There are functions to read the actual number of bytes in the serial port input buffer.
If you want to trigger the execution of a VI when a set number of bytes is received, you have to implement the callback functionality. Write a VI that reads this number of bytes at the serial port. As long as these bytes are not received (or timed out), the VI waits. A reference to the VI to be called can be given to the serial waiting VI. When the required bytes are received, call the VI by reference. The VI have to run in parallel with the rest of the code.
I've tried to be clear but it is not to easy to describe how to do this. Post again if you need. If you explain why you want to do this, maybe there are better solutions in LabVIEW than to mimic procedural langua
ges behavior.
