Hi temptanner,
I see the following challenges in your applications:
1. serial communication does not guarantee determinsm, that means you can't say, if sending the first command to the serial port and receiving the answer needs x seconds, that the second comm will take x seconds as well. X will change siginificantly because a serial comm. is not highly deterministic. If your communication takes 1ms, i would say you will reach the update rate of 10ms but you can't guarantee that.
2. If you would like to have the dio task and serial comm task running parallel, don't use two loops in you rt vi which is set to time-critical priority. Because if one of the loops will go to sleep the entire time-critical thread will sleep, which can or will lead to unexpected results.
Create your dio task in a vi with time-critical priority and the serial communication to a "normal" priority and exchange datas with rt FIFO's in this way you will at least get high determinsm for you dio task.
3. If you like to control your rt vi (buttons on the frontpanel) with a mouse or keyboard, this is not possible directly on your pxi system running a RT OS. You have to make a connection to a host vi, which runs on a general purpose os (windows) and is able to send and receive datas. There is another option to use the labview web server, to be able to control the fp elements of an rt vi in a web browser like internet explorer...
I hope this helps
Evrem
