What method should I use for transfer the latest value without polling?

[Thang Nguyen]

Hi,

I would like to ask which method should I use for transferring latest data between determinism process. I don't want to use single process shared variable with RT FIFO enable since it will polling data. I don't want to use the RT FIFO function because I cannot send the latest value. Queue is not determinism. I am not sure if Notify is determinism or not. Anyone with experience about this?

 

Regards,

Thang Nguyen

[crossrulz]

Since you are talking about deterministic loops, they have to run at a certain rate.  Therefore you will technically need a polling mechanism.

 

What kind of data are you trying to transfer?

[Thang Nguyen]

@Crossrulz: I have 3 array of doubles (640 elements each from a line scan). I guess I can use single process shared variable single element with another counter to tell if this is the latest data or not. How do you think?

 

Edit: Sorry for my brainstorm idea. I forgot that I don't want it polling. I want the blocking feature.

Edited September 10, 2014 by Thang Nguyen

[ned]

Edit: Sorry for my brainstorm idea. I forgot that I don't want it polling. I want the blocking feature.

Blocking and determinism don't really go together. What are you trying to achieve here? Do you want the deterministic loop to wait until it receives a new value (at which point it won't be deterministic anymore), or do you want that loop to run at the same rate consistently regardless of whether there is new data? If the latter, one approach might be a functional global variable, with the "Skip Subroutine if Busy" option set (and add a boolean output that confirms the data is good before you use it, in case it is skipped).

[Thang Nguyen]

You are right. I think the problem is myself, I need to identify clearly what I want. Currently, I am confuse that if I want deterministic or not.