High speed independent event loops?

[Mystogan]

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@Norbert_B wrote:

Yan,

no, the sources for the MAX testpanel is not published. But one thing you should check:

Are there any settings different for the testpanel and your example?

*As far as I can see, there is no different setting between my setting in MAX testpanel and niScope EX Fetch Forever.

If increasing the acquisition rate: What kind of error do you get?

*As you can see, its the problem that I keep on getting (The requested data has been overwritten in memory and can therefore no longer be retrieved)

If it's buffer overflow, you have to modify the example to split up acquisition and display because it's the read function, which is called too infrequently for keeping the buffer at a decent level....

Keyword would be "producer/consumer" for a possible modification.

hope this helps,

Norbert 

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then I try to use this example (https://decibel.ni.com/content/docs/DOC-3441), and keep getting the same error (even without plotting them), cannot use sample rate more than 30MS/s

[Norbert_B]

Yan,

looking into your screenshots shows that you are reading 55.47MS before the error occurs. This is more than a second until the buffer runs over.

Please change the seetings in the niScope EX Fetch Forever.vi to fetch -1 samples per read. This will read all samples available once read is called.

Observe the number of samples fetched (Last Points Fetched) and check if it is increasing. If it does, it seems that you system does not provide sufficient performance for the VI. Is it possible that MAX runs in a different user set?

Norbert 

EDIT: In which slot is the 5105?

[Mystogan]

Hi Norbert,

I changed the sample numbers to fetch to -1, and I can fetch less than 1M samples? And I dont think MAX runs in different user set.

Regards,

Yan.

PXI 5105 is in SLOT 8

[Norbert_B]

Hm, i still see no obvious reason for the examples not to work with >30MS/s.

Could you please give it a try with the 5105 in slot 5 or 6?

I hope the PC/Laptop you are using is capable of x4 connection with the ExpressCard, otherwise i would expect this to be the bottleneck!

Norbert 

[Norbert_B]

You should also try a simulated 5105 device just for verification with the examples.

Norbert 

[Mystogan]

Hi Norbert,

I'm using now the other Computer with other chassis which has no digital card (PXI 5105 is in slot 6 in this chassis)

*remember that I told you earlier about a student who finished his project already?*

And the result is the same: cant fetch more than 30MS/s.

Using simulated 5105? how? *googling it atm*

[Mystogan]

Hi Norbert,

I couldnt find the option to simulate 5105.

[Norbert_B]

Right click "Devices and Interfaces", select "Create New". In the dialog select "Simulated DAQmx device or Modular Instrument".

I'd expect this to work with sample rates >30MS/s. I just want to make sure that the software is not a bottleneck.

Norbert 

[Mystogan]

Hi Norbert, this is what I got.

I've tried to simulate in Slot 2, Slot 3 and even Slot 8, and I can fetch with sample rate more than 30MS/s. BUT, I think the speed is only 5MS/s.

I've simulated again with speed 5MS/s, 10MS/s, 20MS/s, 30MS/s, 40MS/s~60MS/s, and the total points fetched pretty much the same speed. 

I cant upload video of how fast it is. 😞

Regards,

Yan.

*I've emailed NI regarding this problem. I hope they would answer me ASAP*

[Norbert_B]

You are right, it seems that the simulation only goes for 5MS/s, not more and not less.....

This is not what i expected, but we cannot change it for now.

Do you have a real PXIe controller available you can use for a test?

I want to check if that MXI Express is the bottleneck or not....

Norbert