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PXI-6528 Software Trigger

I am using the PXI-6528 DIO on PXI chassis. This board is an opto-isolated TTL DIO. The DAQmx driver permits only true/False (boolean) input/output and neither analog nor digital signals. I am trying to trigger a latched output. Configuring the DAQmx Generate step for Software Trigger (a latching trigger), I find that the step permits Software Trigger only when the Timing Settings/Generation Mode is set to either N Samples or Continuous Samples.

 

HOWEVER, when selecting those Generation Modes, the Step immediately goes into error due to the lack of an input AND does not permit connecting to any True/False variables in the project. Therefore and seemingly, this Step incorrectly permits the user to configure for Software Trigger while simultaneously preventing its use.

 

Any correction to my findings, workaround, or advice???

 

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Hi SOERJ,

 

In regards to your application with the PXI-6528 are you trying to write a single Boolean to toggle a line or are you trying to write a hardware timed digital waveform as the output?

 

I guess a better question is, how often do you need the digital data to change on your PXI-6528 digital lines?

 

I ask because the two modes, 1 Sample (On Demand) and N Samples (or Continuous Samples), are using completely different processes to write data to the specified line.

 

1 Sample (On Demand) mode writes a single sample every iteration of a specified software loop rate.

 

N Samples and Continuous samples use a hardware clock to ensure a digital sample is written with precise timing.

 

The reason you are getting the “Missing inputs” error on the N Samples mode is because you need to provide the task with a digital waveform before the DAQmx Generate step. This ensures the digital samples are written to the buffer of the device, which in turn gives it the ability to write samples in a hardware timed fashion.

 

You can add a digital waveform by adding the Create Digital Step (Add Step >> Create Signal >> Create Digital Signal).

 

Let me know if this information helps and good luck with your application.

Sam Burhans
Senior Product Manager
National Instruments
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