Execute a step once only in signal express

[Bandit]

Hi,

I'm a LabVIEW developer who is currently wrestling with Signal Express. I have a user who wanted a general purpose data logging software application written, then we saw Signal Express and thought 'That looks like what we need'. As he is short of budget and I am short of time we are giving it a go.

I struggled to get to grips with the basic idea of dropping the steps into the area on the left. I thought they executed in order, but that's not so. They seem to run as seperate parallel loops, unless one specifically requires an input that is the output of another.

What I would like to do is have a step that only runs once - say at the beginning or the end of a logging session. One instance would be to set an analog output to a level it was needed at for a complete session, and then to ensure it's set back to 0V when the session is ended.

Another would be to call a LabVIEW.vi once at the begining to set up a serial port. After polling the serial port for data regularly throughout the logging session using a second vi I'd then like to shut it down at the end with a third. All the serial port stuff has to be done in LabVIEW .vi's as Signal Express itself doesn't deal with the serial port. (If Signal Express can do this please point it out to me, as I've missed it).

I hope this is clear enough, but if not let me know and I'll try and clarify what I'm looking for.

Regards,

Bandit.

[JonBowers]

Hi Bandit,

There is a conditional repeat function und the execution control steps. You can use this to repeat code for a specific number of iterations, until a digital line it set or until a signal goes above a certain value. Hopefully you should be able to integrate this with you steps and have the ones you only want to run once outside this statement.

Regards

Jon B
Applications Engineer
NI UK and Ireland

[Bandit]

Thanks Jon, I'll take a look at that.

Regards,

Bandit

[Bandit]

I've taken a look at the conditional executing step. (delay since last posting is mainly due to hols). Howerver, it's not working, primarily because I can't call LabVIEW code from LabVIEW Signal Express. I'm sure this is because I have missed something.

The error messge I get when trying to call LabVIEW vi's is... "Error occured in Run LabVIEW 8.0 VI step. This .vi is not executable. Please verify that the VI is not broken and stored as a Source Distribution (which "Includes vi.lib files") and is within a Linked Library with the ".llb" extension."

The vi is executable (within LabVIEW). It is not broken.

It is stored as a Source Distribution with vi.lib files included.

It is within a .llb linked library.

It is also reenterant, as required in the the Signal Express help files.

I've done everything I can think of to make this work. Any advice on using LabVIEW vi's in Signal Express would be gratefully recieved.

Bandit.