Do I need to set host side shared variables to RT FIFO?

[_Tom_]

Hello there,

in my application a LV host application communicates with compact RIO through shared variables. On cRIO i have some shared vars with RT FIFO enabled. On host side for those vars which are bound to cRIO i did the same. Is that neccessary?

In general I am confused about shared variable settings on both sides, for example when I want network buffering. Do I set buffering on RT side or on PC side or on both, what is the difference?

regards

Thomas

[ninlmartijn]

Dear Thomas,

thank you so much for your post. The shared variable with RT FIFO enabled works the same as the RT FIFO functions on the RT functions palette. The RT FIFO is for communication between the higher priority loop and the normal priority loop. You can see it like this; if the shared variable with RT Fifo enabled is network published there is a communication loop (hidden) which publishes the shared variable to the network port of the cRIO system. The RT FIFO option is only for the communication between your high priority loop and this hidden loop. The hidden loop is executed when the higher priority loop is idle. Again I speak about hidden loop just to create a clear picture.

So for your PC side no RT FIFO is needed. Please notice that by using shared variables you can lose data; for example the cRIO publishes the data faster then your PC can read the data; you will lose data points. Shared variables are based on UDB, you can see it like a radio station which is transmitting. It doesn't matter if people are listing to the radio station. Use the TCP functions (for example theSTM library ) or the network stream API if you don't want to lose data.

Please let me know if you have any further questions,

Best regards,