RT FIFO Read does not return default value

[DBallen]

Hello everyone,

I am working on a RS485 Custom Device (CD) which shall be accessed via input and output channels.

I can send data to the CD, which is read with the "RT FIFO read.vi". The "Element" connector of this VI is an array initialized to 0 (please see attached image). In the event of a timeout I am expecting to get this array. Nevertheless I am getting always after a timeout the last read array. This happens for any timeout value (even 0 ms).

Am I missing here something? I need to get the standard array (initialized to 0) in the event of a timeout.

Any help is highly appreciated!

Regards,

DBallen

[MateuszLoska · Accepted solution]

Hi BBallen,

I tried to replicate this on my computer, however, I was unsuccessful with the code I've created.

As far as I understand, your main aim is to detect the underflow and in case of timeout, you would like to return previously determined value, not the last one - which is the default behaviour of RT FIFO. 

Do you think you could use the below code as a workaround?

Let me know if this works for you and if you can treat it as a sufficient solution.

Mateusz

[DBallen]

Hi Mateusz,

your workaround works. I would expect to get this behavior from the RT FIFO vi, but your solution also provides the functionality I require.

Thank you for your help!

Regards,

Diego