timed daq using timed loop

[ThijsBoeree]

Hi,

I am very very new to labview 8.5 and the whole daqmx thing, i am reading all the stuff here and there but still can't figure out how to build my VI... What i want is the following:

1. A contineously acquisition of 8 channels with a sample frequency of 500 Hz, stored in a file (EDF) every 1 second. For this i can use a simple daqmx assistant that aquires the samples and update the loop every 1 second. I already wrote the EDF thing.

2. Another loop that displayes the data that is coming into my hardware realtime with a higher refresh rate, lets say an updated screen every 25 ms.

Now i was wondering if there is a way to connect the counter of the onboard hardware clock on my USB6215 to an input on a timed loop, so that my timed loop is hardware timed, if that is possible i can make a loop inside a loop where i can write my data every 20st iteration that is exactly (20 * 25) 500 samples...

Thanks in advance,

Best regards,

Thijs Boeree

[BenjaminR]

Hi,

In the link below you have some information about Timed Loops Configuration in order to have an external timing source.

https://www.ni.com/docs/en-US/bundle/labview/page/configuring-timed-loops-and-timed-loops-with-frame...

[ThijsBoeree]

Thank you, i've red the page, but it didn't resolve my problem... I also tried to use "DAQmx Create Timing Source" but this only gives an erro that my device can't work with that?

I really don't know what to do.

Regards,

This

[BenjaminR]

Hi,

Here you have an example VI for Timed Loop with external clock. Note that I use the counter with digital edge with counter and not directly the onboard clock. Hope this can solve your problem.

[ThijsBoeree]

I always get this error:

Possible reason(s):

Measurements: Requested value is not a supported value for this property.

Property: SampQuant.SampMode
You Have Requested: Hardware Timed Single Point
You Can Select: Finite Samples, Continuous Samples

Task Name: _unnamedTask<6>

Has this something to do with my USB6215

Best regards,

Thijs

[KvZ]

Hi Thijs,

Looking at the examples above you are timing Digital I/O. Currently due to hardwate limitation the Hardware Timed Single Point sample mode is not supported on digital I/O.

You can only use Finite Samples or Continuous Samples on a Digital I/O task.

Thanks

Karsten

[ThijsBoeree]

Hi there,

Thank you for responding to my question. I already tried some examples with hardware timed looping and my ni-USB6215 but i get an error message that my device doesn't support some things. If i can't get a loop hardware timed, i have to do it on another way...

This is what i hope you can help me with...:

One program with data-acquisition (analog in 500 Hz 8 channels) update every 1 second (the aquired data needs to be writen one block of 8 * 500 samples every second to a file).

Then another loop...? with the same data but then updated every 25ms, so that i have a smooth scrolling display of my incoming data.

I know the basics of labview and already have writen such a program in labview 6.0 but back then i could also got another analog input VI in my block diagram with the most recent aquired data, i also used daq occurence.

I hope you can help me with the basics of daqmx, one loop updates every 1 second (hardware timed) and the second loop updates every 25 milisecond (for displaying smooth scrolling data).

Best regards,

Thijs Boeree