Is there a way to use a PFI as trigger input (to start/pause code), without assigning it to an acquisition channel

[Frank_Mathijs]

I want to use an external digital signal to start a series of in- and outputs, some calculations, ...  all inside a subvi.

Just using the digital signal as start-trigger for one of the outputs is not really suitable (they are inside existing sub-vi's, that preferrably remain untouched).

The only option I could think of was a digital read, programmed with a shiftregister to do edge detection, and wire this to a case-structure with an empty case when no edge, and the complete in the oter case. But this seems a bit 'clunky'.

An other option would be to initialise a 'dummy' (eg ananlog) input and configure it to wait for a digital trigger (and do nothing with the read data), but again, this seems like a workaaround...

Any other ideassuggestions?

[cedhoc]

Dear Frank,

Depending on which hardware you are using, there is one other option which is to use DAQmx Events. One of those events is the "Change Detection" event. If you register the events to an Events Structure, then the structure will be fired at each changes of a digital line. However, you still have to create a kind of dummy task which is acting on changes of a digital line. See this link for a working example http://zone.ni.com/devzone/cda/epd/p/id/317

Your two options are also possible. In all cases, you will always have to configure a task to use your DAQ hardware for any purposes.

Finally, know that those three options all rely on software. If synchronisation matters, using a real start trigger for a task is the only solution (hardware only).