NI USB 6501 DAQmx Read Timing

[bmeyer67]

I have a USB-6501 device that I need for to read a signal from to cause another action in software. I've discovered that that DAQmxReadDigitalU16() is my limitation on my read loop - without it, my loop operates at near proc speed (~2 GHz), but with it the loop operates at roughly 1 KHz. The problem I am running into is that I need a 4 KHz timing to accurately run the software.

Is there any way in the world that I can speed up the operation of the read function?

All I am reading from the device is a single bit from one port (e.g. port0:0) as either a zero or one with a notification going out on change (both 0 to 1 and 1 to 0).

Would the devices Event Counter be able to help me?  It is possible for my app to be able to take an event number and deduce how many times it is suppose to do its thing - right now, I 'trigger' my app on every change, but it is possible that I could count the changes and trigger the app for the number of times instead. My question though, is will the Event Counter be able to provide me fast enough response times to make up the difference?

I chose the USB-6501 b/c it could operate at a faster rate than what we needed for this simple application.  However, this 1 KHz resolution is far too limiting. (I wish at the very least that this kind of thing would have been mentioned in the specs if it cannot be gotten around.)

Please advise.

Ben

[Dennis_Knutson]

I'm not sure what spec you read but every one I've seen about the 6501 mentions that the acquisition rate is software timed and that means slow. Here's a benchmark. I'm not sure about the counter but you might want to look at an M series board. These have a port that you can use hardware timing.

[bmeyer67]

Sad. It's such a nice device to have such a limitation. I don't have a problem with it being software limited, but the overhead of the device should not be that bad in such a case.

Any how...I got it working using the counter. I just would have preferred not using the counter since I now have to deal with data wraps at some point. My app doesn't particularly care about the number.

And a board is kind of hard to put into a laptop, but I'm not sure i'd get $1k approved for this any way. I'm just modifying something to do some better emulation of another environment.

Thanks though. I'll have to keep the M Series boards in mind for next time...

Ben

[Deliang]

Hello NI-Daq experts:

I use counter digital event example for P2.7 of 6501, but the application stuck at DAQmxReadCounterScalar function, this function was not returned, and the computer can not logoff, until switch off the power to the 6501.

Could you please give me any direction?

Thanks,

Deliang

[Dennis_Knutson]

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Deliang wrote:

Hello NI-Daq experts:

I use counter digital event example for P2.7 of 6501, but the application stuck at DAQmxReadCounterScalar function, this function was not returned, and the computer can not logoff, until switch off the power to the 6501.

Could you please give me any direction?

Thanks,

Deliang

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Your question is not really related to the original thread and according to this, you are not even using LabVIEW. Why did you post here?