Re : User Events on a RT system (LV 2012 SP1)

[Intaris]

I'm involved in trying to shoe-horn some new functionality into an existing program with Host, Real-Time and FPGA aspects to it.

I've run into a situation where I think User Events might be able to help with my signalling between processes.  My questions are:

Are User Events going to introduce jitter into my program because the event queue (I'm stuck with LV 2012 SP1) is unbounded and could theoretically need to allocate data at some random time in space.  Are RT-FIFOs preferable for exactly this reason?  If anyone has experience with Events on a RT System, I'd be glad to hear because something tells me it's not optimal....

Shane

[Apprenti_Alexandre]

Hi Shane,

What do you mean by "signalling between processes" ?

Do you mean you want to share data between multiple loops ? If you do, how many loops do you have ?

[Intaris]

Yes, sharing data between loops.

I have 2-3 loops which may need to share the data.  I say "signalling" because it's more of a producer consumer approach than a simple sharing of data.  i.e. different loops need to tell each other what to do.  The amount of data actually being transmitted (State information) is small.

Shane.

[AlexCESI]

There is many different inter-process communication methods that you can use to share data locally between loops and VIs on RT target.

Are you communicating between a determinstic loop and non-deterministic loop? Or are you communicating between non-detreministic loops ?

Do you need to transfert every value or only the latest ?

For each combination you have a solution :

                                 Deterministic and Non-deterministic Loops            Non-deterministic and Non-deterministic loops

Latest                        Single-process shared variable                                   - Signle-process shared variable

                                 with RT-FIFO ennabled (signle                                    - Local Variable

                                 element)                                                                   - FGV

Every Value              - Single-process shared variable                                  - Queues

                                 with RT-FIFO ennabled (multi-

                                 element)

                                 - RT FIFO functions