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How Do I Enable Digital Filtering on My NI-65xx?

Hardware: PXI/CompactPCI>>Controllers

Problem:
I have an NI-65xx which has the ability to filter my input signals. How do I enable this feature and set the parameters in my program?

Solution:
You can use the digital filter option available on the input lines to eliminate glitches on input data. To enable this option and to set its parameters you need to use a set of DAQmx channel properties.  Note that there are certain caveats about when digital filtering can and cannot be used on Multifunction DAQ boards.

To access these properties in LabVIEW (see attached VI):
  1. Place a DAQmx Channel Property Node on your block diagram, located at Functions » All Functions » NI Measurements » DAQmx - Data Acquisition.
  2. Expand the property node to contain 4 properties
  3. For the first property, select Digital Input » Digital Filter » Enable. Wire a false to this input, which will disable the filter on all of the lines by default (allowing you to enable the filter only on specific lines).
  4. For the second property, select Digital Input » Digital Filter » Minimum Pulse Width. This is where you set the filter pulse width.
  5. For the third property, select Active Channels This will allow you to select specific channels on which you would like to enable the filtering.
  6. Click on the fourth property box and select Digital Input » Digital Filter » Enable. This will enable the filter on the lines that are selected in 'Active Channels'


To access these properties in a text-based language, use the following functions: To enable the digital filter:
DAQmxSetDIDigFltrEnable(TaskHandle taskHandle, const char channel[], bool32 *data);

To set the minimum pulse width of the filter:
DAQmxSetDIDigFltrMinPulseWidth(TaskHandle taskHandle, const char channel[], float64 data);

Related Links:
Product Manuals: NI-6509 Help (User Manual)
KnowledgeBase 3R6J4RX6: PXI-6509 Benchmarks with NI-DAQmx
KnowledgeBase 3QQFQFBP: Why Can't I Tristate My NI 6509 Digital Lines?
KnowledgeBase 3HADUKBH: Digital Filtering with M Series and CompactDAQ


Attachments:


Filtered Digital Waveform.vi

Report Date: 03/31/2004
Last Updated: 02/13/2009
Document ID: 37UH2VI3

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