Architecture Question / Chained Loops

[pierroil]

Thanks. So just a get Notifier status would do. I'll put it in the DAQ loop. The data handling loop is an interesting idea by the way. I'll keep it in mind.

[nathand]

---

@pierroil wrote:
Thanks. So just a get Notifier status would do. I'll put it in the DAQ loop. The data handling loop is an interesting idea by the way. I'll keep it in mind.

---

Make sure you're clear on the difference between "Get Notifier Status" and "Wait on Notification."  You may want to use Wait on Notification with a 0 (or small) timeout instead of Get Notifier Status.

[pierroil]

Why?

[nathand]

If you only care about determining when the value in the notifier changes, then it makes more sense to use Wait on Notification.  If it times out, there was a new notification; if it doesn't, then keep doing what you were doing.  Calling Get Notifier Status repeatedly is basically equivalent to polling a global variable.  Wait on Notification also lets you use it as a timing mechanism (the timeout value) so there's no need for a separate loop timer.

[pierroil]

Wait on notification. If it time out then I have no new command right? I only send DAQ signal ON once.

[pierroil]

Well I'm sending a command like 'ACQUIRE' and only once. So then what to use?

[nathand · Accepted solution]

If it times out, there is no new notification.

I don't see any problem with using a notifier even if you only intend to put in one notification, as a way to start a separate section of code after some parameters are set.  In the message that started the thread you were asking about sending separate Start and Stop commands, which is also a fine use of a notifier and Wait on Notification.

[pierroil]

Here's what I ended up with by the way.

If it times out, then the next state will simply be the last one - i.e. if I was in acquisition mode, I will continue to acquire data. If I was in idle mode, I will continue to be in idle mode. At any moment, shoudl a notification come in, the mode can change. I chose this architecture since I cannot have an exterior signal constantly sending this notification - or if I did, it would be over engineering this. Unless of course... there is a better way to do this...

--

Thanks for your help!

[pierroil]

So I just found out that the wait on Notification function will repeat a message for ever...

Lovely.

[nathand]

---

@pierroil wrote:

So I just found out that the wait on Notification function will repeat a message for ever...

Lovely.

---

No, it won't... could you be more specific about what you're seeing?  Wait on Notification returns a default value if it times out.  However, if you constantly send the same notification, that's still treated as a new notification even though the content is the same.