Why can I not perform continuous sampling of port 0 on USB 6216?

[Xooch]

I have a USB 6216 from NI. I'm trying to capture digital signals using port 0. However, the only mode I can operate in is On Demand sampling. If I select N Samples or Continuous Sampling, I receive the following error in both SignalExpress and Labview 2011's DAQ assistant. What am I not doing correctly?

Error -200077 occurred at DAQ Assistant

Possible Reason(s):

Requested value is not a supported value for this property. The property value may be invalid because it conflicts with another property.

Property: SampTimingType
Requested Value: Sample Clock
You Can Select: On Demand

[Dennis_Knutson · Accepted solution]

Since the 6216 does not have a sample clock for the digital I/O as you can see from reading the spec, any time you attempt to use one, you will get that error message. So, in LabVIEW, every time you want to do a read, you must call a single DAQmx Read set to single sample mode (or the DAQ Assistant configured the same way). How many samples/second you take are going to be highly variable due to windows being non-deterministic.

[crossrulz]

That is just a limitation of the USB6216.  It's DIO are only software timed, which mean they only sample when your program requests data and only one sample per request.  You need to find a DAQ or DIO that supports hardware timed DIO.

[Xooch]

Looks like I'll have to sample as analog inputs and detect levels... Thanks for the quick responses.