Per Cycle Tristate Programming with NI-HSDIO - KnowledgeBase - Support

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Per Cycle Tristate Programming with NI-HSDIO

Primary Software: Driver Software>>NI-HSDIO
Primary Software Version: 1.5
Primary Software Fixed Version: N/A
Secondary Software: N/A
Hardware: Digital I/O (DIO)>>High-Speed

Problem:
How do I program my NI-HSDIO device to tristate on a per-channel, per-cycle basis? When I try to implement this in LabVIEW, I get an "Error -1074118585 occurred at niHSDIO Write Named Waveform (WDT).vi"

Solution:
If you are encountering the error described above, you are most likely using an HSDIO device that does not support per cycle tristate. The NI-655x series does support this feature, which allows for a real time hardware comparison. See the related links below for more information on this subject.

If you do have a NI-655x series device, there are two primary methods that you can use to generate a series of 0's, 1's, and Z's (high impedance). They are to use the niHSDIO Convert Binary to WDT.vi, or to use the Digital Waveform Editor to create an HWS file.

HSDIO Convert Binary to WDT.vi

The niHSDIO Convert Binary to WDT.vi converts unsigned binary data into the digital waveform data type (WDT), and is used to generate extended waveform data (0, 1, Z, H, L, X). This VI has two main inputs of interest: data and drive enable. When the drive enable is 1 (true), the VI will output the waveform from the data input just as it is. However, the VI will output a Z when the drive enable is 0 (false). On a high level, this VI is basically performing a logical OR of the two binary data strings.

The best place to start is the shipping example (LabVIEW >> Help >> Find Examples) called Dynamic Generation with Cycle to Cycle Tristate. This example demonstrates how to generate a dynamic pattern that includes tristated channels. Tristate may be specified on a sample-to-sample and channel-to-channel basis.

Digital Waveform Editor

A second method is to use the Digital Waveform Editor (DWE) software to create an HWS (Hierarchical Waveform Storage) file. Within the DWE, you can graphically create digital waveforms that include high impedance values on a sample-to-sample basis. You can then use this HWS file in conjunction with the shipping example Read HWS File and Generate.