Datasocket writes to FP1600 are unreliable

[Richard2950]

I am trying to control digital outputs on an FP1600 from an FP2000. I can't use the FieldPoint vis, and am forced to use datasocket writes. I have attached 2 files. The vi named "FP1600 write test.vi" illustrates the problem. If you watch the state of the digital output in FieldPoint Explorer and run the vi, you can see that the datasocket write does not change the value. If you run the vi in debug mode (turn on the light bulb), it usually works!! After making any changes to the vi that force a re-compile, it usually works the first time, with the run button active for a noticeable period of time. After that the vi finishes instantly, but doesn't change the value of the output. The second vi in the attached zip file, "FP1
600 R and W test.vi", tries to read the value first, then write it. It is set to wait 500 msec for an updated value on the read, and it should always time out, since nobody is updating the value. The first execution works, but successive executions finish instantly, with no 500 msec delay, no timeout indication, and no setting of the value. Somehow the datasocket transactions are just not taking place. What gives here?

[Mike S. @NI]

Richard,

With LabVIEW 6.x, the first run of an instance of the Datasocket Write function does not always produce the desired results when writing to FieldPoint. The current workaround is to run the function twice instead of once for the first run of every iteration. I have created a VI that will do this for boolean values; just insert this VI into your diagram in place of any datasocket write functions.

Regards
Michael Shasteen
Applications Engineering
National Instruments
www.ni.com/ask

[Richard2950]

Yor workaround still did not function reliably, even when increasing the number of first-time calls from 2 to 10. It also took a long time to finish. When I put a small delay in the For loop (20 msec) it began to work reliably for first-time calls of 2. I am still running on a host computer; I have not tried actually running it on the FP2000 yet.

Rich