occurring.

A new SDK will be built but until then if you email support@picotech.com we can send you the latest example.

Kind Regards,
Karunen

Technical Specialist
Pico Technology
Karunen
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Posts: 194
Joined: Thu Nov 21, 2013 9:22 am


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